Tx proof (revised):

- refactoring: proof generation/checking code was moved from simplewallet.cpp to wallet2.cpp
- allow an arbitrary message to be signed together with txid
- introduce two types (outbound & inbound) of tx proofs; with the same syntax, inbound is selected when <address> belongs to this wallet, outbound otherwise. see GitHub thread for more discussion
- wallet RPC: added get_tx_key, check_tx_key, get_tx_proof, check_tx_proof
- wallet API: moved WalletManagerImpl::checkPayment to Wallet::checkTxKey, added Wallet::getTxProof/checkTxProof
- get_tx_key/check_tx_key: handle additional tx keys by concatenating them into a single string

11 files changed, 770 insertions, 171 deletions

diff --git a/src/wallet/api/wallet.cpp b/src/wallet/api/wallet.cpp
index 8e747d16b..db8911042 100644
--- a/src/wallet/api/wallet.cpp
+++ b/src/wallet/api/wallet.cpp
@@ -1385,24 +1385,148 @@ std::string WalletImpl::getUserNote(const std::string &txid) const
     return m_wallet->get_tx_note(htxid);
 }
 
-std::string WalletImpl::getTxKey(const std::string &txid) const
+std::string WalletImpl::getTxKey(const std::string &txid_str) const
 {
-    cryptonote::blobdata txid_data;
-    if(!epee::string_tools::parse_hexstr_to_binbuff(txid, txid_data) || txid_data.size() != sizeof(crypto::hash))
+    crypto::hash txid;
+    if(!epee::string_tools::hex_to_pod(txid_str, txid))
     {
-      return "";
+        m_status = Status_Error;
+        m_errorString = tr("Failed to parse txid");
+        return "";
     }
-    const crypto::hash htxid = *reinterpret_cast<const crypto::hash*>(txid_data.data());
 
     crypto::secret_key tx_key;
     std::vector<crypto::secret_key> additional_tx_keys;
-    if (m_wallet->get_tx_key(htxid, tx_key, additional_tx_keys))
+    if (m_wallet->get_tx_key(txid, tx_key, additional_tx_keys))
     {
-      return epee::string_tools::pod_to_hex(tx_key);
+        m_status = Status_Ok;
+        std::ostringstream oss;
+        oss << epee::string_tools::pod_to_hex(tx_key);
+        for (size_t i = 0; i < additional_tx_keys.size(); ++i)
+            oss << epee::string_tools::pod_to_hex(additional_tx_keys[i]);
+        return oss.str();
     }
     else
     {
-      return "";
+        m_status = Status_Error;
+        m_errorString = tr("no tx keys found for this txid");
+        return "";
+    }
+}
+
+bool WalletImpl::checkTxKey(const std::string &txid_str, std::string tx_key_str, const std::string &address_str, uint64_t &received, bool &in_pool, uint64_t &confirmations)
+{
+    crypto::hash txid;
+    if (!epee::string_tools::hex_to_pod(txid_str, txid))
+    {
+        m_status = Status_Error;
+        m_errorString = tr("Failed to parse txid");
+        return false;
+    }
+
+    crypto::secret_key tx_key;
+    std::vector<crypto::secret_key> additional_tx_keys;
+    if (!epee::string_tools::hex_to_pod(tx_key_str.substr(0, 64), tx_key))
+    {
+        m_status = Status_Error;
+        m_errorString = tr("Failed to parse tx key");
+        return false;
+    }
+    tx_key_str = tx_key_str.substr(64);
+    while (!tx_key_str.empty())
+    {
+        additional_tx_keys.resize(additional_tx_keys.size() + 1);
+        if (!epee::string_tools::hex_to_pod(tx_key_str.substr(0, 64), additional_tx_keys.back()))
+        {
+            m_status = Status_Error;
+            m_errorString = tr("Failed to parse tx key");
+            return false;
+        }
+        tx_key_str = tx_key_str.substr(64);
+    }
+
+    cryptonote::address_parse_info info;
+    if (!cryptonote::get_account_address_from_str(info, m_wallet->testnet(), address_str))
+    {
+        m_status = Status_Error;
+        m_errorString = tr("Failed to parse address");
+        return false;
+    }
+
+    try
+    {
+        m_wallet->check_tx_key(txid, tx_key, additional_tx_keys, info.address, received, in_pool, confirmations);
+        m_status = Status_Ok;
+        return true;
+    }
+    catch (const std::exception &e)
+    {
+        m_status = Status_Error;
+        m_errorString = e.what();
+        return false;
+    }
+}
+
+std::string WalletImpl::getTxProof(const std::string &txid_str, const std::string &address_str, const std::string &message, std::string &error_str) const
+{
+    crypto::hash txid;
+    if (!epee::string_tools::hex_to_pod(txid_str, txid))
+    {
+        m_status = Status_Error;
+        m_errorString = tr("Failed to parse txid");
+        return "";
+    }
+
+    cryptonote::address_parse_info info;
+    if (!cryptonote::get_account_address_from_str(info, m_wallet->testnet(), address_str))
+    {
+        m_status = Status_Error;
+        m_errorString = tr("Failed to parse address");
+        return "";
+    }
+
+    try
+    {
+        m_status = Status_Ok;
+        return m_wallet->get_tx_proof(txid, info.address, info.is_subaddress, message, error_str);
+    }
+    catch (const std::exception &e)
+    {
+        m_status = Status_Error;
+        m_errorString = e.what();
+        return "";
+    }
+}
+
+bool WalletImpl::checkTxProof(const std::string &txid_str, const std::string &address_str, const std::string &message, const std::string &signature, bool &good, uint64_t &received, bool &in_pool, uint64_t &confirmations)
+{
+    crypto::hash txid;
+    if (!epee::string_tools::hex_to_pod(txid_str, txid))
+    {
+        m_status = Status_Error;
+        m_errorString = tr("Failed to parse txid");
+        return false;
+    }
+
+    cryptonote::address_parse_info info;
+    if (!cryptonote::get_account_address_from_str(info, m_wallet->testnet(), address_str))
+    {
+        m_status = Status_Error;
+        m_errorString = tr("Failed to parse address");
+        return false;
+    }
+
+    try
+    {
+        good = m_wallet->check_tx_proof(txid, info.address, info.is_subaddress, message, signature, received, in_pool, confirmations);
+        m_status = Status_Ok;
+        return true;
+    }
+    catch (const std::exception &e)
+    {
+        m_status = Status_Error;
+        m_errorString = e.what();
+        return false;
     }
 }
 
