Add N/N multisig tx generation and signing

Scheme by luigi1111:

    Multisig for RingCT on Monero

    2 of 2

    User A (coordinator):
    Spendkey b,B
    Viewkey a,A (shared)

    User B:
    Spendkey c,C
    Viewkey a,A (shared)

    Public Address: C+B, A

    Both have their own watch only wallet via C+B, a

    A will coordinate spending process (though B could easily as well, coordinator is more needed for more participants)

    A and B watch for incoming outputs

    B creates "half" key images for discovered output D:
    I2_D = (Hs(aR)+c) * Hp(D)

    B also creates 1.5 random keypairs (one scalar and 2 pubkeys; one on base G and one on base Hp(D)) for each output, storing the scalar(k) (linked to D),
    and sending the pubkeys with I2_D.

    A also creates "half" key images:
    I1_D = (Hs(aR)+b) * Hp(D)

    Then I_D = I1_D + I2_D

    Having I_D allows A to check spent status of course, but more importantly allows A to actually build a transaction prefix (and thus transaction).

    A builds the transaction until most of the way through MLSAG_Gen, adding the 2 pubkeys (per input) provided with I2_D
    to his own generated ones where they are needed (secret row L, R).

    At this point, A has a mostly completed transaction (but with an invalid/incomplete signature). A sends over the tx and includes r,
    which allows B (with the recipient's address) to verify the destination and amount (by reconstructing the stealth address and decoding ecdhInfo).

    B then finishes the signature by computing ss[secret_index][0] = ss[secret_index][0] + k - cc[secret_index]*c (secret indices need to be passed as well).

    B can then broadcast the tx, or send it back to A for broadcasting. Once B has completed the signing (and verified the tx to be valid), he can add the full I_D
    to his cache, allowing him to verify spent status as well.

    NOTE:
    A and B *must* present key A and B to each other with a valid signature proving they know a and b respectively.
    Otherwise, trickery like the following becomes possible:
    A creates viewkey a,A, spendkey b,B, and sends a,A,B to B.
    B creates a fake key C = zG - B. B sends C back to A.
    The combined spendkey C+B then equals zG, allowing B to spend funds at any time!
    The signature fixes this, because B does not know a c corresponding to C (and thus can't produce a signature).

    2 of 3

    User A (coordinator)
    Shared viewkey a,A
    "spendkey" j,J

    User B
    "spendkey" k,K

    User C
    "spendkey" m,M

    A collects K and M from B and C
    B collects J and M from A and C
    C collects J and K from A and B

    A computes N = nG, n = Hs(jK)
    A computes O = oG, o = Hs(jM)

    B anc C compute P = pG, p = Hs(kM) || Hs(mK)
    B and C can also compute N and O respectively if they wish to be able to coordinate

    Address: N+O+P, A

    The rest follows as above. The coordinator possesses 2 of 3 needed keys; he can get the other
    needed part of the signature/key images from either of the other two.

    Alternatively, if secure communication exists between parties:
    A gives j to B
    B gives k to C
    C gives m to A

    Address: J+K+M, A

    3 of 3

    Identical to 2 of 2, except the coordinator must collect the key images from both of the others.
    The transaction must also be passed an additional hop: A -> B -> C (or A -> C -> B), who can then broadcast it
    or send it back to A.

    N-1 of N

    Generally the same as 2 of 3, except participants need to be arranged in a ring to pass their keys around
    (using either the secure or insecure method).
    For example (ignoring viewkey so letters line up):
    [4 of 5]
    User: spendkey
    A: a
    B: b
    C: c
    D: d
    E: e

    a -> B, b -> C, c -> D, d -> E, e -> A

    Order of signing does not matter, it just must reach n-1 users. A "remaining keys" list must be passed around with
    the transaction so the signers know if they should use 1 or both keys.
    Collecting key image parts becomes a little messy, but basically every wallet sends over both of their parts with a tag for each.
    Thia way the coordinating wallet can keep track of which images have been added and which wallet they come from. Reasoning:
    1. The key images must be added only once (coordinator will get key images for key a from both A and B, he must add only one to get the proper key actual key image)
    2. The coordinator must keep track of which helper pubkeys came from which wallet (discussed in 2 of 2 section). The coordinator
    must choose only one set to use, then include his choice in the "remaining keys" list so the other wallets know which of their keys to use.

    You can generalize it further to N-2 of N or even M of N, but I'm not sure there's legitimate demand to justify the complexity. It might
    also be straightforward enough to support with minimal changes from N-1 format.
    You basically just give each user additional keys for each additional "-1" you desire. N-2 would be 3 keys per user, N-3 4 keys, etc.

