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

18 files changed, 1420 insertions, 273 deletions

diff --git a/src/cryptonote_basic/cryptonote_boost_serialization.h b/src/cryptonote_basic/cryptonote_boost_serialization.h
index 760edf9b9..ed8239176 100644
--- a/src/cryptonote_basic/cryptonote_boost_serialization.h
+++ b/src/cryptonote_basic/cryptonote_boost_serialization.h
@@ -253,6 +253,21 @@ namespace boost
   }
 
   template <class Archive>
+  inline void serialize(Archive &a, rct::multisig_kLRki &x, const boost::serialization::version_type ver)
+  {
+    a & x.k;
+    a & x.L;
+    a & x.R;
+    a & x.ki;
+  }
+
+  template <class Archive>
+  inline void serialize(Archive &a, rct::multisig_out &x, const boost::serialization::version_type ver)
+  {
+    a & x.c;
+  }
+
+  template <class Archive>
   inline typename std::enable_if<Archive::is_loading::value, void>::type serializeOutPk(Archive &a, rct::ctkeyV &outPk_, const boost::serialization::version_type ver)
   {
     rct::keyV outPk;
diff --git a/src/cryptonote_core/cryptonote_tx_utils.cpp b/src/cryptonote_core/cryptonote_tx_utils.cpp
index 662420bef..799c27e06 100644
--- a/src/cryptonote_core/cryptonote_tx_utils.cpp
+++ b/src/cryptonote_core/cryptonote_tx_utils.cpp
@@ -46,6 +46,47 @@ using namespace crypto;
 namespace cryptonote
 {
   //---------------------------------------------------------------
+  void classify_addresses(const std::vector<tx_destination_entry> &destinations, const boost::optional<cryptonote::account_public_address>& change_addr, size_t &num_stdaddresses, size_t &num_subaddresses, account_public_address &single_dest_subaddress)
+  {
+    num_stdaddresses = 0;
+    num_subaddresses = 0;
+    std::unordered_set<cryptonote::account_public_address> unique_dst_addresses;
+    for(const tx_destination_entry& dst_entr: destinations)
+    {
+      if (change_addr && dst_entr.addr == change_addr)
+        continue;
+      if (unique_dst_addresses.count(dst_entr.addr) == 0)
+      {
+        unique_dst_addresses.insert(dst_entr.addr);
+        if (dst_entr.is_subaddress)
+        {
+          ++num_subaddresses;
+          single_dest_subaddress = dst_entr.addr;
+        }
+        else
+        {
+          ++num_stdaddresses;
+        }
+      }
+    }
+    LOG_PRINT_L2("destinations include " << num_stdaddresses << " standard addresses and " << num_subaddresses << " subaddresses");
+  }
+  //---------------------------------------------------------------
+  bool generate_key_image_helper_old(const account_keys& ack, const crypto::public_key& tx_public_key, size_t real_output_index, keypair& in_ephemeral, crypto::key_image& ki)
+  {
+     crypto::key_derivation recv_derivation = AUTO_VAL_INIT(recv_derivation);
+     bool r = crypto::generate_key_derivation(tx_public_key, ack.m_view_secret_key, recv_derivation);
+     CHECK_AND_ASSERT_MES(r, false, "key image helper: failed to generate_key_derivation(" << tx_public_key << ", " << ack.m_view_secret_key << ")");
+
+     r = crypto::derive_public_key(recv_derivation, real_output_index, ack.m_account_address.m_spend_public_key, in_ephemeral.pub);
+     CHECK_AND_ASSERT_MES(r, false, "key image helper: failed to derive_public_key(" << recv_derivation << ", " << real_output_index <<  ", " << ack.m_account_address.m_spend_public_key << ")");
+
+     crypto::derive_secret_key(recv_derivation, real_output_index, ack.m_spend_secret_key, in_ephemeral.sec);
+
+     crypto::generate_key_image(in_ephemeral.pub, in_ephemeral.sec, ki);
+     return true;
+  }
+  //---------------------------------------------------------------
   bool construct_miner_tx(size_t height, size_t median_size, uint64_t already_generated_coins, size_t current_block_size, uint64_t fee, const account_public_address &miner_address, transaction& tx, const blobdata& extra_nonce, size_t max_outs, uint8_t hard_fork_version) {
     tx.vin.clear();
     tx.vout.clear();
@@ -161,19 +202,21 @@ namespace cryptonote
     return destinations[0].addr.m_view_public_key;
   }
   //---------------------------------------------------------------
-  bool construct_tx_and_get_tx_key(const account_keys& sender_account_keys, const std::unordered_map<crypto::public_key, subaddress_index>& subaddresses, std::vector<tx_source_entry>& sources, const std::vector<tx_destination_entry>& destinations, const boost::optional<cryptonote::account_public_address>& change_addr, std::vector<uint8_t> extra, transaction& tx, uint64_t unlock_time, crypto::secret_key &tx_key, std::vector<crypto::secret_key> &additional_tx_keys, bool rct, bool bulletproof)
+  bool construct_tx_with_tx_key(const account_keys& sender_account_keys, const std::unordered_map<crypto::public_key, subaddress_index>& subaddresses, std::vector<tx_source_entry>& sources, const std::vector<tx_destination_entry>& destinations, const boost::optional<cryptonote::account_public_address>& change_addr, std::vector<uint8_t> extra, transaction& tx, uint64_t unlock_time, const crypto::secret_key &tx_key, const std::vector<crypto::secret_key> &additional_tx_keys, bool rct, bool bulletproof, rct::multisig_out *msout)
   {
     std::vector<rct::key> amount_keys;
     tx.set_null();
     amount_keys.clear();
+    if (msout)
+    {
+      msout->c.clear();
+    }
 
     tx.version = rct ? 2 : 1;
     tx.unlock_time = unlock_time;
 
     tx.extra = extra;
-    keypair txkey;
-    txkey.sec = rct::rct2sk(rct::skGen());
-    tx_key = txkey.sec;
+    crypto::public_key txkey_pub;
 