diff --git a/src/wallet/api/wallet.h b/src/wallet/api/wallet.h
index 051eda3ba..ecf540f22 100644
--- a/src/wallet/api/wallet.h
+++ b/src/wallet/api/wallet.h
@@ -137,6 +137,9 @@ public:
     virtual bool setUserNote(const std::string &txid, const std::string &note);
     virtual std::string getUserNote(const std::string &txid) const;
     virtual std::string getTxKey(const std::string &txid) const;
+    virtual bool checkTxKey(const std::string &txid, std::string tx_key, const std::string &address, uint64_t &received, bool &in_pool, uint64_t &confirmations);
+    virtual std::string getTxProof(const std::string &txid, const std::string &address, const std::string &message, std::string &error_str) const;
+    virtual bool checkTxProof(const std::string &txid, const std::string &address, const std::string &message, const std::string &signature, bool &good, uint64_t &received, bool &in_pool, uint64_t &confirmations);
     virtual std::string signMessage(const std::string &message);
     virtual bool verifySignedMessage(const std::string &message, const std::string &address, const std::string &signature) const;
     virtual void startRefresh();
diff --git a/src/wallet/api/wallet_manager.cpp b/src/wallet/api/wallet_manager.cpp
index 2326f54d3..ee69ec028 100644
--- a/src/wallet/api/wallet_manager.cpp
+++ b/src/wallet/api/wallet_manager.cpp
@@ -189,155 +189,6 @@ bool WalletManagerImpl::connected(uint32_t *version) const
     return true;
 }
 
-bool WalletManagerImpl::checkPayment(const std::string &address_text, const std::string &txid_text, const std::string &txkey_text, const std::string &daemon_address, uint64_t &received, uint64_t &height, std::string &error) const
-{
-  error = "";
-  cryptonote::blobdata txid_data;
-  if(!epee::string_tools::parse_hexstr_to_binbuff(txid_text, txid_data) || txid_data.size() != sizeof(crypto::hash))
-  {
-    error = tr("failed to parse txid");
-    return false;
-  }
-  crypto::hash txid = *reinterpret_cast<const crypto::hash*>(txid_data.data());
-
-  if (txkey_text.size() < 64 || txkey_text.size() % 64)
-  {
-    error = tr("failed to parse tx key");
-    return false;
-  }
-  crypto::secret_key tx_key;
-  cryptonote::blobdata tx_key_data;
-  if(!epee::string_tools::parse_hexstr_to_binbuff(txkey_text, tx_key_data) || tx_key_data.size() != sizeof(crypto::hash))
-  {
-    error = tr("failed to parse tx key");
-    return false;
-  }
-  tx_key = *reinterpret_cast<const crypto::secret_key*>(tx_key_data.data());
-
-  bool testnet = address_text[0] != '4';
-  cryptonote::address_parse_info info;
-  if(!cryptonote::get_account_address_from_str(info, testnet, address_text))
-  {
-    error = tr("failed to parse address");
-    return false;
-  }
-
-  cryptonote::COMMAND_RPC_GET_TRANSACTIONS::request req;
-  cryptonote::COMMAND_RPC_GET_TRANSACTIONS::response res;
-  req.txs_hashes.push_back(epee::string_tools::pod_to_hex(txid));
-  if (!connect_and_invoke(m_daemonAddress, "/gettransactions", req, res) ||
-      (res.txs.size() != 1 && res.txs_as_hex.size() != 1))
-  {
-    error = tr("failed to get transaction from daemon");
-    return false;
-  }
-  cryptonote::blobdata tx_data;
-  bool ok;
-  if (res.txs.size() == 1)
-    ok = epee::string_tools::parse_hexstr_to_binbuff(res.txs.front().as_hex, tx_data);
-  else
-    ok = epee::string_tools::parse_hexstr_to_binbuff(res.txs_as_hex.front(), tx_data);
-  if (!ok)
-  {
-    error = tr("failed to parse transaction from daemon");
-    return false;
-  }
-  crypto::hash tx_hash, tx_prefix_hash;
-  cryptonote::transaction tx;
-  if (!cryptonote::parse_and_validate_tx_from_blob(tx_data, tx, tx_hash, tx_prefix_hash))
-  {
-    error = tr("failed to validate transaction from daemon");
-    return false;
-  }
-  if (tx_hash != txid)
-  {
-    error = tr("failed to get the right transaction from daemon");
-    return false;
-  }
-
-  crypto::key_derivation derivation;
-  if (!crypto::generate_key_derivation(info.address.m_view_public_key, tx_key, derivation))
-  {
-    error = tr("failed to generate key derivation from supplied parameters");
-    return false;
-  }
-
-  received = 0;
-  try {
-    for (size_t n = 0; n < tx.vout.size(); ++n)
-    {
-      if (typeid(cryptonote::txout_to_key) != tx.vout[n].target.type())
-        continue;
-      const cryptonote::txout_to_key tx_out_to_key = boost::get<cryptonote::txout_to_key>(tx.vout[n].target);
-      crypto::public_key pubkey;
-      derive_public_key(derivation, n, info.address.m_spend_public_key, pubkey);
-      if (pubkey == tx_out_to_key.key)
-      {
-        uint64_t amount;
-        if (tx.version == 1)
-        {
-          amount = tx.vout[n].amount;
-        }
-        else
-        {
-          try
-          {
-            rct::key Ctmp;
-            //rct::key amount_key = rct::hash_to_scalar(rct::scalarmultKey(rct::pk2rct(address.m_view_public_key), rct::sk2rct(tx_key)));
-            crypto::key_derivation derivation;
-            bool r = crypto::generate_key_derivation(info.address.m_view_public_key, tx_key, derivation);
-            if (!r)
-            {
-              LOG_ERROR("Failed to generate key derivation to decode rct output " << n);
-              amount = 0;
-            }
-            else
-            {
-              crypto::secret_key scalar1;
-              crypto::derivation_to_scalar(derivation, n, scalar1);
-              rct::ecdhTuple ecdh_info = tx.rct_signatures.ecdhInfo[n];
-              rct::ecdhDecode(ecdh_info, rct::sk2rct(scalar1));
-              rct::key C = tx.rct_signatures.outPk[n].mask;
-              rct::addKeys2(Ctmp, ecdh_info.mask, ecdh_info.amount, rct::H);
-              if (rct::equalKeys(C, Ctmp))
-                amount = rct::h2d(ecdh_info.amount);
-              else
-                amount = 0;
-            }
-          }
-          catch (...) { amount = 0; }
-        }
-        received += amount;
-      }
-    }
-  }
-  catch(const std::exception &e)
-  {
-    LOG_ERROR("error: " << e.what());
-    error = std::string(tr("error: ")) + e.what();
-    return false;
-  }
-
-  if (received > 0)
-  {
-    LOG_PRINT_L1(get_account_address_as_str(testnet, info.is_subaddress, info.address) << " " << tr("received") << " " << cryptonote::print_money(received) << " " << tr("in txid") << " " << txid);
-  }
-  else
-  {
-    LOG_PRINT_L1(get_account_address_as_str(testnet, info.is_subaddress, info.address) << " " << tr("received nothing in txid") << " " << txid);
-  }
-  if (res.txs.front().in_pool)
-  {
-    height = 0;
-  }
-  else
-  {
-    height = res.txs.front().block_height;
-  }
-
-  return true;
-}
-
 uint64_t WalletManagerImpl::blockchainHeight() const
 {
     cryptonote::COMMAND_RPC_GET_INFO::request ireq;
diff --git a/src/wallet/api/wallet_manager.h b/src/wallet/api/wallet_manager.h
index 8455f0f16..5772eda05 100644
--- a/src/wallet/api/wallet_manager.h
+++ b/src/wallet/api/wallet_manager.h
@@ -55,7 +55,6 @@ public:
     std::string errorString() const;
     void setDaemonAddress(const std::string &address);
     bool connected(uint32_t *version = NULL) const;
-    bool checkPayment(const std::string &address, const std::string &txid, const std::string &txkey, const std::string &daemon_address, uint64_t &received, uint64_t &height, std::string &error) const;
     uint64_t blockchainHeight() const;
     uint64_t blockchainTargetHeight() const;
     uint64_t networkDifficulty() const;
diff --git a/src/wallet/wallet2.cpp b/src/wallet/wallet2.cpp
index 00b096b88..8bc762184 100644
--- a/src/wallet/wallet2.cpp
+++ b/src/wallet/wallet2.cpp
@@ -6208,6 +6208,355 @@ bool wallet2::get_tx_key(const crypto::hash &txid, crypto::secret_key &tx_key, s
   return true;
 }
 