The process is somewhat cumbersome:

To create a N/N multisig wallet:

 - each participant creates a normal wallet
 - each participant runs "prepare_multisig", and sends the resulting string to every other participant
 - each participant runs "make_multisig N A B C D...", with N being the threshold and A B C D... being the strings received from other participants (the threshold must currently equal N)

As txes are received, participants' wallets will need to synchronize so that those new outputs may be spent:

 - each participant runs "export_multisig FILENAME", and sends the FILENAME file to every other participant
 - each participant runs "import_multisig A B C D...", with A B C D... being the filenames received from other participants

Then, a transaction may be initiated:

 - one of the participants runs "transfer ADDRESS AMOUNT"
 - this partly signed transaction will be written to the "multisig_monero_tx" file
 - the initiator sends this file to another participant
 - that other participant runs "sign_multisig multisig_monero_tx"
 - the resulting transaction is written to the "multisig_monero_tx" file again
 - if the threshold was not reached, the file must be sent to another participant, until enough have signed
 - the last participant to sign runs "submit_multisig multisig_monero_tx" to relay the transaction to the Monero network

2 files changed, 538 insertions, 117 deletions

diff --git a/src/simplewallet/simplewallet.cpp b/src/simplewallet/simplewallet.cpp
index 4349b6b92..539301f83 100644
--- a/src/simplewallet/simplewallet.cpp
+++ b/src/simplewallet/simplewallet.cpp
@@ -84,6 +84,7 @@ typedef cryptonote::simple_wallet sw;
 #define MIN_RING_SIZE 5 // Used to inform user about min ring size -- does not track actual protocol
 
 #define OUTPUT_EXPORT_FILE_MAGIC "Monero output export\003"
+#define MULTISIG_EXPORT_FILE_MAGIC "Monero multisig export\001"
 
 #define LOCK_IDLE_SCOPE() \
   bool auto_refresh_enabled = m_auto_refresh_enabled.load(std::memory_order_relaxed); \
@@ -340,6 +341,106 @@ namespace
     }
     return true;
   }
+
+  void handle_transfer_exception(const std::exception_ptr &e)
+  {
+    try
+    {
+      std::rethrow_exception(e);
+    }
+    catch (const tools::error::daemon_busy&)
+    {
+      fail_msg_writer() << tr("daemon is busy. Please try again later.");
+    }
+    catch (const tools::error::no_connection_to_daemon&)
+    {
+      fail_msg_writer() << tr("no connection to daemon. Please make sure daemon is running.");
+    }
+    catch (const tools::error::wallet_rpc_error& e)
+    {
+      LOG_ERROR("RPC error: " << e.to_string());
+      fail_msg_writer() << tr("RPC error: ") << e.what();
+    }
+    catch (const tools::error::get_random_outs_error &e)
+    {
+      fail_msg_writer() << tr("failed to get random outputs to mix: ") << e.what();
+    }
+    catch (const tools::error::not_enough_unlocked_money& e)
+    {
+      LOG_PRINT_L0(boost::format("not enough money to transfer, available only %s, sent amount %s") %
+        print_money(e.available()) %
+        print_money(e.tx_amount()));
+      fail_msg_writer() << tr("Not enough money in unlocked balance");
+    }
+    catch (const tools::error::not_enough_money& e)
+    {
+      LOG_PRINT_L0(boost::format("not enough money to transfer, available only %s, sent amount %s") %
+        print_money(e.available()) %
+        print_money(e.tx_amount()));
+      fail_msg_writer() << tr("Not enough money in unlocked balance");
+    }
+    catch (const tools::error::tx_not_possible& e)
+    {
+      LOG_PRINT_L0(boost::format("not enough money to transfer, available only %s, transaction amount %s = %s + %s (fee)") %
+        print_money(e.available()) %
+        print_money(e.tx_amount() + e.fee())  %
+        print_money(e.tx_amount()) %
+        print_money(e.fee()));
+      fail_msg_writer() << tr("Failed to find a way to create transactions. This is usually due to dust which is so small it cannot pay for itself in fees, or trying to send more money than the unlocked balance, or not leaving enough for fees");
+    }
+    catch (const tools::error::not_enough_outs_to_mix& e)
+    {
+      auto writer = fail_msg_writer();
+      writer << tr("not enough outputs for specified ring size") << " = " << (e.mixin_count() + 1) << ":";
+      for (std::pair<uint64_t, uint64_t> outs_for_amount : e.scanty_outs())
+      {
+        writer << "\n" << tr("output amount") << " = " << print_money(outs_for_amount.first) << ", " << tr("found outputs to use") << " = " << outs_for_amount.second;
+      }
+    }
+    catch (const tools::error::tx_not_constructed&)
+      {
+      fail_msg_writer() << tr("transaction was not constructed");
+    }
+    catch (const tools::error::tx_rejected& e)
+    {
+      fail_msg_writer() << (boost::format(tr("transaction %s was rejected by daemon with status: ")) % get_transaction_hash(e.tx())) << e.status();
+      std::string reason = e.reason();
+      if (!reason.empty())
+        fail_msg_writer() << tr("Reason: ") << reason;
+    }
+    catch (const tools::error::tx_sum_overflow& e)
+    {
+      fail_msg_writer() << e.what();
+    }
+    catch (const tools::error::zero_destination&)
+    {
+      fail_msg_writer() << tr("one of destinations is zero");
+    }
+    catch (const tools::error::tx_too_big& e)
+    {
+      fail_msg_writer() << tr("failed to find a suitable way to split transactions");
+    }
+    catch (const tools::error::transfer_error& e)
+    {
+      LOG_ERROR("unknown transfer error: " << e.to_string());
+      fail_msg_writer() << tr("unknown transfer error: ") << e.what();
+    }
+    catch (const tools::error::multisig_export_needed& e)
+    {
+      LOG_ERROR("Multisig error: " << e.to_string());
+      fail_msg_writer() << tr("Multisig error: ") << e.what();
+    }
+    catch (const tools::error::wallet_internal_error& e)
+    {
+      LOG_ERROR("internal error: " << e.to_string());
+      fail_msg_writer() << tr("internal error: ") << e.what();
+    }
+    catch (const std::exception& e)
+    {
+      LOG_ERROR("unexpected error: " << e.what());
+      fail_msg_writer() << tr("unexpected error: ") << e.what();
+    }
+  }
 }
 
 bool parse_priority(const std::string& arg, uint32_t& priority)
@@ -417,6 +518,11 @@ bool simple_wallet::print_seed(bool encrypted)
   bool success =  false;
   std::string electrum_words;
 
