MMS (Multisig Messaging System): Initial version

8 files changed, 2453 insertions, 7 deletions

diff --git a/src/wallet/CMakeLists.txt b/src/wallet/CMakeLists.txt
index 4e3fb1ae5..8425e4a03 100644
--- a/src/wallet/CMakeLists.txt
+++ b/src/wallet/CMakeLists.txt
@@ -34,7 +34,10 @@ set(wallet_sources
   wallet2.cpp
   wallet_args.cpp
   ringdb.cpp
-  node_rpc_proxy.cpp)
+  node_rpc_proxy.cpp
+  message_store.cpp
+  message_transporter.cpp
+)
 
 set(wallet_private_headers
   wallet2.h
@@ -44,7 +47,9 @@ set(wallet_private_headers
   wallet_rpc_server_commands_defs.h
   wallet_rpc_server_error_codes.h
   ringdb.h
-  node_rpc_proxy.h)
+  node_rpc_proxy.h
+  message_store.h
+  message_transporter.h)
 
 monero_private_headers(wallet
   ${wallet_private_headers})
diff --git a/src/wallet/message_store.cpp b/src/wallet/message_store.cpp
new file mode 100644
index 000000000..ce6f4f52b
--- /dev/null
+++ b/src/wallet/message_store.cpp
@@ -0,0 +1,1445 @@
+// Copyright (c) 2018, The Monero Project
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+//
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "message_store.h"
+#include <boost/archive/portable_binary_oarchive.hpp>
+#include <boost/archive/portable_binary_iarchive.hpp>
+#include <boost/format.hpp>
+#include <boost/algorithm/string.hpp>
+#include <fstream>
+#include <sstream>
+#include "file_io_utils.h"
+#include "storages/http_abstract_invoke.h"
+#include "wallet_errors.h"
+#include "serialization/binary_utils.h"
+#include "common/base58.h"
+#include "common/util.h"
+#include "string_tools.h"
+
+
+#undef MONERO_DEFAULT_LOG_CATEGORY
+#define MONERO_DEFAULT_LOG_CATEGORY "wallet.mms"
+
+namespace mms
+{
+
+message_store::message_store()
+{
+  m_active = false;
+  m_auto_send = false;
+  m_next_message_id = 1;
+  m_num_authorized_signers = 0;
+  m_num_required_signers = 0;
+  m_nettype = cryptonote::network_type::UNDEFINED;
+  m_run = true;
+}
+
+namespace
+{
+  // MMS options handling mirrors what "wallet2" is doing for its options, on-demand init and all
+  // It's not very clean to initialize Bitmessage-specific options here, but going one level further
+  // down still into "message_transporter" for that is a little bit too much
+  struct options
+  {
+    const command_line::arg_descriptor<std::string> bitmessage_address = {"bitmessage-address", mms::message_store::tr("Use PyBitmessage instance at URL <arg>"), "http://localhost:8442/"};
+    const command_line::arg_descriptor<std::string> bitmessage_login = {"bitmessage-login", mms::message_store::tr("Specify <arg> as username:password for PyBitmessage API"), "username:password"};
+  };
+}
+
+void message_store::init_options(boost::program_options::options_description& desc_params)
+{
+  const options opts{};
+  command_line::add_arg(desc_params, opts.bitmessage_address);
+  command_line::add_arg(desc_params, opts.bitmessage_login);
+}
+
+void message_store::init(const multisig_wallet_state &state, const std::string &own_label,
+                         const std::string &own_transport_address, uint32_t num_authorized_signers, uint32_t num_required_signers)
+{
+  m_num_authorized_signers = num_authorized_signers;
+  m_num_required_signers = num_required_signers;
+  m_signers.clear();
+  m_messages.clear();
+  m_next_message_id = 1;
+
+  // The vector "m_signers" gets here once the required number of elements, one for each authorized signer,
+  // and is never changed again. The rest of the code relies on "size(m_signers) == m_num_authorized_signers"
+  // without further checks.
+  authorized_signer signer;
+  for (uint32_t i = 0; i < m_num_authorized_signers; ++i)
+  {
+    signer.me = signer.index == 0;    // Strict convention: The very first signer is fixed as / must be "me"
+    m_signers.push_back(signer);
+    signer.index++;
+  }
+
+  set_signer(state, 0, own_label, own_transport_address, state.address);
+
+  m_nettype = state.nettype;
+  set_active(true);
+  m_filename = state.mms_file;
+  save(state);
+}
+
+void message_store::set_options(const boost::program_options::variables_map& vm)
+{
+  const options opts{};
+  std::string bitmessage_address = command_line::get_arg(vm, opts.bitmessage_address);
+  epee::wipeable_string bitmessage_login = command_line::get_arg(vm, opts.bitmessage_login);
+  set_options(bitmessage_address, bitmessage_login);
+}
+
+void message_store::set_options(const std::string &bitmessage_address, const epee::wipeable_string &bitmessage_login)
+{
+  m_transporter.set_options(bitmessage_address, bitmessage_login);
+}
+
+void message_store::set_signer(const multisig_wallet_state &state,
+                               uint32_t index,
+                               const boost::optional<std::string> &label,
+                               const boost::optional<std::string> &transport_address,
+                               const boost::optional<cryptonote::account_public_address> monero_address)
+{
+  THROW_WALLET_EXCEPTION_IF(index >= m_num_authorized_signers, tools::error::wallet_internal_error, "Invalid signer index " + index);
+  authorized_signer &m = m_signers[index];
+  if (label)
+  {
+    m.label = label.get();
+  }
+  if (transport_address)
+  {
+    m.transport_address = transport_address.get();
+  }
+  if (monero_address)
+  {
+    m.monero_address_known = true;
+    m.monero_address = monero_address.get();
+  }
+  // Save to minimize the chance to loose that info (at least while in beta)
+  save(state);
+}
+
+const authorized_signer &message_store::get_signer(uint32_t index) const
+{
+  THROW_WALLET_EXCEPTION_IF(index >= m_num_authorized_signers, tools::error::wallet_internal_error, "Invalid signer index " + index);
+  return m_signers[index];
+}
+
+bool message_store::signer_config_complete() const
+{
+  for (uint32_t i = 0; i < m_num_authorized_signers; ++i)
+  {
+    const authorized_signer &m = m_signers[i];
+    if (m.label.empty() || m.transport_address.empty() || !m.monero_address_known)
+    {
+      return false;
+    }
+  }
+  return true;
+}
+
+// Check if all signers have a label set (as it's a requirement for starting auto-config
+// by the "manager")
+bool message_store::signer_labels_complete() const
+{
+  for (uint32_t i = 0; i < m_num_authorized_signers; ++i)
+  {
+    const authorized_signer &m = m_signers[i];
+    if (m.label.empty())
+    {
+      return false;
+    }
+  }
+  return true;
+}
+
+void message_store::get_signer_config(std::string &signer_config)
+{
+  std::stringstream oss;
+  boost::archive::portable_binary_oarchive ar(oss);
+  ar << m_signers;
+  signer_config = oss.str();
+}
+
+void message_store::unpack_signer_config(const multisig_wallet_state &state, const std::string &signer_config,
+                                         std::vector<authorized_signer> &signers)
+{
+  try
+  {
+    std::stringstream iss;
+    iss << signer_config;
+    boost::archive::portable_binary_iarchive ar(iss);
+    ar >> signers;
+  }
+  catch (...)
+  {
+    THROW_WALLET_EXCEPTION_IF(true, tools::error::wallet_internal_error, "Invalid structure of signer config");
+  }
+  uint32_t num_signers = (uint32_t)signers.size();
+  THROW_WALLET_EXCEPTION_IF(num_signers != m_num_authorized_signers, tools::error::wallet_internal_error, "Wrong number of signers in config: " + num_signers);
+}
+
+void message_store::process_signer_config(const multisig_wallet_state &state, const std::string &signer_config)
+{
+  // The signers in "signer_config" and the resident wallet signers are matched not by label, but
+  // by Monero address, and ALL labels will be set from "signer_config", even the "me" label.
+  // In the auto-config process as implemented now the auto-config manager is responsible for defining
+  // the labels, and right at the end of the process ALL wallets use the SAME labels. The idea behind this
+  // is preventing problems like duplicate labels and confusion (Bob choosing a label "IamAliceHonest").
+  // (Of course signers are free to re-define any labels they don't like AFTER auto-config.)
+  //
+  // Usually this method will be called with only the "me" signer defined in the wallet, and may
+  // produce unexpected behaviour if that wallet contains additional signers that have nothing to do with
+  // those arriving in "signer_config".
+  std::vector<authorized_signer> signers;
+  unpack_signer_config(state, signer_config, signers);
+  
+  uint32_t new_index = 1;
+  for (uint32_t i = 0; i < m_num_authorized_signers; ++i)
+  {
+    const authorized_signer &m = signers[i];
+    uint32_t index;
+    uint32_t take_index;
+    bool found = get_signer_index_by_monero_address(m.monero_address, index);
+    if (found)
+    {
+      // Redefine existing (probably "me", under usual circumstances)
+      take_index = index;
+    }
+    else
+    {
+      // Add new; neglect that we may erroneously overwrite already defined signers
+      // (but protect "me")
+      take_index = new_index;
+      if ((new_index + 1) < m_num_authorized_signers)
+      {
+        new_index++;
+      }
+    }
+    authorized_signer &modify = m_signers[take_index];
+    modify.label = m.label;  // ALWAYS set label, see comments above
+    if (!modify.me)
+    {
+      modify.transport_address = m.transport_address;
+      modify.monero_address_known = m.monero_address_known;
+      if (m.monero_address_known)
+      {
+        modify.monero_address = m.monero_address;
+      }
+    }
+  }
+  save(state);
+}
+
+void message_store::start_auto_config(const multisig_wallet_state &state)
+{
+  for (uint32_t i = 0; i < m_num_authorized_signers; ++i)
+  {
+    authorized_signer &m = m_signers[i];
+    if (!m.me)
+    {
+      setup_signer_for_auto_config(i, create_auto_config_token(), true);
+    }
+    m.auto_config_running = true;
+  }
+  save(state);
+}
+
+// Check auto-config token string and convert to standardized form;
+// Try to make it as foolproof as possible, with built-in tolerance to make up for
+// errors in transmission that still leave the token recognizable.
+bool message_store::check_auto_config_token(const std::string &raw_token,
+                                            std::string &adjusted_token) const
+{
+  std::string prefix(AUTO_CONFIG_TOKEN_PREFIX);
+  uint32_t num_hex_digits = (AUTO_CONFIG_TOKEN_BYTES + 1) * 2;
+  uint32_t full_length = num_hex_digits + prefix.length();
+  uint32_t raw_length = raw_token.length();
+  std::string hex_digits;
+
+  if (raw_length == full_length)
+  {
+    // Prefix must be there; accept it in any casing
+    std::string raw_prefix(raw_token.substr(0, 3));
+    boost::algorithm::to_lower(raw_prefix);
+    if (raw_prefix != prefix)
+    {
+      return false;
+    }
+    hex_digits = raw_token.substr(3);
+  }
+  else if (raw_length == num_hex_digits)
+  {
+    // Accept the token without the prefix if it's otherwise ok
+    hex_digits = raw_token;
+  }
+  else
+  {
+    return false;
+  }
+
+  // Convert to strict lowercase and correct any common misspellings
+  boost::algorithm::to_lower(hex_digits);
+  std::replace(hex_digits.begin(), hex_digits.end(), 'o', '0');
+  std::replace(hex_digits.begin(), hex_digits.end(), 'i', '1');
+  std::replace(hex_digits.begin(), hex_digits.end(), 'l', '1');
+
+  // Now it must be correct hex with correct checksum, no further tolerance possible
+  std::string token_bytes;
+  if (!epee::string_tools::parse_hexstr_to_binbuff(hex_digits, token_bytes))
+  {
+    return false;
+  }
+  const crypto::hash &hash = crypto::cn_fast_hash(token_bytes.data(), token_bytes.size() - 1);
+  if (token_bytes[AUTO_CONFIG_TOKEN_BYTES] != hash.data[0])
+  {
+    return false;
+  }
+  adjusted_token = prefix + hex_digits;
+  return true;
+}
+
+// Create a new auto-config token with prefix, random 8-hex digits plus 2 checksum digits
+std::string message_store::create_auto_config_token()
+{
+  unsigned char random[AUTO_CONFIG_TOKEN_BYTES];
+  crypto::rand(AUTO_CONFIG_TOKEN_BYTES, random);
+  std::string token_bytes;
+  token_bytes.append((char *)random, AUTO_CONFIG_TOKEN_BYTES);
+
+  // Add a checksum because technically ANY four bytes are a valid token, and without a checksum we would send
+  // auto-config messages "to nowhere" after the slightest typo without knowing it
+  const crypto::hash &hash = crypto::cn_fast_hash(token_bytes.data(), token_bytes.size());
+  token_bytes += hash.data[0];
+  std::string prefix(AUTO_CONFIG_TOKEN_PREFIX);
+  return prefix + epee::string_tools::buff_to_hex_nodelimer(token_bytes);
+}
+
+// Add a message for sending "me" address data to the auto-config transport address
+// that can be derived from the token and activate auto-config
+size_t message_store::add_auto_config_data_message(const multisig_wallet_state &state,
+                                                   const std::string &auto_config_token)
+{
+  authorized_signer &me = m_signers[0];
+  me.auto_config_token = auto_config_token;
+  setup_signer_for_auto_config(0, auto_config_token, false);
+  me.auto_config_running = true;
+
+  auto_config_data data;
+  data.label = me.label;
+  data.transport_address = me.transport_address;
+  data.monero_address = me.monero_address;
+
+  std::stringstream oss;
+  boost::archive::portable_binary_oarchive ar(oss);
+  ar << data;
+
+  return add_message(state, 0, message_type::auto_config_data, message_direction::out, oss.str());
+}
+
+// Process a single message with auto-config data, destined for "message.signer_index"
+void message_store::process_auto_config_data_message(uint32_t id)
+{
+  // "auto_config_data" contains the label that the auto-config data sender uses for "me", but that's
+  // more for completeness' sake, and right now it's not used. In general, the auto-config manager
+  // decides/defines the labels, and right after completing auto-config ALL wallets use the SAME labels.
+
+  const message &m = get_message_ref_by_id(id);
+
+  auto_config_data data;
+  try
+  {
+    std::stringstream iss;
+    iss << m.content;
+    boost::archive::portable_binary_iarchive ar(iss);
+    ar >> data;
+  }
+  catch (...)
+  {
+    THROW_WALLET_EXCEPTION_IF(true, tools::error::wallet_internal_error, "Invalid structure of auto config data");
+  }
+
+  authorized_signer &signer = m_signers[m.signer_index];
+  // "signer.label" does NOT change, see comment above
+  signer.transport_address = data.transport_address;
+  signer.monero_address_known = true;
+  signer.monero_address = data.monero_address;
+  signer.auto_config_running = false;
+}
+
+void message_store::stop_auto_config()
+{
+  for (uint32_t i = 0; i < m_num_authorized_signers; ++i)
+  {
+    authorized_signer &m = m_signers[i];
+    if (!m.me && !m.auto_config_transport_address.empty())
+    {
+      // Try to delete those "unused API" addresses in PyBitmessage, especially since
+      // it seems it's not possible to delete them interactively, only to "disable" them
+      m_transporter.delete_transport_address(m.auto_config_transport_address);
+    }
+    m.auto_config_token.clear();
+    m.auto_config_public_key = crypto::null_pkey;
+    m.auto_config_secret_key = crypto::null_skey;
+    m.auto_config_transport_address.clear();
+    m.auto_config_running = false;
+  }  
+}
+
+void message_store::setup_signer_for_auto_config(uint32_t index, const std::string token, bool receiving)
+{
+  // It may be a little strange to hash the textual hex digits of the auto config token into
+  // 32 bytes and turn that into a Monero public/secret key pair, instead of doing something
+  // much less complicated like directly using the underlying random 40 bits as key for a
+  // symmetric cipher, but everything is there already for encrypting and decrypting messages
+  // with such key pairs, and furthermore it would be trivial to use tokens with a different
+  // number of bytes.
+  //
+  // In the wallet of the auto-config manager each signer except "me" gets set its own
+  // auto-config parameters. In the wallet of somebody using the token to send auto-config
+  // data the auto-config parameters are stored in the "me" signer and taken from there
+  // to send that data.
+  THROW_WALLET_EXCEPTION_IF(index >= m_num_authorized_signers, tools::error::wallet_internal_error, "Invalid signer index " + index);
+  authorized_signer &m = m_signers[index];
+  m.auto_config_token = token;
+  crypto::hash_to_scalar(token.data(), token.size(), m.auto_config_secret_key);
+  crypto::secret_key_to_public_key(m.auto_config_secret_key, m.auto_config_public_key);
+  if (receiving)
+  {
+    m.auto_config_transport_address = m_transporter.derive_and_receive_transport_address(m.auto_config_token);
+  }
+  else
+  {
+    m.auto_config_transport_address = m_transporter.derive_transport_address(m.auto_config_token);
+  }