+void wallet2::check_tx_key(const crypto::hash &txid, const crypto::secret_key &tx_key, const std::vector<crypto::secret_key> &additional_tx_keys, const cryptonote::account_public_address &address, uint64_t &received, bool &in_pool, uint64_t &confirmations)
+{
+  crypto::key_derivation derivation;
+  THROW_WALLET_EXCEPTION_IF(!crypto::generate_key_derivation(address.m_view_public_key, tx_key, derivation), error::wallet_internal_error,
+    "Failed to generate key derivation from supplied parameters");
+
+  std::vector<crypto::key_derivation> additional_derivations;
+  additional_derivations.resize(additional_tx_keys.size());
+  for (size_t i = 0; i < additional_tx_keys.size(); ++i)
+    THROW_WALLET_EXCEPTION_IF(!crypto::generate_key_derivation(address.m_view_public_key, additional_tx_keys[i], additional_derivations[i]), error::wallet_internal_error,
+      "Failed to generate key derivation from supplied parameters");
+
+  check_tx_key_helper(txid, derivation, additional_derivations, address, received, in_pool, confirmations);
+}
+
+void wallet2::check_tx_key_helper(const crypto::hash &txid, const crypto::key_derivation &derivation, const std::vector<crypto::key_derivation> &additional_derivations, const cryptonote::account_public_address &address, uint64_t &received, bool &in_pool, uint64_t &confirmations)
+{
+  COMMAND_RPC_GET_TRANSACTIONS::request req;
+  COMMAND_RPC_GET_TRANSACTIONS::response res;
+  req.txs_hashes.push_back(epee::string_tools::pod_to_hex(txid));
+  m_daemon_rpc_mutex.lock();
+  bool ok = epee::net_utils::invoke_http_json("/gettransactions", req, res, m_http_client);
+  m_daemon_rpc_mutex.unlock();
+  THROW_WALLET_EXCEPTION_IF(!ok || (res.txs.size() != 1 && res.txs_as_hex.size() != 1),
+    error::wallet_internal_error, "Failed to get transaction from daemon");
+
+  cryptonote::blobdata tx_data;
+  if (res.txs.size() == 1)
+    ok = string_tools::parse_hexstr_to_binbuff(res.txs.front().as_hex, tx_data);
+  else
+    ok = string_tools::parse_hexstr_to_binbuff(res.txs_as_hex.front(), tx_data);
+  THROW_WALLET_EXCEPTION_IF(!ok, error::wallet_internal_error, "Failed to parse transaction from daemon");
+
+  crypto::hash tx_hash, tx_prefix_hash;
+  cryptonote::transaction tx;
+  THROW_WALLET_EXCEPTION_IF(!cryptonote::parse_and_validate_tx_from_blob(tx_data, tx, tx_hash, tx_prefix_hash), error::wallet_internal_error,
+    "Failed to validate transaction from daemon");
+  THROW_WALLET_EXCEPTION_IF(tx_hash != txid, error::wallet_internal_error,
+    "Failed to get the right transaction from daemon");
+  THROW_WALLET_EXCEPTION_IF(!additional_derivations.empty() && additional_derivations.size() != tx.vout.size(), error::wallet_internal_error,
+    "The size of additional derivations is wrong");
+
+  received = 0;
+  for (size_t n = 0; n < tx.vout.size(); ++n)
+  {
+    const cryptonote::txout_to_key* const out_key = boost::get<cryptonote::txout_to_key>(std::addressof(tx.vout[n].target));
+    if (!out_key)
+      continue;
+
+    crypto::public_key derived_out_key;
+    derive_public_key(derivation, n, address.m_spend_public_key, derived_out_key);
+    bool found = out_key->key == derived_out_key;
+    crypto::key_derivation found_derivation = derivation;
+    if (!found && !additional_derivations.empty())
+    {
+      derive_public_key(additional_derivations[n], n, address.m_spend_public_key, derived_out_key);
+      found = out_key->key == derived_out_key;
+      found_derivation = additional_derivations[n];
+    }
+
+    if (found)
+    {
+      uint64_t amount;
+      if (tx.version == 1 || tx.rct_signatures.type == rct::RCTTypeNull)
+      {
+        amount = tx.vout[n].amount;
+      }
+      else
+      {
+        crypto::secret_key scalar1;
+        crypto::derivation_to_scalar(found_derivation, n, scalar1);
+        rct::ecdhTuple ecdh_info = tx.rct_signatures.ecdhInfo[n];
+        rct::ecdhDecode(ecdh_info, rct::sk2rct(scalar1));
+        const rct::key C = tx.rct_signatures.outPk[n].mask;
+        rct::key Ctmp;
+        rct::addKeys2(Ctmp, ecdh_info.mask, ecdh_info.amount, rct::H);
+        if (rct::equalKeys(C, Ctmp))
+          amount = rct::h2d(ecdh_info.amount);
+        else
+          amount = 0;
+      }
+      received += amount;
+    }
+  }
+
+  in_pool = res.txs.front().in_pool;
+  confirmations = (uint64_t)-1;
+  if (!in_pool)
+  {
+    std::string err;
+    uint64_t bc_height = get_daemon_blockchain_height(err);
+    if (err.empty())
+      confirmations = bc_height - (res.txs.front().block_height + 1);
+  }
+}
+
+std::string wallet2::get_tx_proof(const crypto::hash &txid, const cryptonote::account_public_address &address, bool is_subaddress, const std::string &message, std::string &error_str)
+{
+  error_str = "";
+  // determine if the address is found in the subaddress hash table (i.e. whether the proof is outbound or inbound)
+  const bool is_out = m_subaddresses.count(address.m_spend_public_key) == 0;
+
+  std::string prefix_data((const char*)&txid, sizeof(crypto::hash));
+  prefix_data += message;
+  crypto::hash prefix_hash;
+  crypto::cn_fast_hash(prefix_data.data(), prefix_data.size(), prefix_hash);
+
+  std::vector<crypto::public_key> shared_secret;
+  std::vector<crypto::signature> sig;
+  std::string sig_str;
+  if (is_out)
+  {
+    crypto::secret_key tx_key;
+    std::vector<crypto::secret_key> additional_tx_keys;
+    if (!get_tx_key(txid, tx_key, additional_tx_keys))
+    {
+      error_str = tr("Tx secret key wasn't found in the wallet file.");
+      return {};
+    }
+
+    const size_t num_sigs = 1 + additional_tx_keys.size();
+    shared_secret.resize(num_sigs);
+    sig.resize(num_sigs);
+
+    shared_secret[0] = rct::rct2pk(rct::scalarmultKey(rct::pk2rct(address.m_view_public_key), rct::sk2rct(tx_key)));
+    crypto::public_key tx_pub_key;
+    if (is_subaddress)
+    {
+      tx_pub_key = rct2pk(rct::scalarmultKey(rct::pk2rct(address.m_spend_public_key), rct::sk2rct(tx_key)));
+      crypto::generate_tx_proof(prefix_hash, tx_pub_key, address.m_view_public_key, address.m_spend_public_key, shared_secret[0], tx_key, sig[0]);
+    }
+    else
+    {
+      crypto::secret_key_to_public_key(tx_key, tx_pub_key);
+      crypto::generate_tx_proof(prefix_hash, tx_pub_key, address.m_view_public_key, boost::none, shared_secret[0], tx_key, sig[0]);
+    }
+    for (size_t i = 1; i < num_sigs; ++i)
+    {
+      shared_secret[i] = rct::rct2pk(rct::scalarmultKey(rct::pk2rct(address.m_view_public_key), rct::sk2rct(additional_tx_keys[i - 1])));
+      if (is_subaddress)
+      {
+        tx_pub_key = rct2pk(rct::scalarmultKey(rct::pk2rct(address.m_spend_public_key), rct::sk2rct(additional_tx_keys[i - 1])));
+        crypto::generate_tx_proof(prefix_hash, tx_pub_key, address.m_view_public_key, address.m_spend_public_key, shared_secret[i], additional_tx_keys[i - 1], sig[i]);
+      }
+      else
+      {
+        crypto::secret_key_to_public_key(additional_tx_keys[i - 1], tx_pub_key);
+        crypto::generate_tx_proof(prefix_hash, tx_pub_key, address.m_view_public_key, boost::none, shared_secret[i], additional_tx_keys[i - 1], sig[i]);
+      }
+    }
+    sig_str = std::string("OutProofV1");
+  }
+  else
+  {
+    // fetch tx pubkey from the daemon
+    COMMAND_RPC_GET_TRANSACTIONS::request req;
+    COMMAND_RPC_GET_TRANSACTIONS::response res;
+    req.txs_hashes.push_back(epee::string_tools::pod_to_hex(txid));
+    m_daemon_rpc_mutex.lock();
+    bool ok = net_utils::invoke_http_json("/gettransactions", req, res, m_http_client);
+    m_daemon_rpc_mutex.unlock();
+    THROW_WALLET_EXCEPTION_IF(!ok || (res.txs.size() != 1 && res.txs_as_hex.size() != 1),
+      error::wallet_internal_error, "Failed to get transaction from daemon");
+
+    cryptonote::blobdata tx_data;
+    if (res.txs.size() == 1)
+      ok = string_tools::parse_hexstr_to_binbuff(res.txs.front().as_hex, tx_data);
+    else
+      ok = string_tools::parse_hexstr_to_binbuff(res.txs_as_hex.front(), tx_data);
+    THROW_WALLET_EXCEPTION_IF(!ok, error::wallet_internal_error, "Failed to parse transaction from daemon");
+
+    crypto::hash tx_hash, tx_prefix_hash;
+    cryptonote::transaction tx;
+    THROW_WALLET_EXCEPTION_IF(!cryptonote::parse_and_validate_tx_from_blob(tx_data, tx, tx_hash, tx_prefix_hash), error::wallet_internal_error,
+      "Failed to validate transaction from daemon");
+    THROW_WALLET_EXCEPTION_IF(tx_hash != txid, error::wallet_internal_error, "Failed to get the right transaction from daemon");
+
+    crypto::public_key tx_pub_key = get_tx_pub_key_from_extra(tx);
+    THROW_WALLET_EXCEPTION_IF(tx_pub_key == null_pkey, error::wallet_internal_error, "Tx pubkey was not found");
+
+    std::vector<crypto::public_key> additional_tx_pub_keys = get_additional_tx_pub_keys_from_extra(tx);
+    const size_t num_sigs = 1 + additional_tx_pub_keys.size();
+    shared_secret.resize(num_sigs);
+    sig.resize(num_sigs);
+
+    const crypto::secret_key& a = m_account.get_keys().m_view_secret_key;
+    shared_secret[0] = rct::rct2pk(rct::scalarmultKey(rct::pk2rct(tx_pub_key), rct::sk2rct(a)));
