reproducibility (#177)

* reproducibility

* wip: ci fixes, drop generate_translations_header.c

* minor fixes

* fix patch

* fix: toolchain

* bump hash

* fix: minor build issue fixes

* fix: x86_64-w64-mingw32

* wip

* wip

* all updated :o

* fix: reduce git size

* update checksum
remove CI

* chore, more optimal dockerfile

* update monero to v0.18.4.6

* update checksum

* update

* minor patch update

* fix: no command specified

* fix: correct path

* alpine

* stupid.

* AAWASTREYDRFUGTIHYJHGUTYFRDTFYVGUBHINJHGTYFRDSRTXDTCFHBJ

1 files changed, 0 insertions, 4309 deletions

diff --git a/patches/wownero/0001-wallet-background-sync-with-just-the-view-key.patch b/patches/wownero/0001-wallet-background-sync-with-just-the-view-key.patch
deleted file mode 100644
index e45deb1..0000000
--- a/patches/wownero/0001-wallet-background-sync-with-just-the-view-key.patch
+++ /dev/null
@@ -1,4309 +0,0 @@
-From 6ebd4546355d3d6ed82e3d30a45ecb06310b958e Mon Sep 17 00:00:00 2001
-From: j-berman <justinberman@protonmail.com>
-Date: Thu, 13 Oct 2022 18:33:33 -0700
-Subject: [PATCH 01/15] wallet: background sync with just the view key
-
-- When background syncing, the wallet wipes the spend key
-from memory and processes all new transactions. The wallet saves
-all receives, spends, and "plausible" spends of receives the
-wallet does not know key images for.
-- When background sync disabled, the wallet processes all
-background synced txs and then clears the background sync cache.
-- Adding "plausible" spends to the background sync cache ensures
-that the wallet does not need to query the daemon to see if any
-received outputs were spent while background sync was enabled.
-This would harm privacy especially for users of 3rd party daemons.
-- To enable the feature in the CLI wallet, the user can set
-background-sync to reuse-wallet-password or
-custom-background-password and the wallet automatically syncs in
-the background when the wallet locks, then processes all
-background synced txs when the wallet is unlocked.
-- The custom-background-password option enables the user to
-open a distinct background wallet that only has a view key saved
-and can be opened/closed/synced separately from the main wallet.
-When the main wallet opens, it processes the background wallet's
-cache.
-- To enable the feature in the RPC wallet, there is a new
-`/setup_background_sync` endpoint.
-- HW, multsig and view-only wallets cannot background sync.
----
- src/cryptonote_basic/account.cpp             |   11 +
- src/cryptonote_basic/account.h               |    1 +
- src/cryptonote_config.h                      |    2 +
- src/simplewallet/simplewallet.cpp            |  204 +++-
- src/simplewallet/simplewallet.h              |    1 +
- src/wallet/api/wallet.cpp                    |  213 +++-
- src/wallet/api/wallet.h                      |   12 +
- src/wallet/api/wallet2_api.h                 |   42 +
- src/wallet/wallet2.cpp                       | 1028 ++++++++++++++++--
- src/wallet/wallet2.h                         |  156 ++-
- src/wallet/wallet_errors.h                   |   39 +
- src/wallet/wallet_rpc_server.cpp             |  162 +++
- src/wallet/wallet_rpc_server.h               |    6 +
- src/wallet/wallet_rpc_server_commands_defs.h |   64 ++
- src/wallet/wallet_rpc_server_error_codes.h   |    2 +
- tests/functional_tests/transfer.py           |  400 ++++++-
- tests/functional_tests/util_resources.py     |   25 +
- tests/functional_tests/wallet.py             |   43 +-
- tests/unit_tests/wipeable_string.cpp         |   12 +
- utils/python-rpc/framework/wallet.py         |   42 +
- 20 files changed, 2336 insertions(+), 129 deletions(-)
-
-diff --git a/src/cryptonote_basic/account.cpp b/src/cryptonote_basic/account.cpp
-index 2ac455fda..4e87d4477 100644
---- a/src/cryptonote_basic/account.cpp
-+++ b/src/cryptonote_basic/account.cpp
-@@ -152,6 +152,17 @@ DISABLE_VS_WARNINGS(4244 4345)
-     m_keys.m_multisig_keys.clear();
-   }
-   //-----------------------------------------------------------------
-+  void account_base::set_spend_key(const crypto::secret_key& spend_secret_key)
-+  {
-+    // make sure derived spend public key matches saved public spend key
-+    crypto::public_key spend_public_key;
-+    crypto::secret_key_to_public_key(spend_secret_key, spend_public_key);
-+    CHECK_AND_ASSERT_THROW_MES(m_keys.m_account_address.m_spend_public_key == spend_public_key,
-+        "Unexpected derived public spend key");
-+
-+    m_keys.m_spend_secret_key = spend_secret_key;
-+  }
-+  //-----------------------------------------------------------------
-   crypto::secret_key account_base::generate(const crypto::secret_key& recovery_key, bool recover, bool two_random)
-   {
-     crypto::secret_key first = generate_keys(m_keys.m_account_address.m_spend_public_key, m_keys.m_spend_secret_key, recovery_key, recover);
-diff --git a/src/cryptonote_basic/account.h b/src/cryptonote_basic/account.h
-index 2ee9545d4..93d1d28f0 100644
---- a/src/cryptonote_basic/account.h
-+++ b/src/cryptonote_basic/account.h
-@@ -95,6 +95,7 @@ namespace cryptonote
-     bool store(const std::string& file_path);
- 
-     void forget_spend_key();
-+    void set_spend_key(const crypto::secret_key& spend_secret_key);
-     const std::vector<crypto::secret_key> &get_multisig_keys() const { return m_keys.m_multisig_keys; }
- 
-     void encrypt_keys(const crypto::chacha_key &key) { m_keys.encrypt(key); }
-diff --git a/src/cryptonote_config.h b/src/cryptonote_config.h
-index 8c0d3ce20..8b5091a46 100644
---- a/src/cryptonote_config.h
-+++ b/src/cryptonote_config.h
-@@ -253,6 +253,8 @@ namespace config
-   const unsigned char HASH_KEY_ENCRYPTED_PAYMENT_ID = 0x8d;
-   const unsigned char HASH_KEY_WALLET = 0x8c;
-   const unsigned char HASH_KEY_WALLET_CACHE = 0x8d;
-+  const unsigned char HASH_KEY_BACKGROUND_CACHE = 0x8e;
-+  const unsigned char HASH_KEY_BACKGROUND_KEYS_FILE = 0x8f;
-   const unsigned char HASH_KEY_RPC_PAYMENT_NONCE = 0x58;
-   const unsigned char HASH_KEY_MEMORY = 'k';
-   const unsigned char HASH_KEY_MULTISIG[] = {'M', 'u', 'l', 't' , 'i', 's', 'i', 'g', 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
-diff --git a/src/simplewallet/simplewallet.cpp b/src/simplewallet/simplewallet.cpp
-index e0a08eec0..83b56c3f4 100644
---- a/src/simplewallet/simplewallet.cpp
-+++ b/src/simplewallet/simplewallet.cpp
-@@ -155,6 +155,17 @@ typedef cryptonote::simple_wallet sw;
-     } \
-   } while(0)
- 
-+#define CHECK_IF_BACKGROUND_SYNCING(msg) \
-+  do \
-+  { \
-+    if (m_wallet->is_background_wallet() || m_wallet->is_background_syncing()) \
-+    { \
-+      std::string type = m_wallet->is_background_wallet() ? "background wallet" : "background syncing wallet"; \
-+      fail_msg_writer() << boost::format(tr("%s %s")) % type % msg; \
-+      return false; \
-+    } \
-+  } while (0)
-+
- static std::string get_human_readable_timespan(std::chrono::seconds seconds);
- static std::string get_human_readable_timespan(uint64_t seconds);
- 
-@@ -325,7 +336,7 @@ namespace
-     auto pwd_container = tools::password_container::prompt(verify, prompt);
-     if (!pwd_container)
-     {
--      tools::fail_msg_writer() << sw::tr("failed to read wallet password");
-+      tools::fail_msg_writer() << sw::tr("failed to read password");
-     }
-     return pwd_container;
-   }
-@@ -335,6 +346,11 @@ namespace
-     return password_prompter(verify ? sw::tr("Enter a new password for the wallet") : sw::tr("Wallet password"), verify);
-   }
- 
-+  boost::optional<tools::password_container> background_sync_cache_password_prompter(bool verify)
-+  {
-+    return password_prompter(verify ? sw::tr("Enter a custom password for the background sync cache") : sw::tr("Background sync cache password"), verify);
-+  }
-+
-   inline std::string interpret_rpc_response(bool ok, const std::string& status)
-   {
-     std::string err;
-@@ -452,6 +468,41 @@ namespace
-     return "invalid";
-   }
- 
-+  const struct
-+  {
-+    const char *name;
-+    tools::wallet2::BackgroundSyncType background_sync_type;
-+  } background_sync_type_names[] =
-+  {
-+    { "off", tools::wallet2::BackgroundSyncOff },
-+    { "reuse-wallet-password", tools::wallet2::BackgroundSyncReusePassword },
-+    { "custom-background-password", tools::wallet2::BackgroundSyncCustomPassword },
-+  };
-+
-+  bool parse_background_sync_type(const std::string &s, tools::wallet2::BackgroundSyncType &background_sync_type)
-+  {
-+    for (size_t n = 0; n < sizeof(background_sync_type_names) / sizeof(background_sync_type_names[0]); ++n)
-+    {
-+      if (s == background_sync_type_names[n].name)
-+      {
-+        background_sync_type = background_sync_type_names[n].background_sync_type;
-+        return true;
-+      }
-+    }
-+    fail_msg_writer() << cryptonote::simple_wallet::tr("failed to parse background sync type");
-+    return false;
-+  }
-+
-+  std::string get_background_sync_type_name(tools::wallet2::BackgroundSyncType type)
-+  {
-+    for (size_t n = 0; n < sizeof(background_sync_type_names) / sizeof(background_sync_type_names[0]); ++n)
-+    {
-+      if (type == background_sync_type_names[n].background_sync_type)
-+        return background_sync_type_names[n].name;
-+    }
-+    return "invalid";
-+  }
-+
-   std::string get_version_string(uint32_t version)
-   {
-     return boost::lexical_cast<std::string>(version >> 16) + "." + boost::lexical_cast<std::string>(version & 0xffff);
-@@ -805,6 +856,7 @@ bool simple_wallet::spendkey(const std::vector<std::string> &args/* = std::vecto
-     fail_msg_writer() << tr("wallet is watch-only and has no spend key");
-     return true;
-   }
-+  CHECK_IF_BACKGROUND_SYNCING("has no spend key");
-   // don't log
-   PAUSE_READLINE();
-   if (m_wallet->key_on_device()) {
-@@ -836,6 +888,7 @@ bool simple_wallet::print_seed(bool encrypted)
-     fail_msg_writer() << tr("wallet is watch-only and has no seed");
-     return true;
-   }
-+  CHECK_IF_BACKGROUND_SYNCING("has no seed");
- 
-   multisig = m_wallet->multisig(&ready);
-   if (multisig)
-@@ -913,6 +966,7 @@ bool simple_wallet::seed_set_language(const std::vector<std::string> &args/* = s
-     fail_msg_writer() << tr("wallet is watch-only and has no seed");
-     return true;
-   }
-+  CHECK_IF_BACKGROUND_SYNCING("has no seed");
- 
-   epee::wipeable_string password;
-   {
-@@ -1059,6 +1113,7 @@ bool simple_wallet::prepare_multisig_main(const std::vector<std::string> &args,
-     fail_msg_writer() << tr("wallet is watch-only and cannot be made multisig");
-     return false;
-   }
-+  CHECK_IF_BACKGROUND_SYNCING("cannot be made multisig");
- 
-   if(m_wallet->get_num_transfer_details())
-   {
-@@ -2195,6 +2250,7 @@ bool simple_wallet::save_known_rings(const std::vector<std::string> &args)
- 
- bool simple_wallet::freeze_thaw(const std::vector<std::string> &args, bool freeze)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot freeze/thaw");
-   if (args.empty())
-   {
-     fail_msg_writer() << boost::format(tr("usage: %s <key_image>|<pubkey>")) % (freeze ? "freeze" : "thaw");
-@@ -2234,6 +2290,7 @@ bool simple_wallet::thaw(const std::vector<std::string> &args)
- 
- bool simple_wallet::frozen(const std::vector<std::string> &args)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot see frozen key images");
-   if (args.empty())
-   {
-     size_t ntd = m_wallet->get_num_transfer_details();
-@@ -3005,6 +3062,57 @@ bool simple_wallet::set_track_uses(const std::vector<std::string> &args/* = std:
-   return true;
- }
- 
-+bool simple_wallet::setup_background_sync(const std::vector<std::string> &args/* = std::vector<std::string>()*/)
-+{
-+  if (m_wallet->multisig())
-+  {
-+    fail_msg_writer() << tr("background sync not implemented for multisig wallet");
-+    return true;
-+  }
-+  if (m_wallet->watch_only())
-+  {
-+    fail_msg_writer() << tr("background sync not implemented for watch only wallet");
-+    return true;
-+  }
-+  if (m_wallet->key_on_device())
-+  {
-+    fail_msg_writer() << tr("command not supported by HW wallet");
-+    return true;
-+  }
-+
-+  tools::wallet2::BackgroundSyncType background_sync_type;
-+  if (!parse_background_sync_type(args[1], background_sync_type))
-+  {
-+    fail_msg_writer() << tr("invalid option");
-+    return true;
-+  }
-+
-+  const auto pwd_container = get_and_verify_password();
-+  if (!pwd_container)
-+    return true;
-+
-+  try
-+  {
-+    boost::optional<epee::wipeable_string> background_cache_password = boost::none;
-+    if (background_sync_type == tools::wallet2::BackgroundSyncCustomPassword)
-+    {
-+      const auto background_pwd_container = background_sync_cache_password_prompter(true);
-+      if (!background_pwd_container)
-+        return true;
-+      background_cache_password = background_pwd_container->password();
-+    }
-+
-+    LOCK_IDLE_SCOPE();
-+    m_wallet->setup_background_sync(background_sync_type, pwd_container->password(), background_cache_password);
-+  }
-+  catch (const std::exception &e)
-+  {
-+    fail_msg_writer() << tr("Error setting background sync type: ") << e.what();
-+  }
-+
-+  return true;
-+}
-+
- bool simple_wallet::set_show_wallet_name_when_locked(const std::vector<std::string> &args/* = std::vector<std::string>()*/)
- {
-   const auto pwd_container = get_and_verify_password();
-@@ -3237,6 +3345,7 @@ bool simple_wallet::apropos(const std::vector<std::string> &args)
- 
- bool simple_wallet::scan_tx(const std::vector<std::string> &args)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot scan tx");
-   if (args.empty())
-   {
-     PRINT_USAGE(USAGE_SCAN_TX);
-@@ -3459,6 +3568,8 @@ simple_wallet::simple_wallet()
-                                   "  Ignore outputs of amount above this threshold when spending. Value 0 is translated to the maximum value (18 million) which disables this filter.\n "
-                                   "ignore-outputs-below <amount>\n "
-                                   "  Ignore outputs of amount below this threshold when spending.\n "
-+                                  "background-sync <off|reuse-wallet-password|custom-background-password>\n "
-+                                  "  Set this to enable scanning in the background with just the view key while the wallet is locked.\n "
-                                   "track-uses <1|0>\n "
-                                   "  Whether to keep track of owned outputs uses.\n "
-                                   "setup-background-mining <1|0>\n "
-@@ -3879,6 +3990,7 @@ bool simple_wallet::set_variable(const std::vector<std::string> &args)
-     success_msg_writer() << "ignore-outputs-above = " << cryptonote::print_money(m_wallet->ignore_outputs_above());
-     success_msg_writer() << "ignore-outputs-below = " << cryptonote::print_money(m_wallet->ignore_outputs_below());
-     success_msg_writer() << "track-uses = " << m_wallet->track_uses();
-+    success_msg_writer() << "background-sync = " << get_background_sync_type_name(m_wallet->background_sync_type());
-     success_msg_writer() << "setup-background-mining = " << setup_background_mining_string;
-     success_msg_writer() << "device-name = " << m_wallet->device_name();
-     success_msg_writer() << "export-format = " << (m_wallet->export_format() == tools::wallet2::ExportFormat::Ascii ? "ascii" : "binary");
-@@ -3897,6 +4009,7 @@ bool simple_wallet::set_variable(const std::vector<std::string> &args)
-   }
-   else
-   {
-+    CHECK_IF_BACKGROUND_SYNCING("cannot change wallet settings");
- 
- #define CHECK_SIMPLE_VARIABLE(name, f, help) do \
-   if (args[0] == name) { \
-@@ -3950,6 +4063,7 @@ bool simple_wallet::set_variable(const std::vector<std::string> &args)
-     CHECK_SIMPLE_VARIABLE("ignore-outputs-above", set_ignore_outputs_above, tr("amount"));
-     CHECK_SIMPLE_VARIABLE("ignore-outputs-below", set_ignore_outputs_below, tr("amount"));
-     CHECK_SIMPLE_VARIABLE("track-uses", set_track_uses, tr("0 or 1"));
-+    CHECK_SIMPLE_VARIABLE("background-sync", setup_background_sync, tr("off (default); reuse-wallet-password (reuse the wallet password to encrypt the background cache); custom-background-password (use a custom background password to encrypt the background cache)"));
-     CHECK_SIMPLE_VARIABLE("show-wallet-name-when-locked", set_show_wallet_name_when_locked, tr("1 or 0"));
-     CHECK_SIMPLE_VARIABLE("inactivity-lock-timeout", set_inactivity_lock_timeout, tr("unsigned integer (seconds, 0 to disable)"));
-     CHECK_SIMPLE_VARIABLE("setup-background-mining", set_setup_background_mining, tr("1/yes or 0/no"));
-@@ -4904,7 +5018,10 @@ std::string simple_wallet::get_mnemonic_language()
- //----------------------------------------------------------------------------------------------------
- boost::optional<tools::password_container> simple_wallet::get_and_verify_password() const
- {
--  auto pwd_container = default_password_prompter(m_wallet_file.empty());
-+  const bool verify = m_wallet_file.empty();
-+  auto pwd_container = (m_wallet->is_background_wallet() && m_wallet->background_sync_type() == tools::wallet2::BackgroundSyncCustomPassword)
-+    ? background_sync_cache_password_prompter(verify)
-+    : default_password_prompter(verify);
-   if (!pwd_container)
-     return boost::none;
- 
-@@ -5208,6 +5325,8 @@ boost::optional<epee::wipeable_string> simple_wallet::open_wallet(const boost::p
-       prefix = tr("Opened watch-only wallet");
-     else if (m_wallet->multisig(&ready, &threshold, &total))
-       prefix = (boost::format(tr("Opened %u/%u multisig wallet%s")) % threshold % total % (ready ? "" : " (not yet finalized)")).str();
-+    else if (m_wallet->is_background_wallet())
-+      prefix = tr("Opened background wallet");
-     else
-       prefix = tr("Opened wallet");
-     message_writer(console_color_white, true) <<
-@@ -5415,6 +5534,10 @@ void simple_wallet::stop_background_mining()
- //----------------------------------------------------------------------------------------------------
- void simple_wallet::check_background_mining(const epee::wipeable_string &password)
- {
-+  // Background mining can be toggled from the main wallet
-+  if (m_wallet->is_background_wallet() || m_wallet->is_background_syncing())
-+    return;
-+
-   tools::wallet2::BackgroundMiningSetupType setup = m_wallet->setup_background_mining();
-   if (setup == tools::wallet2::BackgroundMiningNo)
-   {
-@@ -6287,6 +6410,7 @@ bool simple_wallet::show_blockchain_height(const std::vector<std::string>& args)
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::rescan_spent(const std::vector<std::string> &args)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot rescan spent");
-   if (!m_wallet->is_trusted_daemon())
-   {
-     fail_msg_writer() << tr("this command requires a trusted daemon. Enable with --trusted-daemon");
-@@ -6584,11 +6708,27 @@ void simple_wallet::check_for_inactivity_lock(bool user)
-           "                    B    B                                                           " << std::endl <<
-           "" << std::endl;
-     }
-+
-+    bool started_background_sync = false;
-+    if (!m_wallet->is_background_wallet() &&
-+        m_wallet->background_sync_type() != tools::wallet2::BackgroundSyncOff)
-+    {
-+      LOCK_IDLE_SCOPE();
-+      m_wallet->start_background_sync();
-+      started_background_sync = true;
-+    }
-+
-     while (1)
-     {
-       const char *inactivity_msg = user ? "" : tr("Locked due to inactivity.");
--      tools::msg_writer() << inactivity_msg << (inactivity_msg[0] ? " " : "") << tr("The wallet password is required to unlock the console.");
-+      tools::msg_writer() << inactivity_msg << (inactivity_msg[0] ? " " : "") << (
-+        (m_wallet->is_background_wallet() && m_wallet->background_sync_type() == tools::wallet2::BackgroundSyncCustomPassword)
-+            ? tr("The background password is required to unlock the console.")
-+            : tr("The wallet password is required to unlock the console.")
-+      );
- 
-+      if (m_wallet->is_background_syncing())
-+        tools::msg_writer() << tr("\nSyncing in the background while locked...") << std::endl;
-       const bool show_wallet_name = m_wallet->show_wallet_name_when_locked();
-       if (show_wallet_name)
-       {
-@@ -6600,8 +6740,16 @@ void simple_wallet::check_for_inactivity_lock(bool user)
-       }
-       try
-       {
--        if (get_and_verify_password())
-+        const auto pwd_container = get_and_verify_password();
-+        if (pwd_container)
-+        {
-+          if (started_background_sync)
-+          {
-+            LOCK_IDLE_SCOPE();
-+            m_wallet->stop_background_sync(pwd_container->password());
-+          }
-           break;
-+        }
-       }
-       catch (...) { /* do nothing, just let the loop loop */ }
-     }
-@@ -6628,6 +6776,7 @@ bool simple_wallet::on_command(bool (simple_wallet::*cmd)(const std::vector<std:
- bool simple_wallet::transfer_main(const std::vector<std::string> &args_, bool called_by_mms)
- {
- //  "transfer [index=<N1>[,<N2>,...]] [<priority>] [<ring_size>] <address> <amount> [<payment_id>]"
-+  CHECK_IF_BACKGROUND_SYNCING("cannot transfer");
-   if (!try_connect_to_daemon())
-     return false;
- 
-@@ -7056,6 +7205,7 @@ bool simple_wallet::transfer_main(const std::vector<std::string> &args_, bool ca
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::transfer(const std::vector<std::string> &args_)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot transfer");
-   if (args_.size() < 1)
-   {
-     PRINT_USAGE(USAGE_TRANSFER);
-@@ -7068,6 +7218,7 @@ bool simple_wallet::transfer(const std::vector<std::string> &args_)
- 
- bool simple_wallet::sweep_unmixable(const std::vector<std::string> &args_)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot sweep");
-   if (!try_connect_to_daemon())
-     return true;
- 
-@@ -7175,6 +7326,7 @@ bool simple_wallet::sweep_unmixable(const std::vector<std::string> &args_)
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::sweep_main(uint32_t account, uint64_t below, const std::vector<std::string> &args_)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot sweep");
-   auto print_usage = [this, account, below]()
-   {
-     if (below)
-@@ -7456,6 +7608,7 @@ bool simple_wallet::sweep_main(uint32_t account, uint64_t below, const std::vect
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::sweep_single(const std::vector<std::string> &args_)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot sweep");
-   if (!try_connect_to_daemon())
-     return true;
- 
-@@ -7694,12 +7847,14 @@ bool simple_wallet::sweep_single(const std::vector<std::string> &args_)
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::sweep_all(const std::vector<std::string> &args_)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot sweep");
-   sweep_main(m_current_subaddress_account, 0, args_);
-   return true;
- }
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::sweep_account(const std::vector<std::string> &args_)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot sweep");
-   auto local_args = args_;
-   if (local_args.empty())
-   {
-@@ -7720,6 +7875,7 @@ bool simple_wallet::sweep_account(const std::vector<std::string> &args_)
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::sweep_below(const std::vector<std::string> &args_)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot sweep");
-   uint64_t below = 0;
-   if (args_.size() < 1)
-   {
-@@ -7738,6 +7894,7 @@ bool simple_wallet::sweep_below(const std::vector<std::string> &args_)
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::donate(const std::vector<std::string> &args_)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot donate");
-   std::vector<std::string> local_args = args_;
-   if(local_args.empty() || local_args.size() > 5)
-   {
-@@ -7799,6 +7956,7 @@ bool simple_wallet::donate(const std::vector<std::string> &args_)
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::accept_loaded_tx(const std::function<size_t()> get_num_txes, const std::function<const tools::wallet2::tx_construction_data&(size_t)> &get_tx, const std::string &extra_message)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot load tx");
-   // gather info to ask the user
-   uint64_t amount = 0, amount_to_dests = 0, change = 0;
-   size_t min_ring_size = ~0;
-@@ -7980,6 +8138,8 @@ bool simple_wallet::sign_transfer(const std::vector<std::string> &args_)
-      return true;
-   }
- 
-+  CHECK_IF_BACKGROUND_SYNCING("cannot sign transfer");
-+
-   bool export_raw = false;
-   std::string unsigned_filename = "unsigned_wownero_tx";
-   if (args_.size() > 2 || (args_.size() == 2 && args_[0] != "export_raw"))
-@@ -8086,6 +8246,8 @@ std::string get_tx_key_stream(crypto::secret_key tx_key, std::vector<crypto::sec
- 
- bool simple_wallet::get_tx_key(const std::vector<std::string> &args_)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot get tx key");
-+
-   std::vector<std::string> local_args = args_;
- 
-   if (m_wallet->key_on_device() && m_wallet->get_account().get_device().get_type() != hw::device::TREZOR)
-@@ -8126,6 +8288,8 @@ bool simple_wallet::get_tx_key(const std::vector<std::string> &args_)
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::set_tx_key(const std::vector<std::string> &args_)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot set tx key");
-+
-   std::vector<std::string> local_args = args_;
- 
-   if(local_args.size() != 2 && local_args.size() != 3) {