+}
+
+bool message_store::get_signer_index_by_monero_address(const cryptonote::account_public_address &monero_address, uint32_t &index) const
+{
+  for (uint32_t i = 0; i < m_num_authorized_signers; ++i)
+  {
+    const authorized_signer &m = m_signers[i];
+    if (m.monero_address == monero_address)
+    {
+      index = m.index;
+      return true;
+    }
+  }
+  MWARNING("No authorized signer with Monero address " << account_address_to_string(monero_address));
+  return false;
+}
+
+bool message_store::get_signer_index_by_label(const std::string label, uint32_t &index) const
+{
+  for (uint32_t i = 0; i < m_num_authorized_signers; ++i)
+  {
+    const authorized_signer &m = m_signers[i];
+    if (m.label == label)
+    {
+      index = m.index;
+      return true;
+    }
+  }
+  MWARNING("No authorized signer with label " << label);
+  return false;
+}
+
+void message_store::process_wallet_created_data(const multisig_wallet_state &state, message_type type, const std::string &content)
+{
+  switch(type)
+  {
+  case message_type::key_set:
+    // Result of a "prepare_multisig" command in the wallet
+    // Send the key set to all other signers
+  case message_type::additional_key_set:
+    // Result of a "make_multisig" command or a "exchange_multisig_keys" in the wallet in case of M/N multisig
+    // Send the additional key set to all other signers
+  case message_type::multisig_sync_data:
+    // Result of a "export_multisig_info" command in the wallet
+    // Send the sync data to all other signers
+    for (uint32_t i = 1; i < m_num_authorized_signers; ++i)
+    {
+      add_message(state, i, type, message_direction::out, content);
+    }
+    break;
+
+  case message_type::partially_signed_tx:
+    // Result of a "transfer" command in the wallet, or a "sign_multisig" command
+    // that did not yet result in the minimum number of signatures required
+    // Create a message "from me to me" as a container for the tx data
+    if (m_num_required_signers == 1)
+    {
+      // Probably rare, but possible: The 1 signature is already enough, correct the type
+      // Easier to correct here than asking all callers to detect this rare special case
+      type = message_type::fully_signed_tx;
+    }
+    add_message(state, 0, type, message_direction::in, content);
+    break;
+
+  case message_type::fully_signed_tx:
+    add_message(state, 0, type, message_direction::in, content);
+    break;
+
+  default:
+    THROW_WALLET_EXCEPTION(tools::error::wallet_internal_error, "Illegal message type " + (uint32_t)type);
+    break;
+  }
+}
+
+size_t message_store::add_message(const multisig_wallet_state &state,
+                                  uint32_t signer_index, message_type type, message_direction direction,
+                                  const std::string &content)
+{
+  message m;
+  m.id = m_next_message_id++;
+  m.type = type;
+  m.direction = direction;
+  m.content = content;
+  m.created = (uint64_t)time(NULL);
+  m.modified = m.created;
+  m.sent = 0;
+  m.signer_index = signer_index;
+  if (direction == message_direction::out)
+  {
+    m.state = message_state::ready_to_send;
+  }
+  else
+  {
+    m.state = message_state::waiting;
+  };
+  m.wallet_height = (uint32_t)state.num_transfer_details;
+  if (m.type == message_type::additional_key_set)
+  {
+    m.round = state.multisig_rounds_passed;
+  }
+  else
+  {
+    m.round = 0;
+  }
+  m.signature_count = 0;  // Future expansion for signature counting when signing txs
+  m.hash = crypto::null_hash;
+  m_messages.push_back(m);
+
+  // Save for every new message right away (at least while in beta)
+  save(state);
+
+  MINFO(boost::format("Added %s message %s for signer %s of type %s")
+          % message_direction_to_string(direction) % m.id % signer_index % message_type_to_string(type));
+  return m_messages.size() - 1;
+}
+
+// Get the index of the message with id "id", return false if not found
+bool message_store::get_message_index_by_id(uint32_t id, size_t &index) const
+{
+  for (size_t i = 0; i < m_messages.size(); ++i)
+  {
+    if (m_messages[i].id == id)
+    {
+      index = i;
+      return true;
+    }
+  }
+  MWARNING("No message found with an id of " << id);
+  return false;
+}
+
+// Get the index of the message with id "id" that must exist
+size_t message_store::get_message_index_by_id(uint32_t id) const
+{
+  size_t index;
+  bool found = get_message_index_by_id(id, index);
+  THROW_WALLET_EXCEPTION_IF(!found, tools::error::wallet_internal_error, "Invalid message id " + id);
+  return index;
+}
+
+// Get the modifiable message with id "id" that must exist; private/internal use!
+message& message_store::get_message_ref_by_id(uint32_t id)
+{
+  return m_messages[get_message_index_by_id(id)];
+}
+
+// Get the message with id "id", return false if not found
+// This version of the method allows to check whether id is valid without triggering an error
+bool message_store::get_message_by_id(uint32_t id, message &m) const
+{
+  size_t index;
+  bool found = get_message_index_by_id(id, index);
+  if (found)
+  {
+    m = m_messages[index];
+  }
+  return found;
+}
+
+// Get the message with id "id" that must exist
+message message_store::get_message_by_id(uint32_t id) const
+{
+  message m;
+  bool found = get_message_by_id(id, m);
+  THROW_WALLET_EXCEPTION_IF(!found, tools::error::wallet_internal_error, "Invalid message id " + id);
+  return m;
+}
+
+bool message_store::any_message_of_type(message_type type, message_direction direction) const
+{
+  for (size_t i = 0; i < m_messages.size(); ++i)
+  {
+    if ((m_messages[i].type == type) && (m_messages[i].direction == direction))
+    {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool message_store::any_message_with_hash(const crypto::hash &hash) const
+{
+  for (size_t i = 0; i < m_messages.size(); ++i)
+  {
+    if (m_messages[i].hash == hash)
+    {
+      return true;
+    }
+  }
+  return false;
+}
+
+// Count the ids in the vector that are set i.e. not 0, while ignoring index 0
+// Mostly used to check whether we have a message for each authorized signer except me,
+// with the signer index used as index into 'ids'; the element at index 0, for me,
+// is ignored, to make constant subtractions of 1 for indices when filling the
+// vector unnecessary
+size_t message_store::get_other_signers_id_count(const std::vector<uint32_t> &ids) const
+{
+  size_t count = 0;
+  for (size_t i = 1 /* and not 0 */; i < ids.size(); ++i)
+  {
+    if (ids[i] != 0)
+    {
+      count++;
+    }
+  }
+  return count;
+}
+
+// Is in every element of vector 'ids' (except at index 0) a message id i.e. not 0?
+bool message_store::message_ids_complete(const std::vector<uint32_t> &ids) const
+{
+  return get_other_signers_id_count(ids) == (ids.size() - 1);
+}
+
+void message_store::delete_message(uint32_t id)
+{
+  delete_transport_message(id);
+  size_t index = get_message_index_by_id(id);
+  m_messages.erase(m_messages.begin() + index);
+}
+
+void message_store::delete_all_messages()
+{
+  for (size_t i = 0; i < m_messages.size(); ++i)
+  {
+    delete_transport_message(m_messages[i].id);
+  }
+  m_messages.clear();
+}
+
+// Make a message text, which is "attacker controlled data", reasonably safe to display
+// This is mostly geared towards the safe display of notes sent by "mms note" with a "mms show" command
+void message_store::get_sanitized_message_text(const message &m, std::string &sanitized_text) const
+{
+  sanitized_text.clear();
+
+  // Restrict the size to fend of DOS-style attacks with heaps of data
+  size_t length = std::min(m.content.length(), (size_t)1000);
+
+  for (size_t i = 0; i < length; ++i)
+  {
+    char c = m.content[i];
+    if ((int)c < 32)
+    {
+      // Strip out any controls, especially ESC for getting rid of potentially dangerous
+      // ANSI escape sequences that a console window might interpret
+      c = ' ';
+    }
+    else if ((c == '<') || (c == '>'))
+    {
+      // Make XML or HTML impossible that e.g. might contain scripts that Qt might execute
+      // when displayed in the GUI wallet
+      c = ' ';
+    }
+    sanitized_text += c;
+  }
+}
+
+void message_store::write_to_file(const multisig_wallet_state &state, const std::string &filename)
+{
+  std::stringstream oss;
+  boost::archive::portable_binary_oarchive ar(oss);
+  ar << *this;
+  std::string buf = oss.str();
+
+  crypto::chacha_key key;
+  crypto::generate_chacha_key(&state.view_secret_key, sizeof(crypto::secret_key), key, 1);
+
+  file_data write_file_data = boost::value_initialized<file_data>();
+  write_file_data.magic_string = "MMS";
+  write_file_data.file_version = 0;
+  write_file_data.iv = crypto::rand<crypto::chacha_iv>();
+  std::string encrypted_data;
+  encrypted_data.resize(buf.size());
+  crypto::chacha20(buf.data(), buf.size(), key, write_file_data.iv, &encrypted_data[0]);
+  write_file_data.encrypted_data = encrypted_data;
+
+  std::stringstream file_oss;
+  boost::archive::portable_binary_oarchive file_ar(file_oss);
+  file_ar << write_file_data;
+
+  bool success = epee::file_io_utils::save_string_to_file(filename, file_oss.str());
+  THROW_WALLET_EXCEPTION_IF(!success, tools::error::file_save_error, filename);
+}
+
+void message_store::read_from_file(const multisig_wallet_state &state, const std::string &filename)
+{
+  boost::system::error_code ignored_ec;
+  bool file_exists = boost::filesystem::exists(filename, ignored_ec);
+  if (!file_exists)
+  {
+    // Simply do nothing if the file is not there; allows e.g. easy recovery
+    // from problems with the MMS by deleting the file
+    MERROR("No message store file found: " << filename);
+    return;
+  }
+
+  std::string buf;
+  bool success = epee::file_io_utils::load_file_to_string(filename, buf);
+  THROW_WALLET_EXCEPTION_IF(!success, tools::error::file_read_error, filename);
+
+  file_data read_file_data;
+  try
+  {
+    std::stringstream iss;
+    iss << buf;
+    boost::archive::portable_binary_iarchive ar(iss);
+    ar >> read_file_data;
+  }
+  catch (const std::exception &e)
+  {
+    MERROR("MMS file " << filename << " has bad structure <iv,encrypted_data>: " << e.what());
+    THROW_WALLET_EXCEPTION_IF(true, tools::error::file_read_error, filename);
+  }
+
+  crypto::chacha_key key;
+  crypto::generate_chacha_key(&state.view_secret_key, sizeof(crypto::secret_key), key, 1);
+  std::string decrypted_data;
+  decrypted_data.resize(read_file_data.encrypted_data.size());
+  crypto::chacha20(read_file_data.encrypted_data.data(), read_file_data.encrypted_data.size(), key, read_file_data.iv, &decrypted_data[0]);
+
+  try
+  {
+    std::stringstream iss;
+    iss << decrypted_data;
+    boost::archive::portable_binary_iarchive ar(iss);
+    ar >> *this;
+  }
+  catch (const std::exception &e)
+  {
+    MERROR("MMS file " << filename << " has bad structure: " << e.what());
+    THROW_WALLET_EXCEPTION_IF(true, tools::error::file_read_error, filename);
+  }
+
+  m_filename = filename;
+}
+
+// Save to the same file this message store was loaded from
+// Called after changes deemed "important", to make it less probable to lose messages in case of
+// a crash; a better and long-term solution would of course be to use LMDB ...
+void message_store::save(const multisig_wallet_state &state)
+{
+  if (!m_filename.empty())
+  {
+    write_to_file(state, m_filename);
+  }
+}
+
+bool message_store::get_processable_messages(const multisig_wallet_state &state,
+                                             bool force_sync, std::vector<processing_data> &data_list, std::string &wait_reason)
+{
+  uint32_t wallet_height = (uint32_t)state.num_transfer_details;
+  data_list.clear();
+  wait_reason.clear();
+  // In all scans over all messages looking for complete sets (1 message for each signer),
+  // if there are duplicates, the OLDEST of them is taken. This may not play a role with
+  // any of the current message types, but may with future ones, and it's probably a good
+  // idea to have a clear and somewhat defensive strategy.
+
+  std::vector<uint32_t> auto_config_messages(m_num_authorized_signers, 0);
+  bool any_auto_config = false;
+
+  for (size_t i = 0; i < m_messages.size(); ++i)
+  {
+    message &m = m_messages[i];
+    if ((m.type == message_type::auto_config_data) && (m.state == message_state::waiting))
+    {
+      if (auto_config_messages[m.signer_index] == 0)
+      {
+        auto_config_messages[m.signer_index] = m.id;
+        any_auto_config = true;
+      }
+      // else duplicate auto config data, ignore
+    }
+  }
+
+  if (any_auto_config)
+  {
+    bool auto_config_complete = message_ids_complete(auto_config_messages);
+    if (auto_config_complete)
+    {
+      processing_data data;
+      data.processing = message_processing::process_auto_config_data;
+      data.message_ids = auto_config_messages;
+      data.message_ids.erase(data.message_ids.begin());
+      data_list.push_back(data);
+      return true;
+    }
+    else
+    {
+      wait_reason = tr("Auto-config cannot proceed because auto config data from other signers is not complete");
+      return false;
+      // With ANY auto config data present but not complete refuse to check for any
+      // other processing. Manually delete those messages to abort such an auto config
+      // phase if needed.
+    }
+  }
+
+  // Any signer config that arrived will be processed right away, regardless of other things that may wait
+  for (size_t i = 0; i < m_messages.size(); ++i)
+  {
+    message &m = m_messages[i];
+    if ((m.type == message_type::signer_config) && (m.state == message_state::waiting))
+    {
+      processing_data data;
+      data.processing = message_processing::process_signer_config;
+      data.message_ids.push_back(m.id);
+      data_list.push_back(data);
+      return true;
+    }
+  }
+
+  // ALL of the following processings depend on the signer info being complete
+  if (!signer_config_complete())
+  {
+    wait_reason = tr("The signer config is not complete.");
+    return false;
+  }
+
+  if (!state.multisig)
+  {
+    
+    if (!any_message_of_type(message_type::key_set, message_direction::out))
+    {
+      // With the own key set not yet ready we must do "prepare_multisig" first;
+      // Key sets from other signers may be here already, but if we process them now
+      // the wallet will go multisig too early: we can't produce our own key set any more!
+      processing_data data;
+      data.processing = message_processing::prepare_multisig;
+      data_list.push_back(data);
+      return true;
+    }
+
+    // Ids of key set messages per signer index, to check completeness
+    // Naturally, does not care about the order of the messages and is trivial to secure against
+    // key sets that were received more than once
+    // With full M/N multisig now possible consider only key sets of the right round, i.e.
+    // with not yet multisig the only possible round 0
+    std::vector<uint32_t> key_set_messages(m_num_authorized_signers, 0);
+
+    for (size_t i = 0; i < m_messages.size(); ++i)
+    {
+      message &m = m_messages[i];
+      if ((m.type == message_type::key_set) && (m.state == message_state::waiting)
+          && (m.round == 0))
+      {
+        if (key_set_messages[m.signer_index] == 0)
+        {
+          key_set_messages[m.signer_index] = m.id;
+        }
+        // else duplicate key set, ignore
+      }
+    }
+
+    bool key_sets_complete = message_ids_complete(key_set_messages);
+    if (key_sets_complete)
+    {
+      // Nothing else can be ready to process earlier than this, ignore everything else and give back
+      processing_data data;
+      data.processing = message_processing::make_multisig;
+      data.message_ids = key_set_messages;
+      data.message_ids.erase(data.message_ids.begin());
+      data_list.push_back(data);
+      return true;
+    }
+    else
+    {
+      wait_reason = tr("Wallet can't go multisig because key sets from other signers are missing or not complete.");
+      return false;
+    }
+  }
+
+  if (state.multisig && !state.multisig_is_ready)
+  {
+    // In the case of M/N multisig the call 'wallet2::multisig' returns already true
+    // after "make_multisig" but with calls to "exchange_multisig_keys" still needed, and
+    // sets the parameter 'ready' to false to document this particular "in-between" state.
+    // So what may be possible here, with all necessary messages present, is a call to
+    // "exchange_multisig_keys".
+    // Consider only messages belonging to the next round to do, which has the number
+    // "state.multisig_rounds_passed".
+    std::vector<uint32_t> additional_key_set_messages(m_num_authorized_signers, 0);