+    if (is_subaddress)
+    {
+      crypto::generate_tx_proof(prefix_hash, address.m_view_public_key, tx_pub_key, address.m_spend_public_key, shared_secret[0], a, sig[0]);
+    }
+    else
+    {
+      crypto::generate_tx_proof(prefix_hash, address.m_view_public_key, tx_pub_key, boost::none, shared_secret[0], a, sig[0]);
+    }
+    for (size_t i = 1; i < num_sigs; ++i)
+    {
+      shared_secret[i] = rct::rct2pk(rct::scalarmultKey(rct::pk2rct(additional_tx_pub_keys[i - 1]), rct::sk2rct(a)));
+      if (is_subaddress)
+      {
+        crypto::generate_tx_proof(prefix_hash, address.m_view_public_key, additional_tx_pub_keys[i - 1], address.m_spend_public_key, shared_secret[i], a, sig[i]);
+      }
+      else
+      {
+        crypto::generate_tx_proof(prefix_hash, address.m_view_public_key, additional_tx_pub_keys[i - 1], boost::none, shared_secret[i], a, sig[i]);
+      }
+    }
+    sig_str = std::string("InProofV1");
+  }
+  const size_t num_sigs = shared_secret.size();
+
+  // check if this address actually received any funds
+  crypto::key_derivation derivation;
+  THROW_WALLET_EXCEPTION_IF(!crypto::generate_key_derivation(shared_secret[0], rct::rct2sk(rct::I), derivation), error::wallet_internal_error, "Failed to generate key derivation");
+  std::vector<crypto::key_derivation> additional_derivations(num_sigs - 1);
+  for (size_t i = 1; i < num_sigs; ++i)
+    THROW_WALLET_EXCEPTION_IF(!crypto::generate_key_derivation(shared_secret[i], rct::rct2sk(rct::I), additional_derivations[i - 1]), error::wallet_internal_error, "Failed to generate key derivation");
+  uint64_t received;
+  bool in_pool;
+  uint64_t confirmations;
+  check_tx_key_helper(txid, derivation, additional_derivations, address, received, in_pool, confirmations);
+  if (!received)
+  {
+    error_str = tr("No funds received in this tx.");
+    return {};
+  }
+
+  // concatenate all signature strings
+  for (size_t i = 0; i < num_sigs; ++i)
+    sig_str +=
+      tools::base58::encode(std::string((const char *)&shared_secret[i], sizeof(crypto::public_key))) +
+      tools::base58::encode(std::string((const char *)&sig[i], sizeof(crypto::signature)));
+  return sig_str;
+}
+
+bool wallet2::check_tx_proof(const crypto::hash &txid, const cryptonote::account_public_address &address, bool is_subaddress, const std::string &message, const std::string &sig_str, uint64_t &received, bool &in_pool, uint64_t &confirmations)
+{
+  const bool is_out = sig_str.substr(0, 3) == "Out";
+  const std::string header = is_out ? "OutProofV1" : "InProofV1";
+  const size_t header_len = header.size();
+  THROW_WALLET_EXCEPTION_IF(sig_str.size() < header_len || sig_str.substr(0, header_len) != header, error::wallet_internal_error,
+    "Signature header check error");
+
+  // decode base58
+  std::vector<crypto::public_key> shared_secret(1);
+  std::vector<crypto::signature> sig(1);
+  const size_t pk_len = tools::base58::encode(std::string((const char *)&shared_secret[0], sizeof(crypto::public_key))).size();
+  const size_t sig_len = tools::base58::encode(std::string((const char *)&sig[0], sizeof(crypto::signature))).size();
+  const size_t num_sigs = (sig_str.size() - header_len) / (pk_len + sig_len);
+  THROW_WALLET_EXCEPTION_IF(sig_str.size() != header_len + num_sigs * (pk_len + sig_len), error::wallet_internal_error,
+    "Wrong signature size");
+  shared_secret.resize(num_sigs);
+  sig.resize(num_sigs);
+  for (size_t i = 0; i < num_sigs; ++i)
+  {
+    std::string pk_decoded;
+    std::string sig_decoded;
+    const size_t offset = header_len + i * (pk_len + sig_len);
+    THROW_WALLET_EXCEPTION_IF(!tools::base58::decode(sig_str.substr(offset, pk_len), pk_decoded), error::wallet_internal_error,
+      "Signature decoding error");
+    THROW_WALLET_EXCEPTION_IF(!tools::base58::decode(sig_str.substr(offset + pk_len, sig_len), sig_decoded), error::wallet_internal_error,
+      "Signature decoding error");
+    THROW_WALLET_EXCEPTION_IF(sizeof(crypto::public_key) != pk_decoded.size() || sizeof(crypto::signature) != sig_decoded.size(), error::wallet_internal_error,
+      "Signature decoding error");
+    memcpy(&shared_secret[i], pk_decoded.data(), sizeof(crypto::public_key));
+    memcpy(&sig[i], sig_decoded.data(), sizeof(crypto::signature));
+  }
+
+  // fetch tx pubkey from the daemon
+  COMMAND_RPC_GET_TRANSACTIONS::request req;
+  COMMAND_RPC_GET_TRANSACTIONS::response res;
+  req.txs_hashes.push_back(epee::string_tools::pod_to_hex(txid));
+  m_daemon_rpc_mutex.lock();
+  bool ok = net_utils::invoke_http_json("/gettransactions", req, res, m_http_client);
+  m_daemon_rpc_mutex.unlock();
+  THROW_WALLET_EXCEPTION_IF(!ok || (res.txs.size() != 1 && res.txs_as_hex.size() != 1),
+    error::wallet_internal_error, "Failed to get transaction from daemon");
+
+  cryptonote::blobdata tx_data;
+  if (res.txs.size() == 1)
+    ok = string_tools::parse_hexstr_to_binbuff(res.txs.front().as_hex, tx_data);
+  else
+    ok = string_tools::parse_hexstr_to_binbuff(res.txs_as_hex.front(), tx_data);
+  THROW_WALLET_EXCEPTION_IF(!ok, error::wallet_internal_error, "Failed to parse transaction from daemon");
+
+  crypto::hash tx_hash, tx_prefix_hash;
+  cryptonote::transaction tx;
+  THROW_WALLET_EXCEPTION_IF(!cryptonote::parse_and_validate_tx_from_blob(tx_data, tx, tx_hash, tx_prefix_hash), error::wallet_internal_error,
+    "Failed to validate transaction from daemon");
+  THROW_WALLET_EXCEPTION_IF(tx_hash != txid, error::wallet_internal_error, "Failed to get the right transaction from daemon");
+
+  crypto::public_key tx_pub_key = get_tx_pub_key_from_extra(tx);
+  THROW_WALLET_EXCEPTION_IF(tx_pub_key == null_pkey, error::wallet_internal_error, "Tx pubkey was not found");
+
+  std::vector<crypto::public_key> additional_tx_pub_keys = get_additional_tx_pub_keys_from_extra(tx);
+  THROW_WALLET_EXCEPTION_IF(additional_tx_pub_keys.size() + 1 != num_sigs, error::wallet_internal_error, "Signature size mismatch with additional tx pubkeys");
+
+  std::string prefix_data((const char*)&txid, sizeof(crypto::hash));
+  prefix_data += message;
+  crypto::hash prefix_hash;
+  crypto::cn_fast_hash(prefix_data.data(), prefix_data.size(), prefix_hash);
+
+  // check signature
+  std::vector<int> good_signature(num_sigs, 0);
+  if (is_out)
+  {
+    good_signature[0] = is_subaddress ?
+      crypto::check_tx_proof(prefix_hash, tx_pub_key, address.m_view_public_key, address.m_spend_public_key, shared_secret[0], sig[0]) :
+      crypto::check_tx_proof(prefix_hash, tx_pub_key, address.m_view_public_key, boost::none, shared_secret[0], sig[0]);
+
+    for (size_t i = 0; i < additional_tx_pub_keys.size(); ++i)
+    {
+      good_signature[i + 1] = is_subaddress ?
+        crypto::check_tx_proof(prefix_hash, additional_tx_pub_keys[i], address.m_view_public_key, address.m_spend_public_key, shared_secret[i + 1], sig[i + 1]) :
+        crypto::check_tx_proof(prefix_hash, additional_tx_pub_keys[i], address.m_view_public_key, boost::none, shared_secret[i + 1], sig[i + 1]);
+    }
+  }
+  else
+  {
+    good_signature[0] = is_subaddress ?
+      crypto::check_tx_proof(prefix_hash, address.m_view_public_key, tx_pub_key, address.m_spend_public_key, shared_secret[0], sig[0]) :
+      crypto::check_tx_proof(prefix_hash, address.m_view_public_key, tx_pub_key, boost::none, shared_secret[0], sig[0]);
+
+    for (size_t i = 0; i < additional_tx_pub_keys.size(); ++i)
+    {
+      good_signature[i + 1] = is_subaddress ?
+        crypto::check_tx_proof(prefix_hash, address.m_view_public_key, additional_tx_pub_keys[i], address.m_spend_public_key, shared_secret[i + 1], sig[i + 1]) :
+        crypto::check_tx_proof(prefix_hash, address.m_view_public_key, additional_tx_pub_keys[i], boost::none, shared_secret[i + 1], sig[i + 1]);
+    }
+  }
+
+  if (std::any_of(good_signature.begin(), good_signature.end(), [](int i) { return i > 0; }))
+  {
+    // obtain key derivation by multiplying scalar 1 to the shared secret
+    crypto::key_derivation derivation;
+    if (good_signature[0])
+      THROW_WALLET_EXCEPTION_IF(!crypto::generate_key_derivation(shared_secret[0], rct::rct2sk(rct::I), derivation), error::wallet_internal_error, "Failed to generate key derivation");
+
+    std::vector<crypto::key_derivation> additional_derivations(num_sigs - 1);
+    for (size_t i = 1; i < num_sigs; ++i)
+      if (good_signature[i])
+        THROW_WALLET_EXCEPTION_IF(!crypto::generate_key_derivation(shared_secret[i], rct::rct2sk(rct::I), additional_derivations[i - 1]), error::wallet_internal_error, "Failed to generate key derivation");
+
+    check_tx_key_helper(txid, derivation, additional_derivations, address, received, in_pool, confirmations);
+    return true;
+  }
+  return false;
+}
+
 std::string wallet2::get_wallet_file() const
 {
   return m_wallet_file;
diff --git a/src/wallet/wallet2.h b/src/wallet/wallet2.h
index 6e01d4e28..cff10fa11 100644
--- a/src/wallet/wallet2.h
+++ b/src/wallet/wallet2.h
@@ -684,6 +684,10 @@ namespace tools
     uint32_t get_confirm_backlog_threshold() const { return m_confirm_backlog_threshold; };
 