+  if (m_wallet->multisig())
+  {
+    fail_msg_writer() << tr("wallet is multisig and has no seed");
+    return true;
+  }
   if (m_wallet->watch_only())
   {
     fail_msg_writer() << tr("wallet is watch-only and has no seed");
@@ -468,6 +574,11 @@ bool simple_wallet::encrypted_seed(const std::vector<std::string> &args/* = std:
 
 bool simple_wallet::seed_set_language(const std::vector<std::string> &args/* = std::vector<std::string>()*/)
 {
+  if (m_wallet->multisig())
+  {
+    fail_msg_writer() << tr("wallet is multisig and has no seed");
+    return true;
+  }
   if (m_wallet->watch_only())
   {
     fail_msg_writer() << tr("wallet is watch-only and has no seed");
@@ -594,6 +705,11 @@ bool simple_wallet::prepare_multisig(const std::vector<std::string> &args)
     fail_msg_writer() << tr("This wallet is already multisig");
     return true;
   }
+  if (m_wallet->watch_only())
+  {
+    fail_msg_writer() << tr("wallet is watch-only and cannot be made multisig");
+    return true;
+  }
 
   if(m_wallet->get_num_transfer_details())
   {
@@ -610,8 +726,8 @@ bool simple_wallet::prepare_multisig(const std::vector<std::string> &args)
 
   std::string multisig_info = m_wallet->get_multisig_info();
   success_msg_writer() << multisig_info;
-  success_msg_writer() << "Send this multisig info to all other participants, then use make_multisig <info1> [<info2>...] with others' multisig info";
-  success_msg_writer() << "This includes the PRIVATE view key, so needs to be disclosed only to that multisig wallet's participants ";
+  success_msg_writer() << tr("Send this multisig info to all other participants, then use make_multisig <threshold> <info1> [<info2>...] with others' multisig info");
+  success_msg_writer() << tr("This includes the PRIVATE view key, so needs to be disclosed only to that multisig wallet's participants ");
   return true;
 }
 
@@ -622,6 +738,11 @@ bool simple_wallet::make_multisig(const std::vector<std::string> &args)
     fail_msg_writer() << tr("This wallet is already multisig");
     return true;
   }
+  if (m_wallet->watch_only())
+  {
+    fail_msg_writer() << tr("wallet is watch-only and cannot be made multisig");
+    return true;
+  }
 
   if(m_wallet->get_num_transfer_details())
   {
@@ -663,23 +784,28 @@ bool simple_wallet::make_multisig(const std::vector<std::string> &args)
   }
 
   // remove duplicates
-  for (size_t i = 1; i < secret_keys.size(); ++i)
+  for (size_t i = 0; i < secret_keys.size(); ++i)
   {
-    if (rct::sk2rct(secret_keys[i]) == rct::sk2rct(secret_keys[0]))
+    for (size_t j = i + 1; j < secret_keys.size(); ++j)
     {
-      message_writer() << tr("Duplicate key found, ignoring");
-      secret_keys[i] = secret_keys.back();
-      public_keys[i] = public_keys.back();
-      secret_keys.pop_back();
-      public_keys.pop_back();
-      --i;
+      if (rct::sk2rct(secret_keys[i]) == rct::sk2rct(secret_keys[j]))
+      {
+        message_writer() << tr("Duplicate key found, ignoring");
+        secret_keys[j] = secret_keys.back();
+        public_keys[j] = public_keys.back();
+        secret_keys.pop_back();
+        public_keys.pop_back();
+        --j;
+      }
     }
   }
 
   // people may include their own, weed it out
+  const crypto::secret_key local_skey = m_wallet->get_account().get_keys().m_view_secret_key;
+  const crypto::public_key local_pkey = m_wallet->get_account().get_keys().m_account_address.m_spend_public_key;
   for (size_t i = 0; i < secret_keys.size(); ++i)
   {
-    if (rct::sk2rct(secret_keys[i]) == rct::sk2rct(m_wallet->get_account().get_keys().m_view_secret_key))
+    if (secret_keys[i] == local_skey)
     {
       message_writer() << tr("Local key is present, ignoring");
       secret_keys[i] = secret_keys.back();
@@ -688,9 +814,9 @@ bool simple_wallet::make_multisig(const std::vector<std::string> &args)
       public_keys.pop_back();
       --i;
     }
-    else if (rct::pk2rct(public_keys[i]) == rct::pk2rct(m_wallet->get_account().get_keys().m_account_address.m_spend_public_key))
+    else if (public_keys[i] == local_pkey)
     {
-      fail_msg_writer() << "Found local spend public key, but not local view secret key - something very weird";
+      fail_msg_writer() << tr("Found local spend public key, but not local view secret key - something very weird");
       return true;
     }
   }
@@ -703,17 +829,315 @@ bool simple_wallet::make_multisig(const std::vector<std::string> &args)
   }
   catch (const std::exception &e)
   {
-    fail_msg_writer() << "Error creating multisig: " << e.what();
+    fail_msg_writer() << tr("Error creating multisig: ") << e.what();
     return true;
   }
 