+
+    for (size_t i = 0; i < m_messages.size(); ++i)
+    {
+      message &m = m_messages[i];
+      if ((m.type == message_type::additional_key_set) && (m.state == message_state::waiting)
+         && (m.round == state.multisig_rounds_passed))
+      {
+        if (additional_key_set_messages[m.signer_index] == 0)
+        {
+          additional_key_set_messages[m.signer_index] = m.id;
+        }
+        // else duplicate key set, ignore
+      }
+    }
+
+    bool key_sets_complete = message_ids_complete(additional_key_set_messages);
+    if (key_sets_complete)
+    {
+      processing_data data;
+      data.processing = message_processing::exchange_multisig_keys;
+      data.message_ids = additional_key_set_messages;
+      data.message_ids.erase(data.message_ids.begin());
+      data_list.push_back(data);
+      return true;
+    }
+    else
+    {
+      wait_reason = tr("Wallet can't start another key exchange round because key sets from other signers are missing or not complete.");
+      return false;
+    }
+  }
+
+  // Properly exchanging multisig sync data is easiest and most transparent
+  // for the user if a wallet sends its own data first and processes any received
+  // sync data afterwards so that's the order that the MMS enforces here.
+  // (Technically, it seems to work also the other way round.)
+  //
+  // To check whether a NEW round of syncing is necessary the MMS works with a
+  // "wallet state": new state means new syncing needed.
+  //
+  // The MMS monitors the "wallet state" by recording "wallet heights" as
+  // numbers of transfers present in a wallet at the time of message creation. While
+  // not watertight, this quite simple scheme should already suffice to trigger
+  // and orchestrate a sensible exchange of sync data.
+  if (state.has_multisig_partial_key_images || force_sync)
+  {
+    // Sync is necessary and not yet completed: Processing of transactions
+    // will only be possible again once properly synced
+    // Check first whether we generated already OUR sync info; take note of
+    // any processable sync info from other signers on the way in case we need it
+    bool own_sync_data_created = false;
+    std::vector<uint32_t> sync_messages(m_num_authorized_signers, 0);
+    for (size_t i = 0; i < m_messages.size(); ++i)
+    {
+      message &m = m_messages[i];
+      if ((m.type == message_type::multisig_sync_data) && (force_sync || (m.wallet_height == wallet_height)))
+      // It's data for the same "round" of syncing, on the same "wallet height", therefore relevant
+      // With "force_sync" take ANY waiting sync data, maybe it will work out
+      {
+        if (m.direction == message_direction::out)
+        {
+          own_sync_data_created = true;
+          // Ignore whether sent already or not, and assume as complete if several other signers there
+        }
+        else if ((m.direction == message_direction::in) && (m.state == message_state::waiting))
+        {
+          if (sync_messages[m.signer_index] == 0)
+          {
+            sync_messages[m.signer_index] = m.id;
+          }
+          // else duplicate sync message, ignore
+        }
+      }
+    }
+    if (!own_sync_data_created)
+    {
+      // As explained above, creating sync data BEFORE processing such data from
+      // other signers reliably works, so insist on that here
+      processing_data data;
+      data.processing = message_processing::create_sync_data;
+      data_list.push_back(data);
+      return true;
+    }
+    uint32_t id_count = (uint32_t)get_other_signers_id_count(sync_messages);
+    // Do we have sync data from ALL other signers?
+    bool all_sync_data = id_count == (m_num_authorized_signers - 1);
+    // Do we have just ENOUGH sync data to have a minimal viable sync set?
+    // In cases like 2/3 multisig we don't need messages from ALL other signers, only
+    // from enough of them i.e. num_required_signers minus 1 messages
+    bool enough_sync_data = id_count >= (m_num_required_signers - 1);
+    bool sync = false;
+    wait_reason = tr("Syncing not done because multisig sync data from other signers are missing or not complete.");
+    if (all_sync_data)
+    {
+      sync = true;
+    }
+    else if (enough_sync_data)
+    {
+      if (force_sync)
+      {
+        sync = true;
+      }
+      else
+      {
+        // Don't sync, but give a hint how this minimal set COULD be synced if really wanted
+        wait_reason += (boost::format("\nUse \"mms next sync\" if you want to sync with just %s out of %s authorized signers and transact just with them")
+                                     % (m_num_required_signers - 1) % (m_num_authorized_signers - 1)).str();
+      }
+    }
+    if (sync)
+    {
+      processing_data data;
+      data.processing = message_processing::process_sync_data;
+      for (size_t i = 0; i < sync_messages.size(); ++i)
+      {
+        uint32_t id = sync_messages[i];
+        if (id != 0)
+        {
+          data.message_ids.push_back(id);
+        }
+      }
+      data_list.push_back(data);
+      return true;
+    }
+    else
+    {
+      // We can't proceed to any transactions until we have synced; "wait_reason" already set above
+      return false;
+    }
+  }
+
+  bool waiting_found = false;
+  bool note_found = false;
+  bool sync_data_found = false;
+  for (size_t i = 0; i < m_messages.size(); ++i)
+  {
+    message &m = m_messages[i];
+    if (m.state == message_state::waiting)
+    {
+      waiting_found = true;
+      switch (m.type)
+      {
+      case message_type::fully_signed_tx:
+      {
+        // We can either submit it ourselves, or send it to any other signer for submission
+        processing_data data;
+        data.processing = message_processing::submit_tx;
+        data.message_ids.push_back(m.id);
+        data_list.push_back(data);
+
+        data.processing = message_processing::send_tx;
+        for (uint32_t j = 1; j < m_num_authorized_signers; ++j)
+        {
+          data.receiving_signer_index = j;
+          data_list.push_back(data);
+        }
+        return true;
+      }
+
+      case message_type::partially_signed_tx:
+      {
+        if (m.signer_index == 0)
+        {
+          // We started this ourselves, or signed it but with still signatures missing:
+          // We can send it to any other signer for signing / further signing
+          // In principle it does not make sense to send it back to somebody who
+          // already signed, but the MMS does not / not yet keep track of that,
+          // because that would be somewhat complicated.
+          processing_data data;
+          data.processing = message_processing::send_tx;
+          data.message_ids.push_back(m.id);
+          for (uint32_t j = 1; j < m_num_authorized_signers; ++j)
+          {
+            data.receiving_signer_index = j;
+            data_list.push_back(data);
+          }
+          return true;
+        }
+        else
+        {
+          // Somebody else sent this to us: We can sign it
+          // It would be possible to just pass it on, but that's not directly supported here
+          processing_data data;
+          data.processing = message_processing::sign_tx;
+          data.message_ids.push_back(m.id);
+          data_list.push_back(data);
+          return true;
+        }
+      }
+
+      case message_type::note:
+        note_found = true;
+        break;
+
+      case message_type::multisig_sync_data:
+        sync_data_found = true;
+        break;
+
+      default:
+        break;
+      }
+    }
+  }
+  if (waiting_found)
+  {
+    wait_reason = tr("There are waiting messages, but nothing is ready to process under normal circumstances");
+    if (sync_data_found)
+    {
+      wait_reason += tr("\nUse \"mms next sync\" if you want to force processing of the waiting sync data");
+    }
+    if (note_found)
+    {
+      wait_reason += tr("\nUse \"mms note\" to display the waiting notes");
+    }
+  }
+  else
+  {
+    wait_reason = tr("There are no messages waiting to be processed.");
+  }
+
+  return false;
+}
+
+void message_store::set_messages_processed(const processing_data &data)
+{
+  for (size_t i = 0; i < data.message_ids.size(); ++i)
+  {
+    set_message_processed_or_sent(data.message_ids[i]);
+  }
+}
+
+void message_store::set_message_processed_or_sent(uint32_t id)
+{
+  message &m = get_message_ref_by_id(id);
+  if (m.state == message_state::waiting)
+  {
+    // So far a fairly cautious and conservative strategy: Only delete from Bitmessage
+    // when fully processed (and e.g. not already after reception and writing into
+    // the message store file)
+    delete_transport_message(id);
+    m.state = message_state::processed;
+  }
+  else if (m.state == message_state::ready_to_send)
+  {
+    m.state = message_state::sent;
+  }
+  m.modified = (uint64_t)time(NULL);
+}
+
+void message_store::encrypt(crypto::public_key public_key, const std::string &plaintext,
+                            std::string &ciphertext, crypto::public_key &encryption_public_key, crypto::chacha_iv &iv)
+{
+  crypto::secret_key encryption_secret_key;
+  crypto::generate_keys(encryption_public_key, encryption_secret_key);
+
+  crypto::key_derivation derivation;
+  bool success = crypto::generate_key_derivation(public_key, encryption_secret_key, derivation);
+  THROW_WALLET_EXCEPTION_IF(!success, tools::error::wallet_internal_error, "Failed to generate key derivation for message encryption");
+
+  crypto::chacha_key chacha_key;
+  crypto::generate_chacha_key(&derivation, sizeof(derivation), chacha_key, 1);
+  iv = crypto::rand<crypto::chacha_iv>();
+  ciphertext.resize(plaintext.size());
+  crypto::chacha20(plaintext.data(), plaintext.size(), chacha_key, iv, &ciphertext[0]);
+}
+
+void message_store::decrypt(const std::string &ciphertext, const crypto::public_key &encryption_public_key, const crypto::chacha_iv &iv,
+                            const crypto::secret_key &view_secret_key, std::string &plaintext)
+{
+  crypto::key_derivation derivation;
+  bool success = crypto::generate_key_derivation(encryption_public_key, view_secret_key, derivation);
+  THROW_WALLET_EXCEPTION_IF(!success, tools::error::wallet_internal_error, "Failed to generate key derivation for message decryption");
+  crypto::chacha_key chacha_key;
+  crypto::generate_chacha_key(&derivation, sizeof(derivation), chacha_key, 1);
+  plaintext.resize(ciphertext.size());
+  crypto::chacha20(ciphertext.data(), ciphertext.size(), chacha_key, iv, &plaintext[0]);
+}
+
+void message_store::send_message(const multisig_wallet_state &state, uint32_t id)
+{
+  message &m = get_message_ref_by_id(id);
+  const authorized_signer &me = m_signers[0];
+  const authorized_signer &receiver = m_signers[m.signer_index];
+  transport_message dm;
+  crypto::public_key public_key;
+
+  dm.timestamp = (uint64_t)time(NULL);
+  dm.subject = "MMS V0 " + tools::get_human_readable_timestamp(dm.timestamp);
+  dm.source_transport_address = me.transport_address;
+  dm.source_monero_address = me.monero_address;
+  if (m.type == message_type::auto_config_data)
+  {
+    // Encrypt with the public key derived from the auto-config token, and send to the
+    // transport address likewise derived from that token
+    public_key = me.auto_config_public_key;
+    dm.destination_transport_address = me.auto_config_transport_address;
+    // The destination Monero address is not yet known
+    memset(&dm.destination_monero_address, 0, sizeof(cryptonote::account_public_address));
+  }
+  else
+  {
+    // Encrypt with the receiver's view public key
+    public_key = receiver.monero_address.m_view_public_key;
+    const authorized_signer &receiver = m_signers[m.signer_index];
+    dm.destination_monero_address = receiver.monero_address;
+    dm.destination_transport_address = receiver.transport_address;
+  }
+  encrypt(public_key, m.content, dm.content, dm.encryption_public_key, dm.iv);
+  dm.type = (uint32_t)m.type;
+  dm.hash = crypto::cn_fast_hash(dm.content.data(), dm.content.size());
+  dm.round = m.round;
+
+  crypto::generate_signature(dm.hash, me.monero_address.m_view_public_key, state.view_secret_key, dm.signature);
+
+  m_transporter.send_message(dm);
+
+  m.state=message_state::sent;
+  m.sent= (uint64_t)time(NULL);
+}
+
+bool message_store::check_for_messages(const multisig_wallet_state &state, std::vector<message> &messages)
+{
+  m_run.store(true, std::memory_order_relaxed);
+  const authorized_signer &me = m_signers[0];
+  std::vector<std::string> destinations;
+  destinations.push_back(me.transport_address);
+  for (uint32_t i = 1; i < m_num_authorized_signers; ++i)
+  {
+    const authorized_signer &m = m_signers[i];
+    if (m.auto_config_running)
+    {
+      destinations.push_back(m.auto_config_transport_address);
+    }
+  }
+  std::vector<transport_message> transport_messages;
+  bool r = m_transporter.receive_messages(destinations, transport_messages);
+  if (!m_run.load(std::memory_order_relaxed))
+  {
+    // Stop was called, don't waste time processing the messages
+    // (but once started processing them, don't react to stop request anymore, avoid receiving them "partially)"
+    return false;
+  }
+
+  bool new_messages = false;
+  for (size_t i = 0; i < transport_messages.size(); ++i)
+  {
+    transport_message &rm = transport_messages[i];
+    if (any_message_with_hash(rm.hash))
+    {
+      // Already seen, do not take again
+    }
+    else
+    {
+      uint32_t sender_index;
+      bool take = false;
+      message_type type = static_cast<message_type>(rm.type);
+      crypto::secret_key decrypt_key = state.view_secret_key;
+      if (type == message_type::auto_config_data)
+      {
+        // Find out which signer sent it by checking which auto config transport address
+        // the message was sent to
+        for (uint32_t i = 1; i < m_num_authorized_signers; ++i)
+        {
+          const authorized_signer &m = m_signers[i];
+          if (m.auto_config_transport_address == rm.destination_transport_address)
+          {
+            take = true;
+            sender_index = i;
+            decrypt_key = m.auto_config_secret_key;
+            break;
+          }
+        }
+      }
+      else if (type == message_type::signer_config)
+      {
+        // Typically we can't check yet whether we know the sender, so take from any
+        // and pretend it's from "me" because we might have nothing else yet
+        take = true;
+        sender_index = 0;
+      }
+      else
+      {
+        // Only accept from senders that are known as signer here, otherwise just ignore
+        take = get_signer_index_by_monero_address(rm.source_monero_address, sender_index);
+      }
+      if (take && (type != message_type::auto_config_data))
+      {
+        // If the destination address is known, check it as well; this additional filter
+        // allows using the same transport address for multiple signers
+        take = rm.destination_monero_address == me.monero_address;
+      }
+      if (take)
+      {
+        crypto::hash actual_hash = crypto::cn_fast_hash(rm.content.data(), rm.content.size());
+        THROW_WALLET_EXCEPTION_IF(actual_hash != rm.hash, tools::error::wallet_internal_error, "Message hash mismatch");
+
+        bool signature_valid = crypto::check_signature(actual_hash, rm.source_monero_address.m_view_public_key, rm.signature);
+        THROW_WALLET_EXCEPTION_IF(!signature_valid, tools::error::wallet_internal_error, "Message signature not valid");
+
+        std::string plaintext;
+        decrypt(rm.content, rm.encryption_public_key, rm.iv, decrypt_key, plaintext);
+        size_t index = add_message(state, sender_index, (message_type)rm.type, message_direction::in, plaintext);
+        message &m = m_messages[index];
+        m.hash = rm.hash;
+        m.transport_id = rm.transport_id;
+        m.sent = rm.timestamp;
+        m.round = rm.round;
+        m.signature_count = rm.signature_count;
+        messages.push_back(m);
+        new_messages = true;
+      }
+    }
+  }
+  return new_messages;
+}
+
+void message_store::delete_transport_message(uint32_t id)
+{
+  const message &m = get_message_by_id(id);
+  if (!m.transport_id.empty())
+  {
+    m_transporter.delete_message(m.transport_id);
+  }
+}
+
+std::string message_store::account_address_to_string(const cryptonote::account_public_address &account_address) const
+{
+  return get_account_address_as_str(m_nettype, false, account_address);
+}
+
+const char* message_store::message_type_to_string(message_type type)
+{
+  switch (type)
+  {
+  case message_type::key_set:
+    return tr("key set");
+  case message_type::additional_key_set:
+    return tr("additional key set");
+  case message_type::multisig_sync_data:
+    return tr("multisig sync data");
+  case message_type::partially_signed_tx:
+    return tr("partially signed tx");
+  case message_type::fully_signed_tx:
+    return tr("fully signed tx");
+  case message_type::note:
+    return tr("note");
+  case message_type::signer_config:
+    return tr("signer config");
+  case message_type::auto_config_data:
+    return tr("auto-config data");
+  default:
+    return tr("unknown message type");
+  }
+}
+
+const char* message_store::message_direction_to_string(message_direction direction)
+{
+  switch (direction)
+  {
+  case message_direction::in:
+    return tr("in");
+  case message_direction::out:
+    return tr("out");
+  default:
+    return tr("unknown message direction");
+  }
+}
+
+const char* message_store::message_state_to_string(message_state state)
+{
+  switch (state)
+  {
+  case message_state::ready_to_send:
+    return tr("ready to send");
+  case message_state::sent:
+    return tr("sent");
+  case message_state::waiting:
+    return tr("waiting");
+  case message_state::processed:
+    return tr("processed");
+  case message_state::cancelled:
+    return tr("cancelled");
+  default:
+    return tr("unknown message state");
+  }
+}
+
+// Convert a signer to string suitable for a column in a list, with 'max_width'
+// Format: label: transport_address
+std::string message_store::signer_to_string(const authorized_signer &signer, uint32_t max_width)
+{
+  std::string s = "";
+  s.reserve(max_width);
+  uint32_t avail = max_width;
+  uint32_t label_len = signer.label.length();
+  if (label_len > avail)
+  {
+    s.append(signer.label.substr(0, avail - 2));
+    s.append("..");
+    return s;
+  }
+  s.append(signer.label);
+  avail -= label_len;
+  uint32_t transport_addr_len = signer.transport_address.length();
+  if ((transport_addr_len > 0) && (avail > 10))
+  {
+    s.append(": ");
+    avail -= 2;
+    if (transport_addr_len <= avail)
+    {
+      s.append(signer.transport_address);
+    }
+    else
+    {
+      s.append(signer.transport_address.substr(0, avail-2));
+      s.append("..");
+    }
+  }
+  return s;
+}
+
+}
diff --git a/src/wallet/message_store.h b/src/wallet/message_store.h
new file mode 100644
index 000000000..7d26f7889
--- /dev/null
+++ b/src/wallet/message_store.h
@@ -0,0 +1,420 @@
+// Copyright (c) 2018, The Monero Project
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+//
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#pragma once
+
+#include <cstdlib>
+#include <string>
+#include <vector>
+#include "crypto/hash.h"
+#include <boost/serialization/vector.hpp>
+#include <boost/program_options/variables_map.hpp>
+#include <boost/program_options/options_description.hpp>
+#include <boost/optional/optional.hpp>
+#include "serialization/serialization.h"
+#include "cryptonote_basic/cryptonote_boost_serialization.h"
+#include "cryptonote_basic/account_boost_serialization.h"
+#include "cryptonote_basic/cryptonote_basic.h"
+#include "common/i18n.h"
+#include "common/command_line.h"
+#include "wipeable_string.h"
+#include "message_transporter.h"
+
+#undef MONERO_DEFAULT_LOG_CATEGORY
+#define MONERO_DEFAULT_LOG_CATEGORY "wallet.mms"
+#define AUTO_CONFIG_TOKEN_BYTES 4
+#define AUTO_CONFIG_TOKEN_PREFIX "mms"
+
+namespace mms
+{
+  enum class message_type
+  {
+    key_set,
+    additional_key_set,
+    multisig_sync_data,
+    partially_signed_tx,
+    fully_signed_tx,
+    note,
+    signer_config,
+    auto_config_data
+  };
+
+  enum class message_direction
+  {
+    in,
+    out
+  };
+
+  enum class message_state
+  {
+    ready_to_send,
+    sent,
+
+    waiting,
+    processed,
+
+    cancelled
+  };
+
+  enum class message_processing
+  {
+    prepare_multisig,
+    make_multisig,
+    exchange_multisig_keys,
+    create_sync_data,
+    process_sync_data,
+    sign_tx,
+    send_tx,
+    submit_tx,
+    process_signer_config,
+    process_auto_config_data
+  };
+
+  struct message
+  {
+    uint32_t id;
+    message_type type;
+    message_direction direction;
+    std::string content;
+    uint64_t created;
+    uint64_t modified;
+    uint64_t sent;
+    uint32_t signer_index;
+    crypto::hash hash;
+    message_state state;
+    uint32_t wallet_height;
+    uint32_t round;
+    uint32_t signature_count;
+    std::string transport_id;
+  };
+  // "wallet_height" (for lack of a short name that would describe what it is about)
+  // is the number of transfers present in the wallet at the time of message
+  // construction; used to coordinate generation of sync info (which depends
+  // on the content of the wallet at time of generation)
+
+  struct authorized_signer
+  {
+    std::string label;
+    std::string transport_address;
+    bool monero_address_known;
+    cryptonote::account_public_address monero_address;
+    bool me;
+    uint32_t index;
+    std::string auto_config_token;
+    crypto::public_key auto_config_public_key;
+    crypto::secret_key auto_config_secret_key;
+    std::string auto_config_transport_address;
+    bool auto_config_running;
+
+    authorized_signer()
+    {
+      monero_address_known = false;
+      memset(&monero_address, 0, sizeof(cryptonote::account_public_address));
+      index = 0;
+      auto_config_public_key = crypto::null_pkey;
+      auto_config_secret_key = crypto::null_skey;
+      auto_config_running = false;
+    };
+  };
+
+  struct processing_data
+  {
+    message_processing processing;
+    std::vector<uint32_t> message_ids;
+    uint32_t receiving_signer_index = 0;
+  };
+
+  struct file_transport_message
+  {
+    cryptonote::account_public_address sender_address;
+    crypto::chacha_iv iv;
+    crypto::public_key encryption_public_key;
+    message internal_message;
+  };
+  
+  struct auto_config_data
+  {
+    std::string label;
+    std::string transport_address;
+    cryptonote::account_public_address monero_address;
+  };
+
+  // Overal .mms file structure, with the "message_store" object serialized to and
+  // encrypted in "encrypted_data"
+  struct file_data
+  {
+    std::string magic_string;
+    uint32_t file_version;
+    crypto::chacha_iv iv;
+    std::string encrypted_data;
+  };
+
+    // The following struct provides info about the current state of a "wallet2" object
+  // at the time of a "message_store" method call that those methods need. See on the
+  // one hand a first parameter of this type for several of those methods, and on the
+  // other hand the method "wallet2::get_multisig_wallet_state" which clients like the
+  // CLI wallet can use to get that info.
+  //
+  // Note that in the case of a wallet that is already multisig "address" is NOT the
+  // multisig address, but the "original" wallet address at creation time. Likewise
+  // "view_secret_key" is the original view secret key then.
+  //
+  // This struct definition is here and not in "wallet2.h" to avoid circular imports.
+  struct multisig_wallet_state
+  {
+    cryptonote::account_public_address address;
+    cryptonote::network_type nettype;
+    crypto::secret_key view_secret_key;
+    bool multisig;
+    bool multisig_is_ready;
+    bool has_multisig_partial_key_images;
+    uint32_t multisig_rounds_passed;
+    size_t num_transfer_details;
+    std::string mms_file;
+  };
+
+  class message_store
+  {
+  public:
+    message_store();
+    // Initialize and start to use the MMS, set the first signer, this wallet itself
+    // Filename, if not null and not empty, is used to create the ".mms" file
+    // reset it if already used, with deletion of all signers and messages
+    void init(const multisig_wallet_state &state, const std::string &own_label,
+              const std::string &own_transport_address, uint32_t num_authorized_signers, uint32_t num_required_signers);
+    void set_active(bool active) { m_active = active; };
+    void set_auto_send(bool auto_send) { m_auto_send = auto_send; };
+    void set_options(const boost::program_options::variables_map& vm);
+    void set_options(const std::string &bitmessage_address, const epee::wipeable_string &bitmessage_login);
+    bool get_active() const { return m_active; };
+    bool get_auto_send() const { return m_auto_send; };
+    uint32_t get_num_required_signers() const { return m_num_required_signers; };
+    uint32_t get_num_authorized_signers() const { return m_num_authorized_signers; };
+
+    void set_signer(const multisig_wallet_state &state,
+                    uint32_t index,
+                    const boost::optional<std::string> &label,
+                    const boost::optional<std::string> &transport_address,
+                    const boost::optional<cryptonote::account_public_address> monero_address);
+
+    const authorized_signer &get_signer(uint32_t index) const;
+    bool get_signer_index_by_monero_address(const cryptonote::account_public_address &monero_address, uint32_t &index) const;
+    bool get_signer_index_by_label(const std::string label, uint32_t &index) const;
+    const std::vector<authorized_signer> &get_all_signers() const { return m_signers; };
+    bool signer_config_complete() const;
+    bool signer_labels_complete() const;
+    void get_signer_config(std::string &signer_config);
+    void unpack_signer_config(const multisig_wallet_state &state, const std::string &signer_config,
+                              std::vector<authorized_signer> &signers);
+    void process_signer_config(const multisig_wallet_state &state, const std::string &signer_config);
+
+    void start_auto_config(const multisig_wallet_state &state);
+    bool check_auto_config_token(const std::string &raw_token,
+                                 std::string &adjusted_token) const;
+    size_t add_auto_config_data_message(const multisig_wallet_state &state,
+                                        const std::string &auto_config_token);
+    void process_auto_config_data_message(uint32_t id);
+    void stop_auto_config();
+
+    // Process data just created by "me" i.e. the own local wallet, e.g. as the result of a "prepare_multisig" command
+    // Creates the resulting messages to the right signers
+    void process_wallet_created_data(const multisig_wallet_state &state, message_type type, const std::string &content);
+
+    // Go through all the messages, look at the "ready to process" ones, and check whether any single one
+    // or any group of them can be processed, because they are processable as single messages (like a tx
+    // that is fully signed and thus ready for submit to the net) or because they form a complete group
+    // (e.g. key sets from all authorized signers to make the wallet multisig). If there are multiple
+    // candidates, e.g. in 2/3 multisig sending to one OR the other signer to sign, there will be more
+    // than 1 element in 'data' for the user to choose. If nothing is ready "false" is returned.
+    // The method mostly ignores the order in which the messages were received because messages may be delayed
+    // (e.g. sync data from a signer arrives AFTER a transaction to submit) or because message time stamps
+    // may be wrong so it's not possible to order them reliably.
+    // Messages also may be ready by themselves but the wallet not yet ready for them (e.g. sync data already
+    // arriving when the wallet is not yet multisig because key sets were delayed or were lost altogether.)
+    // If nothing is ready 'wait_reason' may contain further info about the reason why.
+    bool get_processable_messages(const multisig_wallet_state &state,
+                                  bool force_sync,
+                                  std::vector<processing_data> &data_list,
+                                  std::string &wait_reason);
+    void set_messages_processed(const processing_data &data);
+
+    size_t add_message(const multisig_wallet_state &state,
+                       uint32_t signer_index, message_type type, message_direction direction,
+                       const std::string &content);
+    const std::vector<message> &get_all_messages() const { return m_messages; };
+    bool get_message_by_id(uint32_t id, message &m) const;
+    message get_message_by_id(uint32_t id) const;
+    void set_message_processed_or_sent(uint32_t id);
+    void delete_message(uint32_t id);
+    void delete_all_messages();
+    void get_sanitized_message_text(const message &m, std::string &sanitized_text) const;
+
+    void send_message(const multisig_wallet_state &state, uint32_t id);
+    bool check_for_messages(const multisig_wallet_state &state, std::vector<message> &messages);
+    void stop() { m_run.store(false, std::memory_order_relaxed); m_transporter.stop(); }
+
+    void write_to_file(const multisig_wallet_state &state, const std::string &filename);
+    void read_from_file(const multisig_wallet_state &state, const std::string &filename);
+
+    template <class t_archive>
+    inline void serialize(t_archive &a, const unsigned int ver)
+    {
+      a & m_active;
+      a & m_num_authorized_signers;
+      a & m_nettype;
+      a & m_num_required_signers;
+      a & m_signers;
+      a & m_messages;
+      a & m_next_message_id;
+      a & m_auto_send;
+    }
+
+    static const char* message_type_to_string(message_type type);
+    static const char* message_direction_to_string(message_direction direction);
+    static const char* message_state_to_string(message_state state);
+    std::string signer_to_string(const authorized_signer &signer, uint32_t max_width);
+    
+    static const char *tr(const char *str) { return i18n_translate(str, "tools::mms"); }
+    static void init_options(boost::program_options::options_description& desc_params);
+
+  private:
+    bool m_active;
+    uint32_t m_num_authorized_signers;
+    uint32_t m_num_required_signers;
+    bool m_auto_send;
+    cryptonote::network_type m_nettype;
+    std::vector<authorized_signer> m_signers;
+    std::vector<message> m_messages;
+    uint32_t m_next_message_id;
+    std::string m_filename;
+    message_transporter m_transporter;
+    std::atomic<bool> m_run;
+
+    bool get_message_index_by_id(uint32_t id, size_t &index) const;
+    size_t get_message_index_by_id(uint32_t id) const;
+    message& get_message_ref_by_id(uint32_t id);
+    bool any_message_of_type(message_type type, message_direction direction) const;
+    bool any_message_with_hash(const crypto::hash &hash) const;
+    size_t get_other_signers_id_count(const std::vector<uint32_t> &ids) const;
+    bool message_ids_complete(const std::vector<uint32_t> &ids) const;
+    void encrypt(crypto::public_key public_key, const std::string &plaintext,
+                 std::string &ciphertext, crypto::public_key &encryption_public_key, crypto::chacha_iv &iv);
+    void decrypt(const std::string &ciphertext, const crypto::public_key &encryption_public_key, const crypto::chacha_iv &iv,
+                 const crypto::secret_key &view_secret_key, std::string &plaintext);
+    std::string create_auto_config_token();
+    void setup_signer_for_auto_config(uint32_t index, const std::string token, bool receiving);
+    void delete_transport_message(uint32_t id);
+    std::string account_address_to_string(const cryptonote::account_public_address &account_address) const;
+    void save(const multisig_wallet_state &state);
+  };
+}
+
+BOOST_CLASS_VERSION(mms::file_data, 0)
+BOOST_CLASS_VERSION(mms::message_store, 0)
+BOOST_CLASS_VERSION(mms::message, 0)
+BOOST_CLASS_VERSION(mms::file_transport_message, 0)
+BOOST_CLASS_VERSION(mms::authorized_signer, 1)
+BOOST_CLASS_VERSION(mms::auto_config_data, 0)
+
+namespace boost
+{
+  namespace serialization
+  {
+    template <class Archive>
+    inline void serialize(Archive &a, mms::file_data &x, const boost::serialization::version_type ver)
+    {
+      a & x.magic_string;
+      a & x.file_version;
+      a & x.iv;
+      a & x.encrypted_data;
+    }
+
+    template <class Archive>
+    inline void serialize(Archive &a, mms::message &x, const boost::serialization::version_type ver)
+    {
+      a & x.id;
+      a & x.type;
+      a & x.direction;
+      a & x.content;
+      a & x.created;
+      a & x.modified;
+      a & x.sent;
+      a & x.signer_index;
+      a & x.hash;
+      a & x.state;
+      a & x.wallet_height;
+      a & x.round;
+      a & x.signature_count;
+      a & x.transport_id;
+    }
+
+    template <class Archive>
+    inline void serialize(Archive &a, mms::authorized_signer &x, const boost::serialization::version_type ver)
+    {
+      a & x.label;
+      a & x.transport_address;
+      a & x.monero_address_known;