     // if we have a stealth payment id, find it and encrypt it with the tx key now
     std::vector<tx_extra_field> tx_extra_fields;
@@ -193,7 +236,7 @@ namespace cryptonote
             return false;
           }
 
-          if (!encrypt_payment_id(payment_id, view_key_pub, txkey.sec))
+          if (!encrypt_payment_id(payment_id, view_key_pub, tx_key))
           {
             LOG_ERROR("Failed to encrypt payment id");
             return false;
@@ -240,8 +283,17 @@ namespace cryptonote
       in_contexts.push_back(input_generation_context_data());
       keypair& in_ephemeral = in_contexts.back().in_ephemeral;
       crypto::key_image img;
-      const auto& out_key = reinterpret_cast<const crypto::public_key&>(src_entr.outputs[src_entr.real_output].second.dest);
-      if(!generate_key_image_helper(sender_account_keys, subaddresses, out_key, src_entr.real_out_tx_key, src_entr.real_out_additional_tx_keys, src_entr.real_output_in_tx_index, in_ephemeral, img))
+      bool r;
+      if (msout)
+      {
+        r = generate_key_image_helper_old(sender_account_keys, src_entr.real_out_tx_key, src_entr.real_output_in_tx_index, in_ephemeral, img);
+      }
+      else
+      {
+        const auto& out_key = reinterpret_cast<const crypto::public_key&>(src_entr.outputs[src_entr.real_output].second.dest);
+        r = generate_key_image_helper(sender_account_keys, subaddresses, out_key, src_entr.real_out_tx_key, src_entr.real_out_additional_tx_keys, src_entr.real_output_in_tx_index, in_ephemeral, img);
+      }
+      if (!r)
       {
         LOG_ERROR("Key image generation failed!");
         return false;
@@ -261,7 +313,7 @@ namespace cryptonote
       //put key image into tx input
       txin_to_key input_to_key;
       input_to_key.amount = src_entr.amount;
-      input_to_key.k_image = img;
+      input_to_key.k_image = msout ? rct::rct2ki(src_entr.multisig_kLRki.ki) : img;
 
       //fill outputs array and use relative offsets
       for(const tx_source_entry::output_entry& out_entry: src_entr.outputs)
@@ -293,47 +345,29 @@ namespace cryptonote
     // figure out if we need to make additional tx pubkeys
     size_t num_stdaddresses = 0;
     size_t num_subaddresses = 0;
-    std::unordered_set<cryptonote::account_public_address> unique_dst_addresses;
     account_public_address single_dest_subaddress;
-    for(const tx_destination_entry& dst_entr: destinations)
-    {
-      if (change_addr && dst_entr.addr == *change_addr)
-        continue;
-      if (unique_dst_addresses.count(dst_entr.addr) == 0)
-      {
-        unique_dst_addresses.insert(dst_entr.addr);
-        if (dst_entr.is_subaddress)
-        {
-          ++num_subaddresses;
-          single_dest_subaddress = dst_entr.addr;
-        }
-        else
-        {
-          ++num_stdaddresses;
-        }
-      }
-    }
-    LOG_PRINT_L2("destinations include " << num_stdaddresses << " standard addresses and " << num_subaddresses << "subaddresses");
+    classify_addresses(destinations, change_addr, num_stdaddresses, num_subaddresses, single_dest_subaddress);
 
     // if this is a single-destination transfer to a subaddress, we set the tx pubkey to R=s*D
     if (num_stdaddresses == 0 && num_subaddresses == 1)
     {
-      txkey.pub = rct::rct2pk(rct::scalarmultKey(rct::pk2rct(single_dest_subaddress.m_spend_public_key), rct::sk2rct(txkey.sec)));
+      txkey_pub = rct::rct2pk(rct::scalarmultKey(rct::pk2rct(single_dest_subaddress.m_spend_public_key), rct::sk2rct(tx_key)));
     }
     else
     {
-      txkey.pub = rct::rct2pk(rct::scalarmultBase(rct::sk2rct(txkey.sec)));
+      txkey_pub = rct::rct2pk(rct::scalarmultBase(rct::sk2rct(tx_key)));
     }
     remove_field_from_tx_extra(tx.extra, typeid(tx_extra_pub_key));
-    add_tx_pub_key_to_extra(tx, txkey.pub);
+    add_tx_pub_key_to_extra(tx, txkey_pub);
 
     std::vector<crypto::public_key> additional_tx_public_keys;
-    additional_tx_keys.clear();
 