-@@ -8202,6 +8366,8 @@ bool simple_wallet::set_tx_key(const std::vector<std::string> &args_)
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::get_tx_proof(const std::vector<std::string> &args)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot get tx proof");
-+
-   if (args.size() != 2 && args.size() != 3)
-   {
-     PRINT_USAGE(USAGE_GET_TX_PROOF);
-@@ -8408,6 +8574,7 @@ bool simple_wallet::check_tx_proof(const std::vector<std::string> &args)
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::get_spend_proof(const std::vector<std::string> &args)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot get spend proof");
-   if (m_wallet->key_on_device())
-   {
-     fail_msg_writer() << tr("command not supported by HW wallet");
-@@ -8492,6 +8659,7 @@ bool simple_wallet::check_spend_proof(const std::vector<std::string> &args)
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::get_reserve_proof(const std::vector<std::string> &args)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot get reserve proof");
-   if (m_wallet->key_on_device())
-   {
-     fail_msg_writer() << tr("command not supported by HW wallet");
-@@ -9192,6 +9360,8 @@ bool simple_wallet::unspent_outputs(const std::vector<std::string> &args_)
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::rescan_blockchain(const std::vector<std::string> &args_)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot rescan");
-+
-   uint64_t start_height = 0;
-   ResetType reset_type = ResetSoft;
- 
-@@ -9489,6 +9659,7 @@ bool simple_wallet::account(const std::vector<std::string> &args/* = std::vector
-   if (command == "new")
-   {
-     // create a new account and switch to it
-+    CHECK_IF_BACKGROUND_SYNCING("cannot create new account");
-     std::string label = boost::join(local_args, " ");
-     if (label.empty())
-       label = tr("(Untitled account)");
-@@ -9519,6 +9690,7 @@ bool simple_wallet::account(const std::vector<std::string> &args/* = std::vector
-   else if (command == "label" && local_args.size() >= 1)
-   {
-     // set label of the specified account
-+    CHECK_IF_BACKGROUND_SYNCING("cannot modify account");
-     uint32_t index_major;
-     if (!epee::string_tools::get_xtype_from_string(index_major, local_args[0]))
-     {
-@@ -9540,6 +9712,7 @@ bool simple_wallet::account(const std::vector<std::string> &args/* = std::vector
-   }
-   else if (command == "tag" && local_args.size() >= 2)
-   {
-+    CHECK_IF_BACKGROUND_SYNCING("cannot modify account");
-     const std::string tag = local_args[0];
-     std::set<uint32_t> account_indices;
-     for (size_t i = 1; i < local_args.size(); ++i)
-@@ -9564,6 +9737,7 @@ bool simple_wallet::account(const std::vector<std::string> &args/* = std::vector
-   }
-   else if (command == "untag" && local_args.size() >= 1)
-   {
-+    CHECK_IF_BACKGROUND_SYNCING("cannot modify account");
-     std::set<uint32_t> account_indices;
-     for (size_t i = 0; i < local_args.size(); ++i)
-     {
-@@ -9587,6 +9761,7 @@ bool simple_wallet::account(const std::vector<std::string> &args/* = std::vector
-   }
-   else if (command == "tag_description" && local_args.size() >= 1)
-   {
-+    CHECK_IF_BACKGROUND_SYNCING("cannot modify account");
-     const std::string tag = local_args[0];
-     std::string description;
-     if (local_args.size() > 1)
-@@ -9704,6 +9879,7 @@ bool simple_wallet::print_address(const std::vector<std::string> &args/* = std::
-   }
-   else if (local_args[0] == "new")
-   {
-+    CHECK_IF_BACKGROUND_SYNCING("cannot add address");
-     local_args.erase(local_args.begin());
-     std::string label;
-     if (local_args.size() > 0)
-@@ -9716,6 +9892,7 @@ bool simple_wallet::print_address(const std::vector<std::string> &args/* = std::
-   }
-   else if (local_args[0] == "mnew")
-   {
-+    CHECK_IF_BACKGROUND_SYNCING("cannot add addresses");
-     local_args.erase(local_args.begin());
-     if (local_args.size() != 1)
-     {
-@@ -9741,6 +9918,7 @@ bool simple_wallet::print_address(const std::vector<std::string> &args/* = std::
-   }
-   else if (local_args[0] == "one-off")
-   {
-+    CHECK_IF_BACKGROUND_SYNCING("cannot add address");
-     local_args.erase(local_args.begin());
-     std::string label;
-     if (local_args.size() != 2)
-@@ -9759,6 +9937,7 @@ bool simple_wallet::print_address(const std::vector<std::string> &args/* = std::
-   }
-   else if (local_args.size() >= 2 && local_args[0] == "label")
-   {
-+    CHECK_IF_BACKGROUND_SYNCING("cannot modify address");
-     if (!epee::string_tools::get_xtype_from_string(index, local_args[1]))
-     {
-       fail_msg_writer() << tr("failed to parse index: ") << local_args[1];
-@@ -9905,6 +10084,8 @@ bool simple_wallet::print_integrated_address(const std::vector<std::string> &arg
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::address_book(const std::vector<std::string> &args/* = std::vector<std::string>()*/)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot get address book");
-+
-   if (args.size() == 0)
-   {
-   }
-@@ -9965,6 +10146,8 @@ bool simple_wallet::address_book(const std::vector<std::string> &args/* = std::v
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::set_tx_note(const std::vector<std::string> &args)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot set tx note");
-+
-   if (args.size() == 0)
-   {
-     PRINT_USAGE(USAGE_SET_TX_NOTE);
-@@ -9993,6 +10176,8 @@ bool simple_wallet::set_tx_note(const std::vector<std::string> &args)
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::get_tx_note(const std::vector<std::string> &args)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot get tx note");
-+
-   if (args.size() != 1)
-   {
-     PRINT_USAGE(USAGE_GET_TX_NOTE);
-@@ -10018,6 +10203,8 @@ bool simple_wallet::get_tx_note(const std::vector<std::string> &args)
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::set_description(const std::vector<std::string> &args)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot set description");
-+
-   // 0 arguments allowed, for setting the description to empty string
- 
-   std::string description = "";
-@@ -10034,6 +10221,8 @@ bool simple_wallet::set_description(const std::vector<std::string> &args)
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::get_description(const std::vector<std::string> &args)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot get description");
-+
-   if (args.size() != 0)
-   {
-     PRINT_USAGE(USAGE_GET_DESCRIPTION);
-@@ -10092,6 +10281,8 @@ bool simple_wallet::wallet_info(const std::vector<std::string> &args)
-     type = tr("Watch only");
-   else if (m_wallet->multisig(&ready, &threshold, &total))
-     type = (boost::format(tr("%u/%u multisig%s")) % threshold % total % (ready ? "" : " (not yet finalized)")).str();
-+  else if (m_wallet->is_background_wallet())
-+    type = tr("Background wallet");
-   else
-     type = tr("Normal");
-   message_writer() << tr("Type: ") << type;
-@@ -10103,6 +10294,7 @@ bool simple_wallet::wallet_info(const std::vector<std::string> &args)
- //----------------------------------------------------------------------------------------------------
- bool simple_wallet::sign(const std::vector<std::string> &args)
- {
-+  CHECK_IF_BACKGROUND_SYNCING("cannot sign");
-   if (m_wallet->key_on_device())
-   {
-     fail_msg_writer() << tr("command not supported by HW wallet");
-@@ -10210,6 +10402,7 @@ bool simple_wallet::export_key_images(const std::vector<std::string> &args_)
-     fail_msg_writer() << tr("command not supported by HW wallet");
-     return true;
-   }
-+  CHECK_IF_BACKGROUND_SYNCING("cannot export key images");
-   auto args = args_;
- 
-   if (m_wallet->watch_only())
-@@ -10263,6 +10456,7 @@ bool simple_wallet::import_key_images(const std::vector<std::string> &args)
-     fail_msg_writer() << tr("command not supported by HW wallet");
-     return true;
-   }
-+  CHECK_IF_BACKGROUND_SYNCING("cannot import key images");
-   if (!m_wallet->is_trusted_daemon())
-   {
-     fail_msg_writer() << tr("this command requires a trusted daemon. Enable with --trusted-daemon");
-@@ -10371,6 +10565,7 @@ bool simple_wallet::export_outputs(const std::vector<std::string> &args_)
-     fail_msg_writer() << tr("command not supported by HW wallet");
-     return true;
-   }
-+  CHECK_IF_BACKGROUND_SYNCING("cannot export outputs");
-   auto args = args_;
- 
-   bool all = false;
-@@ -10420,6 +10615,7 @@ bool simple_wallet::import_outputs(const std::vector<std::string> &args)
-     fail_msg_writer() << tr("command not supported by HW wallet");
-     return true;
-   }
-+  CHECK_IF_BACKGROUND_SYNCING("cannot import outputs");
-   if (args.size() != 1)
-   {
-     PRINT_USAGE(USAGE_IMPORT_OUTPUTS);
-diff --git a/src/simplewallet/simplewallet.h b/src/simplewallet/simplewallet.h
-index d641dca1b..b98a40713 100644
---- a/src/simplewallet/simplewallet.h
-+++ b/src/simplewallet/simplewallet.h
-@@ -147,6 +147,7 @@ namespace cryptonote
-     bool set_ignore_outputs_above(const std::vector<std::string> &args = std::vector<std::string>());
-     bool set_ignore_outputs_below(const std::vector<std::string> &args = std::vector<std::string>());
-     bool set_track_uses(const std::vector<std::string> &args = std::vector<std::string>());
-+    bool setup_background_sync(const std::vector<std::string> &args = std::vector<std::string>());
-     bool set_show_wallet_name_when_locked(const std::vector<std::string> &args = std::vector<std::string>());
-     bool set_inactivity_lock_timeout(const std::vector<std::string> &args = std::vector<std::string>());
-     bool set_setup_background_mining(const std::vector<std::string> &args = std::vector<std::string>());
-diff --git a/src/wallet/api/wallet.cpp b/src/wallet/api/wallet.cpp
-index e81265ad3..e868fa039 100644
---- a/src/wallet/api/wallet.cpp
-+++ b/src/wallet/api/wallet.cpp
-@@ -54,6 +54,40 @@ using namespace cryptonote;
- #undef MONERO_DEFAULT_LOG_CATEGORY
- #define MONERO_DEFAULT_LOG_CATEGORY "WalletAPI"
- 
-+#define LOCK_REFRESH() \
-+    bool refresh_enabled = m_refreshEnabled; \
-+    m_refreshEnabled = false; \
-+    m_wallet->stop(); \
-+    m_refreshCV.notify_one(); \
-+    boost::mutex::scoped_lock lock(m_refreshMutex); \
-+    boost::mutex::scoped_lock lock2(m_refreshMutex2); \
-+    epee::misc_utils::auto_scope_leave_caller scope_exit_handler = epee::misc_utils::create_scope_leave_handler([&](){ \
-+        /* m_refreshMutex's still locked here */ \
-+        if (refresh_enabled) \
-+            startRefresh(); \
-+    })
-+
-+#define PRE_VALIDATE_BACKGROUND_SYNC() \
-+  do \
-+  { \
-+    clearStatus(); \
-+    if (m_wallet->key_on_device()) \
-+    { \
-+        setStatusError(tr("HW wallet cannot use background sync")); \
-+        return false; \
-+    } \
-+    if (m_wallet->watch_only()) \
-+    { \
-+        setStatusError(tr("View only wallet cannot use background sync")); \
-+        return false; \
-+    } \
-+    if (m_wallet->multisig()) \
-+    { \
-+        setStatusError(tr("Multisig wallet cannot use background sync")); \
-+        return false; \
-+    } \
-+  } while (0)
-+
- namespace Monero {
- 
- namespace {
-@@ -792,6 +826,8 @@ bool WalletImpl::close(bool store)
- 
- std::string WalletImpl::seed(const std::string& seed_offset) const
- {
-+    if (checkBackgroundSync("cannot get seed"))
-+        return std::string();
-     epee::wipeable_string seed;
-     if (m_wallet)
-         m_wallet->get_seed(seed, seed_offset);
-@@ -805,6 +841,8 @@ std::string WalletImpl::getSeedLanguage() const
- 
- void WalletImpl::setSeedLanguage(const std::string &arg)
- {
-+    if (checkBackgroundSync("cannot set seed language"))
-+        return;
-     m_wallet->set_seed_language(arg);
- }
- 
-@@ -828,6 +866,8 @@ void WalletImpl::statusWithErrorString(int& status, std::string& errorString) co
- 
- bool WalletImpl::setPassword(const std::string &password)
- {
-+    if (checkBackgroundSync("cannot change password"))
-+        return false;
-     clearStatus();
-     try {
-         m_wallet->change_password(m_wallet->get_wallet_file(), m_password, password);
-@@ -988,6 +1028,8 @@ bool WalletImpl::lightWalletImportWalletRequest(std::string &payment_id, uint64_
- 
- void WalletImpl::setRefreshFromBlockHeight(uint64_t refresh_from_block_height)
- {
-+    if (checkBackgroundSync("cannot change refresh height"))
-+        return;
-     m_wallet->set_refresh_from_block_height(refresh_from_block_height);
- }
- 
-@@ -1105,6 +1147,8 @@ void WalletImpl::refreshAsync()
- 
- bool WalletImpl::rescanBlockchain()
- {
-+    if (checkBackgroundSync("cannot rescan blockchain"))
-+        return false;
-     clearStatus();
-     m_refreshShouldRescan = true;
-     doRefresh();
-@@ -1113,6 +1157,8 @@ bool WalletImpl::rescanBlockchain()
- 
- void WalletImpl::rescanBlockchainAsync()
- {
-+    if (checkBackgroundSync("cannot rescan blockchain"))
-+        return;
-     m_refreshShouldRescan = true;
-     refreshAsync();
- }
-@@ -1136,7 +1182,7 @@ int WalletImpl::autoRefreshInterval() const
- UnsignedTransaction *WalletImpl::loadUnsignedTx(const std::string &unsigned_filename) {
-   clearStatus();
-   UnsignedTransactionImpl * transaction = new UnsignedTransactionImpl(*this);
--  if (!m_wallet->load_unsigned_tx(unsigned_filename, transaction->m_unsigned_tx_set)){
-+  if (checkBackgroundSync("cannot load tx") || !m_wallet->load_unsigned_tx(unsigned_filename, transaction->m_unsigned_tx_set)){
-     setStatusError(tr("Failed to load unsigned transactions"));
-     transaction->m_status = UnsignedTransaction::Status::Status_Error;
-     transaction->m_errorString = errorString();
-@@ -1156,6 +1202,8 @@ UnsignedTransaction *WalletImpl::loadUnsignedTx(const std::string &unsigned_file
- 
- bool WalletImpl::submitTransaction(const string &fileName) {
-   clearStatus();
-+  if (checkBackgroundSync("cannot submit tx"))
-+    return false;
-   std::unique_ptr<PendingTransactionImpl> transaction(new PendingTransactionImpl(*this));
- 
-   bool r = m_wallet->load_tx(fileName, transaction->m_pending_tx);
-@@ -1179,6 +1227,8 @@ bool WalletImpl::exportKeyImages(const string &filename, bool all)
-     setStatusError(tr("Wallet is view only"));
-     return false;
-   }
-+  if (checkBackgroundSync("cannot export key images"))
-+    return false;
-   
-   try
-   {
-@@ -1199,6 +1249,8 @@ bool WalletImpl::exportKeyImages(const string &filename, bool all)
- 
- bool WalletImpl::importKeyImages(const string &filename)
- {
-+  if (checkBackgroundSync("cannot import key images"))
-+    return false;
-   if (!trustedDaemon()) {
-     setStatusError(tr("Key images can only be imported with a trusted daemon"));
-     return false;
-@@ -1222,6 +1274,8 @@ bool WalletImpl::importKeyImages(const string &filename)
- 
- bool WalletImpl::exportOutputs(const string &filename, bool all)
- {
-+    if (checkBackgroundSync("cannot export outputs"))
-+        return false;
-     if (m_wallet->key_on_device())
-     {
-         setStatusError(string(tr("Not supported on HW wallets.")) + filename);
-@@ -1252,6 +1306,8 @@ bool WalletImpl::exportOutputs(const string &filename, bool all)
- 
- bool WalletImpl::importOutputs(const string &filename)
- {
-+    if (checkBackgroundSync("cannot import outputs"))
-+        return false;
-     if (m_wallet->key_on_device())
-     {
-         setStatusError(string(tr("Not supported on HW wallets.")) + filename);
-@@ -1284,6 +1340,8 @@ bool WalletImpl::importOutputs(const string &filename)
- 
- bool WalletImpl::scanTransactions(const std::vector<std::string> &txids)
- {
-+    if (checkBackgroundSync("cannot scan transactions"))
-+        return false;
-     if (txids.empty())
-     {
-         setStatusError(string(tr("Failed to scan transactions: no transaction ids provided.")));
-@@ -1322,8 +1380,86 @@ bool WalletImpl::scanTransactions(const std::vector<std::string> &txids)
-     return true;
- }
- 
-+bool WalletImpl::setupBackgroundSync(const Wallet::BackgroundSyncType background_sync_type, const std::string &wallet_password, const optional<std::string> &background_cache_password)
-+{
-+    try
-+    {
-+        PRE_VALIDATE_BACKGROUND_SYNC();
-+
-+        tools::wallet2::BackgroundSyncType bgs_type;
-+        switch (background_sync_type)
-+        {
-+            case Wallet::BackgroundSync_Off: bgs_type = tools::wallet2::BackgroundSyncOff; break;
-+            case Wallet::BackgroundSync_ReusePassword: bgs_type = tools::wallet2::BackgroundSyncReusePassword; break;
-+            case Wallet::BackgroundSync_CustomPassword: bgs_type = tools::wallet2::BackgroundSyncCustomPassword; break;
-+            default: setStatusError(tr("Unknown background sync type")); return false;
-+        }
-+
-+        boost::optional<epee::wipeable_string> bgc_password = background_cache_password
-+            ? boost::optional<epee::wipeable_string>(*background_cache_password)
-+            : boost::none;
-+
-+        LOCK_REFRESH();
-+        m_wallet->setup_background_sync(bgs_type, wallet_password, bgc_password);
-+    }
-+    catch (const std::exception &e)
-+    {
-+        LOG_ERROR("Failed to setup background sync: " << e.what());
-+        setStatusError(string(tr("Failed to setup background sync: ")) + e.what());
-+        return false;
-+    }
-+    return true;
-+}
-+
-+Wallet::BackgroundSyncType WalletImpl::getBackgroundSyncType() const
-+{
-+    switch (m_wallet->background_sync_type())
-+    {
-+        case tools::wallet2::BackgroundSyncOff: return Wallet::BackgroundSync_Off;
-+        case tools::wallet2::BackgroundSyncReusePassword: return Wallet::BackgroundSync_ReusePassword;
-+        case tools::wallet2::BackgroundSyncCustomPassword: return Wallet::BackgroundSync_CustomPassword;
-+        default: setStatusError(tr("Unknown background sync type")); return Wallet::BackgroundSync_Off;
-+    }
-+}
-+
-+bool WalletImpl::startBackgroundSync()
-+{
-+    try
-+    {
-+        PRE_VALIDATE_BACKGROUND_SYNC();
-+        LOCK_REFRESH();
-+        m_wallet->start_background_sync();
-+    }
-+    catch (const std::exception &e)
-+    {
-+        LOG_ERROR("Failed to start background sync: " << e.what());
-+        setStatusError(string(tr("Failed to start background sync: ")) + e.what());
-+        return false;
-+    }
-+    return true;
-+}
-+
-+bool WalletImpl::stopBackgroundSync(const std::string &wallet_password)
-+{
-+    try
-+    {
-+        PRE_VALIDATE_BACKGROUND_SYNC();
-+        LOCK_REFRESH();
-+        m_wallet->stop_background_sync(epee::wipeable_string(wallet_password));
-+    }
-+    catch (const std::exception &e)
-+    {
-+        LOG_ERROR("Failed to stop background sync: " << e.what());
-+        setStatusError(string(tr("Failed to stop background sync: ")) + e.what());
-+        return false;
-+    }
-+    return true;
-+}
-+
- void WalletImpl::addSubaddressAccount(const std::string& label)
- {
-+    if (checkBackgroundSync("cannot add account"))
-+        return;
-     m_wallet->add_subaddress_account(label);
- }
- size_t WalletImpl::numSubaddressAccounts() const
-@@ -1336,10 +1472,14 @@ size_t WalletImpl::numSubaddresses(uint32_t accountIndex) const
- }
- void WalletImpl::addSubaddress(uint32_t accountIndex, const std::string& label)
- {
-+    if (checkBackgroundSync("cannot add subbaddress"))
-+        return;
-     m_wallet->add_subaddress(accountIndex, label);
- }
- std::string WalletImpl::getSubaddressLabel(uint32_t accountIndex, uint32_t addressIndex) const
- {
-+    if (checkBackgroundSync("cannot get subbaddress label"))
-+        return "";
-     try
-     {
-         return m_wallet->get_subaddress_label({accountIndex, addressIndex});
-@@ -1353,6 +1493,8 @@ std::string WalletImpl::getSubaddressLabel(uint32_t accountIndex, uint32_t addre
- }
- void WalletImpl::setSubaddressLabel(uint32_t accountIndex, uint32_t addressIndex, const std::string &label)
- {
-+    if (checkBackgroundSync("cannot set subbaddress label"))
-+        return;
-     try
-     {
-         return m_wallet->set_subaddress_label({accountIndex, addressIndex}, label);
-@@ -1366,12 +1508,16 @@ void WalletImpl::setSubaddressLabel(uint32_t accountIndex, uint32_t addressIndex
- 
- MultisigState WalletImpl::multisig() const {
-     MultisigState state;
-+    if (checkBackgroundSync("cannot use multisig"))
-+        return state;
-     state.isMultisig = m_wallet->multisig(&state.isReady, &state.threshold, &state.total);
- 
-     return state;
- }
- 
- string WalletImpl::getMultisigInfo() const {
-+    if (checkBackgroundSync("cannot use multisig"))
-+        return string();
-     try {
-         clearStatus();
-         return m_wallet->get_multisig_first_kex_msg();
-@@ -1384,6 +1530,8 @@ string WalletImpl::getMultisigInfo() const {
- }
- 
- string WalletImpl::makeMultisig(const vector<string>& info, const uint32_t threshold) {
-+    if (checkBackgroundSync("cannot make multisig"))
-+        return string();
-     try {
-         clearStatus();
- 
-@@ -1524,6 +1672,9 @@ PendingTransaction *WalletImpl::createTransactionMultDest(const std::vector<stri
-     PendingTransactionImpl * transaction = new PendingTransactionImpl(*this);
- 
-     do {
-+        if (checkBackgroundSync("cannot create transactions"))
-+            break;
-+
-         std::vector<uint8_t> extra;
-         std::string extra_nonce;
-         vector<cryptonote::tx_destination_entry> dsts;
-@@ -1690,6 +1841,9 @@ PendingTransaction *WalletImpl::createSweepUnmixableTransaction()
-     PendingTransactionImpl * transaction = new PendingTransactionImpl(*this);
- 
-     do {
-+        if (checkBackgroundSync("cannot sweep"))
-+            break;
-+
-         try {
-             transaction->m_pending_tx = m_wallet->create_unmixable_sweep_transactions();
-             pendingTxPostProcess(transaction);
-@@ -1823,11 +1977,15 @@ uint32_t WalletImpl::defaultMixin() const
- 
- void WalletImpl::setDefaultMixin(uint32_t arg)
- {
-+    if (checkBackgroundSync("cannot set default mixin"))
-+        return;
-     m_wallet->default_mixin(arg);
- }
- 
- bool WalletImpl::setCacheAttribute(const std::string &key, const std::string &val)
- {
-+    if (checkBackgroundSync("cannot set cache attribute"))
-+        return false;
-     m_wallet->set_attribute(key, val);
-     return true;
- }
-@@ -1841,6 +1999,8 @@ std::string WalletImpl::getCacheAttribute(const std::string &key) const
- 
- bool WalletImpl::setUserNote(const std::string &txid, const std::string &note)
- {
-+    if (checkBackgroundSync("cannot set user note"))
-+        return false;
-     cryptonote::blobdata txid_data;
-     if(!epee::string_tools::parse_hexstr_to_binbuff(txid, txid_data) || txid_data.size() != sizeof(crypto::hash))
-       return false;
-@@ -1852,6 +2012,8 @@ bool WalletImpl::setUserNote(const std::string &txid, const std::string &note)
- 
- std::string WalletImpl::getUserNote(const std::string &txid) const
- {
-+    if (checkBackgroundSync("cannot get user note"))
-+        return "";
-     cryptonote::blobdata txid_data;
-     if(!epee::string_tools::parse_hexstr_to_binbuff(txid, txid_data) || txid_data.size() != sizeof(crypto::hash))
-       return "";
-@@ -1862,6 +2024,9 @@ std::string WalletImpl::getUserNote(const std::string &txid) const
- 
- std::string WalletImpl::getTxKey(const std::string &txid_str) const
- {
-+    if (checkBackgroundSync("cannot get tx key"))
-+        return "";
-+
-     crypto::hash txid;
-     if(!epee::string_tools::hex_to_pod(txid_str, txid))
-     {
-@@ -1946,6 +2111,9 @@ bool WalletImpl::checkTxKey(const std::string &txid_str, std::string tx_key_str,
- 
- std::string WalletImpl::getTxProof(const std::string &txid_str, const std::string &address_str, const std::string &message) const
- {
-+    if (checkBackgroundSync("cannot get tx proof"))
-+        return "";
-+
-     crypto::hash txid;
-     if (!epee::string_tools::hex_to_pod(txid_str, txid))
-     {
-@@ -2002,6 +2170,9 @@ bool WalletImpl::checkTxProof(const std::string &txid_str, const std::string &ad
- }
- 
- std::string WalletImpl::getSpendProof(const std::string &txid_str, const std::string &message) const {
-+    if (checkBackgroundSync("cannot get spend proof"))
-+        return "";
-+
-     crypto::hash txid;
-     if(!epee::string_tools::hex_to_pod(txid_str, txid))
-     {
-@@ -2044,6 +2215,9 @@ bool WalletImpl::checkSpendProof(const std::string &txid_str, const std::string
- }
- 
- std::string WalletImpl::getReserveProof(bool all, uint32_t account_index, uint64_t amount, const std::string &message) const {
-+    if (checkBackgroundSync("cannot get reserve proof"))
-+        return "";
-+
-     try
-     {
-         clearStatus();
-@@ -2090,6 +2264,9 @@ bool WalletImpl::checkReserveProof(const std::string &address, const std::string
- 
- std::string WalletImpl::signMessage(const std::string &message, const std::string &address)
- {
-+    if (checkBackgroundSync("cannot sign message"))
-+        return "";
-+
-     if (address.empty()) {
-         return m_wallet->sign(message, tools::wallet2::sign_with_spend_key);
-     }
-@@ -2217,6 +2394,16 @@ bool WalletImpl::isDeterministic() const
-     return m_wallet->is_deterministic();
- }
- 
-+bool WalletImpl::isBackgroundSyncing() const
-+{
-+    return m_wallet->is_background_syncing();
-+}
-+
-+bool WalletImpl::isBackgroundWallet() const
-+{
-+    return m_wallet->is_background_wallet();
-+}
-+
- void WalletImpl::clearStatus() const
- {
-     boost::lock_guard<boost::mutex> l(m_statusMutex);
-@@ -2285,9 +2472,7 @@ void WalletImpl::doRefresh()
-             if(rescan)