     bool get_tx_key(const crypto::hash &txid, crypto::secret_key &tx_key, std::vector<crypto::secret_key> &additional_tx_keys) const;
+    void check_tx_key(const crypto::hash &txid, const crypto::secret_key &tx_key, const std::vector<crypto::secret_key> &additional_tx_keys, const cryptonote::account_public_address &address, uint64_t &received, bool &in_pool, uint64_t &confirmations);
+    void check_tx_key_helper(const crypto::hash &txid, const crypto::key_derivation &derivation, const std::vector<crypto::key_derivation> &additional_derivations, const cryptonote::account_public_address &address, uint64_t &received, bool &in_pool, uint64_t &confirmations);
+    std::string get_tx_proof(const crypto::hash &txid, const cryptonote::account_public_address &address, bool is_subaddress, const std::string &message, std::string &error_str);
+    bool check_tx_proof(const crypto::hash &txid, const cryptonote::account_public_address &address, bool is_subaddress, const std::string &message, const std::string &sig_str, uint64_t &received, bool &in_pool, uint64_t &confirmations);
 
    /*!
     * \brief GUI Address book get/store
diff --git a/src/wallet/wallet2_api.h b/src/wallet/wallet2_api.h
index 432c820cb..8d6b2ffa9 100644
--- a/src/wallet/wallet2_api.h
+++ b/src/wallet/wallet2_api.h
@@ -700,6 +700,9 @@ struct Wallet
      */
     virtual std::string getUserNote(const std::string &txid) const = 0;
     virtual std::string getTxKey(const std::string &txid) const = 0;
+    virtual bool checkTxKey(const std::string &txid, std::string tx_key, const std::string &address, uint64_t &received, bool &in_pool, uint64_t &confirmations) = 0;
+    virtual std::string getTxProof(const std::string &txid, const std::string &address, const std::string &message, std::string &error_str) const = 0;
+    virtual bool checkTxProof(const std::string &txid, const std::string &address, const std::string &message, const std::string &signature, bool &good, uint64_t &received, bool &in_pool, uint64_t &confirmations) = 0;
 