   uint32_t total = secret_keys.size() + 1;
-  success_msg_writer() << std::to_string(threshold) << "/" << total << " multisig address: "
+  success_msg_writer() << std::to_string(threshold) << "/" << total << tr(" multisig address: ")
       << m_wallet->get_account().get_public_address_str(m_wallet->testnet());
 
   return true;
 }
 
+bool simple_wallet::export_multisig(const std::vector<std::string> &args)
+{
+  if (!m_wallet->multisig())
+  {
+    fail_msg_writer() << tr("This wallet is not multisig");
+    return true;
+  }
+  if (args.size() != 1)
+  {
+    fail_msg_writer() << tr("usage: export_multisig_info <filename>");
+    return true;
+  }
+  if (m_wallet->ask_password() && !get_and_verify_password())
+    return true;
+
+  const std::string filename = args[0];
+  try
+  {
+    std::vector<tools::wallet2::multisig_info> outs = m_wallet->export_multisig();
+
+    std::stringstream oss;
+    boost::archive::portable_binary_oarchive ar(oss);
+    ar << outs;
+
+    std::string magic(MULTISIG_EXPORT_FILE_MAGIC, strlen(MULTISIG_EXPORT_FILE_MAGIC));
+    const cryptonote::account_public_address &keys = m_wallet->get_account().get_keys().m_account_address;
+    std::string header;
+    header += std::string((const char *)&keys.m_spend_public_key, sizeof(crypto::public_key));
+    header += std::string((const char *)&keys.m_view_public_key, sizeof(crypto::public_key));
+    crypto::hash hash;
+    cn_fast_hash(&m_wallet->get_account().get_keys().m_spend_secret_key, sizeof(crypto::secret_key), (char*)&hash);
+    header += std::string((const char *)&hash, sizeof(crypto::hash));
+    std::string ciphertext = m_wallet->encrypt_with_view_secret_key(header + oss.str());
+    bool r = epee::file_io_utils::save_string_to_file(filename, magic + ciphertext);
+    if (!r)
+    {
+      fail_msg_writer() << tr("failed to save file ") << filename;
+      return true;
+    }
+  }
+  catch (const std::exception &e)
+  {
+    LOG_ERROR("Error exporting multisig info: " << e.what());
+    fail_msg_writer() << tr("Error exporting multisig info: ") << e.what();
+    return true;
+  }
+
+  success_msg_writer() << tr("Multisig info exported to ") << filename;
+  return true;
+}
+
+bool simple_wallet::import_multisig(const std::vector<std::string> &args)
+{
+  uint32_t threshold, total;
+  if (!m_wallet->multisig(&threshold, &total))
+  {
+    fail_msg_writer() << tr("This wallet is not multisig");
+    return true;
+  }
+  if (args.size() < threshold - 1)
+  {
+    fail_msg_writer() << tr("usage: import_multisig_info <filename1> [<filename2>...] - one for each other participant");
+    return true;
+  }
+  if (m_wallet->ask_password() && !get_and_verify_password())
+    return true;
+
+  std::vector<std::vector<tools::wallet2::multisig_info>> info;
+  std::unordered_set<crypto::hash> seen;
+  for (size_t n = 0; n < args.size(); ++n)
+  {
+    const std::string filename = args[n];
+    std::string data;
+    bool r = epee::file_io_utils::load_file_to_string(filename, data);
+    if (!r)
+    {
+      fail_msg_writer() << tr("failed to read file ") << filename;
+      return true;
+    }
+    const size_t magiclen = strlen(MULTISIG_EXPORT_FILE_MAGIC);
+    if (data.size() < magiclen || memcmp(data.data(), MULTISIG_EXPORT_FILE_MAGIC, magiclen))
+    {
+      fail_msg_writer() << tr("Bad multisig info file magic in ") << filename;
+      return true;
+    }
+
+    try
+    {
+      data = m_wallet->decrypt_with_view_secret_key(std::string(data, magiclen));
+    }
+    catch (const std::exception &e)
+    {
+      fail_msg_writer() << tr("Failed to decrypt ") << filename << ": " << e.what();
+      return true;
+    }
+
+    const size_t headerlen = 3 * sizeof(crypto::public_key);
+    if (data.size() < headerlen)
+    {
+      fail_msg_writer() << tr("Bad data size from file ") << filename;
+      return true;
+    }
+    const crypto::public_key &public_spend_key = *(const crypto::public_key*)&data[0];
+    const crypto::public_key &public_view_key = *(const crypto::public_key*)&data[sizeof(crypto::public_key)];
+    const crypto::hash &hash = *(const crypto::hash*)&data[2*sizeof(crypto::public_key)];
+    const cryptonote::account_public_address &keys = m_wallet->get_account().get_keys().m_account_address;
+    if (public_spend_key != keys.m_spend_public_key || public_view_key != keys.m_view_public_key)