-                 m_wallet->rescan_blockchain(false);
-             m_wallet->refresh(trustedDaemon());
--            if (!m_synchronized) {
--                m_synchronized = true;
--            }
-+            m_synchronized = m_wallet->is_synced();
-             // assuming if we have empty history, it wasn't initialized yet
-             // for further history changes client need to update history in
-             // "on_money_received" and "on_money_sent" callbacks
-@@ -2391,6 +2576,24 @@ bool WalletImpl::doInit(const string &daemon_address, const std::string &proxy_a
-     return true;
- }
- 
-+bool WalletImpl::checkBackgroundSync(const std::string &message) const
-+{
-+    clearStatus();
-+    if (m_wallet->is_background_wallet())
-+    {
-+        LOG_ERROR("Background wallets " + message);
-+        setStatusError(tr("Background wallets ") + message);
-+        return true;
-+    }
-+    if (m_wallet->is_background_syncing())
-+    {
-+        LOG_ERROR(message + " while background syncing");
-+        setStatusError(message + tr(" while background syncing. Stop background syncing first."));
-+        return true;
-+    }
-+    return false;
-+}
-+
- bool WalletImpl::parse_uri(const std::string &uri, std::string &address, std::string &payment_id, uint64_t &amount, std::string &tx_description, std::string &recipient_name, std::vector<std::string> &unknown_parameters, std::string &error)
- {
-     return m_wallet->parse_uri(uri, address, payment_id, amount, tx_description, recipient_name, unknown_parameters, error);
-@@ -2409,6 +2612,8 @@ std::string WalletImpl::getDefaultDataDir() const
- bool WalletImpl::rescanSpent()
- {
-   clearStatus();
-+  if (checkBackgroundSync("cannot rescan spent"))
-+    return false;
-   if (!trustedDaemon()) {
-     setStatusError(tr("Rescan spent can only be used with a trusted daemon"));
-     return false;
-diff --git a/src/wallet/api/wallet.h b/src/wallet/api/wallet.h
-index ec2d7e9b3..1f199a72c 100644
---- a/src/wallet/api/wallet.h
-+++ b/src/wallet/api/wallet.h
-@@ -171,6 +171,13 @@ public:
-     bool importOutputs(const std::string &filename) override;
-     bool scanTransactions(const std::vector<std::string> &txids) override;
- 
-+    bool setupBackgroundSync(const BackgroundSyncType background_sync_type, const std::string &wallet_password, const optional<std::string> &background_cache_password = optional<std::string>()) override;
-+    BackgroundSyncType getBackgroundSyncType() const override;
-+    bool startBackgroundSync() override;
-+    bool stopBackgroundSync(const std::string &wallet_password) override;
-+    bool isBackgroundSyncing() const override;
-+    bool isBackgroundWallet() const override;
-+
-     virtual void disposeTransaction(PendingTransaction * t) override;
-     virtual uint64_t estimateTransactionFee(const std::vector<std::pair<std::string, uint64_t>> &destinations,
-                                             PendingTransaction::Priority priority) const override;
-@@ -239,6 +246,7 @@ private:
-     bool isNewWallet() const;
-     void pendingTxPostProcess(PendingTransactionImpl * pending);
-     bool doInit(const std::string &daemon_address, const std::string &proxy_address, uint64_t upper_transaction_size_limit = 0, bool ssl = false);
-+    bool checkBackgroundSync(const std::string &message) const;
- 
- private:
-     friend class PendingTransactionImpl;
-@@ -253,6 +261,10 @@ private:
-     mutable boost::mutex m_statusMutex;
-     mutable int m_status;
-     mutable std::string m_errorString;
-+    // TODO: harden password handling in the wallet API, see relevant discussion
-+    // https://github.com/monero-project/monero-gui/issues/1537
-+    // https://github.com/feather-wallet/feather/issues/72#issuecomment-1405602142
-+    // https://github.com/monero-project/monero/pull/8619#issuecomment-1632951461
-     std::string m_password;
-     std::unique_ptr<TransactionHistoryImpl> m_history;
-     std::unique_ptr<Wallet2CallbackImpl> m_wallet2Callback;
-diff --git a/src/wallet/api/wallet2_api.h b/src/wallet/api/wallet2_api.h
-index 71991df0d..e349df176 100644
---- a/src/wallet/api/wallet2_api.h
-+++ b/src/wallet/api/wallet2_api.h
-@@ -445,6 +445,12 @@ struct Wallet
-         ConnectionStatus_WrongVersion
-     };
- 
-+    enum BackgroundSyncType {
-+        BackgroundSync_Off = 0,
-+        BackgroundSync_ReusePassword = 1,
-+        BackgroundSync_CustomPassword = 2
-+    };
-+
-     virtual ~Wallet() = 0;
-     virtual std::string seed(const std::string& seed_offset = "") const = 0;
-     virtual std::string getSeedLanguage() const = 0;
-@@ -936,6 +942,42 @@ struct Wallet
-      */
-     virtual bool scanTransactions(const std::vector<std::string> &txids) = 0;
- 
-+    /*!
-+     * \brief setupBackgroundSync       - setup background sync mode with just a view key
-+     * \param background_sync_type      - the mode the wallet background syncs in
-+     * \param wallet_password
-+     * \param background_cache_password - custom password to encrypt background cache, only needed for custom password background sync type
-+     * \return                          - true on success
-+     */
-+    virtual bool setupBackgroundSync(const BackgroundSyncType background_sync_type, const std::string &wallet_password, const optional<std::string> &background_cache_password) = 0;
-+
-+    /*!
-+     * \brief getBackgroundSyncType     - get mode the wallet background syncs in
-+     * \return                          - the type, or off if type is unknown
-+     */
-+    virtual BackgroundSyncType getBackgroundSyncType() const = 0;
-+
-+    /**
-+     * @brief startBackgroundSync - sync the chain in the background with just view key
-+     */
-+    virtual bool startBackgroundSync() = 0;
-+
-+    /**
-+     * @brief stopBackgroundSync  - bring back spend key and process background synced txs
-+     * \param wallet_password
-+     */
-+    virtual bool stopBackgroundSync(const std::string &wallet_password) = 0;
-+
-+    /**
-+     * @brief isBackgroundSyncing - returns true if the wallet is background syncing
-+     */
-+    virtual bool isBackgroundSyncing() const = 0;
-+
-+    /**
-+     * @brief isBackgroundWallet - returns true if the wallet is a background wallet
-+     */
-+    virtual bool isBackgroundWallet() const = 0;
-+
-     virtual TransactionHistory * history() = 0;
-     virtual AddressBook * addressBook() = 0;
-     virtual Subaddress * subaddress() = 0;
-diff --git a/src/wallet/wallet2.cpp b/src/wallet/wallet2.cpp
-index 478101af2..535005ab1 100644
---- a/src/wallet/wallet2.cpp
-+++ b/src/wallet/wallet2.cpp
-@@ -157,6 +157,8 @@ static const std::string MULTISIG_SIGNATURE_MAGIC = "SigMultisigPkV1";
- 
- static const std::string ASCII_OUTPUT_MAGIC = "WowneroAsciiDataV1";
- 
-+static const std::string BACKGROUND_WALLET_SUFFIX = ".background";
-+
- boost::mutex tools::wallet2::default_daemon_address_lock;
- std::string tools::wallet2::default_daemon_address = "";
- 
-@@ -1009,14 +1011,14 @@ uint64_t num_priv_multisig_keys_post_setup(uint64_t threshold, uint64_t total)
-  * @param keys_data_key the chacha key that encrypts wallet keys files
-  * @return crypto::chacha_key the chacha key that encrypts the wallet cache files
-  */
--crypto::chacha_key derive_cache_key(const crypto::chacha_key& keys_data_key)
-+crypto::chacha_key derive_cache_key(const crypto::chacha_key& keys_data_key, const unsigned char domain_separator)
- {
-   static_assert(HASH_SIZE == sizeof(crypto::chacha_key), "Mismatched sizes of hash and chacha key");
- 
-   crypto::chacha_key cache_key;
-   epee::mlocked<tools::scrubbed_arr<char, HASH_SIZE+1>> cache_key_data;
-   memcpy(cache_key_data.data(), &keys_data_key, HASH_SIZE);
--  cache_key_data[HASH_SIZE] = config::HASH_KEY_WALLET_CACHE;
-+  cache_key_data[HASH_SIZE] = domain_separator;
-   cn_fast_hash(cache_key_data.data(), HASH_SIZE+1, (crypto::hash&) cache_key);
- 
-   return cache_key;
-@@ -1104,7 +1106,7 @@ wallet_keys_unlocker::wallet_keys_unlocker(wallet2 &w, const boost::optional<too
-   boost::lock_guard<boost::mutex> lock(lockers_lock);
-   if (lockers++ > 0)
-     locked = false;
--  if (!locked || w.is_unattended() || w.ask_password() != tools::wallet2::AskPasswordToDecrypt || w.watch_only())
-+  if (!locked || w.is_unattended() || w.ask_password() != tools::wallet2::AskPasswordToDecrypt || w.watch_only() || w.is_background_syncing())
-   {
-     locked = false;
-     return;
-@@ -1221,6 +1223,11 @@ wallet2::wallet2(network_type nettype, uint64_t kdf_rounds, bool unattended, std
-   m_ignore_outputs_above(MONEY_SUPPLY),
-   m_ignore_outputs_below(0),
-   m_track_uses(false),
-+  m_is_background_wallet(false),
-+  m_background_sync_type(BackgroundSyncOff),
-+  m_background_syncing(false),
-+  m_processing_background_cache(false),
-+  m_custom_background_key(boost::none),
-   m_show_wallet_name_when_locked(false),
-   m_inactivity_lock_timeout(DEFAULT_INACTIVITY_LOCK_TIMEOUT),
-   m_setup_background_mining(BackgroundMiningNo),
-@@ -1869,6 +1876,9 @@ bool has_nonrequested_tx_at_height_or_above_requested(uint64_t height, const std
- //----------------------------------------------------------------------------------------------------
- void wallet2::scan_tx(const std::unordered_set<crypto::hash> &txids)
- {
-+  THROW_WALLET_EXCEPTION_IF(m_background_syncing || m_is_background_wallet, error::wallet_internal_error,
-+    "cannot scan tx from background wallet");
-+
-   // Get the transactions from daemon in batches sorted lowest height to highest
-   tx_entry_data txs_to_scan = get_tx_entries(txids);
-   if (txs_to_scan.tx_entries.empty())
-@@ -2178,11 +2188,11 @@ void wallet2::scan_output(const cryptonote::transaction &tx, bool miner_tx, cons
-   THROW_WALLET_EXCEPTION_IF(i >= tx.vout.size(), error::wallet_internal_error, "Invalid vout index");
- 
-   // if keys are encrypted, ask for password
--  if (m_ask_password == AskPasswordToDecrypt && !m_unattended && !m_watch_only && !m_multisig_rescan_k)
-+  if (m_ask_password == AskPasswordToDecrypt && !m_unattended && !m_watch_only && !m_multisig_rescan_k && !m_background_syncing)
-   {
-     static critical_section password_lock;
-     CRITICAL_REGION_LOCAL(password_lock);
--    if (!m_encrypt_keys_after_refresh)
-+    if (!m_encrypt_keys_after_refresh && !m_processing_background_cache)
-     {
-       boost::optional<epee::wipeable_string> pwd = m_callback->on_get_password(pool ? "output found in pool" : "output received");
-       THROW_WALLET_EXCEPTION_IF(!pwd, error::password_needed, tr("Password is needed to compute key image for incoming wownero"));
-@@ -2194,7 +2204,7 @@ void wallet2::scan_output(const cryptonote::transaction &tx, bool miner_tx, cons
-   crypto::public_key output_public_key;
-   THROW_WALLET_EXCEPTION_IF(!get_output_public_key(tx.vout[i], output_public_key), error::wallet_internal_error, "Failed to get output public key");
- 
--  if (m_multisig)
-+  if (m_multisig || m_background_syncing/*no spend key*/)
-   {
-     tx_scan_info.in_ephemeral.pub = output_public_key;
-     tx_scan_info.in_ephemeral.sec = crypto::null_skey;
-@@ -2451,6 +2461,22 @@ void wallet2::process_new_transaction(const crypto::hash &txid, const cryptonote
-         THROW_WALLET_EXCEPTION_IF(tx.vout.size() != o_indices.size(), error::wallet_internal_error,
-             "transactions outputs size=" + std::to_string(tx.vout.size()) +
-             " not match with daemon response size=" + std::to_string(o_indices.size()));
-+
-+        // we're going to re-process this receive when background sync is disabled
-+        if (m_background_syncing && m_background_sync_data.txs.find(txid) == m_background_sync_data.txs.end())
-+        {
-+          size_t bgs_idx = m_background_sync_data.txs.size();
-+          background_synced_tx_t bgs_tx = {
-+            .index_in_background_sync_data = bgs_idx,
-+            .tx                            = tx,
-+            .output_indices                = o_indices,
-+            .height                        = height,
-+            .block_timestamp               = ts,
-+            .double_spend_seen             = double_spend_seen
-+          };
-+          LOG_PRINT_L2("Adding received tx " << txid << " to background sync data (idx=" << bgs_idx << ")");
-+          m_background_sync_data.txs.insert({txid, std::move(bgs_tx)});
-+        }
-       }
- 
-       for(size_t o: outs)
-@@ -2476,7 +2502,7 @@ void wallet2::process_new_transaction(const crypto::hash &txid, const cryptonote
- 	    td.m_tx = (const cryptonote::transaction_prefix&)tx;
- 	    td.m_txid = txid;
-             td.m_key_image = tx_scan_info[o].ki;
--            td.m_key_image_known = !m_watch_only && !m_multisig;
-+            td.m_key_image_known = !m_watch_only && !m_multisig && !m_background_syncing;
-             if (!td.m_key_image_known)
-             {
-               // we might have cold signed, and have a mapping to key images
-@@ -2666,10 +2692,25 @@ void wallet2::process_new_transaction(const crypto::hash &txid, const cryptonote
-         set_spent(it->second, height);
-         if (!ignore_callbacks && 0 != m_callback)
-           m_callback->on_money_spent(height, txid, tx, amount, tx, td.m_subaddr_index);
-+
-+        if (m_background_syncing && m_background_sync_data.txs.find(txid) == m_background_sync_data.txs.end())
-+        {
-+          size_t bgs_idx = m_background_sync_data.txs.size();
-+          background_synced_tx_t bgs_tx = {
-+            .index_in_background_sync_data = bgs_idx,
-+            .tx                            = tx,
-+            .output_indices                = o_indices,
-+            .height                        = height,
-+            .block_timestamp               = ts,
-+            .double_spend_seen             = double_spend_seen
-+          };
-+          LOG_PRINT_L2("Adding spent tx " << txid << " to background sync data (idx=" << bgs_idx << ")");
-+          m_background_sync_data.txs.insert({txid, std::move(bgs_tx)});
-+        }
-       }
-     }
- 
--    if (!pool && m_track_uses)
-+    if (!pool && (m_track_uses || (m_background_syncing && it == m_key_images.end())))
-     {
-       PERF_TIMER(track_uses);
-       const uint64_t amount = in_to_key.amount;
-@@ -2683,7 +2724,27 @@ void wallet2::process_new_transaction(const crypto::hash &txid, const cryptonote
-           {
-             size_t idx = i->second;
-             THROW_WALLET_EXCEPTION_IF(idx >= m_transfers.size(), error::wallet_internal_error, "Output tracker cache index out of range");
--            m_transfers[idx].m_uses.push_back(std::make_pair(height, txid));
-+
-+            if (m_track_uses)
-+              m_transfers[idx].m_uses.push_back(std::make_pair(height, txid));
-+
-+            // We'll re-process all txs which *might* be spends when we disable
-+            // background sync and retrieve the spend key. We don't know if an
-+            // output is a spend in this tx if we don't know its key image.
-+            if (m_background_syncing && !m_transfers[idx].m_key_image_known && m_background_sync_data.txs.find(txid) == m_background_sync_data.txs.end())
-+            {
-+              size_t bgs_idx = m_background_sync_data.txs.size();
-+              background_synced_tx_t bgs_tx = {
-+                .index_in_background_sync_data = bgs_idx,
-+                .tx                            = tx,
-+                .output_indices                = o_indices,
-+                .height                        = height,
-+                .block_timestamp               = ts,
-+                .double_spend_seen             = double_spend_seen
-+              };
-+              LOG_PRINT_L2("Adding plausible spent tx " << txid << " to background sync data (idx=" << bgs_idx << ")");
-+              m_background_sync_data.txs.insert({txid, std::move(bgs_tx)});
-+            }
-           }
-         }
-       }
-@@ -2693,7 +2754,24 @@ void wallet2::process_new_transaction(const crypto::hash &txid, const cryptonote
-           continue;
-         for (uint64_t offset: offsets)
-           if (offset == td.m_global_output_index)
--            td.m_uses.push_back(std::make_pair(height, txid));
-+          {
-+            if (m_track_uses)
-+              td.m_uses.push_back(std::make_pair(height, txid));
-+            if (m_background_syncing && !td.m_key_image_known && m_background_sync_data.txs.find(txid) == m_background_sync_data.txs.end())
-+            {
-+              size_t bgs_idx = m_background_sync_data.txs.size();
-+              background_synced_tx_t bgs_tx = {
-+                .index_in_background_sync_data = bgs_idx,
-+                .tx                            = tx,
-+                .output_indices                = o_indices,
-+                .height                        = height,
-+                .block_timestamp               = ts,
-+                .double_spend_seen             = double_spend_seen
-+              };
-+              LOG_PRINT_L2("Adding plausible spent tx " << txid << " to background sync data (idx=" << bgs_idx << ")");
-+              m_background_sync_data.txs.insert({txid, std::move(bgs_tx)});
-+            }
-+          }
-       }
-     }
-   }
-@@ -3066,8 +3144,8 @@ void wallet2::pull_blocks(bool first, bool try_incremental, uint64_t start_heigh
-   req.start_height = start_height;
-   req.no_miner_tx = m_refresh_type == RefreshNoCoinbase;
- 
--  req.requested_info = first ? COMMAND_RPC_GET_BLOCKS_FAST::BLOCKS_AND_POOL : COMMAND_RPC_GET_BLOCKS_FAST::BLOCKS_ONLY;
--  if (try_incremental)
-+  req.requested_info = (first && !m_background_syncing) ? COMMAND_RPC_GET_BLOCKS_FAST::BLOCKS_AND_POOL : COMMAND_RPC_GET_BLOCKS_FAST::BLOCKS_ONLY;
-+  if (try_incremental && !m_background_syncing)
-     req.pool_info_since = m_pool_info_query_time;
- 
-   {
-@@ -3094,7 +3172,7 @@ void wallet2::pull_blocks(bool first, bool try_incremental, uint64_t start_heigh
-       << ", height " << blocks_start_height + blocks.size() << ", node height " << res.current_height
-       << ", pool info " << static_cast<unsigned int>(res.pool_info_extent));
- 
--  if (first)
-+  if (first && !m_background_syncing)
-   {
-     if (res.pool_info_extent != COMMAND_RPC_GET_BLOCKS_FAST::NONE)
-     {
-@@ -3606,6 +3684,9 @@ void wallet2::process_unconfirmed_transfer(bool incremental, const crypto::hash
- // incremental update anymore, because with that we might miss some txs altogether.
- void wallet2::update_pool_state(std::vector<std::tuple<cryptonote::transaction, crypto::hash, bool>> &process_txs, bool refreshed, bool try_incremental)
- {
-+  process_txs.clear();
-+  if (m_background_syncing)
-+    return;
-   bool updated = false;
-   if (m_pool_info_query_time != 0 && try_incremental)
-   {
-@@ -4177,6 +4258,8 @@ void wallet2::refresh(bool trusted_daemon, uint64_t start_height, uint64_t & blo
-   }
- 
-   m_first_refresh_done = true;
-+  if (m_background_syncing || m_is_background_wallet)
-+    m_background_sync_data.first_refresh_done = true;
- 
-   LOG_PRINT_L1("Refresh done, blocks received: " << blocks_fetched << ", balance (all accounts): " << print_money(balance_all(false)) << ", unlocked: " << print_money(unlocked_balance_all(false)));
- }
-@@ -4262,6 +4345,14 @@ wallet2::detached_blockchain_data wallet2::detach_blockchain(uint64_t height, st
-       td.m_uses.pop_back();
-   }
- 
-+  for (auto it = m_background_sync_data.txs.begin(); it != m_background_sync_data.txs.end(); )
-+  {
-+    if(height <= it->second.height)
-+      it = m_background_sync_data.txs.erase(it);
-+    else
-+      ++it;
-+  }
-+
-   if (output_tracker_cache)
-     output_tracker_cache->clear();
- 
-@@ -4336,8 +4427,12 @@ void wallet2::handle_reorg(uint64_t height, std::map<std::pair<uint64_t, uint64_
-   //               C
-   THROW_WALLET_EXCEPTION_IF(height < m_blockchain.offset() && m_blockchain.size() > m_blockchain.offset(),
-       error::wallet_internal_error, "Daemon claims reorg below last checkpoint");
-+
-   detached_blockchain_data dbd = detach_blockchain(height, output_tracker_cache);
- 
-+  if (m_background_syncing && height < m_background_sync_data.start_height)
-+    m_background_sync_data.start_height = height;
-+
-   if (m_callback)
-     m_callback->on_reorg(height, dbd.detached_blockchain.size(), dbd.detached_tx_hashes.size());
- }
-@@ -4347,6 +4442,7 @@ bool wallet2::deinit()
-   if(m_is_initialized) {
-     m_is_initialized = false;
-     unlock_keys_file();
-+    unlock_background_keys_file();
-     m_account.deinit();
-   }
-   return true;
-@@ -4373,6 +4469,7 @@ bool wallet2::clear()
-   m_device_last_key_image_sync = 0;
-   m_pool_info_query_time = 0;
-   m_skip_to_height = 0;
-+  m_background_sync_data = background_sync_data_t{};
-   return true;
- }
- //----------------------------------------------------------------------------------------------------
-@@ -4391,13 +4488,30 @@ void wallet2::clear_soft(bool keep_key_images)
-   m_scanned_pool_txs[1].clear();
-   m_pool_info_query_time = 0;
-   m_skip_to_height = 0;
-+  m_background_sync_data = background_sync_data_t{};
- 
-   cryptonote::block b;
-   generate_genesis(b);
-   m_blockchain.push_back(get_block_hash(b));
-   m_last_block_reward = cryptonote::get_outs_money_amount(b.miner_tx);
- }
--
-+//----------------------------------------------------------------------------------------------------
-+void wallet2::clear_user_data()
-+{
-+  for (auto i = m_confirmed_txs.begin(); i != m_confirmed_txs.end(); ++i)
-+    i->second.m_dests.clear();
-+  for (auto i = m_unconfirmed_txs.begin(); i != m_unconfirmed_txs.end(); ++i)
-+    i->second.m_dests.clear();
-+  for (auto i = m_transfers.begin(); i != m_transfers.end(); ++i)
-+    i->m_frozen = false;
-+  m_tx_keys.clear();
-+  m_tx_notes.clear();
-+  m_address_book.clear();
-+  m_subaddress_labels.clear();
-+  m_attributes.clear();
-+  m_account_tags = std::pair<serializable_map<std::string, std::string>, std::vector<std::string>>();
-+}
-+//----------------------------------------------------------------------------------------------------
- /*!
-  * \brief Stores wallet information to wallet file.
-  * \param  keys_file_name Name of wallet file
-@@ -4409,16 +4523,35 @@ bool wallet2::store_keys(const std::string& keys_file_name, const epee::wipeable
- {
-   boost::optional<wallet2::keys_file_data> keys_file_data = get_keys_file_data(password, watch_only);
-   CHECK_AND_ASSERT_MES(keys_file_data != boost::none, false, "failed to generate wallet keys data");
--
-+  return store_keys_file_data(keys_file_name, keys_file_data.get());
-+}
-+//----------------------------------------------------------------------------------------------------
-+bool wallet2::store_keys(const std::string& keys_file_name, const crypto::chacha_key& key, bool watch_only, bool background_keys_file)
-+{
-+  boost::optional<wallet2::keys_file_data> keys_file_data = get_keys_file_data(key, watch_only, background_keys_file);
-+  CHECK_AND_ASSERT_MES(keys_file_data != boost::none, false, "failed to generate wallet keys data");
-+  return store_keys_file_data(keys_file_name, keys_file_data.get(), background_keys_file);
-+}
-+//----------------------------------------------------------------------------------------------------
-+bool wallet2::store_keys_file_data(const std::string& keys_file_name, wallet2::keys_file_data &keys_file_data, bool background_keys_file)
-+{
-   std::string tmp_file_name = keys_file_name + ".new";
-   std::string buf;
--  bool r = ::serialization::dump_binary(keys_file_data.get(), buf);
-+  bool r = ::serialization::dump_binary(keys_file_data, buf);
-   r = r && save_to_file(tmp_file_name, buf);
-   CHECK_AND_ASSERT_MES(r, false, "failed to generate wallet keys file " << tmp_file_name);
- 
--  unlock_keys_file();
-+  if (!background_keys_file)
-+    unlock_keys_file();
-+  else
-+    unlock_background_keys_file();
-+
-   std::error_code e = tools::replace_file(tmp_file_name, keys_file_name);
--  lock_keys_file();
-+
-+  if (!background_keys_file)
-+    lock_keys_file();
-+  else
-+    lock_background_keys_file(keys_file_name);
- 
-   if (e) {
-     boost::filesystem::remove(tmp_file_name);
-@@ -4430,26 +4563,27 @@ bool wallet2::store_keys(const std::string& keys_file_name, const epee::wipeable
- }
- //----------------------------------------------------------------------------------------------------
- boost::optional<wallet2::keys_file_data> wallet2::get_keys_file_data(const epee::wipeable_string& password, bool watch_only)
-+{
-+  crypto::chacha_key key;
-+  crypto::generate_chacha_key(password.data(), password.size(), key, m_kdf_rounds);
-+  verify_password_with_cached_key(key);
-+  return get_keys_file_data(key, watch_only);
-+}
-+//----------------------------------------------------------------------------------------------------
-+boost::optional<wallet2::keys_file_data> wallet2::get_keys_file_data(const crypto::chacha_key& key, bool watch_only, bool background_keys_file)
- {
-   epee::byte_slice account_data;
-   std::string multisig_signers;
-   std::string multisig_derivations;
-   cryptonote::account_base account = m_account;
- 
--  crypto::chacha_key key;
--  crypto::generate_chacha_key(password.data(), password.size(), key, m_kdf_rounds);
--
--  // We use m_cache_key as a deterministic test to see if given key corresponds to original password
--  const crypto::chacha_key cache_key = derive_cache_key(key);
--  THROW_WALLET_EXCEPTION_IF(cache_key != m_cache_key, error::invalid_password);