+      a & x.monero_address;
+      a & x.me;
+      a & x.index;
+      if (ver < 1)
+      {
+        return;
+      }
+      a & x.auto_config_token;
+      a & x.auto_config_public_key;
+      a & x.auto_config_secret_key;
+      a & x.auto_config_transport_address;
+      a & x.auto_config_running;  
+    }
+
+    template <class Archive>
+    inline void serialize(Archive &a, mms::auto_config_data &x, const boost::serialization::version_type ver)
+    {
+      a & x.label;
+      a & x.transport_address;
+      a & x.monero_address;
+    }
+
+    template <class Archive>
+    inline void serialize(Archive &a, mms::file_transport_message &x, const boost::serialization::version_type ver)
+    {
+      a & x.sender_address;
+      a & x.iv;
+      a & x.encryption_public_key;
+      a & x.internal_message;
+    }
+
+    template <class Archive>
+    inline void serialize(Archive &a, crypto::chacha_iv &x, const boost::serialization::version_type ver)
+    {
+      a & x.data;
+    }
+
+  }
+}
diff --git a/src/wallet/message_transporter.cpp b/src/wallet/message_transporter.cpp
new file mode 100644
index 000000000..eafd13d3b
--- /dev/null
+++ b/src/wallet/message_transporter.cpp
@@ -0,0 +1,317 @@
+// Copyright (c) 2018, The Monero Project
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+//
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "message_transporter.h"
+#include "string_coding.h"
+#include <boost/format.hpp>
+#include "wallet_errors.h"
+#include "net/http_client.h"
+#include "net/net_parse_helpers.h"
+#include <algorithm>
+
+#undef MONERO_DEFAULT_LOG_CATEGORY
+#define MONERO_DEFAULT_LOG_CATEGORY "wallet.mms"
+#define PYBITMESSAGE_DEFAULT_API_PORT 8442
+
+namespace mms
+{
+
+namespace bitmessage_rpc
+{
+
+  struct message_info
+  {
+    uint32_t encodingType;
+    std::string toAddress;
+    uint32_t read;
+    std::string msgid;
+    std::string message;
+    std::string fromAddress;
+    std::string receivedTime;
+    std::string subject;
+
+    BEGIN_KV_SERIALIZE_MAP()
+      KV_SERIALIZE(encodingType)
+      KV_SERIALIZE(toAddress)
+      KV_SERIALIZE(read)
+      KV_SERIALIZE(msgid)
+      KV_SERIALIZE(message);
+      KV_SERIALIZE(fromAddress)
+      KV_SERIALIZE(receivedTime)
+      KV_SERIALIZE(subject)
+    END_KV_SERIALIZE_MAP()
+  };
+
+  struct inbox_messages_response
+  {
+    std::vector<message_info> inboxMessages;
+
+    BEGIN_KV_SERIALIZE_MAP()
+      KV_SERIALIZE(inboxMessages)
+    END_KV_SERIALIZE_MAP()
+  };
+
+}
+
+message_transporter::message_transporter()
+{
+  m_run = true;
+}
+
+void message_transporter::set_options(const std::string &bitmessage_address, const epee::wipeable_string &bitmessage_login)
+{
+  m_bitmessage_url = bitmessage_address;
+  epee::net_utils::http::url_content address_parts{};
+  epee::net_utils::parse_url(m_bitmessage_url, address_parts);
+  if (address_parts.port == 0)
+  {
+    address_parts.port = PYBITMESSAGE_DEFAULT_API_PORT;
+  }
+  m_bitmessage_login = bitmessage_login;
+
+  m_http_client.set_server(address_parts.host, std::to_string(address_parts.port), boost::none);
+}
+
+bool message_transporter::receive_messages(const std::vector<std::string> &destination_transport_addresses,
+                                           std::vector<transport_message> &messages)
+{
+  // The message body of the Bitmessage message is basically the transport message, as JSON (and nothing more).
+  // Weeding out other, non-MMS messages is done in a simple way: If it deserializes without error, it's an MMS message
+  // That JSON is Base64-encoded by the MMS because the Monero epee JSON serializer does not escape anything and happily
+  // includes even 0 (NUL) in strings, which might confuse Bitmessage or at least display confusingly in the client.
+  // There is yet another Base64-encoding of course as part of the Bitmessage API for the message body parameter
+  // The Bitmessage API call "getAllInboxMessages" gives back a JSON array with all the messages (despite using
+  // XML-RPC for the calls, and not JSON-RPC ...)
+  m_run.store(true, std::memory_order_relaxed);
+  std::string request;
+  start_xml_rpc_cmd(request, "getAllInboxMessages");
+  end_xml_rpc_cmd(request);
+  std::string answer;
+  post_request(request, answer);
+
+  std::string json = get_str_between_tags(answer, "<string>", "</string>");
+  bitmessage_rpc::inbox_messages_response bitmessage_res;
+  epee::serialization::load_t_from_json(bitmessage_res, json);
+  size_t size = bitmessage_res.inboxMessages.size();
+  messages.clear();
+
+  for (size_t i = 0; i < size; ++i)
+  {
+    if (!m_run.load(std::memory_order_relaxed))
+    {
+      // Stop was called, don't waste time processing any more messages
+      return false;
+    }
+    const bitmessage_rpc::message_info &message_info = bitmessage_res.inboxMessages[i];
+    if (std::find(destination_transport_addresses.begin(), destination_transport_addresses.end(), message_info.toAddress) != destination_transport_addresses.end())
+    {
+      transport_message message;
+      bool is_mms_message = false;
+      try
+      {
+        // First Base64-decoding: The message body is Base64 in the Bitmessage API
+        std::string message_body = epee::string_encoding::base64_decode(message_info.message);
+        // Second Base64-decoding: The MMS uses Base64 to hide non-textual data in its JSON from Bitmessage
+        json = epee::string_encoding::base64_decode(message_body);
+        epee::serialization::load_t_from_json(message, json);
+        is_mms_message = true;
+      }
+      catch(const std::exception& e)
+      {
+      }
+      if (is_mms_message)
+      {
+        message.transport_id = message_info.msgid;
+        messages.push_back(message);
+      }
+    }
+  }
+
+  return true;
+}
+
+bool message_transporter::send_message(const transport_message &message)
+{
+  // <toAddress> <fromAddress> <subject> <message> [encodingType [TTL]]
+  std::string request;
+  start_xml_rpc_cmd(request, "sendMessage");
+  add_xml_rpc_string_param(request, message.destination_transport_address);
+  add_xml_rpc_string_param(request, message.source_transport_address);
+  add_xml_rpc_base64_param(request, message.subject);
+  std::string json = epee::serialization::store_t_to_json(message);
+  std::string message_body = epee::string_encoding::base64_encode(json);  // See comment in "receive_message" about reason for (double-)Base64 encoding
+  add_xml_rpc_base64_param(request, message_body);
+  add_xml_rpc_integer_param(request, 2);
+  end_xml_rpc_cmd(request);
+  std::string answer;
+  post_request(request, answer);
+  return true;
+}
+
+bool message_transporter::delete_message(const std::string &transport_id)
+{
+  std::string request;
+  start_xml_rpc_cmd(request, "trashMessage");
+  add_xml_rpc_string_param(request, transport_id);
+  end_xml_rpc_cmd(request);
+  std::string answer;
+  post_request(request, answer);
+  return true;
+}
+
+// Deterministically derive a transport / Bitmessage address from 'seed' (the 10-hex-digits
+// auto-config token will be used), but do not set it up for receiving in PyBitmessage as
+// well, because it's possible the address will only ever be used to SEND auto-config data
+std::string message_transporter::derive_transport_address(const std::string &seed)
+{
+  std::string request;
+  start_xml_rpc_cmd(request, "getDeterministicAddress");
+  add_xml_rpc_base64_param(request, seed);
+  add_xml_rpc_integer_param(request, 4);  // addressVersionNumber
+  add_xml_rpc_integer_param(request, 1);  // streamNumber
+  end_xml_rpc_cmd(request);
+  std::string answer;
+  post_request(request, answer);
+  std::string address = get_str_between_tags(answer, "<string>", "</string>");
+  return address;
+}
+
+// Derive a transport address and configure it for receiving in PyBitmessage, typically
+// for receiving auto-config messages by the wallet of the auto-config organizer
+std::string message_transporter::derive_and_receive_transport_address(const std::string &seed)
+{
+  // We need to call both "get_deterministic_address" AND "createDeterministicAddresses"
+  // because we won't get back the address from the latter call if it exists already
+  std::string address = derive_transport_address(seed);
+
+  std::string request;
+  start_xml_rpc_cmd(request, "createDeterministicAddresses");
+  add_xml_rpc_base64_param(request, seed);
+  add_xml_rpc_integer_param(request, 1);  // numberOfAddresses
+  add_xml_rpc_integer_param(request, 4);  // addressVersionNumber
+  end_xml_rpc_cmd(request);
+  std::string answer;
+  post_request(request, answer);
+
+  return address;
+}
+
+bool message_transporter::delete_transport_address(const std::string &transport_address)
+{
+  std::string request;
+  start_xml_rpc_cmd(request, "deleteAddress");
+  add_xml_rpc_string_param(request, transport_address);
+  end_xml_rpc_cmd(request);
+  std::string answer;
+  return post_request(request, answer);
+}
+
+bool message_transporter::post_request(const std::string &request, std::string &answer)
+{
+  // Somehow things do not work out if one tries to connect "m_http_client" to Bitmessage
+  // and keep it connected over the course of several calls. But with a new connection per
+  // call and disconnecting after the call there is no problem (despite perhaps a small
+  // slowdown)
+  epee::net_utils::http::fields_list additional_params;
+
+  // Basic access authentication according to RFC 7617 (which the epee HTTP classes do not seem to support?)
+  // "m_bitmessage_login" just contains what is needed here, "user:password"
+  std::string auth_string = epee::string_encoding::base64_encode((const unsigned char*)m_bitmessage_login.data(), m_bitmessage_login.size());
+  auth_string.insert(0, "Basic ");
+  additional_params.push_back(std::make_pair("Authorization", auth_string));
+
+  additional_params.push_back(std::make_pair("Content-Type", "application/xml; charset=utf-8"));
+  const epee::net_utils::http::http_response_info* response = NULL;
+  std::chrono::milliseconds timeout = std::chrono::seconds(15);
+  bool r = m_http_client.invoke("/", "POST", request, timeout, std::addressof(response), std::move(additional_params));
+  if (r)
+  {
+    answer = response->m_body;
+  }
+  else
+  {
+    LOG_ERROR("POST request to Bitmessage failed: " << request.substr(0, 300));
+    THROW_WALLET_EXCEPTION(tools::error::no_connection_to_bitmessage, m_bitmessage_url);
+  }
+  m_http_client.disconnect();  // see comment above
+  std::string string_value = get_str_between_tags(answer, "<string>", "</string>");
+  if ((string_value.find("API Error") == 0) || (string_value.find("RPC ") == 0))
+  {
+    THROW_WALLET_EXCEPTION(tools::error::bitmessage_api_error, string_value);
+  }
+
+  return r;
+}
+
+// Pick some string between two delimiters
+// When parsing the XML returned by PyBitmessage, don't bother to fully parse it but as a little hack rely on the
+// fact that e.g. a single string returned will be, however deeply nested in "<params><param><value>...", delivered
+// between the very first "<string>" and "</string>" tags to be found in the XML
+std::string message_transporter::get_str_between_tags(const std::string &s, const std::string &start_delim, const std::string &stop_delim)
+{
+  size_t first_delim_pos = s.find(start_delim);
+  if (first_delim_pos != std::string::npos)
+  {
+    size_t end_pos_of_first_delim = first_delim_pos + start_delim.length();
+    size_t last_delim_pos = s.find(stop_delim);
+    if (last_delim_pos != std::string::npos)
+    {
+      return s.substr(end_pos_of_first_delim, last_delim_pos - end_pos_of_first_delim);
+    }
+  }
+  return std::string();
+}
+
+void message_transporter::start_xml_rpc_cmd(std::string &xml, const std::string &method_name)
+{
+  xml = (boost::format("<?xml version=\"1.0\"?><methodCall><methodName>%s</methodName><params>") % method_name).str();
+}
+
+void message_transporter::add_xml_rpc_string_param(std::string &xml, const std::string &param)
+{
+  xml += (boost::format("<param><value><string>%s</string></value></param>") % param).str();
+}
+
+void message_transporter::add_xml_rpc_base64_param(std::string &xml, const std::string &param)
+{
+  // Bitmessage expects some arguments Base64-encoded, but it wants them as parameters of type "string", not "base64" that is also part of XML-RPC
+  std::string encoded_param = epee::string_encoding::base64_encode(param);
+  xml += (boost::format("<param><value><string>%s</string></value></param>") % encoded_param).str();
+}
+
+void message_transporter::add_xml_rpc_integer_param(std::string &xml, const int32_t &param)
+{
+  xml += (boost::format("<param><value><int>%i</int></value></param>") % param).str();
+}
+
+void message_transporter::end_xml_rpc_cmd(std::string &xml)
+{
+  xml += "</params></methodCall>";
+}
+
+}
diff --git a/src/wallet/message_transporter.h b/src/wallet/message_transporter.h
new file mode 100644
index 000000000..8291311ce
--- /dev/null
+++ b/src/wallet/message_transporter.h
@@ -0,0 +1,113 @@
+// Copyright (c) 2018, The Monero Project
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+//
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#pragma once
+#include "serialization/keyvalue_serialization.h"
+#include "cryptonote_basic/cryptonote_basic.h"
+#include "cryptonote_basic/cryptonote_boost_serialization.h"
+#include "cryptonote_basic/account_boost_serialization.h"
+#include "cryptonote_basic/cryptonote_basic.h"
+#include "net/http_server_impl_base.h"
+#include "net/http_client.h"
+#include "common/util.h"
+#include "wipeable_string.h"
+#include "serialization/keyvalue_serialization.h"
+#include <vector>
+
+namespace mms
+{
+
+struct transport_message
+{
+  cryptonote::account_public_address source_monero_address;
+  std::string source_transport_address;
+  cryptonote::account_public_address destination_monero_address;
+  std::string destination_transport_address;
+  crypto::chacha_iv iv;
+  crypto::public_key encryption_public_key;
+  uint64_t timestamp;
+  uint32_t type;
+  std::string subject;
+  std::string content;
+  crypto::hash hash;
+  crypto::signature signature;
+  uint32_t round;
+  uint32_t signature_count;
+  std::string transport_id;
+
+  BEGIN_KV_SERIALIZE_MAP()
+    KV_SERIALIZE(source_monero_address)
+    KV_SERIALIZE(source_transport_address)
+    KV_SERIALIZE(destination_monero_address)
+    KV_SERIALIZE(destination_transport_address)
+    KV_SERIALIZE_VAL_POD_AS_BLOB(iv)
+    KV_SERIALIZE_VAL_POD_AS_BLOB(encryption_public_key)
+    KV_SERIALIZE(timestamp)
+    KV_SERIALIZE(type)
+    KV_SERIALIZE(subject)
+    KV_SERIALIZE(content)
+    KV_SERIALIZE_VAL_POD_AS_BLOB(hash)
+    KV_SERIALIZE_VAL_POD_AS_BLOB(signature)
+    KV_SERIALIZE(round)
+    KV_SERIALIZE(signature_count)
+    KV_SERIALIZE(transport_id)
+  END_KV_SERIALIZE_MAP()
+};
+
+class message_transporter
+{
+public:
+  message_transporter();
+  void set_options(const std::string &bitmessage_address, const epee::wipeable_string &bitmessage_login);
+  bool send_message(const transport_message &message);
+  bool receive_messages(const std::vector<std::string> &destination_transport_addresses,
+                        std::vector<transport_message> &messages);
+  bool delete_message(const std::string &transport_id);
+  void stop() { m_run.store(false, std::memory_order_relaxed); }
+  std::string derive_transport_address(const std::string &seed);
+  std::string derive_and_receive_transport_address(const std::string &seed);
+  bool delete_transport_address(const std::string &transport_address);
+
+private:
+  epee::net_utils::http::http_simple_client m_http_client;
+  std::string m_bitmessage_url;
+  epee::wipeable_string m_bitmessage_login;
+  std::atomic<bool> m_run;
+
+  bool post_request(const std::string &request, std::string &answer);
+  static std::string get_str_between_tags(const std::string &s, const std::string &start_delim, const std::string &stop_delim);
+
+  static void start_xml_rpc_cmd(std::string &xml, const std::string &method_name);
+  static void add_xml_rpc_string_param(std::string &xml, const std::string &param);
+  static void add_xml_rpc_base64_param(std::string &xml, const std::string &param);
+  static void add_xml_rpc_integer_param(std::string &xml, const int32_t &param);
+  static void end_xml_rpc_cmd(std::string &xml);
+
+};
+
+}
diff --git a/src/wallet/wallet2.cpp b/src/wallet/wallet2.cpp
index 097278961..0d2faca54 100644
--- a/src/wallet/wallet2.cpp
+++ b/src/wallet/wallet2.cpp
@@ -226,7 +226,7 @@ struct options {
   const command_line::arg_descriptor<std::string> tx_notify = { "tx-notify" , "Run a program for each new incoming transaction, '%s' will be replaced by the transaction hash" , "" };
 };
 