+    {
+      fail_msg_writer() << (boost::format(tr("Multisig info from %s is for a different account")) % filename).str();
+      return true;
+    }
+    crypto::hash this_hash;
+    cn_fast_hash(&m_wallet->get_account().get_keys().m_spend_secret_key, sizeof(crypto::secret_key), (char*)&this_hash);
+    if (this_hash == hash)
+    {
+      message_writer() << (boost::format(tr("Multisig info from %s is from this wallet, ignored")) % filename).str();
+      continue;
+    }
+    if (seen.find(hash) != seen.end())
+    {
+      message_writer() << (boost::format(tr("Multisig info from %s already seen, ignored")) % filename).str();
+      continue;
+    }
+    seen.insert(hash);
+
+    try
+    {
+      std::string body(data, headerlen);
+      std::istringstream iss(body);
+      std::vector<tools::wallet2::multisig_info> i;
+      boost::archive::portable_binary_iarchive ar(iss);
+      ar >> i;
+      message_writer() << (boost::format(tr("%u outputs found in %s")) % boost::lexical_cast<std::string>(i.size()) % filename).str();
+      info.push_back(std::move(i));
+    }
+    catch (const std::exception &e)
+    {
+      fail_msg_writer() << tr("Failed to import multisig info: ") << e.what();
+      return true;
+    }
+  }
+
+  LOCK_IDLE_SCOPE();
+
+  // all read and parsed, actually import
+  try
+  {
+    size_t n_outputs = m_wallet->import_multisig(info);
+    // Clear line "Height xxx of xxx"
+    std::cout << "\r                                                                \r";
+    success_msg_writer() << tr("Multisig info imported");
+  }
+  catch (const std::exception &e)
+  {
+    fail_msg_writer() << tr("Failed to import multisig info: ") << e.what();
+    return true;
+  }
+  if (m_trusted_daemon)
+  {
+    try
+    {
+      m_wallet->rescan_spent();
+    }
+    catch (const std::exception &e)
+    {
+      message_writer() << tr("Failed to update spent status after importing multisig info: ") << e.what();
+    }
+  }
+  else
+  {
+    message_writer() << tr("Untrusted daemon, spent status may be incorrect. Use a trusted daemon and run \"rescan_spent\"");
+  }
+  return true;
+}
+
+bool simple_wallet::accept_loaded_tx(const tools::wallet2::multisig_tx_set &txs)
+{
+  std::string extra_message;
+  return accept_loaded_tx([&txs](){return txs.m_ptx.size();}, [&txs](size_t n)->const tools::wallet2::tx_construction_data&{return txs.m_ptx[n].construction_data;}, extra_message);
+}
+
+bool simple_wallet::sign_multisig(const std::vector<std::string> &args)
+{
+  if(!m_wallet->multisig())
+  {
+    fail_msg_writer() << tr("This is not a multisig wallet");
+    return true;
+  }
+  if (args.size() != 1)
+  {
+    fail_msg_writer() << tr("usage: sign_multisig <filename>");
+    return true;
+  }
+  if (m_wallet->ask_password() && !get_and_verify_password()) { return true; }
+
+  std::string filename = args[0];
+  std::vector<crypto::hash> txids;
+  uint32_t signers = 0;
+  try
+  {
+    bool r = m_wallet->sign_multisig_tx_from_file(filename, txids, [&](const tools::wallet2::multisig_tx_set &tx){ signers = tx.m_signers.size(); return accept_loaded_tx(tx); });
+    if (!r)
+    {
+      fail_msg_writer() << tr("Failed to sign multisig transaction");
+      return true;
+    }
+  }
+  catch (const tools::error::multisig_export_needed& e)
+  {
+    fail_msg_writer() << tr("Multisig error: ") << e.what();
+    return true;
+  }
+  catch (const std::exception &e)
+  {
+    fail_msg_writer() << tr("Failed to sign multisig transaction: ") << e.what();
+    return true;
+  }
+
+  if (txids.empty())
+  {
+    uint32_t threshold;
+    m_wallet->multisig(&threshold);
+    uint32_t signers_needed = threshold - signers - 1;
+    success_msg_writer(true) << tr("Transaction successfully signed to file ") << filename << ", "
+        << signers_needed << " more signer(s) needed";
+    return true;
+  }
+  else
+  {
+    std::string txids_as_text;
+    for (const auto &txid: txids)
+    {
+      if (!txids_as_text.empty())
+        txids_as_text += (", ");
+      txids_as_text += epee::string_tools::pod_to_hex(txid);
+    }
+    success_msg_writer(true) << tr("Transaction successfully signed to file ") << filename << ", txid " << txids_as_text;
+    success_msg_writer(true) << tr("It may be relayed to the network with submit_multisig");