--
-   if (m_ask_password == AskPasswordToDecrypt && !m_unattended && !m_watch_only)
-   {
-     account.encrypt_viewkey(key);
-     account.decrypt_keys(key);
-   }
- 
--  if (watch_only)
-+  if (watch_only || background_keys_file)
-     account.forget_spend_key();
- 
-   account.encrypt_keys(key);
-@@ -4584,6 +4718,9 @@ boost::optional<wallet2::keys_file_data> wallet2::get_keys_file_data(const epee:
-   value2.SetInt(m_track_uses ? 1 : 0);
-   json.AddMember("track_uses", value2, json.GetAllocator());
- 
-+  value2.SetInt(m_background_sync_type);
-+  json.AddMember("background_sync_type", value2, json.GetAllocator());
-+
-   value2.SetInt(m_show_wallet_name_when_locked ? 1 : 0);
-   json.AddMember("show_wallet_name_when_locked", value2, json.GetAllocator());
- 
-@@ -4641,6 +4778,12 @@ boost::optional<wallet2::keys_file_data> wallet2::get_keys_file_data(const epee:
-   value2.SetInt(m_enable_multisig ? 1 : 0);
-   json.AddMember("enable_multisig", value2, json.GetAllocator());
- 
-+  if (m_background_sync_type == BackgroundSyncCustomPassword && !background_keys_file && m_custom_background_key)
-+  {
-+    value.SetString(reinterpret_cast<const char*>(m_custom_background_key.get().data()), m_custom_background_key.get().size());
-+    json.AddMember("custom_background_key", value, json.GetAllocator());
-+  }
-+
-   // Serialize the JSON object
-   rapidjson::StringBuffer buffer;
-   rapidjson::Writer<rapidjson::StringBuffer> writer(buffer);
-@@ -4667,13 +4810,81 @@ void wallet2::setup_keys(const epee::wipeable_string &password)
-     m_account.decrypt_viewkey(key);
-   }
- 
--  m_cache_key = derive_cache_key(key);
-+  m_cache_key = derive_cache_key(key, config::HASH_KEY_WALLET_CACHE);
- 
-   get_ringdb_key();
- }
- //----------------------------------------------------------------------------------------------------
-+void validate_background_cache_password_usage(const tools::wallet2::BackgroundSyncType background_sync_type, const boost::optional<epee::wipeable_string> &background_cache_password, const bool multisig, const bool watch_only, const bool key_on_device)
-+{
-+  THROW_WALLET_EXCEPTION_IF(multisig || watch_only || key_on_device, error::wallet_internal_error, multisig
-+      ? "Background sync not implemented for multisig wallets" : watch_only
-+      ? "Background sync not implemented for view only wallets"
-+      : "Background sync not implemented for HW wallets");
-+
-+  switch (background_sync_type)
-+  {
-+    case tools::wallet2::BackgroundSyncOff:
-+    {
-+      THROW_WALLET_EXCEPTION(error::wallet_internal_error, "background sync is not enabled");
-+      break;
-+    }
-+    case tools::wallet2::BackgroundSyncReusePassword:
-+    {
-+      THROW_WALLET_EXCEPTION_IF(background_cache_password, error::wallet_internal_error,
-+          "unexpected custom background cache password");
-+      break;
-+    }
-+    case tools::wallet2::BackgroundSyncCustomPassword:
-+    {
-+      THROW_WALLET_EXCEPTION_IF(!background_cache_password, error::wallet_internal_error,
-+          "expected custom background cache password");
-+      break;
-+    }
-+    default: THROW_WALLET_EXCEPTION(error::wallet_internal_error, "unknown background sync type");
-+  }
-+}
-+//----------------------------------------------------------------------------------------------------
-+void get_custom_background_key(const epee::wipeable_string &password, crypto::chacha_key &custom_background_key, const uint64_t kdf_rounds)
-+{
-+  crypto::chacha_key key;
-+  crypto::generate_chacha_key(password.data(), password.size(), key, kdf_rounds);
-+  custom_background_key = derive_cache_key(key, config::HASH_KEY_BACKGROUND_KEYS_FILE);
-+}
-+//----------------------------------------------------------------------------------------------------
-+const crypto::chacha_key wallet2::get_cache_key()
-+{
-+  if (m_background_sync_type == BackgroundSyncCustomPassword && m_background_syncing)
-+  {
-+    THROW_WALLET_EXCEPTION_IF(!m_custom_background_key, error::wallet_internal_error, "Custom background key not set");
-+    // Domain separate keys used to encrypt background keys file and cache
-+    return derive_cache_key(m_custom_background_key.get(), config::HASH_KEY_BACKGROUND_CACHE);
-+  }
-+  else
-+  {
-+    return m_cache_key;
-+  }
-+}
-+//----------------------------------------------------------------------------------------------------
-+void wallet2::verify_password_with_cached_key(const epee::wipeable_string &password)
-+{
-+  crypto::chacha_key key;
-+  crypto::generate_chacha_key(password.data(), password.size(), key, m_kdf_rounds);
-+  verify_password_with_cached_key(key);
-+}
-+//----------------------------------------------------------------------------------------------------
-+void wallet2::verify_password_with_cached_key(const crypto::chacha_key &key)
-+{
-+  // We use m_cache_key as a deterministic test to see if given key corresponds to original password
-+  const crypto::chacha_key cache_key = derive_cache_key(key, config::HASH_KEY_WALLET_CACHE);
-+  THROW_WALLET_EXCEPTION_IF(cache_key != m_cache_key, error::invalid_password);
-+}
-+//----------------------------------------------------------------------------------------------------
- void wallet2::change_password(const std::string &filename, const epee::wipeable_string &original_password, const epee::wipeable_string &new_password)
- {
-+  THROW_WALLET_EXCEPTION_IF(m_background_syncing || m_is_background_wallet, error::wallet_internal_error,
-+      "cannot change password from background wallet");
-+
-   if (m_ask_password == AskPasswordToDecrypt && !m_unattended && !m_watch_only)
-     decrypt_keys(original_password);
-   setup_keys(new_password);
-@@ -4732,8 +4943,24 @@ bool wallet2::load_keys_buf(const std::string& keys_buf, const epee::wipeable_st
-   std::string account_data;
-   account_data.resize(keys_file_data.account_data.size());
-   crypto::chacha20(keys_file_data.account_data.data(), keys_file_data.account_data.size(), key, keys_file_data.iv, &account_data[0]);
--  if (json.Parse(account_data.c_str()).HasParseError() || !json.IsObject())
-+  const bool try_v0_format = json.Parse(account_data.c_str()).HasParseError() || !json.IsObject();
-+  if (try_v0_format)
-     crypto::chacha8(keys_file_data.account_data.data(), keys_file_data.account_data.size(), key, keys_file_data.iv, &account_data[0]);
-+
-+  // Check if it's a background keys file if both of the above formats fail
-+  {
-+    m_is_background_wallet = false;
-+    m_background_syncing = false;
-+    cryptonote::account_base account_data_check;
-+    if (try_v0_format && !epee::serialization::load_t_from_binary(account_data_check, account_data))
-+    {
-+      get_custom_background_key(password, key, m_kdf_rounds);
-+      crypto::chacha20(keys_file_data.account_data.data(), keys_file_data.account_data.size(), key, keys_file_data.iv, &account_data[0]);
-+      m_is_background_wallet = !json.Parse(account_data.c_str()).HasParseError() && json.IsObject();
-+      m_background_syncing = m_is_background_wallet; // start a background wallet background syncing
-+    }
-+  }
-+
-   // The contents should be JSON if the wallet follows the new format.
-   if (json.Parse(account_data.c_str()).HasParseError())
-   {
-@@ -4771,6 +4998,7 @@ bool wallet2::load_keys_buf(const std::string& keys_buf, const epee::wipeable_st
-     m_ignore_outputs_above = MONEY_SUPPLY;
-     m_ignore_outputs_below = 0;
-     m_track_uses = false;
-+    m_background_sync_type = BackgroundSyncOff;
-     m_show_wallet_name_when_locked = false;
-     m_inactivity_lock_timeout = DEFAULT_INACTIVITY_LOCK_TIMEOUT;
-     m_setup_background_mining = BackgroundMiningNo;
-@@ -4788,6 +5016,7 @@ bool wallet2::load_keys_buf(const std::string& keys_buf, const epee::wipeable_st
-     m_credits_target = 0;
-     m_enable_multisig = false;
-     m_allow_mismatched_daemon_version = true;
-+    m_custom_background_key = boost::none;
-   }
-   else if(json.IsObject())
-   {
-@@ -5024,6 +5253,39 @@ bool wallet2::load_keys_buf(const std::string& keys_buf, const epee::wipeable_st
-     m_credits_target = field_credits_target;
-     GET_FIELD_FROM_JSON_RETURN_ON_ERROR(json, enable_multisig, int, Int, false, false);
-     m_enable_multisig = field_enable_multisig;
-+
-+    GET_FIELD_FROM_JSON_RETURN_ON_ERROR(json, background_sync_type, BackgroundSyncType, Int, false, BackgroundSyncOff);
-+    m_background_sync_type = field_background_sync_type;
-+
-+    // Load encryption key used to encrypt background cache
-+    crypto::chacha_key custom_background_key;
-+    m_custom_background_key = boost::none;
-+    if (m_background_sync_type == BackgroundSyncCustomPassword && !m_is_background_wallet)
-+    {
-+      if (!json.HasMember("custom_background_key"))
-+      {
-+        LOG_ERROR("Field custom_background_key not found in JSON");
-+        return false;
-+      }
-+      else if (!json["custom_background_key"].IsString())
-+      {
-+        LOG_ERROR("Field custom_background_key found in JSON, but not String");
-+        return false;
-+      }
-+      else if (json["custom_background_key"].GetStringLength() != sizeof(crypto::chacha_key))
-+      {
-+        LOG_ERROR("Field custom_background_key found in JSON, but not correct length");
-+        return false;
-+      }
-+      const char *field_custom_background_key = json["custom_background_key"].GetString();
-+      memcpy(custom_background_key.data(), field_custom_background_key, sizeof(crypto::chacha_key));
-+      m_custom_background_key = boost::optional<crypto::chacha_key>(custom_background_key);
-+      LOG_PRINT_L1("Loaded custom background key derived from custom password");
-+    }
-+    else if (json.HasMember("custom_background_key"))
-+    {
-+      LOG_ERROR("Unexpected field custom_background_key found in JSON");
-+    }
-   }
-   else
-   {
-@@ -5087,12 +5349,17 @@ bool wallet2::load_keys_buf(const std::string& keys_buf, const epee::wipeable_st
-   const cryptonote::account_keys& keys = m_account.get_keys();
-   hw::device &hwdev = m_account.get_device();
-   r = r && hwdev.verify_keys(keys.m_view_secret_key,  keys.m_account_address.m_view_public_key);
--  if (!m_watch_only && !m_multisig && hwdev.device_protocol() != hw::device::PROTOCOL_COLD)
-+  if (!m_watch_only && !m_multisig && hwdev.device_protocol() != hw::device::PROTOCOL_COLD && !m_is_background_wallet)
-     r = r && hwdev.verify_keys(keys.m_spend_secret_key, keys.m_account_address.m_spend_public_key);
-   THROW_WALLET_EXCEPTION_IF(!r, error::wallet_files_doesnt_correspond, m_keys_file, m_wallet_file);
- 
-   if (r)
--    setup_keys(password);
-+  {
-+    if (!m_is_background_wallet)
-+      setup_keys(password);
-+    else
-+      m_custom_background_key = boost::optional<crypto::chacha_key>(key);
-+  }
- 
-   return true;
- }
-@@ -5107,11 +5374,12 @@ bool wallet2::load_keys_buf(const std::string& keys_buf, const epee::wipeable_st
-  * can be used prior to rewriting wallet keys file, to ensure user has entered the correct password
-  *
-  */
--bool wallet2::verify_password(const epee::wipeable_string& password)
-+bool wallet2::verify_password(const epee::wipeable_string& password, crypto::secret_key &spend_key_out)
- {
-   // this temporary unlocking is necessary for Windows (otherwise the file couldn't be loaded).
-   unlock_keys_file();
--  bool r = verify_password(m_keys_file, password, m_account.get_device().device_protocol() == hw::device::PROTOCOL_COLD || m_watch_only || m_multisig, m_account.get_device(), m_kdf_rounds);
-+  const bool no_spend_key = m_account.get_device().device_protocol() == hw::device::PROTOCOL_COLD || m_watch_only || m_multisig || m_is_background_wallet;
-+  bool r = verify_password(m_keys_file, password, no_spend_key, m_account.get_device(), m_kdf_rounds, spend_key_out);
-   lock_keys_file();
-   return r;
- }
-@@ -5129,7 +5397,7 @@ bool wallet2::verify_password(const epee::wipeable_string& password)
-  * can be used prior to rewriting wallet keys file, to ensure user has entered the correct password
-  *
-  */
--bool wallet2::verify_password(const std::string& keys_file_name, const epee::wipeable_string& password, bool no_spend_key, hw::device &hwdev, uint64_t kdf_rounds)
-+bool wallet2::verify_password(const std::string& keys_file_name, const epee::wipeable_string& password, bool no_spend_key, hw::device &hwdev, uint64_t kdf_rounds, crypto::secret_key &spend_key_out)
- {
-   rapidjson::Document json;
-   wallet2::keys_file_data keys_file_data;
-@@ -5146,9 +5414,22 @@ bool wallet2::verify_password(const std::string& keys_file_name, const epee::wip
-   std::string account_data;
-   account_data.resize(keys_file_data.account_data.size());
-   crypto::chacha20(keys_file_data.account_data.data(), keys_file_data.account_data.size(), key, keys_file_data.iv, &account_data[0]);
--  if (json.Parse(account_data.c_str()).HasParseError() || !json.IsObject())
-+  const bool try_v0_format = json.Parse(account_data.c_str()).HasParseError() || !json.IsObject();
-+  if (try_v0_format)
-     crypto::chacha8(keys_file_data.account_data.data(), keys_file_data.account_data.size(), key, keys_file_data.iv, &account_data[0]);
- 
-+  // Check if it's a background keys file if both of the above formats fail
-+  {
-+    cryptonote::account_base account_data_check;
-+    if (try_v0_format && !epee::serialization::load_t_from_binary(account_data_check, account_data))
-+    {
-+      get_custom_background_key(password, key, kdf_rounds);
-+      crypto::chacha20(keys_file_data.account_data.data(), keys_file_data.account_data.size(), key, keys_file_data.iv, &account_data[0]);
-+      const bool is_background_wallet = json.Parse(account_data.c_str()).HasParseError() && json.IsObject();
-+      no_spend_key = no_spend_key || is_background_wallet;
-+    }
-+  }
-+
-   // The contents should be JSON if the wallet follows the new format.
-   if (json.Parse(account_data.c_str()).HasParseError())
-   {
-@@ -5173,6 +5454,7 @@ bool wallet2::verify_password(const std::string& keys_file_name, const epee::wip
-   r = r && hwdev.verify_keys(keys.m_view_secret_key,  keys.m_account_address.m_view_public_key);
-   if(!no_spend_key)
-     r = r && hwdev.verify_keys(keys.m_spend_secret_key, keys.m_account_address.m_spend_public_key);
-+  spend_key_out = (!no_spend_key && r) ? keys.m_spend_secret_key : crypto::null_skey;
-   return r;
- }
- 
-@@ -5184,9 +5466,7 @@ void wallet2::encrypt_keys(const crypto::chacha_key &key)
- 
- void wallet2::decrypt_keys(const crypto::chacha_key &key)
- {
--  // We use m_cache_key as a deterministic test to see if given key corresponds to original password
--  const crypto::chacha_key cache_key = derive_cache_key(key);
--  THROW_WALLET_EXCEPTION_IF(cache_key != m_cache_key, error::invalid_password);
-+  verify_password_with_cached_key(key);
- 
-   m_account.encrypt_viewkey(key);
-   m_account.decrypt_keys(key);
-@@ -5862,11 +6142,30 @@ void wallet2::rewrite(const std::string& wallet_name, const epee::wipeable_strin
- {
-   if (wallet_name.empty())
-     return;
-+  THROW_WALLET_EXCEPTION_IF(m_background_syncing || m_is_background_wallet, error::wallet_internal_error,
-+    "cannot change wallet settings from background wallet");
-   prepare_file_names(wallet_name);
-   boost::system::error_code ignored_ec;
-   THROW_WALLET_EXCEPTION_IF(!boost::filesystem::exists(m_keys_file, ignored_ec), error::file_not_found, m_keys_file);
-   bool r = store_keys(m_keys_file, password, m_watch_only);
-   THROW_WALLET_EXCEPTION_IF(!r, error::file_save_error, m_keys_file);
-+
-+  // Update the background keys file when we rewrite the main wallet keys file
-+  if (m_background_sync_type == BackgroundSyncCustomPassword && m_custom_background_key)
-+  {
-+    const std::string background_keys_filename = make_background_keys_file_name(wallet_name);
-+    if (!lock_background_keys_file(background_keys_filename))
-+    {
-+      LOG_ERROR("Background keys file " << background_keys_filename << " is opened by another wallet program and cannot be rewritten");
-+      return; // not fatal, background keys file will just have different wallet settings
-+    }
-+    store_background_keys(m_custom_background_key.get());
-+    store_background_cache(m_custom_background_key.get(), true/*do_reset_background_sync_data*/);
-+  }
-+  else if (m_background_sync_type == BackgroundSyncReusePassword)
-+  {
-+    reset_background_sync_data(m_background_sync_data);
-+  }
- }
- /*!
-  * \brief Writes to a file named based on the normal wallet (doesn't generate key, assumes it's already there)
-@@ -5900,6 +6199,16 @@ bool wallet2::wallet_valid_path_format(const std::string& file_path)
-   return !file_path.empty();
- }
- //----------------------------------------------------------------------------------------------------
-+std::string wallet2::make_background_wallet_file_name(const std::string &wallet_file)
-+{
-+  return wallet_file + BACKGROUND_WALLET_SUFFIX;
-+}
-+//----------------------------------------------------------------------------------------------------
-+std::string wallet2::make_background_keys_file_name(const std::string &wallet_file)
-+{
-+  return make_background_wallet_file_name(wallet_file) + ".keys";
-+}
-+//----------------------------------------------------------------------------------------------------
- bool wallet2::parse_long_payment_id(const std::string& payment_id_str, crypto::hash& payment_id)
- {
-   cryptonote::blobdata payment_id_data;
-@@ -6135,10 +6444,81 @@ void wallet2::load(const std::string& wallet_, const epee::wipeable_string& pass
-     THROW_WALLET_EXCEPTION_IF(true, error::file_read_error, "failed to load keys from buffer");
-   }
- 
--  wallet_keys_unlocker unlocker(*this, m_ask_password == AskPasswordToDecrypt && !m_unattended && !m_watch_only, password);
-+  wallet_keys_unlocker unlocker(*this, m_ask_password == AskPasswordToDecrypt && !m_unattended && !m_watch_only && !m_is_background_wallet, password);
- 
-   //keys loaded ok!
-   //try to load wallet cache. but even if we failed, it is not big problem
-+  load_wallet_cache(use_fs, cache_buf);
-+
-+  if (!m_persistent_rpc_client_id)
-+    set_rpc_client_secret_key(rct::rct2sk(rct::skGen()));
-+
-+  // Wallets used to wipe, but not erase, old unused multisig key info, which lead to huge memory leaks.
-+  // Here we erase these multisig keys if they're zero'd out to free up space.
-+  for (auto &td : m_transfers)
-+  {
-+    auto mk_it = td.m_multisig_k.begin();
-+    while (mk_it != td.m_multisig_k.end())
-+    {
-+      if (*mk_it == rct::zero())
-+        mk_it = td.m_multisig_k.erase(mk_it);
-+      else
-+        ++mk_it;
-+    }
-+  }
-+
-+  cryptonote::block genesis;
-+  generate_genesis(genesis);
-+  crypto::hash genesis_hash = get_block_hash(genesis);
-+
-+  if (m_blockchain.empty())
-+  {
-+    m_blockchain.push_back(genesis_hash);
-+    m_last_block_reward = cryptonote::get_outs_money_amount(genesis.miner_tx);
-+  }
-+  else
-+  {
-+    check_genesis(genesis_hash);
-+  }
-+
-+  trim_hashchain();
-+
-+  if (get_num_subaddress_accounts() == 0)
-+    add_subaddress_account(tr("Primary account"));
-+
-+  try
-+  {
-+    find_and_save_rings(false);
-+  }
-+  catch (const std::exception &e)
-+  {
-+    MERROR("Failed to save rings, will try again next time");
-+  }
-+
-+  try
-+  {
-+    if (use_fs)
-+      m_message_store.read_from_file(get_multisig_wallet_state(), m_mms_file, m_load_deprecated_formats);
-+  }
-+  catch (const std::exception &e)
-+  {
-+    MERROR("Failed to initialize MMS, it will be unusable");
-+  }
-+
-+  try
-+  {
-+    if (use_fs)
-+      process_background_cache_on_open();
-+  }
-+  catch (const std::exception &e)
-+  {
-+    MERROR("Failed to process background cache on open: " << e.what());
-+  }
-+}
-+//----------------------------------------------------------------------------------------------------
-+void wallet2::load_wallet_cache(const bool use_fs, const std::string& cache_buf)
-+{
-+  boost::system::error_code e;
-   bool cache_missing = use_fs ? (!boost::filesystem::exists(m_wallet_file, e) || e) : cache_buf.empty();
-   if (cache_missing)
-   {
-@@ -6165,7 +6545,7 @@ void wallet2::load(const std::string& wallet_, const epee::wipeable_string& pass
-       THROW_WALLET_EXCEPTION_IF(!r, error::wallet_internal_error, "internal error: failed to deserialize \"" + m_wallet_file + '\"');
-       std::string cache_data;
-       cache_data.resize(cache_file_data.cache_data.size());
--      crypto::chacha20(cache_file_data.cache_data.data(), cache_file_data.cache_data.size(), m_cache_key, cache_file_data.iv, &cache_data[0]);
-+      crypto::chacha20(cache_file_data.cache_data.data(), cache_file_data.cache_data.size(), get_cache_key(), cache_file_data.iv, &cache_data[0]);
- 
-       try {
-         bool loaded = false;
-@@ -6255,60 +6635,76 @@ void wallet2::load(const std::string& wallet_, const epee::wipeable_string& pass
-       m_account_public_address.m_view_public_key  != m_account.get_keys().m_account_address.m_view_public_key,
-       error::wallet_files_doesnt_correspond, m_keys_file, m_wallet_file);
-   }
-+}
-+//----------------------------------------------------------------------------------------------------
-+void wallet2::process_background_cache_on_open()
-+{
-+  if (m_wallet_file.empty())
-+    return;
-+  if (m_background_syncing || m_is_background_wallet)
-+    return;
-+  if (m_background_sync_type == BackgroundSyncOff)
-+    return;
- 
--  if (!m_persistent_rpc_client_id)
--    set_rpc_client_secret_key(rct::rct2sk(rct::skGen()));
-+  if (m_background_sync_type == BackgroundSyncReusePassword)
-+  {
-+    const background_sync_data_t background_sync_data = m_background_sync_data;
-+    const hashchain blockchain = m_blockchain;
-+    process_background_cache(background_sync_data, blockchain, m_last_block_reward);
- 
--  // Wallets used to wipe, but not erase, old unused multisig key info, which lead to huge memory leaks.
--  // Here we erase these multisig keys if they're zero'd out to free up space.
--  for (auto &td : m_transfers)
-+    // Reset the background cache after processing
-+    reset_background_sync_data(m_background_sync_data);
-+  }
-+  else if (m_background_sync_type == BackgroundSyncCustomPassword)
-   {
--    auto mk_it = td.m_multisig_k.begin();
--    while (mk_it != td.m_multisig_k.end())
-+    // If the background wallet files don't exist, recreate them
-+    const std::string background_keys_file = make_background_keys_file_name(m_wallet_file);
-+    const std::string background_wallet_file = make_background_wallet_file_name(m_wallet_file);
-+    const bool background_keys_file_exists = boost::filesystem::exists(background_keys_file);
-+    const bool background_wallet_exists = boost::filesystem::exists(background_wallet_file);
-+
-+    THROW_WALLET_EXCEPTION_IF(!lock_background_keys_file(background_keys_file), error::background_wallet_already_open, background_wallet_file);
-+    THROW_WALLET_EXCEPTION_IF(!m_custom_background_key, error::wallet_internal_error, "Custom background key not set");
-+
-+    if (!background_keys_file_exists)
-     {
--      if (*mk_it == rct::zero())
--        mk_it = td.m_multisig_k.erase(mk_it);
--      else
--        ++mk_it;
-+      MDEBUG("Background keys file not found, restoring");
-+      store_background_keys(m_custom_background_key.get());
-     }
--  }
- 
--  cryptonote::block genesis;
--  generate_genesis(genesis);
--  crypto::hash genesis_hash = get_block_hash(genesis);
-+    if (!background_wallet_exists)
-+    {
-+      MDEBUG("Background cache not found, restoring");
-+      store_background_cache(m_custom_background_key.get(), true/*do_reset_background_sync_data*/);
-+      return;
-+    }
- 
--  if (m_blockchain.empty())
--  {
--    m_blockchain.push_back(genesis_hash);
--    m_last_block_reward = cryptonote::get_outs_money_amount(genesis.miner_tx);
--  }
--  else
--  {
--    check_genesis(genesis_hash);
--  }
-+    MDEBUG("Loading background cache");
- 
--  trim_hashchain();
-+    // Set up a minimal background wallet2 instance
-+    std::unique_ptr<wallet2> background_w2(new wallet2(m_nettype));
-+    background_w2->m_is_background_wallet = true;
-+    background_w2->m_background_syncing = true;
-+    background_w2->m_background_sync_type = m_background_sync_type;
-+    background_w2->m_custom_background_key = m_custom_background_key;
- 
--  if (get_num_subaddress_accounts() == 0)
--    add_subaddress_account(tr("Primary account"));
-+    cryptonote::account_base account = m_account;
-+    account.forget_spend_key();
-+    background_w2->m_account = account;
- 
--  try
--  {
--    find_and_save_rings(false);
--  }
--  catch (const std::exception &e)
--  {
--    MERROR("Failed to save rings, will try again next time");
--  }
--  
--  try
--  {
--    if (use_fs)
--      m_message_store.read_from_file(get_multisig_wallet_state(), m_mms_file, m_load_deprecated_formats);
-+    // Load background cache from file
-+    background_w2->clear();
-+    background_w2->prepare_file_names(background_wallet_file);
-+    background_w2->load_wallet_cache(true/*use_fs*/);
-+
-+    process_background_cache(background_w2->m_background_sync_data, background_w2->m_blockchain, background_w2->m_last_block_reward);
-+
-+    // Reset the background cache after processing
-+    store_background_cache(m_custom_background_key.get(), true/*do_reset_background_sync_data*/);
-   }
--  catch (const std::exception &e)