     // we don't need to include additional tx keys if:
     //   - all the destinations are standard addresses
     //   - there's only one destination which is a subaddress
     bool need_additional_txkeys = num_subaddresses > 0 && (num_stdaddresses > 0 || num_subaddresses > 1);
+    if (need_additional_txkeys)
+      CHECK_AND_ASSERT_MES(destinations.size() == additional_tx_keys.size(), false, "Wrong amount of additional tx keys");
 
     uint64_t summary_outs_money = 0;
     //fill outputs
@@ -348,7 +382,7 @@ namespace cryptonote
       keypair additional_txkey;
       if (need_additional_txkeys)
       {
-        additional_txkey.sec = rct::rct2sk(rct::skGen());
+        additional_txkey.sec = additional_tx_keys[output_index];
         if (dst_entr.is_subaddress)
           additional_txkey.pub = rct::rct2pk(rct::scalarmultKey(rct::pk2rct(dst_entr.addr.m_spend_public_key), rct::sk2rct(additional_txkey.sec)));
         else
@@ -359,20 +393,19 @@ namespace cryptonote
       if (change_addr && dst_entr.addr == *change_addr)
       {
         // sending change to yourself; derivation = a*R
-        r = crypto::generate_key_derivation(txkey.pub, sender_account_keys.m_view_secret_key, derivation);
-        CHECK_AND_ASSERT_MES(r, false, "at creation outs: failed to generate_key_derivation(" << txkey.pub << ", " << sender_account_keys.m_view_secret_key << ")");
+        r = crypto::generate_key_derivation(txkey_pub, sender_account_keys.m_view_secret_key, derivation);
+        CHECK_AND_ASSERT_MES(r, false, "at creation outs: failed to generate_key_derivation(" << txkey_pub << ", " << sender_account_keys.m_view_secret_key << ")");
       }
       else
       {
         // sending to the recipient; derivation = r*A (or s*C in the subaddress scheme)
-        r = crypto::generate_key_derivation(dst_entr.addr.m_view_public_key, dst_entr.is_subaddress && need_additional_txkeys ? additional_txkey.sec : txkey.sec, derivation);
-        CHECK_AND_ASSERT_MES(r, false, "at creation outs: failed to generate_key_derivation(" << dst_entr.addr.m_view_public_key << ", " << (dst_entr.is_subaddress && need_additional_txkeys ? additional_txkey.sec : txkey.sec) << ")");
+        r = crypto::generate_key_derivation(dst_entr.addr.m_view_public_key, dst_entr.is_subaddress && need_additional_txkeys ? additional_txkey.sec : tx_key, derivation);
+        CHECK_AND_ASSERT_MES(r, false, "at creation outs: failed to generate_key_derivation(" << dst_entr.addr.m_view_public_key << ", " << (dst_entr.is_subaddress && need_additional_txkeys ? additional_txkey.sec : tx_key) << ")");
       }
 
       if (need_additional_txkeys)
       {
         additional_tx_public_keys.push_back(additional_txkey.pub);
-        additional_tx_keys.push_back(additional_txkey.sec);
       }
 
       if (tx.version > 1)
@@ -393,10 +426,11 @@ namespace cryptonote
       output_index++;
       summary_outs_money += dst_entr.amount;
     }
+    CHECK_AND_ASSERT_MES(additional_tx_public_keys.size() == additional_tx_keys.size(), false, "Internal error creating additional public keys");
 
     remove_field_from_tx_extra(tx.extra, typeid(tx_extra_additional_pub_keys));
 
-    LOG_PRINT_L2("tx pubkey: " << txkey.pub);
+    LOG_PRINT_L2("tx pubkey: " << txkey_pub);
     if (need_additional_txkeys)
     {
       LOG_PRINT_L2("additional tx pubkeys: ");
@@ -492,6 +526,7 @@ namespace cryptonote
       rct::keyV destinations;
       std::vector<uint64_t> inamounts, outamounts;
       std::vector<unsigned int> index;
+      std::vector<rct::multisig_kLRki> kLRki;
       for (size_t i = 0; i < sources.size(); ++i)
       {
         rct::ctkey ctkey;
@@ -504,6 +539,10 @@ namespace cryptonote
         inSk.push_back(ctkey);
         // inPk: (public key, commitment)
         // will be done when filling in mixRing
+        if (msout)
+        {
+          kLRki.push_back(sources[i].multisig_kLRki);
+        }
       }
       for (size_t i = 0; i < tx.vout.size(); ++i)
       {
@@ -553,9 +592,9 @@ namespace cryptonote
       get_transaction_prefix_hash(tx, tx_prefix_hash);
       rct::ctkeyV outSk;
       if (use_simple_rct)
-        tx.rct_signatures = rct::genRctSimple(rct::hash2rct(tx_prefix_hash), inSk, destinations, inamounts, outamounts, amount_in - amount_out, mixRing, amount_keys, index, outSk, bulletproof);
+        tx.rct_signatures = rct::genRctSimple(rct::hash2rct(tx_prefix_hash), inSk, destinations, inamounts, outamounts, amount_in - amount_out, mixRing, amount_keys, msout ? &kLRki : NULL, msout, index, outSk, bulletproof);
       else
-        tx.rct_signatures = rct::genRct(rct::hash2rct(tx_prefix_hash), inSk, destinations, outamounts, mixRing, amount_keys, sources[0].real_output, outSk, bulletproof); // same index assumption
+        tx.rct_signatures = rct::genRct(rct::hash2rct(tx_prefix_hash), inSk, destinations, outamounts, mixRing, amount_keys, msout ? &kLRki[0] : NULL, msout, sources[0].real_output, outSk, bulletproof); // same index assumption
 
       CHECK_AND_ASSERT_MES(tx.vout.size() == outSk.size(), false, "outSk size does not match vout");
 