+  }
+  return true;
+}
+
+bool simple_wallet::submit_multisig(const std::vector<std::string> &args)
+{
+  uint32_t threshold;
+  if (!m_wallet->multisig(&threshold))
+  {
+    fail_msg_writer() << tr("This is not a multisig wallet");
+    return true;
+  }
+  if (args.size() != 1)
+  {
+    fail_msg_writer() << tr("usage: submit_multisig <filename>");
+    return true;
+  }
+  if (m_wallet->ask_password() && !get_and_verify_password()) { return true; }
+
+  if (!try_connect_to_daemon())
+    return true;
+
+  std::string filename = args[0];
+  try
+  {
+    tools::wallet2::multisig_tx_set txs;
+    bool r = m_wallet->load_multisig_tx_from_file(filename, txs, [&](const tools::wallet2::multisig_tx_set &tx){ return accept_loaded_tx(tx); });
+    if (!r)
+    {
+      fail_msg_writer() << tr("Failed to load multisig transaction from file");
+      return true;
+    }
+    if (txs.m_signers.size() < threshold)
+    {
+      fail_msg_writer() << (boost::format(tr("Multisig transaction signed by only %u signers, needs %u more signatures"))
+          % txs.m_signers.size() % (threshold - txs.m_signers.size())).str();
+      return true;
+    }
+
+    // actually commit the transactions
+    for (auto &ptx: txs.m_ptx)
+    {
+      m_wallet->commit_tx(ptx);
+      success_msg_writer(true) << tr("Transaction successfully submitted, transaction ") << get_transaction_hash(ptx.tx) << ENDL
+          << tr("You can check its status by using the `show_transfers` command.");
+    }
+  }
+  catch (const std::exception &e)
+  {
+    handle_transfer_exception(std::current_exception());
+  }
+  catch (...)
+  {
+    LOG_ERROR("unknown error");
+    fail_msg_writer() << tr("unknown error");
+  }
+
+  return true;
+}
+
 bool simple_wallet::set_always_confirm_transfers(const std::vector<std::string> &args/* = std::vector<std::string>()*/)
 {
   const auto pwd_container = get_and_verify_password();
@@ -1297,11 +1721,26 @@ simple_wallet::simple_wallet()
   m_cmd_binder.set_handler("make_multisig", boost::bind(&simple_wallet::make_multisig, this, _1),
                            tr("make_multisig <threshold> <string1> [<string>...]"),
                            tr("Turn this wallet into a multisig wallet"));
+  m_cmd_binder.set_handler("export_multisig_info",
+                           boost::bind(&simple_wallet::export_multisig, this, _1),
+                           tr("export_multisig <filename>"),
+                           tr("Export multisig info for other participants"));
+  m_cmd_binder.set_handler("import_multisig_info",
+                           boost::bind(&simple_wallet::import_multisig, this, _1),
+                           tr("import_multisig <filename> [<filename>...]"),
+                           tr("Import multisig info from other participants"));
+  m_cmd_binder.set_handler("sign_multisig",
+                           boost::bind(&simple_wallet::sign_multisig, this, _1),
+                           tr("sign_multisig <filename>"),
+                           tr("Sign a multisig transaction from a file"));
+  m_cmd_binder.set_handler("submit_multisig",
+                           boost::bind(&simple_wallet::submit_multisig, this, _1),
+                           tr("submit_multisig <filename>"),
+                           tr("Submit a signed multisig transaction from a file"));
   m_cmd_binder.set_handler("help",
                            boost::bind(&simple_wallet::help, this, _1),
                            tr("help [<command>]"),
                            tr("Show the help section or the documentation about a <command>."));
-  m_cmd_binder.set_handler("help", boost::bind(&simple_wallet::help, this, _1), tr("Show this help"));
 }
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::set_variable(const std::vector<std::string> &args)
@@ -2345,6 +2784,12 @@ bool simple_wallet::save(const std::vector<std::string> &args)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::save_watch_only(const std::vector<std::string> &args/* = std::vector<std::string>()*/)
 {
+  if (m_wallet->multisig())
+  {
+    fail_msg_writer() << tr("wallet is multisig and cannot save a watch-only version");
+    return true;
+  }
+
   const auto pwd_container = tools::password_container::prompt(true, tr("Password for new watch-only wallet"));
 