-+  else
-   {
--    MERROR("Failed to initialize MMS, it will be unusable");
-+    THROW_WALLET_EXCEPTION(error::wallet_internal_error, "unknown background sync type");
-   }
- }
- //----------------------------------------------------------------------------------------------------
-@@ -6390,6 +6786,8 @@ void wallet2::store_to(const std::string &path, const epee::wipeable_string &pas
-     same_file = canonical_old_path == canonical_new_path;
-   }
- 
-+  THROW_WALLET_EXCEPTION_IF(m_is_background_wallet && !same_file, error::wallet_internal_error,
-+    "Cannot save background wallet files to a different location");
- 
-   if (!same_file)
-   {
-@@ -6406,6 +6804,21 @@ void wallet2::store_to(const std::string &path, const epee::wipeable_string &pas
-       }
-     }
-   }
-+  else if (m_background_sync_type == BackgroundSyncCustomPassword && m_background_syncing && !m_is_background_wallet)
-+  {
-+    // We're background syncing, so store the wallet cache as a background cache
-+    // keeping the background sync data
-+    try
-+    {
-+      THROW_WALLET_EXCEPTION_IF(!m_custom_background_key, error::wallet_internal_error, "Custom background key not set");
-+      store_background_cache(m_custom_background_key.get(), false/*do_reset_background_sync_data*/);
-+    }
-+    catch (const std::exception &e)
-+    {
-+      MERROR("Failed to store background cache while background syncing: " << e.what());
-+    }
-+    return;
-+  }
- 
-   // get wallet cache data
-   boost::optional<wallet2::cache_file_data> cache_file_data = get_cache_file_data();
-@@ -6499,6 +6912,22 @@ void wallet2::store_to(const std::string &path, const epee::wipeable_string &pas
-     // store should only exist if the MMS is really active
-     m_message_store.write_to_file(get_multisig_wallet_state(), m_mms_file);
-   }
-+
-+  if (m_background_sync_type == BackgroundSyncCustomPassword && !m_background_syncing && !m_is_background_wallet)
-+  {
-+    // Update the background wallet cache when we store the main wallet cache
-+    // Note: if background syncing when this is called, it means the background
-+    // wallet is open and was already stored above
-+    try
-+    {
-+      THROW_WALLET_EXCEPTION_IF(!m_custom_background_key, error::wallet_internal_error, "Custom background key not set");
-+      store_background_cache(m_custom_background_key.get(), true/*do_reset_background_sync_data*/);
-+    }
-+    catch (const std::exception &e)
-+    {
-+      MERROR("Failed to update background cache: " << e.what());
-+    }
-+  }
- }
- //----------------------------------------------------------------------------------------------------
- boost::optional<wallet2::cache_file_data> wallet2::get_cache_file_data()
-@@ -6516,7 +6945,7 @@ boost::optional<wallet2::cache_file_data> wallet2::get_cache_file_data()
-     std::string cipher;
-     cipher.resize(cache_file_data.get().cache_data.size());
-     cache_file_data.get().iv = crypto::rand<crypto::chacha_iv>();
--    crypto::chacha20(cache_file_data.get().cache_data.data(), cache_file_data.get().cache_data.size(), m_cache_key, cache_file_data.get().iv, &cipher[0]);
-+    crypto::chacha20(cache_file_data.get().cache_data.data(), cache_file_data.get().cache_data.size(), get_cache_key(), cache_file_data.get().iv, &cipher[0]);
-     cache_file_data.get().cache_data = cipher;
-     return cache_file_data;
-   }
-@@ -8586,6 +9015,34 @@ bool wallet2::is_keys_file_locked() const
-   return m_keys_file_locker->locked();
- }
- 
-+bool wallet2::lock_background_keys_file(const std::string &background_keys_file)
-+{
-+  if (background_keys_file.empty() || !boost::filesystem::exists(background_keys_file))
-+    return true;
-+  if (m_background_keys_file_locker && m_background_keys_file_locker->locked())
-+    return true;
-+  m_background_keys_file_locker.reset(new tools::file_locker(background_keys_file));
-+  return m_background_keys_file_locker->locked();
-+}
-+
-+bool wallet2::unlock_background_keys_file()
-+{
-+  if (!m_background_keys_file_locker)
-+  {
-+    MDEBUG("background keys file locker is not set");
-+    return false;
-+  }
-+  m_background_keys_file_locker.reset();
-+  return true;
-+}
-+
-+bool wallet2::is_background_keys_file_locked() const
-+{
-+  if (!m_background_keys_file_locker)
-+    return false;
-+  return m_background_keys_file_locker->locked();
-+}
-+
- bool wallet2::tx_add_fake_output(std::vector<std::vector<tools::wallet2::get_outs_entry>> &outs, uint64_t global_index, const crypto::public_key& output_public_key, const rct::key& mask, uint64_t real_index, bool unlocked, std::unordered_set<crypto::public_key> &valid_public_keys_cache) const
- {
-   if (!unlocked) // don't add locked outs
-@@ -13909,6 +14366,413 @@ bool wallet2::import_key_images(signed_tx_set & signed_tx, size_t offset, bool o
-   return import_key_images(signed_tx.key_images, offset, only_selected_transfers ? boost::make_optional(selected_transfers) : boost::none);
- }
- 
-+/*
-+  In background sync mode, we use just the view key when the wallet is scanning
-+  to identify all txs where:
-+
-+    1. We received an output.
-+    2. We spent an output.
-+    3. We *may* have spent a received output but we didn't know for sure because
-+       the spend key was not loaded while background sync was enabled.
-+
-+  When the user is ready to use the spend key again, we call this function to
-+  process all those background synced transactions with the spend key loaded,
-+  so that we can properly generate key images for the transactions which we
-+  we were not able to do so for while background sync was enabled. This allows
-+  us to determine *all* receives and spends the user completed while the wallet
-+  had background sync enabled. Once this function completes, we can continue
-+  scanning from where the background sync left off.
-+
-+  Txs of type 3 (txs which we *may* have spent received output(s)) are txs where
-+  1+ rings contain an output that the user received and the wallet does not know
-+  the associated key image for that output. We don't know if the user spent in
-+  this type of tx or not. This function will generate key images for all outputs
-+  we don't know key images for, and then check if those outputs were spent in
-+  the txs of type 3.
-+
-+  By storing this type of "plausible spend tx" when scanning in background sync
-+  mode, we avoid the need to query the daemon with key images when background
-+  sync mode is disabled to see if those key images were spent. This would
-+  reveal key images to 3rd party nodes for users who don't run their own.
-+  Although this is not a perfect solution to avoid revealing key images to a 3rd
-+  party node (since tx submission trivially reveals key images to a node), it's
-+  probably better than revealing *unused* key images to a 3rd party node, which
-+  would enable the 3rd party to deduce that a tx is spending an output at least
-+  X old when the key image is included in the chain.
-+*/
-+void wallet2::process_background_cache(const background_sync_data_t &background_sync_data, const hashchain &background_synced_chain, uint64_t last_block_reward)
-+{
-+  // We expect the spend key to be in a decrypted state while
-+  // m_processing_background_cache is true
-+  m_processing_background_cache = true;
-+  auto done_processing = epee::misc_utils::create_scope_leave_handler([&, this]() {
-+    m_processing_background_cache = false;
-+  });
-+
-+  if (m_background_syncing || m_multisig || m_watch_only || key_on_device())
-+    return;
-+
-+  if (!background_sync_data.first_refresh_done)
-+  {
-+    MDEBUG("Skipping processing background cache, background cache has not synced yet");
-+    return;
-+  }
-+
-+  // Skip processing if wallet cache is synced higher than background cache
-+  const uint64_t current_height = m_blockchain.size();
-+  const uint64_t background_height = background_synced_chain.size();
-+  MDEBUG("Background cache height " << background_height << " , wallet height " << current_height);
-+  if (current_height > background_height)
-+  {
-+    MWARNING("Skipping processing background cache, synced height is higher than background cache");
-+    return;
-+  }
-+
-+  if (m_refresh_from_block_height  < background_sync_data.wallet_refresh_from_block_height ||
-+      m_subaddress_lookahead_major > background_sync_data.subaddress_lookahead_major ||
-+      m_subaddress_lookahead_minor > background_sync_data.subaddress_lookahead_minor ||
-+      m_refresh_type               < background_sync_data.wallet_refresh_type)
-+  {
-+    MWARNING("Skipping processing background cache, background wallet sync settings did not match main wallet's");
-+    MDEBUG("Wallet settings: " <<
-+      ", m_refresh_from_block_height: "  << m_refresh_from_block_height  << " vs " << background_sync_data.wallet_refresh_from_block_height <<
-+      ", m_subaddress_lookahead_major: " << m_subaddress_lookahead_major << " vs " << background_sync_data.subaddress_lookahead_major <<
-+      ", m_subaddress_lookahead_minor: " << m_subaddress_lookahead_minor << " vs " << background_sync_data.subaddress_lookahead_minor <<
-+      ", m_refresh_type: "               << m_refresh_type               << " vs " << background_sync_data.wallet_refresh_type);
-+    return;
-+  }
-+
-+  // Sort background synced txs in the order they appeared in the cache so that
-+  // we process them in the order they appeared in the chain. Thus if tx2 spends
-+  // from tx1, we will know because tx1 is processed before tx2.
-+  std::vector<std::pair<crypto::hash, background_synced_tx_t>> sorted_bgs_cache(background_sync_data.txs.begin(), background_sync_data.txs.end());
-+  std::sort(sorted_bgs_cache.begin(), sorted_bgs_cache.end(),
-+    [](const std::pair<crypto::hash, background_synced_tx_t>& l, const std::pair<crypto::hash, background_synced_tx_t>& r)
-+      {
-+        uint64_t left_index = l.second.index_in_background_sync_data;
-+        uint64_t right_index = r.second.index_in_background_sync_data;
-+        THROW_WALLET_EXCEPTION_IF(
-+            (left_index < right_index && l.second.height > r.second.height) ||
-+            (left_index > right_index && l.second.height < r.second.height),
-+            error::wallet_internal_error, "Unexpected background sync data order");
-+        return left_index < right_index;
-+      });
-+
-+  // All txs in the background cache should have height >= sync start height,
-+  // but not fatal if not
-+  if (!sorted_bgs_cache.empty() && sorted_bgs_cache[0].second.height < background_sync_data.start_height)
-+    MWARNING("First tx in background cache has height (" << sorted_bgs_cache[0].second.height << ") lower than sync start height (" << background_sync_data.start_height << ")");
-+
-+  // We want to process all background synced txs in order to make sure
-+  // the wallet state updates correctly. First we remove all txs from the wallet
-+  // from before the background sync start height, then re-process them in
-+  // chronological order. The background cache should contain a superset of
-+  // *all* the wallet's txs from after the background sync start height.
-+  MDEBUG("Processing " << background_sync_data.txs.size() << " background synced txs starting from height " << background_sync_data.start_height);
-+  detached_blockchain_data dbd = detach_blockchain(background_sync_data.start_height);
-+
-+  for (const auto &bgs_tx : sorted_bgs_cache)
-+  {
-+    MDEBUG("Processing background synced tx " << bgs_tx.first);
-+
-+    process_new_transaction(bgs_tx.first, bgs_tx.second.tx, bgs_tx.second.output_indices, bgs_tx.second.height, 0, bgs_tx.second.block_timestamp,
-+        cryptonote::is_coinbase(bgs_tx.second.tx), false/*pool*/, bgs_tx.second.double_spend_seen, {}, {}, true/*ignore_callbacks*/);
-+
-+    // Re-set destination addresses if they were previously set
-+    if (m_confirmed_txs.find(bgs_tx.first) != m_confirmed_txs.end() &&
-+        dbd.detached_confirmed_txs_dests.find(bgs_tx.first) != dbd.detached_confirmed_txs_dests.end())
-+    {
-+      m_confirmed_txs[bgs_tx.first].m_dests = std::move(dbd.detached_confirmed_txs_dests[bgs_tx.first]);
-+    }
-+  }
-+
-+  m_blockchain = background_synced_chain;
-+  m_last_block_reward = last_block_reward;
-+
-+  MDEBUG("Finished processing background sync data");
-+}
-+//----------------------------------------------------------------------------------------------------
-+void wallet2::reset_background_sync_data(background_sync_data_t &background_sync_data)
-+{
-+  background_sync_data.first_refresh_done = false;
-+  background_sync_data.start_height = get_blockchain_current_height();
-+  background_sync_data.txs.clear();
-+
-+  background_sync_data.wallet_refresh_from_block_height = m_refresh_from_block_height;
-+  background_sync_data.subaddress_lookahead_major = m_subaddress_lookahead_major;
-+  background_sync_data.subaddress_lookahead_minor = m_subaddress_lookahead_minor;
-+  background_sync_data.wallet_refresh_type = m_refresh_type;
-+}
-+//----------------------------------------------------------------------------------------------------
-+void wallet2::store_background_cache(const crypto::chacha_key &custom_background_key, const bool do_reset_background_sync_data)
-+{
-+  MDEBUG("Storing background cache (do_reset_background_sync_data=" << do_reset_background_sync_data << ")");
-+
-+  THROW_WALLET_EXCEPTION_IF(m_background_sync_type != BackgroundSyncCustomPassword, error::wallet_internal_error,
-+      "Can only write a background cache when using a custom background password");
-+  THROW_WALLET_EXCEPTION_IF(m_wallet_file.empty(), error::wallet_internal_error,
-+      "No wallet file known, can't store background cache");
-+
-+  std::unique_ptr<wallet2> background_w2(new wallet2(m_nettype));
-+  background_w2->prepare_file_names(make_background_wallet_file_name(m_wallet_file));
-+
-+  // Make sure background wallet is opened by this wallet
-+  THROW_WALLET_EXCEPTION_IF(!lock_background_keys_file(background_w2->m_keys_file),
-+      error::background_wallet_already_open, background_w2->m_wallet_file);
-+
-+  // Load a background wallet2 instance using this wallet2 instance
-+  std::string this_wallet2;
-+  bool r = ::serialization::dump_binary(*this, this_wallet2);
-+  THROW_WALLET_EXCEPTION_IF(!r, error::wallet_internal_error, "Failed to serialize wallet cache");
-+
-+  background_w2->clear();
-+  r = ::serialization::parse_binary(this_wallet2, *background_w2);
-+  THROW_WALLET_EXCEPTION_IF(!r, error::wallet_internal_error, "Failed to deserialize wallet cache");
-+
-+  // Clear sensitive data from background cache not needed to sync
-+  background_w2->clear_user_data();
-+
-+  background_w2->m_is_background_wallet = true;
-+  if (do_reset_background_sync_data)
-+    reset_background_sync_data(background_w2->m_background_sync_data);
-+  else
-+    background_w2->m_background_sync_data = m_background_sync_data;
-+  background_w2->m_background_syncing = true;
-+
-+  background_w2->m_custom_background_key = boost::optional<crypto::chacha_key>(custom_background_key);
-+  background_w2->m_background_sync_type = m_background_sync_type;
-+  background_w2->store();
-+
-+  MDEBUG("Background cache stored (" << background_w2->m_transfers.size() << " transfers, " << background_w2->m_background_sync_data.txs.size() << " background synced txs)");
-+}
-+//----------------------------------------------------------------------------------------------------
-+void wallet2::store_background_keys(const crypto::chacha_key &custom_background_key)
-+{
-+  MDEBUG("Storing background keys");
-+
-+  THROW_WALLET_EXCEPTION_IF(m_wallet_file.empty(), error::wallet_internal_error,
-+      "No wallet file known, can't store background keys");
-+
-+  const std::string background_keys_file = make_background_keys_file_name(m_wallet_file);
-+  bool r = store_keys(background_keys_file, custom_background_key, false/*watch_only*/, true/*background_keys_file*/);
-+  THROW_WALLET_EXCEPTION_IF(!r, error::file_save_error, background_keys_file);
-+  THROW_WALLET_EXCEPTION_IF(!is_background_keys_file_locked(), error::wallet_internal_error, background_keys_file + "\" should be locked");
-+
-+  // GUI uses the address file to differentiate non-mainnet wallets in the UI
-+  const std::string background_address_file = make_background_wallet_file_name(m_wallet_file) + ".address.txt";
-+  if (m_nettype != MAINNET && !boost::filesystem::exists(background_address_file))
-+  {
-+    r = save_to_file(background_address_file, m_account.get_public_address_str(m_nettype), true);
-+    if (!r) MERROR("String with address text not saved");
-+  }
-+
-+  MDEBUG("Background keys stored");
-+}
-+//----------------------------------------------------------------------------------------------------
-+void wallet2::write_background_sync_wallet(const epee::wipeable_string &wallet_password, const epee::wipeable_string &background_cache_password)
-+{
-+  MDEBUG("Storing background sync wallet");
-+  THROW_WALLET_EXCEPTION_IF(m_background_sync_type != BackgroundSyncCustomPassword, error::wallet_internal_error,
-+      "Can only write a background sync wallet when using a custom background password");
-+  THROW_WALLET_EXCEPTION_IF(m_background_syncing || m_is_background_wallet, error::wallet_internal_error,
-+      "Can't write background sync wallet from an existing background cache");
-+  THROW_WALLET_EXCEPTION_IF(wallet_password == background_cache_password,
-+      error::background_custom_password_same_as_wallet_password);
-+
-+  // Set the background encryption key
-+  crypto::chacha_key custom_background_key;
-+  get_custom_background_key(background_cache_password, custom_background_key, m_kdf_rounds);
-+
-+  // Keep the background encryption key in memory so the main wallet can update
-+  // the background cache when it stores the main wallet cache
-+  m_custom_background_key = boost::optional<crypto::chacha_key>(custom_background_key);
-+
-+  if (m_wallet_file.empty() || m_keys_file.empty())
-+    return;
-+
-+  // Save background keys file, then background cache, then update main wallet settings
-+  store_background_keys(custom_background_key);
-+  store_background_cache(custom_background_key, true/*do_reset_background_sync_data*/);
-+  bool r = store_keys(m_keys_file, wallet_password, false/*watch_only*/);
-+  THROW_WALLET_EXCEPTION_IF(!r, error::file_save_error, m_keys_file);
-+
-+  MDEBUG("Background sync wallet saved successfully");
-+}
-+//----------------------------------------------------------------------------------------------------
-+void wallet2::setup_background_sync(BackgroundSyncType background_sync_type, const epee::wipeable_string &wallet_password, const boost::optional<epee::wipeable_string> &background_cache_password)
-+{
-+  MDEBUG("Setting background sync to type " << background_sync_type);
-+  THROW_WALLET_EXCEPTION_IF(m_background_syncing || m_is_background_wallet, error::wallet_internal_error,
-+      "Can't set background sync type from an existing background cache");
-+  verify_password_with_cached_key(wallet_password);
-+
-+  if (background_sync_type != BackgroundSyncOff)
-+    validate_background_cache_password_usage(background_sync_type, background_cache_password, m_multisig, m_watch_only, key_on_device());
-+
-+  THROW_WALLET_EXCEPTION_IF(background_sync_type == BackgroundSyncCustomPassword && wallet_password == background_cache_password,
-+      error::background_custom_password_same_as_wallet_password);
-+
-+  if (m_background_sync_type == background_sync_type && background_sync_type != BackgroundSyncCustomPassword)
-+    return; // No need to make any changes
-+
-+  if (!m_wallet_file.empty())
-+  {
-+    // Delete existing background files if they already exist
-+    const std::string old_background_wallet_file = make_background_wallet_file_name(m_wallet_file);
-+    const std::string old_background_keys_file = make_background_keys_file_name(m_wallet_file);
-+    const std::string old_background_address_file = old_background_wallet_file + ".address.txt";
-+
-+    // Make sure no other program is using the background wallet
-+    THROW_WALLET_EXCEPTION_IF(!lock_background_keys_file(old_background_keys_file),
-+        error::background_wallet_already_open, old_background_wallet_file);
-+
-+    if (boost::filesystem::exists(old_background_wallet_file))
-+      if (!boost::filesystem::remove(old_background_wallet_file))
-+        LOG_ERROR("Error deleting background wallet file: " << old_background_wallet_file);
-+
-+    if (boost::filesystem::exists(old_background_keys_file))
-+      if (!boost::filesystem::remove(old_background_keys_file))
-+        LOG_ERROR("Error deleting background keys file: " << old_background_keys_file);
-+
-+    if (boost::filesystem::exists(old_background_address_file))
-+      if (!boost::filesystem::remove(old_background_address_file))
-+        LOG_ERROR("Error deleting background address file: " << old_background_address_file);
-+  }
-+
-+  m_background_sync_type = background_sync_type;
-+  m_custom_background_key = boost::none;
-+
-+  // Write the new files
-+  switch (background_sync_type)
-+  {
-+    case BackgroundSyncOff:
-+    case BackgroundSyncReusePassword: rewrite(m_wallet_file, wallet_password); break;
-+    case BackgroundSyncCustomPassword: write_background_sync_wallet(wallet_password, background_cache_password.get()); break;
-+    default: THROW_WALLET_EXCEPTION(error::wallet_internal_error, "unknown background sync type");
-+  }
-+
-+  MDEBUG("Done setting background sync type");
-+}
-+//----------------------------------------------------------------------------------------------------
-+/*
-+  When background syncing, the wallet scans using just the view key, without
-+  keeping the spend key in decrypted state. When a user returns to the wallet
-+  and decrypts the spend key, the wallet processes the background synced txs,
-+  then the wallet picks up scanning normally right where the background sync
-+  left off.
-+*/
-+void wallet2::start_background_sync()
-+{
-+  THROW_WALLET_EXCEPTION_IF(m_background_sync_type == BackgroundSyncOff, error::wallet_internal_error,
-+      "must setup background sync first before using background sync");
-+  THROW_WALLET_EXCEPTION_IF(m_is_background_wallet, error::wallet_internal_error,
-+      "Can't start background syncing from a background wallet (it is always background syncing)");
-+
-+  MDEBUG("Starting background sync");
-+
-+  if (m_background_syncing)
-+  {
-+    MDEBUG("Already background syncing");
-+    return;
-+  }
-+
-+  if (m_background_sync_type == BackgroundSyncCustomPassword && !m_wallet_file.empty())
-+  {
-+    // Save the current state of the wallet cache. Only necessary when using a
-+    // custom background password which uses distinct background wallet to sync.
-+    // When reusing wallet password to sync we reuse the main wallet cache.
-+    store();
-+
-+    // Wipe user data from the background wallet cache not needed to sync.
-+    // Only wipe user data from background cache if wallet cache is stored
-+    // on disk; otherwise we could lose the data.
-+    clear_user_data();
-+
-+    // Wipe m_cache_key since it can be used to decrypt main wallet cache
-+    m_cache_key.scrub();
-+  }
-+
-+  reset_background_sync_data(m_background_sync_data);
-+  m_background_syncing = true;
-+
-+  // Wipe the spend key from memory
-+  m_account.forget_spend_key();
-+
-+  MDEBUG("Background sync started at height " << m_background_sync_data.start_height);
-+}
-+//----------------------------------------------------------------------------------------------------
-+void wallet2::stop_background_sync(const epee::wipeable_string &wallet_password, const crypto::secret_key &spend_secret_key)
-+{
-+  MDEBUG("Stopping background sync");
-+
-+  // Verify provided password and spend secret key. If no spend secret key is
-+  // provided, recover it from the wallet keys file
-+  crypto::secret_key recovered_spend_key = crypto::null_skey;
-+  if (!m_wallet_file.empty())
-+  {
-+    THROW_WALLET_EXCEPTION_IF(!verify_password(wallet_password, recovered_spend_key), error::invalid_password);
-+  }
-+  else
-+  {
-+    verify_password_with_cached_key(wallet_password);
-+  }
-+
-+  if (spend_secret_key != crypto::null_skey)
-+  {
-+    THROW_WALLET_EXCEPTION_IF(!m_wallet_file.empty() && spend_secret_key != recovered_spend_key,
-+        error::invalid_spend_key);
-+    MDEBUG("Setting spend secret key with the provided key");
-+    recovered_spend_key = spend_secret_key;
-+  }
-+
-+  // Verify private spend key derives to wallet's public spend key
-+  const auto verify_spend_key = [this](crypto::secret_key &recovered_spend_key) -> bool
-+  {
-+    crypto::public_key spend_public_key;
-+    return recovered_spend_key != crypto::null_skey &&
-+        crypto::secret_key_to_public_key(recovered_spend_key, spend_public_key) &&
-+        m_account.get_keys().m_account_address.m_spend_public_key == spend_public_key;
-+  };
-+  THROW_WALLET_EXCEPTION_IF(!verify_spend_key(recovered_spend_key), error::invalid_spend_key);
-+
-+  THROW_WALLET_EXCEPTION_IF(m_background_sync_type == BackgroundSyncOff, error::wallet_internal_error,
-+      "must setup background sync first before using background sync");
-+  THROW_WALLET_EXCEPTION_IF(m_is_background_wallet, error::wallet_internal_error,
-+      "Can't stop background syncing from a background wallet");
-+
-+  if (!m_background_syncing)
-+    return;