@@ -567,13 +606,34 @@ namespace cryptonote
     return true;
   }
   //---------------------------------------------------------------
+  bool construct_tx_and_get_tx_key(const account_keys& sender_account_keys, const std::unordered_map<crypto::public_key, subaddress_index>& subaddresses, std::vector<tx_source_entry>& sources, const std::vector<tx_destination_entry>& destinations, const boost::optional<cryptonote::account_public_address>& change_addr, std::vector<uint8_t> extra, transaction& tx, uint64_t unlock_time, crypto::secret_key &tx_key, std::vector<crypto::secret_key> &additional_tx_keys, bool rct, bool bulletproof, rct::multisig_out *msout)
+  {
+    keypair txkey = keypair::generate();
+    tx_key = txkey.sec;
+
+    // figure out if we need to make additional tx pubkeys
+    size_t num_stdaddresses = 0;
+    size_t num_subaddresses = 0;
+    account_public_address single_dest_subaddress;
+    classify_addresses(destinations, change_addr, num_stdaddresses, num_subaddresses, single_dest_subaddress);
+    bool need_additional_txkeys = num_subaddresses > 0 && (num_stdaddresses > 0 || num_subaddresses > 1);
+    if (need_additional_txkeys)
+    {
+      additional_tx_keys.clear();
+      for (const auto &d: destinations)
+        additional_tx_keys.push_back(keypair::generate().sec);
+    }
+
+    return construct_tx_with_tx_key(sender_account_keys, subaddresses, sources, destinations, change_addr, extra, tx, unlock_time, tx_key, additional_tx_keys, rct, bulletproof, msout);
+  }
+  //---------------------------------------------------------------
   bool construct_tx(const account_keys& sender_account_keys, std::vector<tx_source_entry>& sources, const std::vector<tx_destination_entry>& destinations, const boost::optional<cryptonote::account_public_address>& change_addr, std::vector<uint8_t> extra, transaction& tx, uint64_t unlock_time)
   {
      std::unordered_map<crypto::public_key, cryptonote::subaddress_index> subaddresses;
      subaddresses[sender_account_keys.m_account_address.m_spend_public_key] = {0,0};
      crypto::secret_key tx_key;
      std::vector<crypto::secret_key> additional_tx_keys;
-     return construct_tx_and_get_tx_key(sender_account_keys, subaddresses, sources, destinations, change_addr, extra, tx, unlock_time, tx_key, additional_tx_keys);
+     return construct_tx_and_get_tx_key(sender_account_keys, subaddresses, sources, destinations, change_addr, extra, tx, unlock_time, tx_key, additional_tx_keys, false, false, NULL);
   }
   //---------------------------------------------------------------
   bool generate_genesis_block(
diff --git a/src/cryptonote_core/cryptonote_tx_utils.h b/src/cryptonote_core/cryptonote_tx_utils.h
index d72f5d13b..2b6cf26db 100644
--- a/src/cryptonote_core/cryptonote_tx_utils.h
+++ b/src/cryptonote_core/cryptonote_tx_utils.h
@@ -51,6 +51,7 @@ namespace cryptonote
     uint64_t amount;                    //money
     bool rct;                           //true if the output is rct
     rct::key mask;                      //ringct amount mask
+    rct::multisig_kLRki multisig_kLRki; //multisig info
 
     void push_output(uint64_t idx, const crypto::public_key &k, uint64_t amount) { outputs.push_back(std::make_pair(idx, rct::ctkey({rct::pk2rct(k), rct::zeroCommit(amount)}))); }
 
@@ -87,8 +88,9 @@ namespace cryptonote
 
   //---------------------------------------------------------------
   crypto::public_key get_destination_view_key_pub(const std::vector<tx_destination_entry> &destinations, const account_keys &sender_keys);
-  bool construct_tx(const account_keys& sender_account_keys, std::vector<tx_source_entry>& sources, const std::vector<tx_destination_entry>& destinations, const boost::optional<cryptonote::account_public_address>& change_addr, std::vector<uint8_t> extra, transaction& tx, uint64_t unlock_time);
-  bool construct_tx_and_get_tx_key(const account_keys& sender_account_keys, const std::unordered_map<crypto::public_key, subaddress_index>& subaddresses, std::vector<tx_source_entry>& sources, const std::vector<tx_destination_entry>& destinations, const boost::optional<cryptonote::account_public_address>& change_addr, std::vector<uint8_t> extra, transaction& tx, uint64_t unlock_time, crypto::secret_key &tx_key, std::vector<crypto::secret_key> &additional_tx_keys, bool rct = false, bool bulletproof = false);
+  bool construct_tx(const account_keys& sender_account_keys, std::vector<tx_source_entry> &sources, const std::vector<tx_destination_entry>& destinations, const boost::optional<cryptonote::account_public_address>& change_addr, std::vector<uint8_t> extra, transaction& tx, uint64_t unlock_time);
+  bool construct_tx_with_tx_key(const account_keys& sender_account_keys, const std::unordered_map<crypto::public_key, subaddress_index>& subaddresses, std::vector<tx_source_entry>& sources, const std::vector<tx_destination_entry>& destinations, const boost::optional<cryptonote::account_public_address>& change_addr, std::vector<uint8_t> extra, transaction& tx, uint64_t unlock_time, const crypto::secret_key &tx_key, const std::vector<crypto::secret_key> &additional_tx_keys, bool rct = false, bool bulletproof = false, rct::multisig_out *msout = NULL);
+  bool construct_tx_and_get_tx_key(const account_keys& sender_account_keys, const std::unordered_map<crypto::public_key, subaddress_index>& subaddresses, std::vector<tx_source_entry>& sources, const std::vector<tx_destination_entry>& destinations, const boost::optional<cryptonote::account_public_address>& change_addr, std::vector<uint8_t> extra, transaction& tx, uint64_t unlock_time, crypto::secret_key &tx_key, std::vector<crypto::secret_key> &additional_tx_keys, bool rct = false, bool bulletproof = false, rct::multisig_out *msout = NULL);
 