   if (!pwd_container)
@@ -2638,9 +3083,12 @@ bool simple_wallet::refresh(const std::vector<std::string>& args)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::show_balance_unlocked(bool detailed)
 {
+  std::string extra;
+  if (m_wallet->has_multisig_partial_key_images())
+    extra = tr(" (Some owned outputs have partial key images - import_multisig_info needed)");
   success_msg_writer() << tr("Currently selected account: [") << m_current_subaddress_account << tr("] ") << m_wallet->get_subaddress_label({m_current_subaddress_account, 0});
   success_msg_writer() << tr("Balance: ") << print_money(m_wallet->balance(m_current_subaddress_account)) << ", "
-    << tr("unlocked balance: ") << print_money(m_wallet->unlocked_balance(m_current_subaddress_account));
+    << tr("unlocked balance: ") << print_money(m_wallet->unlocked_balance(m_current_subaddress_account)) << extra;
   std::map<uint32_t, uint64_t> balance_per_subaddress = m_wallet->balance_per_subaddress(m_current_subaddress_account);
   std::map<uint32_t, uint64_t> unlocked_balance_per_subaddress = m_wallet->unlocked_balance_per_subaddress(m_current_subaddress_account);
   if (!detailed || balance_per_subaddress.empty())
@@ -2734,7 +3182,7 @@ bool simple_wallet::show_incoming_transfers(const std::vector<std::string>& args
       }
       std::string verbose_string;
       if (verbose)
-        verbose_string = (boost::format("%68s%68s") % td.get_public_key() % (td.m_key_image_known ? epee::string_tools::pod_to_hex(td.m_key_image) : std::string('?', 64))).str();
+        verbose_string = (boost::format("%68s%68s") % td.get_public_key() % (td.m_key_image_known ? epee::string_tools::pod_to_hex(td.m_key_image) : td.m_key_image_partial ? (epee::string_tools::pod_to_hex(td.m_key_image) + "/p") : std::string(64, '?'))).str();
       message_writer(td.m_spent ? console_color_magenta : console_color_green, false) <<
         boost::format("%21s%8s%12s%8s%16u%68s%16u%s") %
         print_money(td.amount()) %
@@ -2998,101 +3446,6 @@ bool simple_wallet::print_ring_members(const std::vector<tools::wallet2::pending
   return true;
 }
 //----------------------------------------------------------------------------------------------------
-static void handle_transfer_exception(const std::exception_ptr &e)
-{
-  try
-  {
-    std::rethrow_exception(e);
-  }
-  catch (const tools::error::daemon_busy&)
-  {
-    fail_msg_writer() << tr("daemon is busy. Please try again later.");
-  }
-  catch (const tools::error::no_connection_to_daemon&)
-  {
-    fail_msg_writer() << tr("no connection to daemon. Please make sure daemon is running.");
-  }
-  catch (const tools::error::wallet_rpc_error& e)
-  {
-    LOG_ERROR("RPC error: " << e.to_string());
-    fail_msg_writer() << tr("RPC error: ") << e.what();
-  }
-  catch (const tools::error::get_random_outs_error &e)
-  {
-    fail_msg_writer() << tr("failed to get random outputs to mix: ") << e.what();
-  }
-  catch (const tools::error::not_enough_unlocked_money& e)
-  {
-    LOG_PRINT_L0(boost::format("not enough money to transfer, available only %s, sent amount %s") %
-      print_money(e.available()) %
-      print_money(e.tx_amount()));
-    fail_msg_writer() << tr("Not enough money in unlocked balance");
-  }
-  catch (const tools::error::not_enough_money& e)
-  {
-    LOG_PRINT_L0(boost::format("not enough money to transfer, available only %s, sent amount %s") %
-      print_money(e.available()) %
-      print_money(e.tx_amount()));
-    fail_msg_writer() << tr("Not enough money in unlocked balance");
-  }
-  catch (const tools::error::tx_not_possible& e)
-  {
-    LOG_PRINT_L0(boost::format("not enough money to transfer, available only %s, transaction amount %s = %s + %s (fee)") %
-      print_money(e.available()) %
-      print_money(e.tx_amount() + e.fee())  %
-      print_money(e.tx_amount()) %
-      print_money(e.fee()));
-    fail_msg_writer() << tr("Failed to find a way to create transactions. This is usually due to dust which is so small it cannot pay for itself in fees, or trying to send more money than the unlocked balance, or not leaving enough for fees");
-  }
-  catch (const tools::error::not_enough_outs_to_mix& e)
-  {
-    auto writer = fail_msg_writer();
-    writer << tr("not enough outputs for specified ring size") << " = " << (e.mixin_count() + 1) << ":";
-    for (std::pair<uint64_t, uint64_t> outs_for_amount : e.scanty_outs())
-    {
-      writer << "\n" << tr("output amount") << " = " << print_money(outs_for_amount.first) << ", " << tr("found outputs to use") << " = " << outs_for_amount.second;
-    }
-  }
-  catch (const tools::error::tx_not_constructed&)
-  {
-    fail_msg_writer() << tr("transaction was not constructed");
-  }
-  catch (const tools::error::tx_rejected& e)
-  {
-    fail_msg_writer() << (boost::format(tr("transaction %s was rejected by daemon with status: ")) % get_transaction_hash(e.tx())) << e.status();
-    std::string reason = e.reason();
-    if (!reason.empty())
-      fail_msg_writer() << tr("Reason: ") << reason;
-  }
-  catch (const tools::error::tx_sum_overflow& e)
-  {
-    fail_msg_writer() << e.what();
-  }
-  catch (const tools::error::zero_destination&)
-  {
-    fail_msg_writer() << tr("one of destinations is zero");
-  }
-  catch (const tools::error::tx_too_big& e)
-  {
-    fail_msg_writer() << tr("failed to find a suitable way to split transactions");
-  }
-  catch (const tools::error::transfer_error& e)
-  {
-    LOG_ERROR("unknown transfer error: " << e.to_string());
-    fail_msg_writer() << tr("unknown transfer error: ") << e.what();
-  }
-  catch (const tools::error::wallet_internal_error& e)
-  {
-    LOG_ERROR("internal error: " << e.to_string());
-    fail_msg_writer() << tr("internal error: ") << e.what();
-  }
-  catch (const std::exception& e)
-  {
-    LOG_ERROR("unexpected error: " << e.what());
-    fail_msg_writer() << tr("unexpected error: ") << e.what();
-  }
-}
-//----------------------------------------------------------------------------------------------------
 bool simple_wallet::transfer_main(int transfer_type, const std::vector<std::string> &args_)
 {
 //  "transfer [index=<N1>[,<N2>,...]] [<priority>] [<ring_size>] <address> <amount> [<payment_id>]"
@@ -3419,7 +3772,19 @@ bool simple_wallet::transfer_main(int transfer_type, const std::vector<std::stri
     }
 