-+
-+  // Copy background cache, we're about to overwrite it
-+  const background_sync_data_t background_sync_data = m_background_sync_data;
-+  const hashchain background_synced_chain = m_blockchain;
-+  const uint64_t last_block_reward = m_last_block_reward;
-+
-+  if (m_background_sync_type == BackgroundSyncCustomPassword && !m_wallet_file.empty())
-+  {
-+    // Reload the wallet from disk
-+    load(m_wallet_file, wallet_password);
-+    THROW_WALLET_EXCEPTION_IF(!verify_spend_key(recovered_spend_key), error::invalid_spend_key);
-+  }
-+  m_background_syncing = false;
-+
-+  // Set the plaintext spend key
-+  m_account.set_spend_key(recovered_spend_key);
-+
-+  // Encrypt the spend key when done if needed
-+  epee::misc_utils::auto_scope_leave_caller keys_reencryptor;
-+  if (m_ask_password == AskPasswordToDecrypt && !m_unattended && !m_watch_only)
-+    keys_reencryptor = epee::misc_utils::create_scope_leave_handler([&, this]{encrypt_keys(wallet_password);});
-+
-+  // Now we can use the decrypted spend key to process background cache
-+  process_background_cache(background_sync_data, background_synced_chain, last_block_reward);
-+
-+  // Reset the background cache after processing
-+  reset_background_sync_data(m_background_sync_data);
-+
-+  MDEBUG("Background sync stopped");
-+}
-+//----------------------------------------------------------------------------------------------------
- wallet2::payment_container wallet2::export_payments() const
- {
-   payment_container payments;
-diff --git a/src/wallet/wallet2.h b/src/wallet/wallet2.h
-index b620ea265..632298726 100644
---- a/src/wallet/wallet2.h
-+++ b/src/wallet/wallet2.h
-@@ -256,6 +256,20 @@ private:
-       BackgroundMiningNo = 2,
-     };
- 
-+    enum BackgroundSyncType {
-+      BackgroundSyncOff = 0,
-+      BackgroundSyncReusePassword = 1,
-+      BackgroundSyncCustomPassword = 2,
-+    };
-+
-+    static BackgroundSyncType background_sync_type_from_str(const std::string &background_sync_type_str)
-+    {
-+      if (background_sync_type_str == "off") return BackgroundSyncOff;
-+      if (background_sync_type_str == "reuse-wallet-password") return BackgroundSyncReusePassword;
-+      if (background_sync_type_str == "custom-background-password") return BackgroundSyncCustomPassword;
-+      throw std::logic_error("Unknown background sync type");
-+    };
-+
-     enum ExportFormat {
-       Binary = 0,
-       Ascii,
-@@ -282,7 +296,12 @@ private:
-     //! Just parses variables.
-     static std::unique_ptr<wallet2> make_dummy(const boost::program_options::variables_map& vm, bool unattended, const std::function<boost::optional<password_container>(const char *, bool)> &password_prompter);
- 
--    static bool verify_password(const std::string& keys_file_name, const epee::wipeable_string& password, bool no_spend_key, hw::device &hwdev, uint64_t kdf_rounds);
-+    static bool verify_password(const std::string& keys_file_name, const epee::wipeable_string& password, bool no_spend_key, hw::device &hwdev, uint64_t kdf_rounds)
-+    {
-+      crypto::secret_key spend_key = crypto::null_skey;
-+      return verify_password(keys_file_name, password, no_spend_key, hwdev, kdf_rounds, spend_key);
-+    };
-+    static bool verify_password(const std::string& keys_file_name, const epee::wipeable_string& password, bool no_spend_key, hw::device &hwdev, uint64_t kdf_rounds, crypto::secret_key &spend_key_out);
-     static bool query_device(hw::device::device_type& device_type, const std::string& keys_file_name, const epee::wipeable_string& password, uint64_t kdf_rounds = 1);
- 
-     wallet2(cryptonote::network_type nettype = cryptonote::MAINNET, uint64_t kdf_rounds = 1, bool unattended = false, std::unique_ptr<epee::net_utils::http::http_client_factory> http_client_factory = std::unique_ptr<epee::net_utils::http::http_client_factory>(new net::http::client_factory()));
-@@ -792,6 +811,54 @@ private:
-       END_SERIALIZE()
-     };
- 
-+    struct background_synced_tx_t
-+    {
-+      uint64_t index_in_background_sync_data;
-+      cryptonote::transaction tx;
-+      std::vector<uint64_t> output_indices;
-+      uint64_t height;
-+      uint64_t block_timestamp;
-+      bool double_spend_seen;
-+
-+      BEGIN_SERIALIZE_OBJECT()
-+        VERSION_FIELD(0)
-+        VARINT_FIELD(index_in_background_sync_data)
-+
-+        // prune tx; don't need to keep signature data
-+        if (!tx.serialize_base(ar))
-+          return false;
-+
-+        FIELD(output_indices)
-+        VARINT_FIELD(height)
-+        VARINT_FIELD(block_timestamp)
-+        FIELD(double_spend_seen)
-+      END_SERIALIZE()
-+    };
-+
-+    struct background_sync_data_t
-+    {
-+      bool first_refresh_done = false;
-+      uint64_t start_height = 0;
-+      serializable_unordered_map<crypto::hash, background_synced_tx_t> txs;
-+
-+      // Relevant wallet settings
-+      uint64_t wallet_refresh_from_block_height;
-+      size_t subaddress_lookahead_major;
-+      size_t subaddress_lookahead_minor;
-+      RefreshType wallet_refresh_type;
-+
-+      BEGIN_SERIALIZE_OBJECT()
-+        VERSION_FIELD(0)
-+        FIELD(first_refresh_done)
-+        FIELD(start_height)
-+        FIELD(txs)
-+        FIELD(wallet_refresh_from_block_height)
-+        VARINT_FIELD(subaddress_lookahead_major)
-+        VARINT_FIELD(subaddress_lookahead_minor)
-+        VARINT_FIELD(wallet_refresh_type)
-+      END_SERIALIZE()
-+    };
-+
-     typedef std::tuple<uint64_t, crypto::public_key, rct::key> get_outs_entry;
- 
-     struct parsed_block
-@@ -980,7 +1047,8 @@ private:
-     /*!
-      * \brief verifies given password is correct for default wallet keys file
-      */
--    bool verify_password(const epee::wipeable_string& password);
-+    bool verify_password(const epee::wipeable_string& password) {crypto::secret_key key = crypto::null_skey; return verify_password(password, key);};
-+    bool verify_password(const epee::wipeable_string& password, crypto::secret_key &spend_key_out);
-     cryptonote::account_base& get_account(){return m_account;}
-     const cryptonote::account_base& get_account()const{return m_account;}
- 
-@@ -1076,6 +1144,7 @@ private:
-     cryptonote::network_type nettype() const { return m_nettype; }
-     bool watch_only() const { return m_watch_only; }
-     bool multisig(bool *ready = NULL, uint32_t *threshold = NULL, uint32_t *total = NULL) const;
-+    bool is_background_wallet() const { return m_is_background_wallet; }
-     bool has_multisig_partial_key_images() const;
-     bool has_unknown_key_images() const;
-     bool get_multisig_seed(epee::wipeable_string& seed, const epee::wipeable_string &passphrase = std::string()) const;
-@@ -1283,11 +1352,17 @@ private:
-         return;
-       }
-       a & m_has_ever_refreshed_from_node;
-+      if(ver < 31)
-+      {
-+        m_background_sync_data = background_sync_data_t{};
-+        return;
-+      }
-+      a & m_background_sync_data;
-     }
- 
-     BEGIN_SERIALIZE_OBJECT()
-       MAGIC_FIELD("wownero wallet cache")
--      VERSION_FIELD(1)
-+      VERSION_FIELD(2)
-       FIELD(m_blockchain)
-       FIELD(m_transfers)
-       FIELD(m_account_public_address)
-@@ -1319,6 +1394,12 @@ private:
-         return true;
-       }
-       FIELD(m_has_ever_refreshed_from_node)
-+      if (version < 2)
-+      {
-+        m_background_sync_data = background_sync_data_t{};
-+        return true;
-+      }
-+      FIELD(m_background_sync_data)
-     END_SERIALIZE()
- 
-     /*!
-@@ -1334,6 +1415,8 @@ private:
-      * \return                Whether path is valid format
-      */
-     static bool wallet_valid_path_format(const std::string& file_path);
-+    static std::string make_background_wallet_file_name(const std::string &wallet_file);
-+    static std::string make_background_keys_file_name(const std::string &wallet_file);
-     static bool parse_long_payment_id(const std::string& payment_id_str, crypto::hash& payment_id);
-     static bool parse_short_payment_id(const std::string& payment_id_str, crypto::hash8& payment_id);
-     static bool parse_payment_id(const std::string& payment_id_str, crypto::hash& payment_id);
-@@ -1382,6 +1465,9 @@ private:
-     void ignore_outputs_below(uint64_t value) { m_ignore_outputs_below = value; }
-     bool track_uses() const { return m_track_uses; }
-     void track_uses(bool value) { m_track_uses = value; }
-+    BackgroundSyncType background_sync_type() const { return m_background_sync_type; }
-+    void setup_background_sync(BackgroundSyncType background_sync_type, const epee::wipeable_string &wallet_password, const boost::optional<epee::wipeable_string> &background_cache_password);
-+    bool is_background_syncing() const { return m_background_syncing; }
-     bool show_wallet_name_when_locked() const { return m_show_wallet_name_when_locked; }
-     void show_wallet_name_when_locked(bool value) { m_show_wallet_name_when_locked = value; }
-     BackgroundMiningSetupType setup_background_mining() const { return m_setup_background_mining; }
-@@ -1696,6 +1782,9 @@ private:
-     uint64_t get_bytes_sent() const;
-     uint64_t get_bytes_received() const;
- 
-+    void start_background_sync();
-+    void stop_background_sync(const epee::wipeable_string &wallet_password, const crypto::secret_key &spend_secret_key = crypto::null_skey);
-+
-     // MMS -------------------------------------------------------------------------------------------------
-     mms::message_store& get_message_store() { return m_message_store; };
-     const mms::message_store& get_message_store() const { return m_message_store; };
-@@ -1731,6 +1820,9 @@ private:
-      * \return                Whether it was successful.
-      */
-     bool store_keys(const std::string& keys_file_name, const epee::wipeable_string& password, bool watch_only = false);
-+    bool store_keys(const std::string& keys_file_name, const crypto::chacha_key& key, bool watch_only = false, bool background_keys_file = false);
-+    boost::optional<wallet2::keys_file_data> get_keys_file_data(const crypto::chacha_key& key, bool watch_only = false, bool background_keys_file = false);
-+    bool store_keys_file_data(const std::string& keys_file_name, wallet2::keys_file_data &keys_file_data, bool background_keys_file = false);
-     /*!
-      * \brief Load wallet keys information from wallet file.
-      * \param keys_file_name Name of wallet file
-@@ -1744,6 +1836,7 @@ private:
-      */
-     bool load_keys_buf(const std::string& keys_buf, const epee::wipeable_string& password);
-     bool load_keys_buf(const std::string& keys_buf, const epee::wipeable_string& password, boost::optional<crypto::chacha_key>& keys_to_encrypt);
-+    void load_wallet_cache(const bool use_fs, const std::string& cache_buf = "");
-     void process_new_transaction(const crypto::hash &txid, const cryptonote::transaction& tx, const std::vector<uint64_t> &o_indices, uint64_t height, uint8_t block_version, uint64_t ts, bool miner_tx, bool pool, bool double_spend_seen, const tx_cache_data &tx_cache_data, std::map<std::pair<uint64_t, uint64_t>, size_t> *output_tracker_cache = NULL, bool ignore_callbacks = false);
-     bool should_skip_block(const cryptonote::block &b, uint64_t height) const;
-     void process_new_blockchain_entry(const cryptonote::block& b, const cryptonote::block_complete_entry& bche, const parsed_block &parsed_block, const crypto::hash& bl_id, uint64_t height, const std::vector<tx_cache_data> &tx_cache_data, size_t tx_cache_data_offset, std::map<std::pair<uint64_t, uint64_t>, size_t> *output_tracker_cache = NULL);
-@@ -1752,6 +1845,15 @@ private:
-     void get_short_chain_history(std::list<crypto::hash>& ids, uint64_t granularity = 1) const;
-     bool clear();
-     void clear_soft(bool keep_key_images=false);
-+    /*
-+     * clear_user_data clears data created by the user, which is mostly data
-+     * that a view key cannot identify on chain. This function was initially
-+     * added to ensure that a "background" wallet (a wallet that syncs with just
-+     * a view key hot in memory) does not have any sensitive data loaded that it
-+     * does not need in order to sync. Future devs should take care to ensure
-+     * that this function deletes data that is not useful for background syncing
-+     */
-+    void clear_user_data();
-     void pull_blocks(bool first, bool try_incremental, uint64_t start_height, uint64_t& blocks_start_height, const std::list<crypto::hash> &short_chain_history, std::vector<cryptonote::block_complete_entry> &blocks, std::vector<cryptonote::COMMAND_RPC_GET_BLOCKS_FAST::block_output_indices> &o_indices, uint64_t &current_height);
-     void pull_hashes(uint64_t start_height, uint64_t& blocks_start_height, const std::list<crypto::hash> &short_chain_history, std::vector<crypto::hash> &hashes);
-     void fast_refresh(uint64_t stop_height, uint64_t &blocks_start_height, std::list<crypto::hash> &short_chain_history, bool force = false);
-@@ -1803,10 +1905,23 @@ private:
-     bool get_ring(const crypto::chacha_key &key, const crypto::key_image &key_image, std::vector<uint64_t> &outs);
-     crypto::chacha_key get_ringdb_key();
-     void setup_keys(const epee::wipeable_string &password);
-+    const crypto::chacha_key get_cache_key();
-+    void verify_password_with_cached_key(const epee::wipeable_string &password);
-+    void verify_password_with_cached_key(const crypto::chacha_key &key);
-     size_t get_transfer_details(const crypto::key_image &ki) const;
-     tx_entry_data get_tx_entries(const std::unordered_set<crypto::hash> &txids);
-     void sort_scan_tx_entries(std::vector<process_tx_entry_t> &unsorted_tx_entries);
-     void process_scan_txs(const tx_entry_data &txs_to_scan, const tx_entry_data &txs_to_reprocess, const std::unordered_set<crypto::hash> &tx_hashes_to_reprocess, detached_blockchain_data &dbd);
-+    void write_background_sync_wallet(const epee::wipeable_string &wallet_password, const epee::wipeable_string &background_cache_password);
-+    void process_background_cache_on_open();
-+    void process_background_cache(const background_sync_data_t &background_sync_data, const hashchain &background_chain, uint64_t last_block_reward);
-+    void reset_background_sync_data(background_sync_data_t &background_sync_data);
-+    void store_background_cache(const crypto::chacha_key &custom_background_key, const bool do_reset_background_sync_data = true);
-+    void store_background_keys(const crypto::chacha_key &custom_background_key);
-+
-+    bool lock_background_keys_file(const std::string &background_keys_file);
-+    bool unlock_background_keys_file();
-+    bool is_background_keys_file_locked() const;
- 
-     void register_devices();
-     hw::device& lookup_device(const std::string & device_descriptor);
-@@ -1922,6 +2037,8 @@ private:
-     uint64_t m_ignore_outputs_above;
-     uint64_t m_ignore_outputs_below;
-     bool m_track_uses;
-+    bool m_is_background_wallet;
-+    BackgroundSyncType m_background_sync_type;
-     bool m_show_wallet_name_when_locked;
-     uint32_t m_inactivity_lock_timeout;
-     BackgroundMiningSetupType m_setup_background_mining;
-@@ -1967,6 +2084,7 @@ private:
- 
-     uint64_t m_last_block_reward;
-     std::unique_ptr<tools::file_locker> m_keys_file_locker;
-+    std::unique_ptr<tools::file_locker> m_background_keys_file_locker;
-     
-     mms::message_store m_message_store;
-     bool m_original_keys_available;
-@@ -1974,6 +2092,7 @@ private:
-     crypto::secret_key m_original_view_secret_key;
- 
-     crypto::chacha_key m_cache_key;
-+    boost::optional<crypto::chacha_key> m_custom_background_key = boost::none;
-     std::shared_ptr<wallet_keys_unlocker> m_encrypt_keys_after_refresh;
- 
-     bool m_unattended;
-@@ -1989,9 +2108,13 @@ private:
- 
-     static boost::mutex default_daemon_address_lock;
-     static std::string default_daemon_address;
-+
-+    bool m_background_syncing;
-+    bool m_processing_background_cache;
-+    background_sync_data_t m_background_sync_data;
-   };
- }
--BOOST_CLASS_VERSION(tools::wallet2, 30)
-+BOOST_CLASS_VERSION(tools::wallet2, 31)
- BOOST_CLASS_VERSION(tools::wallet2::transfer_details, 12)
- BOOST_CLASS_VERSION(tools::wallet2::multisig_info, 1)
- BOOST_CLASS_VERSION(tools::wallet2::multisig_info::LR, 0)
-@@ -2007,6 +2130,8 @@ BOOST_CLASS_VERSION(tools::wallet2::signed_tx_set, 1)
- BOOST_CLASS_VERSION(tools::wallet2::tx_construction_data, 4)
- BOOST_CLASS_VERSION(tools::wallet2::pending_tx, 3)
- BOOST_CLASS_VERSION(tools::wallet2::multisig_sig, 1)
-+BOOST_CLASS_VERSION(tools::wallet2::background_synced_tx_t, 0)
-+BOOST_CLASS_VERSION(tools::wallet2::background_sync_data_t, 0)
- 
- namespace boost
- {
-@@ -2505,6 +2630,29 @@ namespace boost
-         return;
-       a & x.multisig_sigs;
-     }
-+
-+    template <class Archive>
-+    inline void serialize(Archive& a, tools::wallet2::background_synced_tx_t &x, const boost::serialization::version_type ver)
-+    {
-+      a & x.index_in_background_sync_data;
-+      a & x.tx;
-+      a & x.output_indices;
-+      a & x.height;
-+      a & x.block_timestamp;
-+      a & x.double_spend_seen;
-+    }
-+
-+    template <class Archive>
-+    inline void serialize(Archive& a, tools::wallet2::background_sync_data_t &x, const boost::serialization::version_type ver)
-+    {
-+      a & x.first_refresh_done;
-+      a & x.start_height;
-+      a & x.txs.parent();
-+      a & x.wallet_refresh_from_block_height;
-+      a & x.subaddress_lookahead_major;
-+      a & x.subaddress_lookahead_minor;
-+      a & x.wallet_refresh_type;
-+    }
-   }
- }
- 
-diff --git a/src/wallet/wallet_errors.h b/src/wallet/wallet_errors.h
-index c077313d4..c54cd3499 100644
---- a/src/wallet/wallet_errors.h
-+++ b/src/wallet/wallet_errors.h
-@@ -63,6 +63,7 @@ namespace tools
-     //       invalid_password
-     //       invalid_priority
-     //       invalid_multisig_seed
-+    //       invalid_spend_key
-     //       refresh_error *
-     //         acc_outs_lookup_error
-     //         block_parse_error
-@@ -97,6 +98,9 @@ namespace tools
-     //       wallet_files_doesnt_correspond
-     //       scan_tx_error *
-     //         wont_reprocess_recent_txs_via_untrusted_daemon
-+    //       background_sync_error *
-+    //         background_wallet_already_open
-+    //         background_custom_password_same_as_wallet_password
-     //
-     // * - class with protected ctor
- 
-@@ -304,6 +308,16 @@ namespace tools
-       std::string to_string() const { return wallet_logic_error::to_string(); }
-     };
- 
-+    struct invalid_spend_key : public wallet_logic_error
-+    {
-+      explicit invalid_spend_key(std::string&& loc)
-+        : wallet_logic_error(std::move(loc), "invalid spend key")
-+      {
-+      }
-+
-+      std::string to_string() const { return wallet_logic_error::to_string(); }
-+    };
-+
-     //----------------------------------------------------------------------------------------------------
-     struct invalid_pregenerated_random : public wallet_logic_error
-     {
-@@ -947,6 +961,31 @@ namespace tools
-       }
-     };
-     //----------------------------------------------------------------------------------------------------
-+    struct background_sync_error : public wallet_logic_error
-+    {
-+    protected:
-+      explicit background_sync_error(std::string&& loc, const std::string& message)
-+        : wallet_logic_error(std::move(loc), message)
-+      {
-+      }
-+    };
-+    //----------------------------------------------------------------------------------------------------
-+    struct background_wallet_already_open : public background_sync_error
-+    {
-+      explicit background_wallet_already_open(std::string&& loc, const std::string& background_wallet_file)
-+        : background_sync_error(std::move(loc), "background wallet " + background_wallet_file + " is already opened by another wallet program")
-+      {
-+      }
-+    };
-+    //----------------------------------------------------------------------------------------------------
-+    struct background_custom_password_same_as_wallet_password : public background_sync_error
-+    {
-+      explicit background_custom_password_same_as_wallet_password(std::string&& loc)
-+        : background_sync_error(std::move(loc), "custom background password must be different than wallet password")
-+      {
-+      }
-+    };
-+    //----------------------------------------------------------------------------------------------------
- 
- #if !defined(_MSC_VER)
- 
-diff --git a/src/wallet/wallet_rpc_server.cpp b/src/wallet/wallet_rpc_server.cpp
-index 1c7c45034..21e69ea0e 100644
---- a/src/wallet/wallet_rpc_server.cpp
-+++ b/src/wallet/wallet_rpc_server.cpp
-@@ -73,6 +73,54 @@ using namespace epee;
-     } \
-   } while(0)
- 
-+#define CHECK_IF_BACKGROUND_SYNCING() \
-+  do \
-+  { \
-+    if (!m_wallet) { return not_open(er); } \
-+    if (m_wallet->is_background_wallet()) \
-+    { \
-+      er.code = WALLET_RPC_ERROR_CODE_IS_BACKGROUND_WALLET; \
-+      er.message = "This command is disabled for background wallets."; \
-+      return false; \
-+    } \
-+    if (m_wallet->is_background_syncing()) \
-+    { \
-+      er.code = WALLET_RPC_ERROR_CODE_IS_BACKGROUND_SYNCING; \
-+      er.message = "This command is disabled while background syncing. Stop background syncing to use this command."; \
-+      return false; \
-+    } \
-+  } while(0)
-+
-+#define PRE_VALIDATE_BACKGROUND_SYNC() \
-+  do \
-+  { \
-+    if (!m_wallet) { return not_open(er); } \
-+    if (m_restricted) \
-+    { \
-+      er.code = WALLET_RPC_ERROR_CODE_DENIED; \
-+      er.message = "Command unavailable in restricted mode."; \
-+      return false; \
-+    } \
-+    if (m_wallet->key_on_device()) \
-+    { \
-+      er.code = WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR; \
-+      er.message = "Command not supported by HW wallet"; \
-+      return false; \
-+    } \
-+    if (m_wallet->multisig()) \
-+    { \
-+      er.code = WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR; \
-+      er.message = "Multisig wallet cannot enable background sync"; \
-+      return false; \
-+    } \
-+    if (m_wallet->watch_only()) \
-+    { \
-+      er.code = WALLET_RPC_ERROR_CODE_WATCH_ONLY; \
-+      er.message = "Watch-only wallet cannot enable background sync"; \
-+      return false; \
-+    } \
-+  } while (0)
-+
- namespace
- {
-   const command_line::arg_descriptor<std::string, true> arg_rpc_bind_port = {"rpc-bind-port", "Sets bind port for server"};
-@@ -291,6 +339,9 @@ namespace tools
-   {
-     if (!m_wallet)
-       return;
-+    // Background mining can be toggled from the main wallet
-+    if (m_wallet->is_background_wallet() || m_wallet->is_background_syncing())
-+      return;
- 
-     tools::wallet2::BackgroundMiningSetupType setup = m_wallet->setup_background_mining();
-     if (setup == tools::wallet2::BackgroundMiningNo)
-@@ -581,6 +632,7 @@ namespace tools
-   bool wallet_rpc_server::on_create_address(const wallet_rpc::COMMAND_RPC_CREATE_ADDRESS::request& req, wallet_rpc::COMMAND_RPC_CREATE_ADDRESS::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
-     try
-     {
-       if (req.count < 1 || req.count > 64) {
-@@ -618,6 +670,7 @@ namespace tools
-   bool wallet_rpc_server::on_label_address(const wallet_rpc::COMMAND_RPC_LABEL_ADDRESS::request& req, wallet_rpc::COMMAND_RPC_LABEL_ADDRESS::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
-     try
-     {
-       m_wallet->set_subaddress_label(req.index, req.label);
-@@ -680,6 +733,7 @@ namespace tools
-   bool wallet_rpc_server::on_create_account(const wallet_rpc::COMMAND_RPC_CREATE_ACCOUNT::request& req, wallet_rpc::COMMAND_RPC_CREATE_ACCOUNT::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
-     try
-     {
-       m_wallet->add_subaddress_account(req.label);
-@@ -697,6 +751,7 @@ namespace tools
-   bool wallet_rpc_server::on_label_account(const wallet_rpc::COMMAND_RPC_LABEL_ACCOUNT::request& req, wallet_rpc::COMMAND_RPC_LABEL_ACCOUNT::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
-     try
-     {
-       m_wallet->set_subaddress_label({req.account_index, 0}, req.label);
-@@ -712,6 +767,7 @@ namespace tools
-   bool wallet_rpc_server::on_get_account_tags(const wallet_rpc::COMMAND_RPC_GET_ACCOUNT_TAGS::request& req, wallet_rpc::COMMAND_RPC_GET_ACCOUNT_TAGS::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
-     const std::pair<std::map<std::string, std::string>, std::vector<std::string>> account_tags = m_wallet->get_account_tags();
-     for (const std::pair<const std::string, std::string>& p : account_tags.first)
-     {
-@@ -731,6 +787,7 @@ namespace tools
-   bool wallet_rpc_server::on_tag_accounts(const wallet_rpc::COMMAND_RPC_TAG_ACCOUNTS::request& req, wallet_rpc::COMMAND_RPC_TAG_ACCOUNTS::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
-     try
-     {
-       m_wallet->set_account_tag(req.accounts, req.tag);
-@@ -746,6 +803,7 @@ namespace tools
-   bool wallet_rpc_server::on_untag_accounts(const wallet_rpc::COMMAND_RPC_UNTAG_ACCOUNTS::request& req, wallet_rpc::COMMAND_RPC_UNTAG_ACCOUNTS::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
-     try
-     {
-       m_wallet->set_account_tag(req.accounts, "");
-@@ -761,6 +819,7 @@ namespace tools
-   bool wallet_rpc_server::on_set_account_tag_description(const wallet_rpc::COMMAND_RPC_SET_ACCOUNT_TAG_DESCRIPTION::request& req, wallet_rpc::COMMAND_RPC_SET_ACCOUNT_TAG_DESCRIPTION::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