     /*
      * \brief signMessage - sign a message with the spend private key
@@ -819,19 +822,6 @@ struct WalletManager
      */
     virtual std::vector<std::string> findWallets(const std::string &path) = 0;
 
-    /*!
-     * \brief checkPayment - checks a payment was made using a txkey
-     * \param address - the address the payment was sent to
-     * \param txid - the transaction id for that payment
-     * \param txkey - the transaction's secret key
-     * \param daemon_address - the address (host and port) to the daemon to request transaction data
-     * \param received - if succesful, will hold the amount of monero received
-     * \param height - if succesful, will hold the height of the transaction (0 if only in the pool)
-     * \param error - if unsuccesful, will hold an error string with more information about the error
-     * \return - true is succesful, false otherwise
-     */
-    virtual bool checkPayment(const std::string &address, const std::string &txid, const std::string &txkey, const std::string &daemon_address, uint64_t &received, uint64_t &height, std::string &error) const = 0;
-
     //! returns verbose error string regarding last error;
     virtual std::string errorString() const = 0;
 
diff --git a/src/wallet/wallet_rpc_server.cpp b/src/wallet/wallet_rpc_server.cpp
index f5838d013..dca8ebd7e 100644
--- a/src/wallet/wallet_rpc_server.cpp
+++ b/src/wallet/wallet_rpc_server.cpp
@@ -623,6 +623,8 @@ namespace tools
       if (req.get_tx_key)
       {
         res.tx_key = epee::string_tools::pod_to_hex(ptx_vector.back().tx_key);
+        for (const crypto::secret_key& additional_tx_key : ptx_vector.back().additional_tx_keys)
+          res.tx_key += epee::string_tools::pod_to_hex(additional_tx_key);
       }
       res.fee = ptx_vector.back().fee;
 