   bool generate_genesis_block(
       block& bl
@@ -115,6 +117,7 @@ namespace boost
       a & x.amount;
       a & x.rct;
       a & x.mask;
+      a & x.multisig_kLRki;
     }
 
     template <class Archive>
diff --git a/src/ringct/rctSigs.cpp b/src/ringct/rctSigs.cpp
index 38b213e8b..24ab08778 100644
--- a/src/ringct/rctSigs.cpp
+++ b/src/ringct/rctSigs.cpp
@@ -122,7 +122,7 @@ namespace rct {
     // Gen creates a signature which proves that for some column in the keymatrix "pk"
     //   the signer knows a secret key for each row in that column
     // Ver verifies that the MG sig was created correctly        
-    mgSig MLSAG_Gen(const key &message, const keyM & pk, const keyV & xx, const unsigned int index, size_t dsRows) {
+    mgSig MLSAG_Gen(const key &message, const keyM & pk, const keyV & xx, const multisig_kLRki *kLRki, key *mscout, const unsigned int index, size_t dsRows) {
         mgSig rv;
         size_t cols = pk.size();
         CHECK_AND_ASSERT_THROW_MES(cols >= 2, "Error! What is c if cols = 1!");
@@ -134,6 +134,8 @@ namespace rct {
         }
         CHECK_AND_ASSERT_THROW_MES(xx.size() == rows, "Bad xx size");
         CHECK_AND_ASSERT_THROW_MES(dsRows <= rows, "Bad dsRows size");
+        CHECK_AND_ASSERT_THROW_MES((kLRki && mscout) || (!kLRki && !mscout), "Only one of kLRki/mscout is present");
+        CHECK_AND_ASSERT_THROW_MES(!kLRki || dsRows == 1, "Multisig requires exactly 1 dsRows");
 
         size_t i = 0, j = 0, ii = 0;
         key c, c_old, L, R, Hi;
@@ -148,13 +150,22 @@ namespace rct {
         toHash[0] = message;
         DP("here1");
         for (i = 0; i < dsRows; i++) {
-            skpkGen(alpha[i], aG[i]); //need to save alphas for later..
-            Hi = hashToPoint(pk[index][i]);
-            aHP[i] = scalarmultKey(Hi, alpha[i]);
             toHash[3 * i + 1] = pk[index][i];
-            toHash[3 * i + 2] = aG[i];
-            toHash[3 * i + 3] = aHP[i];
-            rv.II[i] = scalarmultKey(Hi, xx[i]);
+            if (kLRki) {
+              // multisig
+              alpha[i] = kLRki->k;
+              toHash[3 * i + 2] = kLRki->L;
+              toHash[3 * i + 3] = kLRki->R;
+              rv.II[i] = kLRki->ki;
+            }
+            else {
+              Hi = hashToPoint(pk[index][i]);
+              skpkGen(alpha[i], aG[i]); //need to save alphas for later..
+              aHP[i] = scalarmultKey(Hi, alpha[i]);
+              toHash[3 * i + 2] = aG[i];
+              toHash[3 * i + 3] = aHP[i];
+              rv.II[i] = scalarmultKey(Hi, xx[i]);
+            }
             precomp(Ip[i].k, rv.II[i]);
         }
         size_t ndsRows = 3 * dsRows; //non Double Spendable Rows (see identity chains paper)
@@ -198,7 +209,9 @@ namespace rct {
         }
         for (j = 0; j < rows; j++) {
             sc_mulsub(rv.ss[index][j].bytes, c.bytes, xx[j].bytes, alpha[j].bytes);
-        }        
+        }
+        if (mscout)
+          *mscout = c;
         return rv;
     }
     
@@ -393,7 +406,7 @@ namespace rct {
     //   this shows that sum inputs = sum outputs
     //Ver:    
     //   verifies the above sig is created corretly
-    mgSig proveRctMG(const key &message, const ctkeyM & pubs, const ctkeyV & inSk, const ctkeyV &outSk, const ctkeyV & outPk, unsigned int index, key txnFeeKey) {
+    mgSig proveRctMG(const key &message, const ctkeyM & pubs, const ctkeyV & inSk, const ctkeyV &outSk, const ctkeyV & outPk, const multisig_kLRki *kLRki, key *mscout, unsigned int index, key txnFeeKey) {
         mgSig mg;
         //setup vars
         size_t cols = pubs.size();
@@ -405,6 +418,7 @@ namespace rct {
         }
         CHECK_AND_ASSERT_THROW_MES(inSk.size() == rows, "Bad inSk size");
         CHECK_AND_ASSERT_THROW_MES(outSk.size() == outPk.size(), "Bad outSk/outPk size");
+        CHECK_AND_ASSERT_THROW_MES((kLRki && mscout) || (!kLRki && !mscout), "Only one of kLRki/mscout is present");
 
         keyV sk(rows + 1);
         keyV tmp(rows + 1);
@@ -437,7 +451,7 @@ namespace rct {
         for (size_t j = 0; j < outPk.size(); j++) {
             sc_sub(sk[rows].bytes, sk[rows].bytes, outSk[j].mask.bytes); //subtract output masks in last row..
         }
-        return MLSAG_Gen(message, M, sk, index, rows);
+        return MLSAG_Gen(message, M, sk, kLRki, mscout, index, rows);
     }
 