-     try
-     {
-       m_wallet->set_account_tag_description(req.tag, req.description);
-@@ -791,6 +850,7 @@ namespace tools
-   bool wallet_rpc_server::on_freeze(const wallet_rpc::COMMAND_RPC_FREEZE::request& req, wallet_rpc::COMMAND_RPC_FREEZE::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
-     try
-     {
-       if (req.key_image.empty())
-@@ -819,6 +879,7 @@ namespace tools
-   bool wallet_rpc_server::on_thaw(const wallet_rpc::COMMAND_RPC_THAW::request& req, wallet_rpc::COMMAND_RPC_THAW::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
-     try
-     {
-       if (req.key_image.empty())
-@@ -847,6 +908,7 @@ namespace tools
-   bool wallet_rpc_server::on_frozen(const wallet_rpc::COMMAND_RPC_FROZEN::request& req, wallet_rpc::COMMAND_RPC_FROZEN::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
-     try
-     {
-       if (req.key_image.empty())
-@@ -874,6 +936,8 @@ namespace tools
-   //------------------------------------------------------------------------------------------------------------------------------
-   bool wallet_rpc_server::validate_transfer(const std::list<wallet_rpc::transfer_destination>& destinations, const std::string& payment_id, std::vector<cryptonote::tx_destination_entry>& dsts, std::vector<uint8_t>& extra, bool at_least_one_destination, epee::json_rpc::error& er)
-   {
-+    CHECK_IF_BACKGROUND_SYNCING();
-+
-     crypto::hash8 integrated_payment_id = crypto::null_hash8;
-     std::string extra_nonce;
-     for (auto it = destinations.begin(); it != destinations.end(); it++)
-@@ -1203,6 +1267,7 @@ namespace tools
-     }
- 
-     CHECK_MULTISIG_ENABLED();
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     cryptonote::blobdata blob;
-     if (!epee::string_tools::parse_hexstr_to_binbuff(req.unsigned_txset, blob))
-@@ -1284,6 +1349,7 @@ namespace tools
-       er.message = "command not supported by watch-only wallet";
-       return false;
-     }
-+    CHECK_IF_BACKGROUND_SYNCING();
-     if(req.unsigned_txset.empty() && req.multisig_txset.empty())
-     {
-       er.code = WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR;
-@@ -1553,6 +1619,7 @@ namespace tools
-     }
- 
-     CHECK_MULTISIG_ENABLED();
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     try
-     {
-@@ -2114,6 +2181,7 @@ namespace tools
-             er.message = "The wallet is watch-only. Cannot retrieve seed.";
-             return false;
-           }
-+          CHECK_IF_BACKGROUND_SYNCING();
-           if (!m_wallet->is_deterministic())
-           {
-             er.code = WALLET_RPC_ERROR_CODE_NON_DETERMINISTIC;
-@@ -2142,6 +2210,7 @@ namespace tools
-             er.message = "The wallet is watch-only. Cannot retrieve spend key.";
-             return false;
-           }
-+          CHECK_IF_BACKGROUND_SYNCING();
-           epee::wipeable_string key = epee::to_hex::wipeable_string(m_wallet->get_account().get_keys().m_spend_secret_key);
-           res.key = std::string(key.data(), key.size());
-       }
-@@ -2163,6 +2232,7 @@ namespace tools
-       er.message = "Command unavailable in restricted mode.";
-       return false;
-     }
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     try
-     {
-@@ -2176,6 +2246,79 @@ namespace tools
-     return true;
-   }
-   //------------------------------------------------------------------------------------------------------------------------------
-+  bool wallet_rpc_server::on_setup_background_sync(const wallet_rpc::COMMAND_RPC_SETUP_BACKGROUND_SYNC::request& req, wallet_rpc::COMMAND_RPC_SETUP_BACKGROUND_SYNC::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-+  {
-+    try
-+    {
-+      PRE_VALIDATE_BACKGROUND_SYNC();
-+      const tools::wallet2::BackgroundSyncType background_sync_type = tools::wallet2::background_sync_type_from_str(req.background_sync_type);
-+      boost::optional<epee::wipeable_string> background_cache_password = boost::none;
-+      if (background_sync_type == tools::wallet2::BackgroundSyncCustomPassword)
-+        background_cache_password = boost::optional<epee::wipeable_string>(req.background_cache_password);
-+      m_wallet->setup_background_sync(background_sync_type, req.wallet_password, background_cache_password);
-+    }
-+    catch (...)
-+    {
-+      handle_rpc_exception(std::current_exception(), er, WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR);
-+      return false;
-+    }
-+    return true;
-+  }
-+  //------------------------------------------------------------------------------------------------------------------------------
-+  bool wallet_rpc_server::on_start_background_sync(const wallet_rpc::COMMAND_RPC_START_BACKGROUND_SYNC::request& req, wallet_rpc::COMMAND_RPC_START_BACKGROUND_SYNC::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-+  {
-+    try
-+    {
-+      PRE_VALIDATE_BACKGROUND_SYNC();
-+      m_wallet->start_background_sync();
-+    }
-+    catch (...)
-+    {
-+      handle_rpc_exception(std::current_exception(), er, WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR);
-+      return false;
-+    }
-+    return true;
-+  }
-+  //------------------------------------------------------------------------------------------------------------------------------
-+  bool wallet_rpc_server::on_stop_background_sync(const wallet_rpc::COMMAND_RPC_STOP_BACKGROUND_SYNC::request& req, wallet_rpc::COMMAND_RPC_STOP_BACKGROUND_SYNC::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-+  {
-+    try
-+    {
-+      PRE_VALIDATE_BACKGROUND_SYNC();
-+      crypto::secret_key spend_secret_key = crypto::null_skey;
-+
-+      // Load the spend key from seed if seed is provided
-+      if (!req.seed.empty())
-+      {
-+        crypto::secret_key recovery_key;
-+        std::string language;
-+
-+        if (!crypto::ElectrumWords::words_to_bytes(req.seed, recovery_key, language))
-+        {
-+          er.code = WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR;
-+          er.message = "Electrum-style word list failed verification";
-+          return false;
-+        }
-+
-+        if (!req.seed_offset.empty())
-+          recovery_key = cryptonote::decrypt_key(recovery_key, req.seed_offset);
-+
-+        // generate spend key
-+        cryptonote::account_base account;
-+        account.generate(recovery_key, true, false);
-+        spend_secret_key = account.get_keys().m_spend_secret_key;
-+      }
-+
-+      m_wallet->stop_background_sync(req.wallet_password, spend_secret_key);
-+    }
-+    catch (...)
-+    {
-+      handle_rpc_exception(std::current_exception(), er, WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR);
-+      return false;
-+    }
-+    return true;
-+  }
-+  //------------------------------------------------------------------------------------------------------------------------------
-   bool wallet_rpc_server::on_sign(const wallet_rpc::COMMAND_RPC_SIGN::request& req, wallet_rpc::COMMAND_RPC_SIGN::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-@@ -2185,6 +2328,7 @@ namespace tools
-       er.message = "Command unavailable in restricted mode.";
-       return false;
-     }
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     tools::wallet2::message_signature_type_t signature_type = tools::wallet2::sign_with_spend_key;
-     if (req.signature_type == "spend" || req.signature_type == "")
-@@ -2277,6 +2421,7 @@ namespace tools
-       er.message = "Command unavailable in restricted mode.";
-       return false;
-     }
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     if (req.txids.size() != req.notes.size())
-     {
-@@ -2349,6 +2494,7 @@ namespace tools
-       er.message = "Command unavailable in restricted mode.";
-       return false;
-     }
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     m_wallet->set_attribute(req.key, req.value);
- 
-@@ -2376,6 +2522,7 @@ namespace tools
-   bool wallet_rpc_server::on_get_tx_key(const wallet_rpc::COMMAND_RPC_GET_TX_KEY::request& req, wallet_rpc::COMMAND_RPC_GET_TX_KEY::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     crypto::hash txid;
-     if (!epee::string_tools::hex_to_pod(req.txid, txid))
-@@ -2467,6 +2614,7 @@ namespace tools
-   bool wallet_rpc_server::on_get_tx_proof(const wallet_rpc::COMMAND_RPC_GET_TX_PROOF::request& req, wallet_rpc::COMMAND_RPC_GET_TX_PROOF::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     crypto::hash txid;
-     if (!epee::string_tools::hex_to_pod(req.txid, txid))
-@@ -2583,6 +2731,7 @@ namespace tools
-   bool wallet_rpc_server::on_get_reserve_proof(const wallet_rpc::COMMAND_RPC_GET_RESERVE_PROOF::request& req, wallet_rpc::COMMAND_RPC_GET_RESERVE_PROOF::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     boost::optional<std::pair<uint32_t, uint64_t>> account_minreserve;
-     if (!req.all)
-@@ -2825,6 +2974,7 @@ namespace tools
-       er.message = "command not supported by HW wallet";
-       return false;
-     }
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     try
-     {
-@@ -2854,6 +3004,7 @@ namespace tools
-       er.message = "command not supported by HW wallet";
-       return false;
-     }
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     cryptonote::blobdata blob;
-     if (!epee::string_tools::parse_hexstr_to_binbuff(req.outputs_data_hex, blob))
-@@ -2879,6 +3030,7 @@ namespace tools
-   bool wallet_rpc_server::on_export_key_images(const wallet_rpc::COMMAND_RPC_EXPORT_KEY_IMAGES::request& req, wallet_rpc::COMMAND_RPC_EXPORT_KEY_IMAGES::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
-     try
-     {
-       std::pair<uint64_t, std::vector<std::pair<crypto::key_image, crypto::signature>>> ski = m_wallet->export_key_images(req.all);
-@@ -2915,6 +3067,7 @@ namespace tools
-       er.message = "This command requires a trusted daemon.";
-       return false;
-     }
-+    CHECK_IF_BACKGROUND_SYNCING();
-     try
-     {
-       std::vector<std::pair<crypto::key_image, crypto::signature>> ski;
-@@ -2983,6 +3136,7 @@ namespace tools
-   bool wallet_rpc_server::on_get_address_book(const wallet_rpc::COMMAND_RPC_GET_ADDRESS_BOOK_ENTRY::request& req, wallet_rpc::COMMAND_RPC_GET_ADDRESS_BOOK_ENTRY::response& res, epee::json_rpc::error& er, const connection_context *ctx)
-   {
-     if (!m_wallet) return not_open(er);
-+    CHECK_IF_BACKGROUND_SYNCING();
-     const auto ab = m_wallet->get_address_book();
-     if (req.entries.empty())
-     {
-@@ -3028,6 +3182,7 @@ namespace tools
-       er.message = "Command unavailable in restricted mode.";
-       return false;
-     }
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     cryptonote::address_parse_info info;
-     er.message = "";
-@@ -3070,6 +3225,7 @@ namespace tools
-       er.message = "Command unavailable in restricted mode.";
-       return false;
-     }
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     const auto ab = m_wallet->get_address_book();
-     if (req.index >= ab.size())
-@@ -3132,6 +3288,7 @@ namespace tools
-       er.message = "Command unavailable in restricted mode.";
-       return false;
-     }
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     const auto ab = m_wallet->get_address_book();
-     if (req.index >= ab.size())
-@@ -3202,6 +3359,7 @@ namespace tools
-           er.message = "Command unavailable in restricted mode.";
-           return false;
-       }
-+      CHECK_IF_BACKGROUND_SYNCING();
- 
-       std::unordered_set<crypto::hash> txids;
-       std::list<std::string>::const_iterator i = req.txids.begin();
-@@ -3241,6 +3399,7 @@ namespace tools
-       er.message = "Command unavailable in restricted mode.";
-       return false;
-     }
-+    CHECK_IF_BACKGROUND_SYNCING();
-     try
-     {
-       m_wallet->rescan_spent();
-@@ -3505,6 +3664,7 @@ namespace tools
-       er.message = "Command unavailable in restricted mode.";
-       return false;
-     }
-+    CHECK_IF_BACKGROUND_SYNCING();
-     if (m_wallet->verify_password(req.old_password))
-     {
-       try
-@@ -4032,6 +4192,7 @@ namespace tools
-       er.message = "wallet is watch-only and cannot be made multisig";
-       return false;
-     }
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     res.multisig_info = m_wallet->get_multisig_first_kex_msg();
-     return true;
-@@ -4059,6 +4220,7 @@ namespace tools
-       er.message = "wallet is watch-only and cannot be made multisig";
-       return false;
-     }
-+    CHECK_IF_BACKGROUND_SYNCING();
- 
-     try
-     {
-diff --git a/src/wallet/wallet_rpc_server.h b/src/wallet/wallet_rpc_server.h
-index 3308d1751..c2329aafe 100644
---- a/src/wallet/wallet_rpc_server.h
-+++ b/src/wallet/wallet_rpc_server.h
-@@ -160,6 +160,9 @@ namespace tools
-         MAP_JON_RPC_WE("set_log_categories", on_set_log_categories, wallet_rpc::COMMAND_RPC_SET_LOG_CATEGORIES)
-         MAP_JON_RPC_WE("estimate_tx_size_and_weight", on_estimate_tx_size_and_weight, wallet_rpc::COMMAND_RPC_ESTIMATE_TX_SIZE_AND_WEIGHT)
-         MAP_JON_RPC_WE("get_version",        on_get_version,        wallet_rpc::COMMAND_RPC_GET_VERSION)
-+        MAP_JON_RPC_WE("setup_background_sync", on_setup_background_sync, wallet_rpc::COMMAND_RPC_SETUP_BACKGROUND_SYNC)
-+        MAP_JON_RPC_WE("start_background_sync", on_start_background_sync, wallet_rpc::COMMAND_RPC_START_BACKGROUND_SYNC)
-+        MAP_JON_RPC_WE("stop_background_sync", on_stop_background_sync, wallet_rpc::COMMAND_RPC_STOP_BACKGROUND_SYNC)
-       END_JSON_RPC_MAP()
-     END_URI_MAP2()
- 
-@@ -251,6 +254,9 @@ namespace tools
-       bool on_set_log_categories(const wallet_rpc::COMMAND_RPC_SET_LOG_CATEGORIES::request& req, wallet_rpc::COMMAND_RPC_SET_LOG_CATEGORIES::response& res, epee::json_rpc::error& er, const connection_context *ctx = NULL);
-       bool on_estimate_tx_size_and_weight(const wallet_rpc::COMMAND_RPC_ESTIMATE_TX_SIZE_AND_WEIGHT::request& req, wallet_rpc::COMMAND_RPC_ESTIMATE_TX_SIZE_AND_WEIGHT::response& res, epee::json_rpc::error& er, const connection_context *ctx = NULL);
-       bool on_get_version(const wallet_rpc::COMMAND_RPC_GET_VERSION::request& req, wallet_rpc::COMMAND_RPC_GET_VERSION::response& res, epee::json_rpc::error& er, const connection_context *ctx = NULL);
-+      bool on_setup_background_sync(const wallet_rpc::COMMAND_RPC_SETUP_BACKGROUND_SYNC::request& req, wallet_rpc::COMMAND_RPC_SETUP_BACKGROUND_SYNC::response& res, epee::json_rpc::error& er, const connection_context *ctx = NULL);
-+      bool on_start_background_sync(const wallet_rpc::COMMAND_RPC_START_BACKGROUND_SYNC::request& req, wallet_rpc::COMMAND_RPC_START_BACKGROUND_SYNC::response& res, epee::json_rpc::error& er, const connection_context *ctx = NULL);
-+      bool on_stop_background_sync(const wallet_rpc::COMMAND_RPC_STOP_BACKGROUND_SYNC::request& req, wallet_rpc::COMMAND_RPC_STOP_BACKGROUND_SYNC::response& res, epee::json_rpc::error& er, const connection_context *ctx = NULL);
- 
-       //json rpc v2
-       bool on_query_key(const wallet_rpc::COMMAND_RPC_QUERY_KEY::request& req, wallet_rpc::COMMAND_RPC_QUERY_KEY::response& res, epee::json_rpc::error& er, const connection_context *ctx = NULL);
-diff --git a/src/wallet/wallet_rpc_server_commands_defs.h b/src/wallet/wallet_rpc_server_commands_defs.h
-index 2ce39f667..72a35eb73 100644
---- a/src/wallet/wallet_rpc_server_commands_defs.h
-+++ b/src/wallet/wallet_rpc_server_commands_defs.h
-@@ -2698,5 +2698,69 @@ namespace wallet_rpc
-     typedef epee::misc_utils::struct_init<response_t> response;
-   };
- 
-+  struct COMMAND_RPC_SETUP_BACKGROUND_SYNC
-+  {
-+    struct request_t
-+    {
-+      std::string background_sync_type;
-+      std::string wallet_password;
-+      std::string background_cache_password;
-+
-+      BEGIN_KV_SERIALIZE_MAP()
-+        KV_SERIALIZE(background_sync_type)
-+        KV_SERIALIZE(wallet_password)
-+        KV_SERIALIZE_OPT(background_cache_password, (std::string)"")
-+      END_KV_SERIALIZE_MAP()
-+    };
-+    typedef epee::misc_utils::struct_init<request_t> request;
-+
-+    struct response_t
-+    {
-+      BEGIN_KV_SERIALIZE_MAP()
-+      END_KV_SERIALIZE_MAP()
-+    };
-+    typedef epee::misc_utils::struct_init<response_t> response;
-+  };
-+
-+  struct COMMAND_RPC_START_BACKGROUND_SYNC
-+  {
-+    struct request_t
-+    {
-+      BEGIN_KV_SERIALIZE_MAP()
-+      END_KV_SERIALIZE_MAP()
-+    };
-+    typedef epee::misc_utils::struct_init<request_t> request;
-+
-+    struct response_t
-+    {
-+      BEGIN_KV_SERIALIZE_MAP()
-+      END_KV_SERIALIZE_MAP()
-+    };
-+    typedef epee::misc_utils::struct_init<response_t> response;
-+  };
-+
-+  struct COMMAND_RPC_STOP_BACKGROUND_SYNC
-+  {
-+    struct request_t
-+    {
-+      std::string wallet_password;
-+      std::string seed;
-+      std::string seed_offset;
-+
-+      BEGIN_KV_SERIALIZE_MAP()
-+        KV_SERIALIZE(wallet_password)
-+        KV_SERIALIZE_OPT(seed, (std::string)"")
-+        KV_SERIALIZE_OPT(seed_offset, (std::string)"")
-+      END_KV_SERIALIZE_MAP()
-+    };
-+    typedef epee::misc_utils::struct_init<request_t> request;
-+
-+    struct response_t
-+    {
-+      BEGIN_KV_SERIALIZE_MAP()
-+      END_KV_SERIALIZE_MAP()
-+    };
-+    typedef epee::misc_utils::struct_init<response_t> response;
-+  };
- }
- }
-diff --git a/src/wallet/wallet_rpc_server_error_codes.h b/src/wallet/wallet_rpc_server_error_codes.h
-index 541d29f86..4756c191c 100644
---- a/src/wallet/wallet_rpc_server_error_codes.h
-+++ b/src/wallet/wallet_rpc_server_error_codes.h
-@@ -81,3 +81,5 @@
- #define WALLET_RPC_ERROR_CODE_DISABLED               -48
- #define WALLET_RPC_ERROR_CODE_PROXY_ALREADY_DEFINED  -49
- #define WALLET_RPC_ERROR_CODE_NONZERO_UNLOCK_TIME    -50
-+#define WALLET_RPC_ERROR_CODE_IS_BACKGROUND_WALLET   -51
-+#define WALLET_RPC_ERROR_CODE_IS_BACKGROUND_SYNCING  -52
-diff --git a/tests/functional_tests/transfer.py b/tests/functional_tests/transfer.py
-index 4063911f4..60eb09a10 100755
---- a/tests/functional_tests/transfer.py
-+++ b/tests/functional_tests/transfer.py
-@@ -30,6 +30,7 @@
- 
- from __future__ import print_function
- import json
-+import util_resources
- import pprint
- from deepdiff import DeepDiff
- pp = pprint.PrettyPrinter(indent=2)
-@@ -46,6 +47,17 @@ seeds = [
-     'dilute gutter certain antics pamphlet macro enjoy left slid guarded bogeys upload nineteen bomb jubilee enhanced irritate turnip eggs swung jukebox loudly reduce sedan slid',
- ]
- 
-+def diff_transfers(actual_transfers, expected_transfers, ignore_order = True):
-+    # The payments containers aren't ordered; re-scanning can lead to diff orders
-+    diff = DeepDiff(actual_transfers, expected_transfers, ignore_order = ignore_order)
-+    if diff != {}:
-+        pp.pprint(diff)
-+    assert diff == {}
-+
-+def diff_incoming_transfers(actual_transfers, expected_transfers):
-+    # wallet2 m_transfers container is ordered and order should be the same across rescans
-+    diff_transfers(actual_transfers, expected_transfers, ignore_order = False)
-+
- class TransferTest():
-     def run_test(self):
-         self.reset()
-@@ -63,6 +75,8 @@ class TransferTest():
-         self.check_is_key_image_spent()
-         self.check_scan_tx()
-         self.check_subtract_fee_from_outputs()
-+        self.check_background_sync()
-+        self.check_background_sync_reorg_recovery()
- 
-     def reset(self):
-         print('Resetting blockchain')
-@@ -840,12 +854,6 @@ class TransferTest():
- 
-         print('Testing scan_tx')
- 
--        def diff_transfers(actual_transfers, expected_transfers):
--            diff = DeepDiff(actual_transfers, expected_transfers)
--            if diff != {}:
--                pp.pprint(diff)
--            assert diff == {}
--
-         # set up sender_wallet
-         sender_wallet = self.wallet[0]
-         try: sender_wallet.close_wallet()
-@@ -1127,5 +1135,385 @@ class TransferTest():
-         except AssertionError:
-             pass
- 
-+    def check_background_sync(self):
-+        daemon = Daemon()
-+
-+        print('Testing background sync')
-+
-+        # Some helper functions
-+        def stop_with_wrong_inputs(wallet, wallet_password, seed = ''):
-+            invalid = False
-+            try: wallet.stop_background_sync(wallet_password = wallet_password, seed = seed)
-+            except: invalid = True
-+            assert invalid
-+
-+        def open_with_wrong_password(wallet, filename, password):
-+            invalid_password = False
-+            try: wallet.open_wallet(filename, password = password)
-+            except: invalid_password = True
-+            assert invalid_password
-+
-+        def restore_wallet(wallet, seed, filename = '', password = ''):
-+            wallet.close_wallet()
-+            if filename != '':
-+                util_resources.remove_wallet_files(filename)
-+            wallet.restore_deterministic_wallet(seed = seed, filename = filename, password = password)
-+            wallet.auto_refresh(enable = False)
-+            assert wallet.get_transfers() == {}
-+
-+        def assert_correct_transfers(wallet, expected_transfers, expected_inc_transfers, expected_balance):
-+            diff_transfers(wallet.get_transfers(), expected_transfers)
-+            diff_incoming_transfers(wallet.incoming_transfers(transfer_type = 'all'), expected_inc_transfers)
-+            assert wallet.get_balance().balance == expected_balance
-+
-+        # Set up sender_wallet. Prepare to sweep single output to receiver.
-+        # We're testing a sweep because it makes sure background sync can
-+        # properly pick up txs which do not have a change output back to sender.
-+        sender_wallet = self.wallet[0]
-+        try: sender_wallet.close_wallet()
-+        except: pass
-+        sender_wallet.restore_deterministic_wallet(seed = seeds[0])
-+        sender_wallet.auto_refresh(enable = False)
-+        sender_wallet.refresh()
-+        res = sender_wallet.incoming_transfers(transfer_type = 'available')
-+        unlocked = [x for x in res.transfers if x.unlocked and x.amount > 0]
-+        assert len(unlocked) > 0
-+        ki = unlocked[0].key_image
-+        amount = unlocked[0].amount
-+        spent_txid = unlocked[0].tx_hash
-+        sender_wallet.refresh()
-+        res = sender_wallet.get_transfers()
-+        out_len = 0 if 'out' not in res else len(res.out)
-+        sender_starting_balance = sender_wallet.get_balance().balance
-+
-+        # Background sync type options
-+        reuse_password = sender_wallet.background_sync_options.reuse_password
-+        custom_password = sender_wallet.background_sync_options.custom_password
-+
-+        # set up receiver_wallet
-+        receiver_wallet = self.wallet[1]
-+        try: receiver_wallet.close_wallet()
-+        except: pass
-+        receiver_wallet.restore_deterministic_wallet(seed = seeds[1])
-+        receiver_wallet.auto_refresh(enable = False)
-+        receiver_wallet.refresh()
-+        res = receiver_wallet.get_transfers()
-+        in_len = 0 if 'in' not in res else len(res['in'])
-+        receiver_starting_balance = receiver_wallet.get_balance().balance
-+
-+        # transfer from sender_wallet to receiver_wallet
-+        dst = '44Kbx4sJ7JDRDV5aAhLJzQCjDz2ViLRduE3ijDZu3osWKBjMGkV1XPk4pfDUMqt1Aiezvephdqm6YD19GKFD9ZcXVUTp6BW'
-+        res = sender_wallet.sweep_single(dst, key_image = ki)
-+        assert len(res.tx_hash) == 32*2
-+        txid = res.tx_hash
-+        assert res.fee > 0
-+        fee = res.fee
-+        assert res.amount == amount - fee
-+
-+        expected_sender_balance = sender_starting_balance - amount
-+        expected_receiver_balance = receiver_starting_balance + (amount - fee)
-+
-+        print('Checking background sync on outgoing wallet')
-+        sender_wallet.setup_background_sync(background_sync_type = reuse_password)
-+        sender_wallet.start_background_sync()
-+        # Mine block to an uninvolved wallet
-+        daemon.generateblocks('46r4nYSevkfBUMhuykdK3gQ98XDqDTYW1hNLaXNvjpsJaSbNtdXh1sKMsdVgqkaihChAzEy29zEDPMR3NHQvGoZCLGwTerK', 1)
-+        # sender should still be able to scan the transfer normally because we
-+        # spent an output that had a known key image
-+        sender_wallet.refresh()
-+        transfers = sender_wallet.get_transfers()
-+        assert 'pending' not in transfers or len(transfers.pending) == 0
-+        assert 'pool' not in transfers or len (transfers.pool) == 0
-+        assert len(transfers.out) == out_len + 1
-+        tx = [x for x in transfers.out if x.txid == txid]
-+        assert len(tx) == 1
-+        tx = tx[0]
-+        assert tx.amount == amount - fee
-+        assert tx.fee == fee
-+        assert len(tx.destinations) == 1
-+        assert tx.destinations[0].amount == amount - fee
-+        assert tx.destinations[0].address == dst
-+        incoming_transfers = sender_wallet.incoming_transfers(transfer_type = 'all')
-+        assert len([x for x in incoming_transfers.transfers if x.tx_hash == spent_txid and x.key_image == ki and x.spent]) == 1
-+        assert sender_wallet.get_balance().balance == expected_sender_balance
-+
-+        # Restore and check background syncing outgoing wallet
-+        restore_wallet(sender_wallet, seeds[0])
-+        sender_wallet.setup_background_sync(background_sync_type = reuse_password)
-+        sender_wallet.start_background_sync()
-+        sender_wallet.refresh()
-+        for i, out_tx in enumerate(transfers.out):