-void do_prepare_file_names(const std::string& file_path, std::string& keys_file, std::string& wallet_file)
+void do_prepare_file_names(const std::string& file_path, std::string& keys_file, std::string& wallet_file, std::string &mms_file)
 {
   keys_file = file_path;
   wallet_file = file_path;
@@ -238,6 +238,7 @@ void do_prepare_file_names(const std::string& file_path, std::string& keys_file,
   {//provided wallet file name
     keys_file += ".keys";
   }
+  mms_file = file_path + ".mms";
 }
 
 uint64_t calculate_fee(uint64_t fee_per_kb, size_t bytes, uint64_t fee_multiplier)
@@ -330,6 +331,7 @@ std::unique_ptr<tools::wallet2> make_basic(const boost::program_options::variabl
   wallet->init(std::move(daemon_address), std::move(login), 0, false, *trusted_daemon);
   boost::filesystem::path ringdb_path = command_line::get_arg(vm, opts.shared_ringdb_dir);
   wallet->set_ring_database(ringdb_path.string());
+  wallet->get_message_store().set_options(vm);
   wallet->device_name(device_name);
   wallet->device_derivation_path(device_derivation_path);
 
@@ -907,6 +909,8 @@ wallet2::wallet2(network_type nettype, uint64_t kdf_rounds, bool unattended):
   m_light_wallet_connected(false),
   m_light_wallet_balance(0),
   m_light_wallet_unlocked_balance(0),
+  m_original_keys_available(false),
+  m_message_store(),
   m_key_device_type(hw::device::device_type::SOFTWARE),
   m_ring_history_saved(false),
   m_ringdb(),
@@ -956,6 +960,7 @@ void wallet2::init_options(boost::program_options::options_description& desc_par
   command_line::add_arg(desc_params, opts.stagenet);
   command_line::add_arg(desc_params, opts.shared_ringdb_dir);
   command_line::add_arg(desc_params, opts.kdf_rounds);
+  mms::message_store::init_options(desc_params);
   command_line::add_arg(desc_params, opts.hw_device);
   command_line::add_arg(desc_params, opts.hw_device_derivation_path);
   command_line::add_arg(desc_params, opts.tx_notify);
@@ -3184,6 +3189,9 @@ bool wallet2::store_keys(const std::string& keys_file_name, const epee::wipeable
   value2.SetUint(m_subaddress_lookahead_minor);
   json.AddMember("subaddress_lookahead_minor", value2, json.GetAllocator());
 