     // actually commit the transactions
-    if (m_wallet->watch_only())
+    if (m_wallet->multisig())
+    {
+      bool r = m_wallet->save_multisig_tx(ptx_vector, "multisig_monero_tx");
+      if (!r)
+      {
+        fail_msg_writer() << tr("Failed to write transaction(s) to file");
+      }
+      else
+      {
+        success_msg_writer(true) << tr("Unsigned transaction(s) successfully written to file: ") << "multisig_monero_tx";
+      }
+    }
+    else if (m_wallet->watch_only())
     {
       bool r = m_wallet->save_tx(ptx_vector, "unsigned_monero_tx");
       if (!r)
@@ -3515,7 +3880,19 @@ bool simple_wallet::sweep_unmixable(const std::vector<std::string> &args_)
     }
 
     // actually commit the transactions
-    if (m_wallet->watch_only())
+    if (m_wallet->multisig())
+    {
+      bool r = m_wallet->save_multisig_tx(ptx_vector, "multisig_monero_tx");
+      if (!r)
+      {
+        fail_msg_writer() << tr("Failed to write transaction(s) to file");
+      }
+      else
+      {
+        success_msg_writer(true) << tr("Unsigned transaction(s) successfully written to file: ") << "multisig_monero_tx";
+      }
+    }
+    else if (m_wallet->watch_only())
     {
       bool r = m_wallet->save_tx(ptx_vector, "unsigned_monero_tx");
       if (!r)
@@ -3734,7 +4111,19 @@ bool simple_wallet::sweep_main(uint64_t below, const std::vector<std::string> &a
     }
 
     // actually commit the transactions
-    if (m_wallet->watch_only())
+    if (m_wallet->multisig())
+    {
+      bool r = m_wallet->save_multisig_tx(ptx_vector, "multisig_monero_tx");
+      if (!r)
+      {
+        fail_msg_writer() << tr("Failed to write transaction(s) to file");
+      }
+      else
+      {
+        success_msg_writer(true) << tr("Unsigned transaction(s) successfully written to file: ") << "multisig_monero_tx";
+      }
+    }
+    else if (m_wallet->watch_only())
     {
       bool r = m_wallet->save_tx(ptx_vector, "unsigned_monero_tx");
       if (!r)
@@ -3925,7 +4314,19 @@ bool simple_wallet::sweep_single(const std::vector<std::string> &args_)
     }
 
     // actually commit the transactions
-    if (m_wallet->watch_only())
+    if (m_wallet->multisig())
+    {
+      bool r = m_wallet->save_multisig_tx(ptx_vector, "multisig_monero_tx");
+      if (!r)
+      {
+        fail_msg_writer() << tr("Failed to write transaction(s) to file");
+      }
+      else
+      {
+        success_msg_writer(true) << tr("Unsigned transaction(s) successfully written to file: ") << "multisig_monero_tx";
+      }
+    }
+    else if (m_wallet->watch_only())
     {
       bool r = m_wallet->save_tx(ptx_vector, "unsigned_monero_tx");
       if (!r)
@@ -4014,6 +4415,11 @@ bool simple_wallet::sweep_single(const std::vector<std::string> &args_)
     LOG_ERROR("unknown transfer error: " << e.to_string());
     fail_msg_writer() << tr("unknown transfer error: ") << e.what();
   }
+  catch (const tools::error::multisig_export_needed& e)
+  {
+    LOG_ERROR("Multisig error: " << e.to_string());
+    fail_msg_writer() << tr("Multisig error: ") << e.what();
+  }
   catch (const tools::error::wallet_internal_error& e)
   {
     LOG_ERROR("internal error: " << e.to_string());
@@ -4226,6 +4632,11 @@ bool simple_wallet::accept_loaded_tx(const tools::wallet2::signed_tx_set &txs)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::sign_transfer(const std::vector<std::string> &args_)
 {
+  if(m_wallet->multisig())
+  {
+     fail_msg_writer() << tr("This is a multisig wallet, it can only sign with sign_multisig");
+     return true;
+  }
   if(m_wallet->watch_only())
   {
      fail_msg_writer() << tr("This is a watch only wallet");
@@ -5519,6 +5930,11 @@ bool simple_wallet::sign(const std::vector<std::string> &args)
     fail_msg_writer() << tr("wallet is watch-only and cannot sign");
     return true;
   }
+  if (m_wallet->multisig())
+  {
+    fail_msg_writer() << tr("This wallet is multisig and cannot sign");
+    return true;
+  }
   if (m_wallet->ask_password() && !get_and_verify_password()) { return true; }
   std::string filename = args[0];
   std::string data;
diff --git a/src/simplewallet/simplewallet.h b/src/simplewallet/simplewallet.h
index 676870a81..ebe830f69 100644
--- a/src/simplewallet/simplewallet.h
+++ b/src/simplewallet/simplewallet.h
@@ -190,6 +190,11 @@ namespace cryptonote
     bool print_fee_info(const std::vector<std::string> &args);
     bool prepare_multisig(const std::vector<std::string>& args);
     bool make_multisig(const std::vector<std::string>& args);
+    bool export_multisig(const std::vector<std::string>& args);
+    bool import_multisig(const std::vector<std::string>& args);
+    bool accept_loaded_tx(const tools::wallet2::multisig_tx_set &txs);
+    bool sign_multisig(const std::vector<std::string>& args);
+    bool submit_multisig(const std::vector<std::string>& args);
 
     uint64_t get_daemon_blockchain_height(std::string& err);
     bool try_connect_to_daemon(bool silent = false, uint32_t* version = nullptr);