@@ -685,6 +687,8 @@ namespace tools
         if (req.get_tx_keys)
         {
           res.tx_key_list.push_back(epee::string_tools::pod_to_hex(ptx.tx_key));
+          for (const crypto::secret_key& additional_tx_key : ptx.additional_tx_keys)
+            res.tx_key_list.back() += epee::string_tools::pod_to_hex(additional_tx_key);
         }
         // Compute amount leaving wallet in tx. By convention dests does not include change outputs
         ptx_amount = 0;
@@ -1396,6 +1400,163 @@ namespace tools
     res.value = m_wallet->get_attribute(req.key);
     return true;
   }
+  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)
+  {
+    if (!m_wallet) return not_open(er);
+
+    crypto::hash txid;
+    if (!epee::string_tools::hex_to_pod(req.txid, txid))
+    {
+      er.code = WALLET_RPC_ERROR_CODE_WRONG_TXID;
+      er.message = "TX ID has invalid format";
+      return false;
+    }
+
+    crypto::secret_key tx_key;
+    std::vector<crypto::secret_key> additional_tx_keys;
+    if (!m_wallet->get_tx_key(txid, tx_key, additional_tx_keys))
+    {
+      er.code = WALLET_RPC_ERROR_CODE_NO_TXKEY;
+      er.message = "No tx secret key is stored for this tx";
+      return false;
+    }
+
+    std::ostringstream oss;
+    oss << epee::string_tools::pod_to_hex(tx_key);
+    for (size_t i = 0; i < additional_tx_keys.size(); ++i)
+      oss << epee::string_tools::pod_to_hex(additional_tx_keys[i]);
+    res.tx_key = oss.str();
+    return true;
+  }
+  //------------------------------------------------------------------------------------------------------------------------------
+  bool wallet_rpc_server::on_check_tx_key(const wallet_rpc::COMMAND_RPC_CHECK_TX_KEY::request& req, wallet_rpc::COMMAND_RPC_CHECK_TX_KEY::response& res, epee::json_rpc::error& er)
+  {
+    if (!m_wallet) return not_open(er);
+
+    crypto::hash txid;
+    if (!epee::string_tools::hex_to_pod(req.txid, txid))
+    {
+      er.code = WALLET_RPC_ERROR_CODE_WRONG_TXID;
+      er.message = "TX ID has invalid format";
+      return false;
+    }
+
+    std::string tx_key_str = req.tx_key;
+    crypto::secret_key tx_key;
+    if (!epee::string_tools::hex_to_pod(tx_key_str.substr(0, 64), tx_key))
+    {
+      er.code = WALLET_RPC_ERROR_CODE_WRONG_KEY;
+      er.message = "Tx key has invalid format";
+      return false;
+    }
+    tx_key_str = tx_key_str.substr(64);
+    std::vector<crypto::secret_key> additional_tx_keys;
+    while (!tx_key_str.empty())
+    {
+      additional_tx_keys.resize(additional_tx_keys.size() + 1);
+      if (!epee::string_tools::hex_to_pod(tx_key_str.substr(0, 64), additional_tx_keys.back()))
+      {
+        er.code = WALLET_RPC_ERROR_CODE_WRONG_KEY;
+        er.message = "Tx key has invalid format";
+        return false;
+      }
+      tx_key_str = tx_key_str.substr(64);
+    }
+
+    cryptonote::address_parse_info info;
+    if(!get_account_address_from_str(info, m_wallet->testnet(), req.address))
+    {
+      er.code = WALLET_RPC_ERROR_CODE_WRONG_ADDRESS;
+      er.message = "Invalid address";
+      return false;
+    }
+
+    try
+    {
+      m_wallet->check_tx_key(txid, tx_key, additional_tx_keys, info.address, res.received, res.in_pool, res.confirmations);
+    }
+    catch (const std::exception &e)
+    {
+      er.code = WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR;
+      er.message = e.what();
+      return false;
+    }
+    return true;
+  }
+  //------------------------------------------------------------------------------------------------------------------------------
+  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)
+  {
+    if (!m_wallet) return not_open(er);
+
+    crypto::hash txid;
+    if (!epee::string_tools::hex_to_pod(req.txid, txid))
+    {
+      er.code = WALLET_RPC_ERROR_CODE_WRONG_TXID;
+      er.message = "TX ID has invalid format";
+      return false;
+    }
+
+    cryptonote::address_parse_info info;
+    if(!get_account_address_from_str(info, m_wallet->testnet(), req.address))
+    {
+      er.code = WALLET_RPC_ERROR_CODE_WRONG_ADDRESS;
+      er.message = "Invalid address";
+      return false;
+    }
+
+    try
+    {
+      res.signature = m_wallet->get_tx_proof(txid, info.address, info.is_subaddress, req.message, er.message);
+      if (res.signature.empty())
+      {
+        er.code = WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR;
+        return false;
+      }
+    }
+    catch (const std::exception &e)
+    {
+      er.code = WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR;
+      er.message = e.what();
+      return false;
+    }
+    return true;
+  }
+  //------------------------------------------------------------------------------------------------------------------------------
+  bool wallet_rpc_server::on_check_tx_proof(const wallet_rpc::COMMAND_RPC_CHECK_TX_PROOF::request& req, wallet_rpc::COMMAND_RPC_CHECK_TX_PROOF::response& res, epee::json_rpc::error& er)
+  {
+    if (!m_wallet) return not_open(er);
+
+    crypto::hash txid;
+    if (!epee::string_tools::hex_to_pod(req.txid, txid))
+    {
+      er.code = WALLET_RPC_ERROR_CODE_WRONG_TXID;
+      er.message = "TX ID has invalid format";
+      return false;
+    }
+
+    cryptonote::address_parse_info info;
+    if(!get_account_address_from_str(info, m_wallet->testnet(), req.address))
+    {
+      er.code = WALLET_RPC_ERROR_CODE_WRONG_ADDRESS;
+      er.message = "Invalid address";
+      return false;
+    }
+
+    try
+    {
+      uint64_t received;
+      bool in_pool;
+      uint64_t confirmations;
+      res.good = m_wallet->check_tx_proof(txid, info.address, info.is_subaddress, req.message, req.signature, res.received, res.in_pool, res.confirmations);
+    }
+    catch (const std::exception &e)
+    {
+      er.code = WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR;
+      er.message = e.what();
+      return false;
+    }
+    return true;
+  }
   //------------------------------------------------------------------------------------------------------------------------------
   bool wallet_rpc_server::on_get_transfers(const wallet_rpc::COMMAND_RPC_GET_TRANSFERS::request& req, wallet_rpc::COMMAND_RPC_GET_TRANSFERS::response& res, epee::json_rpc::error& er)
   {
diff --git a/src/wallet/wallet_rpc_server.h b/src/wallet/wallet_rpc_server.h
index 36a853a1a..87e442bae 100644
--- a/src/wallet/wallet_rpc_server.h
+++ b/src/wallet/wallet_rpc_server.h
@@ -93,6 +93,10 @@ namespace tools
         MAP_JON_RPC_WE("get_tx_notes",       on_get_tx_notes,       wallet_rpc::COMMAND_RPC_GET_TX_NOTES)
         MAP_JON_RPC_WE("set_attribute",      on_set_attribute,      wallet_rpc::COMMAND_RPC_SET_ATTRIBUTE)
         MAP_JON_RPC_WE("get_attribute",      on_get_attribute,      wallet_rpc::COMMAND_RPC_GET_ATTRIBUTE)
+        MAP_JON_RPC_WE("get_tx_key",         on_get_tx_key,         wallet_rpc::COMMAND_RPC_GET_TX_KEY)
+        MAP_JON_RPC_WE("check_tx_key",       on_check_tx_key,       wallet_rpc::COMMAND_RPC_CHECK_TX_KEY)
+        MAP_JON_RPC_WE("get_tx_proof",       on_get_tx_proof,       wallet_rpc::COMMAND_RPC_GET_TX_PROOF)
+        MAP_JON_RPC_WE("check_tx_proof",     on_check_tx_proof,     wallet_rpc::COMMAND_RPC_CHECK_TX_PROOF)
         MAP_JON_RPC_WE("get_transfers",      on_get_transfers,      wallet_rpc::COMMAND_RPC_GET_TRANSFERS)
         MAP_JON_RPC_WE("get_transfer_by_txid", on_get_transfer_by_txid, wallet_rpc::COMMAND_RPC_GET_TRANSFER_BY_TXID)
         MAP_JON_RPC_WE("sign",               on_sign,               wallet_rpc::COMMAND_RPC_SIGN)
@@ -140,6 +144,10 @@ namespace tools
       bool on_get_tx_notes(const wallet_rpc::COMMAND_RPC_GET_TX_NOTES::request& req, wallet_rpc::COMMAND_RPC_GET_TX_NOTES::response& res, epee::json_rpc::error& er);
       bool on_set_attribute(const wallet_rpc::COMMAND_RPC_SET_ATTRIBUTE::request& req, wallet_rpc::COMMAND_RPC_SET_ATTRIBUTE::response& res, epee::json_rpc::error& er);
       bool on_get_attribute(const wallet_rpc::COMMAND_RPC_GET_ATTRIBUTE::request& req, wallet_rpc::COMMAND_RPC_GET_ATTRIBUTE::response& res, epee::json_rpc::error& er);
+      bool 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);
+      bool on_check_tx_key(const wallet_rpc::COMMAND_RPC_CHECK_TX_KEY::request& req, wallet_rpc::COMMAND_RPC_CHECK_TX_KEY::response& res, epee::json_rpc::error& er);
+      bool 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);
+      bool on_check_tx_proof(const wallet_rpc::COMMAND_RPC_CHECK_TX_PROOF::request& req, wallet_rpc::COMMAND_RPC_CHECK_TX_PROOF::response& res, epee::json_rpc::error& er);
       bool on_get_transfers(const wallet_rpc::COMMAND_RPC_GET_TRANSFERS::request& req, wallet_rpc::COMMAND_RPC_GET_TRANSFERS::response& res, epee::json_rpc::error& er);
       bool on_get_transfer_by_txid(const wallet_rpc::COMMAND_RPC_GET_TRANSFER_BY_TXID::request& req, wallet_rpc::COMMAND_RPC_GET_TRANSFER_BY_TXID::response& res, epee::json_rpc::error& er);
       bool on_sign(const wallet_rpc::COMMAND_RPC_SIGN::request& req, wallet_rpc::COMMAND_RPC_SIGN::response& res, epee::json_rpc::error& er);
diff --git a/src/wallet/wallet_rpc_server_commands_defs.h b/src/wallet/wallet_rpc_server_commands_defs.h
index 9bcc5138a..2e7c7c76f 100644
--- a/src/wallet/wallet_rpc_server_commands_defs.h
+++ b/src/wallet/wallet_rpc_server_commands_defs.h
@@ -828,6 +828,114 @@ namespace wallet_rpc
     };
   };
 