+  value2.SetInt(m_original_keys_available ? 1 : 0);
+  json.AddMember("original_keys_available", value2, json.GetAllocator());
+
   value2.SetUint(1);
   json.AddMember("encrypted_secret_keys", value2, json.GetAllocator());
 
@@ -3193,6 +3201,18 @@ bool wallet2::store_keys(const std::string& keys_file_name, const epee::wipeable
   value.SetString(m_device_derivation_path.c_str(), m_device_derivation_path.size());
   json.AddMember("device_derivation_path", value, json.GetAllocator());
 
+  std::string original_address;
+  std::string original_view_secret_key;
+  if (m_original_keys_available)
+  {  
+    original_address = get_account_address_as_str(m_nettype, false, m_original_address);
+    value.SetString(original_address.c_str(), original_address.length());
+    json.AddMember("original_address", value, json.GetAllocator());
+    original_view_secret_key = epee::string_tools::pod_to_hex(m_original_view_secret_key);
+    value.SetString(original_view_secret_key.c_str(), original_view_secret_key.length());
+    json.AddMember("original_view_secret_key", value, json.GetAllocator());
+  }
+  
   // Serialize the JSON object
   rapidjson::StringBuffer buffer;
   rapidjson::Writer<rapidjson::StringBuffer> writer(buffer);
@@ -3311,6 +3331,7 @@ bool wallet2::load_keys(const std::string& keys_file_name, const epee::wipeable_
     m_ignore_fractional_outputs = true;
     m_subaddress_lookahead_major = SUBADDRESS_LOOKAHEAD_MAJOR;
     m_subaddress_lookahead_minor = SUBADDRESS_LOOKAHEAD_MINOR;
+    m_original_keys_available = false;
     m_device_name = "";
     m_device_derivation_path = "";
     m_key_device_type = hw::device::device_type::SOFTWARE;
@@ -3483,6 +3504,35 @@ bool wallet2::load_keys(const std::string& keys_file_name, const epee::wipeable_
 