-+            if 'destinations' in out_tx:
-+                del transfers.out[i]['destinations'] # destinations are not expected after wallet restore
-+        # sender's balance should be higher because can't detect spends while
-+        # background sync enabled, only receives
-+        background_bal = sender_wallet.get_balance().balance
-+        assert background_bal > expected_sender_balance
-+        background_transfers = sender_wallet.get_transfers()
-+        assert 'out' not in background_transfers or len(background_transfers.out) == 0
-+        assert 'in' in background_transfers and len(background_transfers['in']) > 0
-+        background_incoming_transfers = sender_wallet.incoming_transfers(transfer_type = 'all')
-+        assert len(background_incoming_transfers) == len(incoming_transfers)
-+        assert len([x for x in background_incoming_transfers.transfers if x.spent or x.key_image != '']) == 0
-+        assert len([x for x in background_incoming_transfers.transfers if x.tx_hash == spent_txid]) == 1
-+
-+        # Try to stop background sync with the wrong seed
-+        stop_with_wrong_inputs(sender_wallet, wallet_password = '', seed = seeds[1])
-+
-+        # Stop background sync and check transfers update correctly
-+        sender_wallet.stop_background_sync(wallet_password = '', seed = seeds[0])
-+        assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
-+
-+        # Check stopping a wallet with wallet files saved to disk
-+        for background_sync_type in [reuse_password, custom_password]:
-+            restore_wallet(sender_wallet, seeds[0], 'test1', 'test_password')
-+            background_cache_password = None if background_sync_type == reuse_password else 'background_password'
-+            sender_wallet.setup_background_sync(background_sync_type = background_sync_type, wallet_password = 'test_password', background_cache_password = background_cache_password)
-+            sender_wallet.start_background_sync()
-+            sender_wallet.refresh()
-+            assert_correct_transfers(sender_wallet, background_transfers, background_incoming_transfers, background_bal)
-+            stop_with_wrong_inputs(sender_wallet, 'wrong_password')
-+            sender_wallet.stop_background_sync(wallet_password = 'test_password')
-+            assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
-+
-+        # Close wallet while background syncing, then reopen
-+        for background_sync_type in [reuse_password, custom_password]:
-+            restore_wallet(sender_wallet, seeds[0], 'test1', 'test_password')
-+            background_cache_password = None if background_sync_type == reuse_password else 'background_password'
-+            sender_wallet.setup_background_sync(background_sync_type = background_sync_type, wallet_password = 'test_password', background_cache_password = background_cache_password)
-+            sender_wallet.start_background_sync()
-+            sender_wallet.refresh()
-+            assert_correct_transfers(sender_wallet, background_transfers, background_incoming_transfers, background_bal)
-+            sender_wallet.close_wallet()
-+            open_with_wrong_password(sender_wallet, 'test1', 'wrong_password')
-+            sender_wallet.open_wallet('test1', password = 'test_password')
-+            # It should reopen with spend key loaded and correctly scan all transfers
-+            assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
-+
-+        # Close wallet while syncing normally, then reopen
-+        for background_sync_type in [reuse_password, custom_password]:
-+            restore_wallet(sender_wallet, seeds[0], 'test1', 'test_password')
-+            background_cache_password = None if background_sync_type == reuse_password else 'background_password'
-+            sender_wallet.setup_background_sync(background_sync_type = background_sync_type, wallet_password = 'test_password', background_cache_password = background_cache_password)
-+            sender_wallet.refresh()
-+            assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
-+            sender_wallet.close_wallet()
-+            open_with_wrong_password(sender_wallet, 'test1', 'wrong_password')
-+            sender_wallet.open_wallet('test1', password = 'test_password')
-+            assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
-+
-+        # Create background cache using custom password, then use it to sync, then reopen main wallet
-+        for background_cache_password in ['background_password', '']:
-+            restore_wallet(sender_wallet, seeds[0], 'test1', 'test_password')
-+            assert not util_resources.file_exists('test1.background')
-+            assert not util_resources.file_exists('test1.background.keys')
-+            sender_wallet.setup_background_sync(background_sync_type = custom_password, wallet_password = 'test_password', background_cache_password = background_cache_password)
-+            assert util_resources.file_exists('test1.background')
-+            assert util_resources.file_exists('test1.background.keys')
-+            sender_wallet.close_wallet()
-+            open_with_wrong_password(sender_wallet, 'test1.background', 'test_password')
-+            sender_wallet.open_wallet('test1.background', password = background_cache_password)
-+            sender_wallet.refresh()
-+            assert_correct_transfers(sender_wallet, background_transfers, background_incoming_transfers, background_bal)
-+            sender_wallet.close_wallet()
-+            sender_wallet.open_wallet('test1', password = 'test_password')
-+            assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
-+
-+        # Check that main wallet keeps background cache encrypted with custom password in sync
-+        restore_wallet(sender_wallet, seeds[0], 'test1', 'test_password')
-+        sender_wallet.setup_background_sync(background_sync_type = background_sync_type, wallet_password = 'test_password', background_cache_password = 'background_password')
-+        sender_wallet.refresh()
-+        assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
-+        sender_wallet.close_wallet()
-+        sender_wallet.open_wallet('test1.background', password = 'background_password')
-+        assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
-+
-+        # Try using wallet password as custom background password
-+        restore_wallet(sender_wallet, seeds[0], 'test1', 'test_password')
-+        assert not util_resources.file_exists('test1.background')
-+        assert not util_resources.file_exists('test1.background.keys')
-+        same_password = False
-+        try: sender_wallet.setup_background_sync(background_sync_type = custom_password, wallet_password = 'test_password', background_cache_password = 'test_password')
-+        except: same_password = True
-+        assert same_password
-+        assert not util_resources.file_exists('test1.background')
-+        assert not util_resources.file_exists('test1.background.keys')
-+
-+        # Turn off background sync
-+        for background_sync_type in [reuse_password, custom_password]:
-+            restore_wallet(sender_wallet, seeds[0], 'test1', 'test_password')
-+            background_cache_password = None if background_sync_type == reuse_password else 'background_password'
-+            sender_wallet.setup_background_sync(background_sync_type = background_sync_type, wallet_password = 'test_password', background_cache_password = background_cache_password)
-+            if background_sync_type == custom_password:
-+                assert util_resources.file_exists('test1.background')
-+                assert util_resources.file_exists('test1.background.keys')
-+                sender_wallet.close_wallet()
-+                assert util_resources.file_exists('test1.background')
-+                assert util_resources.file_exists('test1.background.keys')
-+            else:
-+                assert not util_resources.file_exists('test1.background')
-+                assert not util_resources.file_exists('test1.background.keys')
-+                sender_wallet.close_wallet()
-+                assert not util_resources.file_exists('test1.background')
-+                assert not util_resources.file_exists('test1.background.keys')
-+            sender_wallet.open_wallet('test1', password = 'test_password')
-+            sender_wallet.setup_background_sync(background_sync_type = sender_wallet.background_sync_options.off, wallet_password = 'test_password')
-+            assert not util_resources.file_exists('test1.background')
-+            assert not util_resources.file_exists('test1.background.keys')
-+            sender_wallet.close_wallet()
-+            assert not util_resources.file_exists('test1.background')
-+            assert not util_resources.file_exists('test1.background.keys')
-+            sender_wallet.open_wallet('test1', password = 'test_password')
-+
-+        # Sanity check against outgoing wallet restored at height 0
-+        sender_wallet.close_wallet()
-+        sender_wallet.restore_deterministic_wallet(seed = seeds[0], restore_height = 0)
-+        sender_wallet.refresh()
-+        assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
-+
-+        print('Checking background sync on incoming wallet')
-+        receiver_wallet.setup_background_sync(background_sync_type = reuse_password)
-+        receiver_wallet.start_background_sync()
-+        receiver_wallet.refresh()
-+        transfers = receiver_wallet.get_transfers()
-+        assert 'pending' not in transfers or len(transfers.pending) == 0
-+        assert 'pool' not in transfers or len (transfers.pool) == 0
-+        assert len(transfers['in']) == in_len + 1
-+        tx = [x for x in transfers['in'] if x.txid == txid]
-+        assert len(tx) == 1
-+        tx = tx[0]
-+        assert tx.amount == amount - fee
-+        assert tx.fee == fee
-+        incoming_transfers = receiver_wallet.incoming_transfers(transfer_type = 'all')
-+        assert len([x for x in incoming_transfers.transfers if x.tx_hash == txid and x.key_image == '' and not x.spent]) == 1
-+        assert receiver_wallet.get_balance().balance == expected_receiver_balance
-+
-+        # Restore and check background syncing incoming wallet
-+        restore_wallet(receiver_wallet, seeds[1])
-+        receiver_wallet.setup_background_sync(background_sync_type = reuse_password)
-+        receiver_wallet.start_background_sync()
-+        receiver_wallet.refresh()
-+        if 'out' in transfers:
-+            for i, out_tx in enumerate(transfers.out):
-+                if 'destinations' in out_tx:
-+                    del transfers.out[i]['destinations'] # destinations are not expected after wallet restore
-+        background_bal = receiver_wallet.get_balance().balance
-+        assert background_bal >= expected_receiver_balance
-+        background_transfers = receiver_wallet.get_transfers()
-+        assert 'out' not in background_transfers or len(background_transfers.out) == 0
-+        assert 'in' in background_transfers and len(background_transfers['in']) > 0
-+        background_incoming_transfers = receiver_wallet.incoming_transfers(transfer_type = 'all')
-+        assert len(background_incoming_transfers) == len(incoming_transfers)
-+        assert len([x for x in background_incoming_transfers.transfers if x.spent or x.key_image != '']) == 0
-+        assert len([x for x in background_incoming_transfers.transfers if x.tx_hash == txid]) == 1
-+
-+        # Stop background sync and check transfers update correctly
-+        receiver_wallet.stop_background_sync(wallet_password = '', seed = seeds[1])
-+        diff_transfers(receiver_wallet.get_transfers(), transfers)
-+        incoming_transfers = receiver_wallet.incoming_transfers(transfer_type = 'all')
-+        assert len(background_incoming_transfers) == len(incoming_transfers)
-+        assert len([x for x in incoming_transfers.transfers if x.tx_hash == txid and x.key_image != '' and not x.spent]) == 1
-+        assert receiver_wallet.get_balance().balance == expected_receiver_balance
-+
-+        # Check a fresh incoming wallet with wallet files saved to disk and encrypted with password
-+        restore_wallet(receiver_wallet, seeds[1], 'test2', 'test_password')
-+        receiver_wallet.setup_background_sync(background_sync_type = reuse_password, wallet_password = 'test_password')
-+        receiver_wallet.start_background_sync()
-+        receiver_wallet.refresh()
-+        assert_correct_transfers(receiver_wallet, background_transfers, background_incoming_transfers, background_bal)
-+        stop_with_wrong_inputs(receiver_wallet, 'wrong_password')
-+        receiver_wallet.stop_background_sync(wallet_password = 'test_password')
-+        assert_correct_transfers(receiver_wallet, transfers, incoming_transfers, expected_receiver_balance)
-+
-+        # Close receiver's wallet while background sync is enabled then reopen
-+        restore_wallet(receiver_wallet, seeds[1], 'test2', 'test_password')
-+        receiver_wallet.setup_background_sync(background_sync_type = reuse_password, wallet_password = 'test_password')
-+        receiver_wallet.start_background_sync()
-+        receiver_wallet.refresh()
-+        diff_transfers(receiver_wallet.get_transfers(), background_transfers)
-+        diff_incoming_transfers(receiver_wallet.incoming_transfers(transfer_type = 'all'), background_incoming_transfers)
-+        assert receiver_wallet.get_balance().balance == background_bal
-+        receiver_wallet.close_wallet()
-+        receiver_wallet.open_wallet('test2', password = 'test_password')
-+        # It should reopen with spend key loaded and correctly scan all transfers
-+        assert_correct_transfers(receiver_wallet, transfers, incoming_transfers, expected_receiver_balance)
-+
-+        # Sanity check against incoming wallet restored at height 0
-+        receiver_wallet.close_wallet()
-+        receiver_wallet.restore_deterministic_wallet(seed = seeds[1], restore_height = 0)
-+        receiver_wallet.refresh()
-+        assert_correct_transfers(receiver_wallet, transfers, incoming_transfers, expected_receiver_balance)
-+
-+        # Clean up
-+        util_resources.remove_wallet_files('test1')
-+        util_resources.remove_wallet_files('test2')
-+        for i in range(2):
-+            self.wallet[i].close_wallet()
-+            self.wallet[i].restore_deterministic_wallet(seed = seeds[i])
-+
-+    def check_background_sync_reorg_recovery(self):
-+        daemon = Daemon()
-+
-+        print('Testing background sync reorg recovery')
-+
-+        # Disconnect daemon from peers
-+        daemon.out_peers(0)
-+
-+        # Background sync type options
-+        sender_wallet = self.wallet[0]
-+        reuse_password = sender_wallet.background_sync_options.reuse_password
-+        custom_password = sender_wallet.background_sync_options.custom_password
-+
-+        for background_sync_type in [reuse_password, custom_password]:
-+            # Set up wallet saved to disk
-+            sender_wallet.close_wallet()
-+            util_resources.remove_wallet_files('test1')
-+            sender_wallet.restore_deterministic_wallet(seed = seeds[0], filename = 'test1', password = '')
-+            sender_wallet.auto_refresh(enable = False)
-+            sender_wallet.refresh()
-+            sender_starting_balance = sender_wallet.get_balance().balance
-+
-+            # Send tx and mine a block
-+            amount = 1000000000000
-+            assert sender_starting_balance > amount
-+            dst = {'address': '44Kbx4sJ7JDRDV5aAhLJzQCjDz2ViLRduE3ijDZu3osWKBjMGkV1XPk4pfDUMqt1Aiezvephdqm6YD19GKFD9ZcXVUTp6BW', 'amount': amount}
-+            res = sender_wallet.transfer([dst])
-+            assert len(res.tx_hash) == 32*2
-+            txid = res.tx_hash
-+
-+            daemon.generateblocks('46r4nYSevkfBUMhuykdK3gQ98XDqDTYW1hNLaXNvjpsJaSbNtdXh1sKMsdVgqkaihChAzEy29zEDPMR3NHQvGoZCLGwTerK', 1)
-+
-+            # Make sure the wallet can see the tx
-+            sender_wallet.refresh()
-+            transfers = sender_wallet.get_transfers()
-+            assert 'pool' not in transfers or len (transfers.pool) == 0
-+            tx = [x for x in transfers.out if x.txid == txid]
-+            assert len(tx) == 1
-+            tx = tx[0]
-+            assert sender_wallet.get_balance().balance < (sender_starting_balance - amount)
-+
-+            # Pop the block while background syncing
-+            background_cache_password = None if background_sync_type == reuse_password else 'background_password'
-+            sender_wallet.setup_background_sync(background_sync_type = background_sync_type, wallet_password = '', background_cache_password = background_cache_password)
-+            sender_wallet.start_background_sync()
-+            daemon.pop_blocks(1)
-+            daemon.flush_txpool()
-+
-+            daemon.generateblocks('46r4nYSevkfBUMhuykdK3gQ98XDqDTYW1hNLaXNvjpsJaSbNtdXh1sKMsdVgqkaihChAzEy29zEDPMR3NHQvGoZCLGwTerK', 1)
-+
-+            # Make sure the wallet can no longer see the tx
-+            sender_wallet.refresh()
-+            sender_wallet.stop_background_sync(wallet_password = '', seed = seeds[0])
-+            transfers = sender_wallet.get_transfers()
-+            no_tx = [x for x in transfers.out if x.txid == txid]
-+            assert len(no_tx) == 0
-+            assert sender_wallet.get_balance().balance == sender_starting_balance
-+
-+        # Clean up
-+        daemon.out_peers(12)
-+        util_resources.remove_wallet_files('test1')
-+        self.wallet[0].close_wallet()
-+        self.wallet[0].restore_deterministic_wallet(seed = seeds[0])
-+
- if __name__ == '__main__':
-     TransferTest().run_test()
-diff --git a/tests/functional_tests/util_resources.py b/tests/functional_tests/util_resources.py
-index e030312da..3ca6fdb86 100755
---- a/tests/functional_tests/util_resources.py
-+++ b/tests/functional_tests/util_resources.py
-@@ -37,6 +37,8 @@
- from __future__ import print_function
- import subprocess
- import psutil
-+import os
-+import errno
- 
- def available_ram_gb():
-     ram_bytes = psutil.virtual_memory().available
-@@ -51,3 +53,26 @@ def get_time_pi_seconds(cores, app_dir='.'):
-     miliseconds = int(decoded)
- 
-     return miliseconds / 1000.0
-+
-+def remove_file(name):
-+    WALLET_DIRECTORY = os.environ['WALLET_DIRECTORY']
-+    assert WALLET_DIRECTORY != ''
-+    try:
-+        os.unlink(WALLET_DIRECTORY + '/' + name)
-+    except OSError as e:
-+        if e.errno != errno.ENOENT:
-+            raise
-+
-+def get_file_path(name):
-+    WALLET_DIRECTORY = os.environ['WALLET_DIRECTORY']
-+    assert WALLET_DIRECTORY != ''
-+    return WALLET_DIRECTORY + '/' + name
-+
-+def remove_wallet_files(name):
-+    for suffix in ['', '.keys', '.background', '.background.keys', '.address.txt']:
-+        remove_file(name + suffix)
-+
-+def file_exists(name):
-+    WALLET_DIRECTORY = os.environ['WALLET_DIRECTORY']
-+    assert WALLET_DIRECTORY != ''
-+    return os.path.isfile(WALLET_DIRECTORY + '/' + name)
-diff --git a/tests/functional_tests/wallet.py b/tests/functional_tests/wallet.py
-index 1ad05c98f..8182cecb2 100755
---- a/tests/functional_tests/wallet.py
-+++ b/tests/functional_tests/wallet.py
-@@ -34,8 +34,7 @@
- 
- from __future__ import print_function
- import sys
--import os
--import errno
-+import util_resources
- 
- from framework.wallet import Wallet
- from framework.daemon import Daemon
-@@ -54,24 +53,6 @@ class WalletTest():
-       self.change_password()
-       self.store()
- 
--    def remove_file(self, name):
--        WALLET_DIRECTORY = os.environ['WALLET_DIRECTORY']
--        assert WALLET_DIRECTORY != ''
--        try:
--            os.unlink(WALLET_DIRECTORY + '/' + name)
--        except OSError as e:
--            if e.errno != errno.ENOENT:
--                raise
--
--    def remove_wallet_files(self, name):
--        for suffix in ['', '.keys']:
--            self.remove_file(name + suffix)
--
--    def file_exists(self, name):
--        WALLET_DIRECTORY = os.environ['WALLET_DIRECTORY']
--        assert WALLET_DIRECTORY != ''
--        return os.path.isfile(WALLET_DIRECTORY + '/' + name)
--
-     def reset(self):
-         print('Resetting blockchain')
-         daemon = Daemon()
-@@ -333,7 +314,7 @@ class WalletTest():
-         try: wallet.close_wallet()
-         except: pass
- 
--        self.remove_wallet_files('test1')
-+        util_resources.remove_wallet_files('test1')
- 
-         seed = 'velvet lymph giddy number token physics poetry unquoted nibs useful sabotage limits benches lifestyle eden nitrogen anvil fewest avoid batch vials washing fences goat unquoted'
-         res = wallet.restore_deterministic_wallet(seed = seed, filename = 'test1')
-@@ -359,7 +340,7 @@ class WalletTest():
- 
-         wallet.close_wallet()
- 
--        self.remove_wallet_files('test1')
-+        util_resources.remove_wallet_files('test1')
- 
-     def store(self):
-         print('Testing store')
-@@ -369,22 +350,26 @@ class WalletTest():
-         try: wallet.close_wallet()
-         except: pass
- 
--        self.remove_wallet_files('test1')
-+        util_resources.remove_wallet_files('test1')
- 
-         seed = 'velvet lymph giddy number token physics poetry unquoted nibs useful sabotage limits benches lifestyle eden nitrogen anvil fewest avoid batch vials washing fences goat unquoted'
-         res = wallet.restore_deterministic_wallet(seed = seed, filename = 'test1')
-         assert res.address == '42ey1afDFnn4886T7196doS9GPMzexD9gXpsZJDwVjeRVdFCSoHnv7KPbBeGpzJBzHRCAs9UxqeoyFQMYbqSWYTfJJQAWDm'
-         assert res.seed == seed
- 
--        self.remove_file('test1')
--        assert self.file_exists('test1.keys')
--        assert not self.file_exists('test1')
-+        util_resources.remove_file('test1')
-+        assert util_resources.file_exists('test1.keys')
-+        assert not util_resources.file_exists('test1')
-         wallet.store()
--        assert self.file_exists('test1.keys')
--        assert self.file_exists('test1')
-+        assert util_resources.file_exists('test1.keys')
-+        assert util_resources.file_exists('test1')
- 
-         wallet.close_wallet()
--        self.remove_wallet_files('test1')
-+
-+        wallet.open_wallet(filename = 'test1', password = '')
-+        wallet.close_wallet()
-+
-+        util_resources.remove_wallet_files('test1')
- 
- 
- if __name__ == '__main__':
-diff --git a/tests/unit_tests/wipeable_string.cpp b/tests/unit_tests/wipeable_string.cpp
-index ef6964f9e..25121a02e 100644
---- a/tests/unit_tests/wipeable_string.cpp
-+++ b/tests/unit_tests/wipeable_string.cpp
-@@ -211,3 +211,15 @@ TEST(wipeable_string, to_hex)
-   ASSERT_TRUE(epee::to_hex::wipeable_string(epee::span<const uint8_t>((const uint8_t*)"", 0)) == epee::wipeable_string(""));
-   ASSERT_TRUE(epee::to_hex::wipeable_string(epee::span<const uint8_t>((const uint8_t*)"abc", 3)) == epee::wipeable_string("616263"));
- }
-+
-+TEST(wipeable_string, to_string)
-+{
-+  // Converting a wipeable_string to a string defeats the purpose of wipeable_string,
-+  // but nice to know this works
-+  std::string str;
-+  {
-+    epee::wipeable_string wipeable_str("foo");
-+    str = std::string(wipeable_str.data(), wipeable_str.size());
-+  }
-+  ASSERT_TRUE(str == std::string("foo"));
-+}
-diff --git a/utils/python-rpc/framework/wallet.py b/utils/python-rpc/framework/wallet.py
-index 1e10e1f86..bff33a561 100644
---- a/utils/python-rpc/framework/wallet.py
-+++ b/utils/python-rpc/framework/wallet.py
-@@ -1138,3 +1138,45 @@ class Wallet(object):
-             'id': '0'
-         }
-         return self.rpc.send_json_rpc_request(frozen)
-+
-+    class BackgroundSyncOptions(object):
-+        def __init__(self):
-+            self.off = 'off'
-+            self.reuse_password = 'reuse-wallet-password'
-+            self.custom_password = 'custom-background-password'
-+    background_sync_options = BackgroundSyncOptions()
-+
-+    def setup_background_sync(self, background_sync_type = background_sync_options.off, wallet_password = '', background_cache_password = ''):
-+        setup_background_sync = {
-+            'method': 'setup_background_sync',
-+            'jsonrpc': '2.0',
-+            'params' : {
-+                'background_sync_type': background_sync_type,
-+                'wallet_password': wallet_password,
-+                'background_cache_password': background_cache_password,
-+            },
-+            'id': '0'
-+        }
-+        return self.rpc.send_json_rpc_request(setup_background_sync)
-+
-+    def start_background_sync(self):
-+        start_background_sync = {
-+            'method': 'start_background_sync',
-+            'jsonrpc': '2.0',
-+            'params' : {},
-+            'id': '0'
-+        }
-+        return self.rpc.send_json_rpc_request(start_background_sync)
-+
-+    def stop_background_sync(self, wallet_password = '', seed = '', seed_offset = ''):
-+        stop_background_sync = {
-+            'method': 'stop_background_sync',
-+            'jsonrpc': '2.0',
-+            'params' : {
-+                'wallet_password': wallet_password,
-+                'seed': seed,
-+                'seed_offset': seed_offset,
-+            },
-+            'id': '0'
-+        }
-+        return self.rpc.send_json_rpc_request(stop_background_sync)
--- 
-2.48.0
-