 
@@ -448,12 +462,13 @@ namespace rct {
     //   inSk is x, a_in corresponding to signing index
     //       a_out, Cout is for the output commitment
     //       index is the signing index..
-    mgSig proveRctMGSimple(const key &message, const ctkeyV & pubs, const ctkey & inSk, const key &a , const key &Cout, unsigned int index) {
+    mgSig proveRctMGSimple(const key &message, const ctkeyV & pubs, const ctkey & inSk, const key &a , const key &Cout, const multisig_kLRki *kLRki, key *mscout, unsigned int index) {
         mgSig mg;
         //setup vars
         size_t rows = 1;
         size_t cols = pubs.size();
         CHECK_AND_ASSERT_THROW_MES(cols >= 1, "Empty pubs");
+        CHECK_AND_ASSERT_THROW_MES((kLRki && mscout) || (!kLRki && !mscout), "Only one of kLRki/mscout is present");
         keyV tmp(rows + 1);
         keyV sk(rows + 1);
         size_t i;
@@ -464,7 +479,7 @@ namespace rct {
             sk[0] = copy(inSk.dest);
             sc_sub(sk[1].bytes, inSk.mask.bytes, a.bytes);  
         }
-        return MLSAG_Gen(message, M, sk, index, rows);
+        return MLSAG_Gen(message, M, sk, kLRki, mscout, index, rows);
     }
 
 
@@ -598,13 +613,14 @@ namespace rct {
     //   must know the destination private key to find the correct amount, else will return a random number
     //   Note: For txn fees, the last index in the amounts vector should contain that
     //   Thus the amounts vector will be "one" longer than the destinations vectort
-    rctSig genRct(const key &message, const ctkeyV & inSk, const keyV & destinations, const vector<xmr_amount> & amounts, const ctkeyM &mixRing, const keyV &amount_keys, unsigned int index, ctkeyV &outSk, bool bulletproof) {
+    rctSig genRct(const key &message, const ctkeyV & inSk, const keyV & destinations, const vector<xmr_amount> & amounts, const ctkeyM &mixRing, const keyV &amount_keys, const multisig_kLRki *kLRki, multisig_out *msout, unsigned int index, ctkeyV &outSk, bool bulletproof) {
         CHECK_AND_ASSERT_THROW_MES(amounts.size() == destinations.size() || amounts.size() == destinations.size() + 1, "Different number of amounts/destinations");
         CHECK_AND_ASSERT_THROW_MES(amount_keys.size() == destinations.size(), "Different number of amount_keys/destinations");
         CHECK_AND_ASSERT_THROW_MES(index < mixRing.size(), "Bad index into mixRing");
         for (size_t n = 0; n < mixRing.size(); ++n) {
           CHECK_AND_ASSERT_THROW_MES(mixRing[n].size() == inSk.size(), "Bad mixRing size");
         }
+        CHECK_AND_ASSERT_THROW_MES((kLRki && msout) || (!kLRki && !msout), "Only one of kLRki/msout is present");
 
         rctSig rv;
         rv.type = bulletproof ? RCTTypeFullBulletproof : RCTTypeFull;
@@ -653,21 +669,23 @@ namespace rct {
         key txnFeeKey = scalarmultH(d2h(rv.txnFee));
 
         rv.mixRing = mixRing;
-        rv.p.MGs.push_back(proveRctMG(get_pre_mlsag_hash(rv), rv.mixRing, inSk, outSk, rv.outPk, index, txnFeeKey));
+        if (msout)
+          msout->c.resize(1);
+        rv.p.MGs.push_back(proveRctMG(get_pre_mlsag_hash(rv), rv.mixRing, inSk, outSk, rv.outPk, kLRki, msout ? &msout->c[0] : NULL, index, txnFeeKey));
         return rv;
     }
 
-    rctSig genRct(const key &message, const ctkeyV & inSk, const ctkeyV  & inPk, const keyV & destinations, const vector<xmr_amount> & amounts, const keyV &amount_keys, const int mixin) {
+    rctSig genRct(const key &message, const ctkeyV & inSk, const ctkeyV  & inPk, const keyV & destinations, const vector<xmr_amount> & amounts, const keyV &amount_keys, const multisig_kLRki *kLRki, multisig_out *msout, const int mixin) {
         unsigned int index;
         ctkeyM mixRing;
         ctkeyV outSk;
         tie(mixRing, index) = populateFromBlockchain(inPk, mixin);
-        return genRct(message, inSk, destinations, amounts, mixRing, amount_keys, index, outSk, false);
+        return genRct(message, inSk, destinations, amounts, mixRing, amount_keys, kLRki, msout, index, outSk, false);
     }
     