+  struct COMMAND_RPC_GET_TX_KEY
+  {
+    struct request
+    {
+      std::string txid;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(txid)
+      END_KV_SERIALIZE_MAP()
+    };
+
+    struct response
+    {
+      std::string tx_key;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(tx_key)
+      END_KV_SERIALIZE_MAP()
+    };
+  };
+
+  struct COMMAND_RPC_CHECK_TX_KEY
+  {
+    struct request
+    {
+      std::string txid;
+      std::string tx_key;
+      std::string address;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(txid)
+        KV_SERIALIZE(tx_key)
+        KV_SERIALIZE(address)
+      END_KV_SERIALIZE_MAP()
+    };
+
+    struct response
+    {
+      uint64_t received;
+      bool in_pool;
+      uint64_t confirmations;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(received)
+        KV_SERIALIZE(in_pool)
+        KV_SERIALIZE(confirmations)
+      END_KV_SERIALIZE_MAP()
+    };
+  };
+
+  struct COMMAND_RPC_GET_TX_PROOF
+  {
+    struct request
+    {
+      std::string txid;
+      std::string address;
+      std::string message;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(txid)
+        KV_SERIALIZE(address)
+        KV_SERIALIZE(message)
+      END_KV_SERIALIZE_MAP()
+    };
+
+    struct response
+    {
+      std::string signature;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(signature)
+      END_KV_SERIALIZE_MAP()
+    };
+  };
+
+  struct COMMAND_RPC_CHECK_TX_PROOF
+  {
+    struct request
+    {
+      std::string txid;
+      std::string address;
+      std::string message;
+      std::string signature;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(txid)
+        KV_SERIALIZE(address)
+        KV_SERIALIZE(message)
+        KV_SERIALIZE(signature)
+      END_KV_SERIALIZE_MAP()
+    };
+
+    struct response
+    {
+      bool good;
+      uint64_t received;
+      bool in_pool;
+      uint64_t confirmations;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(good)
+        KV_SERIALIZE(received)
+        KV_SERIALIZE(in_pool)
+        KV_SERIALIZE(confirmations)
+      END_KV_SERIALIZE_MAP()
+    };
+  };
+
   struct transfer_entry
   {
     std::string txid;
diff --git a/src/wallet/wallet_rpc_server_error_codes.h b/src/wallet/wallet_rpc_server_error_codes.h
index e74e9110b..74f2999b6 100644
--- a/src/wallet/wallet_rpc_server_error_codes.h
+++ b/src/wallet/wallet_rpc_server_error_codes.h
@@ -54,3 +54,5 @@
 #define WALLET_RPC_ERROR_CODE_WALLET_ALREADY_EXISTS  -21
 #define WALLET_RPC_ERROR_CODE_INVALID_PASSWORD       -22
 #define WALLET_RPC_ERROR_CODE_NO_WALLET_DIR          -23
+#define WALLET_RPC_ERROR_CODE_NO_TXKEY               -24
+#define WALLET_RPC_ERROR_CODE_WRONG_KEY              -25