     GET_FIELD_FROM_JSON_RETURN_ON_ERROR(json, device_derivation_path, std::string, String, false, std::string());
     m_device_derivation_path = field_device_derivation_path;
+    
+    if (json.HasMember("original_keys_available"))
+    {
+      GET_FIELD_FROM_JSON_RETURN_ON_ERROR(json, original_keys_available, int, Int, false, false);
+      m_original_keys_available = field_original_keys_available;
+      if (m_original_keys_available)
+      {
+        GET_FIELD_FROM_JSON_RETURN_ON_ERROR(json, original_address, std::string, String, true, std::string());
+        address_parse_info info;
+        bool ok = get_account_address_from_str(info, m_nettype, field_original_address);
+        if (!ok)
+        {
+          LOG_ERROR("Failed to parse original_address from JSON");
+          return false;
+        }
+        m_original_address = info.address;
+        GET_FIELD_FROM_JSON_RETURN_ON_ERROR(json, original_view_secret_key, std::string, String, true, std::string());
+        ok = epee::string_tools::hex_to_pod(field_original_view_secret_key, m_original_view_secret_key);
+        if (!ok)
+        {
+          LOG_ERROR("Failed to parse original_view_secret_key from JSON");
+          return false;
+        }
+      }
+    }
+    else
+    {
+      m_original_keys_available = false;
+    }
   }
   else
   {
@@ -3809,6 +3859,10 @@ void wallet2::generate(const std::string& wallet_, const epee::wipeable_string&
   m_key_device_type = hw::device::device_type::SOFTWARE;
   setup_keys(password);
 
+  // Not possible to restore a multisig wallet that is able to activate the MMS
+  // (because the original keys are not (yet) part of the restore info)
+  m_original_keys_available = false;
+
   create_keys_file(wallet_, false, password, m_nettype != MAINNET || create_address_file);
   setup_new_blockchain();
 
@@ -3846,6 +3900,7 @@ crypto::secret_key wallet2::generate(const std::string& wallet_, const epee::wip
   m_multisig = false;
   m_multisig_threshold = 0;
   m_multisig_signers.clear();
+  m_original_keys_available = false;
   m_key_device_type = hw::device::device_type::SOFTWARE;
   setup_keys(password);
 
@@ -3934,6 +3989,7 @@ void wallet2::generate(const std::string& wallet_, const epee::wipeable_string&
   m_multisig = false;
   m_multisig_threshold = 0;
   m_multisig_signers.clear();
+  m_original_keys_available = false;
   m_key_device_type = hw::device::device_type::SOFTWARE;
   setup_keys(password);
 
@@ -3974,6 +4030,7 @@ void wallet2::generate(const std::string& wallet_, const epee::wipeable_string&
   m_multisig = false;
   m_multisig_threshold = 0;
   m_multisig_signers.clear();
+  m_original_keys_available = false;
   m_key_device_type = hw::device::device_type::SOFTWARE;
   setup_keys(password);
 
@@ -4015,6 +4072,7 @@ void wallet2::restore(const std::string& wallet_, const epee::wipeable_string& p
   m_multisig = false;
   m_multisig_threshold = 0;
   m_multisig_signers.clear();
+  m_original_keys_available = false;
   setup_keys(password);
   m_device_name = device_name;
 
@@ -4127,6 +4185,15 @@ std::string wallet2::make_multisig(const epee::wipeable_string &password,
       m_multisig_derivations = derivations;
     }
   }
+  
+  if (!m_original_keys_available)
+  {
+    // Save the original i.e. non-multisig keys so the MMS can continue to use them to encrypt and decrypt messages
+    // (making a wallet multisig overwrites those keys, see account_base::make_multisig)
+    m_original_address = m_account.get_keys().m_account_address;
+    m_original_view_secret_key = m_account.get_keys().m_view_secret_key;
+    m_original_keys_available = true;
+  }
 
   clear();
   MINFO("Creating view key...");
@@ -4560,8 +4627,8 @@ void wallet2::write_watch_only_wallet(const std::string& wallet_name, const epee
 //----------------------------------------------------------------------------------------------------
 void wallet2::wallet_exists(const std::string& file_path, bool& keys_file_exists, bool& wallet_file_exists)
 {
-  std::string keys_file, wallet_file;
-  do_prepare_file_names(file_path, keys_file, wallet_file);
+  std::string keys_file, wallet_file, mms_file;
+  do_prepare_file_names(file_path, keys_file, wallet_file, mms_file);
 
   boost::system::error_code ignore;
   keys_file_exists = boost::filesystem::exists(keys_file, ignore);
@@ -4615,7 +4682,7 @@ bool wallet2::parse_payment_id(const std::string& payment_id_str, crypto::hash&
 //----------------------------------------------------------------------------------------------------
 bool wallet2::prepare_file_names(const std::string& file_path)
 {
-  do_prepare_file_names(file_path, m_keys_file, m_wallet_file);
+  do_prepare_file_names(file_path, m_keys_file, m_wallet_file, m_mms_file);
   return true;
 }
 //----------------------------------------------------------------------------------------------------
@@ -4808,6 +4875,8 @@ void wallet2::load(const std::string& wallet_, const epee::wipeable_string& pass
   {
     MERROR("Failed to save rings, will try again next time");
   }
+  
+  m_message_store.read_from_file(get_multisig_wallet_state(), m_mms_file);
 }
 //----------------------------------------------------------------------------------------------------
 void wallet2::trim_hashchain()
@@ -4913,6 +4982,7 @@ void wallet2::store_to(const std::string &path, const epee::wipeable_string &pas
   const std::string old_file = m_wallet_file;
   const std::string old_keys_file = m_keys_file;
   const std::string old_address_file = m_wallet_file + ".address.txt";
+  const std::string old_mms_file = m_mms_file;
 
   // save keys to the new file
   // if we here, main wallet file is saved and we only need to save keys and address files
@@ -4942,6 +5012,14 @@ void wallet2::store_to(const std::string &path, const epee::wipeable_string &pas
     if (!r) {
       LOG_ERROR("error removing file: " << old_address_file);
     }
+    // remove old message store file
+    if (boost::filesystem::exists(old_mms_file))
+    {
+      r = boost::filesystem::remove(old_mms_file);
+      if (!r) {
+        LOG_ERROR("error removing file: " << old_mms_file);
+      }
+    }
   } else {
     // save to new file
 #ifdef WIN32
@@ -4967,6 +5045,14 @@ void wallet2::store_to(const std::string &path, const epee::wipeable_string &pas
     std::error_code e = tools::replace_file(new_file, m_wallet_file);
     THROW_WALLET_EXCEPTION_IF(e, error::file_save_error, m_wallet_file, e);
   }
+  
+  if (m_message_store.get_active())
+  {
+    // While the "m_message_store" object of course always exist, a file for the message
+    // store should only exist if the MMS is really active
+    m_message_store.write_to_file(get_multisig_wallet_state(), m_mms_file);
+  }
+  
 }
 //----------------------------------------------------------------------------------------------------
 uint64_t wallet2::balance(uint32_t index_major) const
@@ -12030,6 +12116,29 @@ void wallet2::generate_genesis(cryptonote::block& b) const {
   cryptonote::generate_genesis_block(b, get_config(m_nettype).GENESIS_TX, get_config(m_nettype).GENESIS_NONCE);
 }
 //----------------------------------------------------------------------------------------------------
+mms::multisig_wallet_state wallet2::get_multisig_wallet_state() const
+{
+  mms::multisig_wallet_state state;
+  state.nettype = m_nettype;
+  state.multisig = multisig(&state.multisig_is_ready);
+  state.has_multisig_partial_key_images = has_multisig_partial_key_images();
+  state.multisig_rounds_passed = m_multisig_rounds_passed;
+  state.num_transfer_details = m_transfers.size();
+  if (state.multisig)
+  {
+    THROW_WALLET_EXCEPTION_IF(!m_original_keys_available, error::wallet_internal_error, "MMS use not possible because own original Monero address not available");
+    state.address = m_original_address;
+    state.view_secret_key = m_original_view_secret_key;
+  }
+  else
+  {
+    state.address = m_account.get_keys().m_account_address;
+    state.view_secret_key = m_account.get_keys().m_view_secret_key;
+  }
+  state.mms_file=m_mms_file;
+  return state;
+}
+//----------------------------------------------------------------------------------------------------
 wallet_device_callback * wallet2::get_device_callback()
 {
   if (!m_device_callback){
diff --git a/src/wallet/wallet2.h b/src/wallet/wallet2.h
index 91c68bf3c..ace01a235 100644
--- a/src/wallet/wallet2.h
+++ b/src/wallet/wallet2.h
@@ -61,6 +61,7 @@
 #include "wallet_errors.h"
 #include "common/password.h"
 #include "node_rpc_proxy.h"
+#include "message_store.h"
 
 #undef MONERO_DEFAULT_LOG_CATEGORY
 #define MONERO_DEFAULT_LOG_CATEGORY "wallet.wallet2"
@@ -674,7 +675,7 @@ namespace tools
     bool init(std::string daemon_address = "http://localhost:8080",
       boost::optional<epee::net_utils::http::login> daemon_login = boost::none, uint64_t upper_transaction_weight_limit = 0, bool ssl = false, bool trusted_daemon = false);
 
-    void stop() { m_run.store(false, std::memory_order_relaxed); }
+    void stop() { m_run.store(false, std::memory_order_relaxed); m_message_store.stop(); }
 
     i_wallet2_callback* callback() const { return m_callback; }
     void callback(i_wallet2_callback* callback) { m_callback = callback; }
@@ -1218,6 +1219,11 @@ namespace tools
     bool unblackball_output(const std::pair<uint64_t, uint64_t> &output);
     bool is_output_blackballed(const std::pair<uint64_t, uint64_t> &output) const;
 
+    // MMS -------------------------------------------------------------------------------------------------
+    mms::message_store& get_message_store() { return m_message_store; };
+    const mms::message_store& get_message_store() const { return m_message_store; };
+    mms::multisig_wallet_state get_multisig_wallet_state() const;
+
     bool lock_keys_file();
     bool unlock_keys_file();
     bool is_keys_file_locked() const;
@@ -1320,6 +1326,7 @@ namespace tools
     std::string m_daemon_address;
     std::string m_wallet_file;
     std::string m_keys_file;
+    std::string m_mms_file;
     epee::net_utils::http::http_simple_client m_http_client;
     hashchain m_blockchain;
     std::unordered_map<crypto::hash, unconfirmed_transfer_details> m_unconfirmed_txs;
@@ -1420,6 +1427,11 @@ namespace tools
 
     uint64_t m_last_block_reward;
     std::unique_ptr<tools::file_locker> m_keys_file_locker;
+    
+    mms::message_store m_message_store;
+    bool m_original_keys_available;
+    cryptonote::account_public_address m_original_address;
+    crypto::secret_key m_original_view_secret_key;
 
     crypto::chacha_key m_cache_key;
     boost::optional<epee::wipeable_string> m_encrypt_keys_after_refresh;
diff --git a/src/wallet/wallet_errors.h b/src/wallet/wallet_errors.h
index e2caee5d2..35862bda1 100644
--- a/src/wallet/wallet_errors.h
+++ b/src/wallet/wallet_errors.h
@@ -821,6 +821,31 @@ namespace tools
       std::string m_wallet_file;
     };
     //----------------------------------------------------------------------------------------------------
+    struct mms_error : public wallet_logic_error
+    {
+    protected:
+      explicit mms_error(std::string&& loc, const std::string& message)
+        : wallet_logic_error(std::move(loc), message)
+      {
+      }
+    };
+    //----------------------------------------------------------------------------------------------------
+    struct no_connection_to_bitmessage : public mms_error
+    {
+      explicit no_connection_to_bitmessage(std::string&& loc, const std::string& address)
+        : mms_error(std::move(loc), "no connection to PyBitmessage at address " + address)
+      {
+      }
+    };
+    //----------------------------------------------------------------------------------------------------
+    struct bitmessage_api_error : public mms_error
+    {
+      explicit bitmessage_api_error(std::string&& loc, const std::string& error_string)
+        : mms_error(std::move(loc), "PyBitmessage returned " + error_string)
+      {
+      }
+    };
+    //----------------------------------------------------------------------------------------------------
 
 #if !defined(_MSC_VER)