     //RCT simple    
     //for post-rct only
-    rctSig genRctSimple(const key &message, const ctkeyV & inSk, const keyV & destinations, const vector<xmr_amount> &inamounts, const vector<xmr_amount> &outamounts, xmr_amount txnFee, const ctkeyM & mixRing, const keyV &amount_keys, const std::vector<unsigned int> & index, ctkeyV &outSk, bool bulletproof) {
+    rctSig genRctSimple(const key &message, const ctkeyV & inSk, const keyV & destinations, const vector<xmr_amount> &inamounts, const vector<xmr_amount> &outamounts, xmr_amount txnFee, const ctkeyM & mixRing, const keyV &amount_keys, const std::vector<multisig_kLRki> *kLRki, multisig_out *msout, const std::vector<unsigned int> & index, ctkeyV &outSk, bool bulletproof) {
         CHECK_AND_ASSERT_THROW_MES(inamounts.size() > 0, "Empty inamounts");
         CHECK_AND_ASSERT_THROW_MES(inamounts.size() == inSk.size(), "Different number of inamounts/inSk");
         CHECK_AND_ASSERT_THROW_MES(outamounts.size() == destinations.size(), "Different number of amounts/destinations");
@@ -677,6 +695,10 @@ namespace rct {
         for (size_t n = 0; n < mixRing.size(); ++n) {
           CHECK_AND_ASSERT_THROW_MES(index[n] < mixRing[n].size(), "Bad index into mixRing");
         }
+        CHECK_AND_ASSERT_THROW_MES((kLRki && msout) || (!kLRki && !msout), "Only one of kLRki/msout is present");
+        if (kLRki && msout) {
+          CHECK_AND_ASSERT_THROW_MES(kLRki->size() == inamounts.size(), "Mismatched kLRki/inamounts sizes");
+        }
 
         rctSig rv;
         rv.type = bulletproof ? RCTTypeSimpleBulletproof : RCTTypeSimple;
@@ -736,13 +758,15 @@ namespace rct {
         DP(rv.pseudoOuts[i]);
 
         key full_message = get_pre_mlsag_hash(rv);
+        if (msout)
+          msout->c.resize(inamounts.size());
         for (i = 0 ; i < inamounts.size(); i++) {
-            rv.p.MGs[i] = proveRctMGSimple(full_message, rv.mixRing[i], inSk[i], a[i], rv.pseudoOuts[i], index[i]);
+            rv.p.MGs[i] = proveRctMGSimple(full_message, rv.mixRing[i], inSk[i], a[i], rv.pseudoOuts[i], kLRki ? &(*kLRki)[i]: NULL, msout ? &msout->c[i] : NULL, index[i]);
         }
         return rv;
     }
 
-    rctSig genRctSimple(const key &message, const ctkeyV & inSk, const ctkeyV & inPk, const keyV & destinations, const vector<xmr_amount> &inamounts, const vector<xmr_amount> &outamounts, const keyV &amount_keys, xmr_amount txnFee, unsigned int mixin) {
+    rctSig genRctSimple(const key &message, const ctkeyV & inSk, const ctkeyV & inPk, const keyV & destinations, const vector<xmr_amount> &inamounts, const vector<xmr_amount> &outamounts, const keyV &amount_keys, const std::vector<multisig_kLRki> *kLRki, multisig_out *msout, xmr_amount txnFee, unsigned int mixin) {
         std::vector<unsigned int> index;
         index.resize(inPk.size());
         ctkeyM mixRing;
@@ -752,7 +776,7 @@ namespace rct {
           mixRing[i].resize(mixin+1);
           index[i] = populateFromBlockchainSimple(mixRing[i], inPk[i], mixin);
         }
-        return genRctSimple(message, inSk, destinations, inamounts, outamounts, txnFee, mixRing, amount_keys, index, outSk, false);
+        return genRctSimple(message, inSk, destinations, inamounts, outamounts, txnFee, mixRing, amount_keys, kLRki, msout, index, outSk, false);
     }
 
     //RingCT protocol
@@ -822,8 +846,14 @@ namespace rct {
 
           return true;
         }
-        catch(...)
+        catch (const std::exception &e)
         {
+          LOG_PRINT_L1("Error in verRct: " << e.what());
+          return false;
+        }
+        catch (...)
+        {
+          LOG_PRINT_L1("Error in verRct, but not an actual exception");
           return false;
         }
     }
@@ -920,7 +950,16 @@ namespace rct {
         return true;
       }
       // we can get deep throws from ge_frombytes_vartime if input isn't valid
-      catch (...) { return false; }
+      catch (const std::exception &e)
+      {
+        LOG_PRINT_L1("Error in verRct: " << e.what());
+        return false;
+      }
+      catch (...)
+      {
+        LOG_PRINT_L1("Error in verRct, but not an actual exception");
+        return false;
+      }
     }
 
     //RingCT protocol
@@ -988,4 +1027,27 @@ namespace rct {
       key mask;
       return decodeRctSimple(rv, sk, i, mask);
     }
+
+    bool signMultisig(rctSig &rv, const std::vector<unsigned int> &indices, const keyV &k, const multisig_out &msout, const key &secret_key) {
+        CHECK_AND_ASSERT_MES(rv.type == RCTTypeFull || rv.type == RCTTypeSimple || rv.type == RCTTypeFullBulletproof || rv.type == RCTTypeSimpleBulletproof,
+            false, "unsupported rct type");
+        CHECK_AND_ASSERT_MES(indices.size() == k.size(), false, "Mismatched k/indices sizes");
+        CHECK_AND_ASSERT_MES(k.size() == rv.p.MGs.size(), false, "Mismatched k/MGs size");
+        CHECK_AND_ASSERT_MES(k.size() == msout.c.size(), false, "Mismatched k/msout.c size");
+        if (rv.type == RCTTypeFull || rv.type == RCTTypeFullBulletproof)
+        {
+          CHECK_AND_ASSERT_MES(rv.p.MGs.size() == 1, false, "MGs not a single element");
+        }
+        for (size_t n = 0; n < indices.size(); ++n) {
+            CHECK_AND_ASSERT_MES(indices[n] < rv.p.MGs[n].ss.size(), false, "Index out of range");
+            CHECK_AND_ASSERT_MES(!rv.p.MGs[n].ss[indices[n]].empty(), false, "empty ss line");
+        }
+
+        for (size_t n = 0; n < indices.size(); ++n) {
+            rct::key diff;
+            sc_mulsub(diff.bytes, msout.c[n].bytes, secret_key.bytes, k[n].bytes);
+            sc_add(rv.p.MGs[n].ss[indices[n]][0].bytes, rv.p.MGs[n].ss[indices[n]][0].bytes, diff.bytes);
+        }
+        return true;
+    }
 }
diff --git a/src/ringct/rctSigs.h b/src/ringct/rctSigs.h
index 46c9cb2df..e83083a98 100644
--- a/src/ringct/rctSigs.h
+++ b/src/ringct/rctSigs.h
@@ -73,7 +73,7 @@ namespace rct {
     //   the signer knows a secret key for each row in that column
     // Ver verifies that the MG sig was created correctly
     keyV keyImageV(const keyV &xx);
-    mgSig MLSAG_Gen(const key &message, const keyM & pk, const keyV & xx, const unsigned int index, size_t dsRows);
+    mgSig MLSAG_Gen(const key &message, const keyM & pk, const keyV & xx, const multisig_kLRki *kLRki, key *mscout, const unsigned int index, size_t dsRows);
     bool MLSAG_Ver(const key &message, const keyM &pk, const mgSig &sig, size_t dsRows);
     //mgSig MLSAG_Gen_Old(const keyM & pk, const keyV & xx, const int index);
 
@@ -95,8 +95,8 @@ namespace rct {
     //   this shows that sum inputs = sum outputs
     //Ver:
     //   verifies the above sig is created corretly
-    mgSig proveRctMG(const ctkeyM & pubs, const ctkeyV & inSk, const keyV &outMasks, const ctkeyV & outPk, unsigned int index, key txnFee, const key &message);
-    mgSig proveRctMGSimple(const key & message, const ctkeyV & pubs, const ctkey & inSk, const key &a , const key &Cout, unsigned int index);
+    mgSig proveRctMG(const ctkeyM & pubs, const ctkeyV & inSk, const keyV &outMasks, const ctkeyV & outPk, const multisig_kLRki *kLRki, key *mscout, unsigned int index, key txnFee, const key &message);
+    mgSig proveRctMGSimple(const key & message, const ctkeyV & pubs, const ctkey & inSk, const key &a , const key &Cout, const multisig_kLRki *kLRki, key *mscout, unsigned int index);
     bool verRctMG(const mgSig &mg, const ctkeyM & pubs, const ctkeyV & outPk, key txnFee, const key &message);
     bool verRctMGSimple(const key &message, const mgSig &mg, const ctkeyV & pubs, const key & C);
 
@@ -118,10 +118,10 @@ namespace rct {
     //decodeRct: (c.f. http://eprint.iacr.org/2015/1098 section 5.1.1)
     //   uses the attached ecdh info to find the amounts represented by each output commitment
     //   must know the destination private key to find the correct amount, else will return a random number
-    rctSig genRct(const key &message, const ctkeyV & inSk, const keyV & destinations, const std::vector<xmr_amount> & amounts, const ctkeyM &mixRing, const keyV &amount_keys, unsigned int index, ctkeyV &outSk, bool bulletproof);
-    rctSig genRct(const key &message, const ctkeyV & inSk, const ctkeyV  & inPk, const keyV & destinations, const std::vector<xmr_amount> & amounts, const keyV &amount_keys, const int mixin);
-    rctSig genRctSimple(const key & message, const ctkeyV & inSk, const ctkeyV & inPk, const keyV & destinations, const std::vector<xmr_amount> & inamounts, const std::vector<xmr_amount> & outamounts, const keyV &amount_keys, xmr_amount txnFee, unsigned int mixin);
-    rctSig genRctSimple(const key & message, const ctkeyV & inSk, const keyV & destinations, const std::vector<xmr_amount> & inamounts, const std::vector<xmr_amount> & outamounts, xmr_amount txnFee, const ctkeyM & mixRing, const keyV &amount_keys, const std::vector<unsigned int> & index, ctkeyV &outSk, bool bulletproof);
+    rctSig genRct(const key &message, const ctkeyV & inSk, const keyV & destinations, const std::vector<xmr_amount> & amounts, const ctkeyM &mixRing, const keyV &amount_keys, const multisig_kLRki *kLRki, multisig_out *msout, unsigned int index, ctkeyV &outSk, bool bulletproof);
+    rctSig genRct(const key &message, const ctkeyV & inSk, const ctkeyV  & inPk, const keyV & destinations, const std::vector<xmr_amount> & amounts, const keyV &amount_keys, const multisig_kLRki *kLRki, multisig_out *msout, const int mixin);
+    rctSig genRctSimple(const key & message, const ctkeyV & inSk, const ctkeyV & inPk, const keyV & destinations, const std::vector<xmr_amount> & inamounts, const std::vector<xmr_amount> & outamounts, const keyV &amount_keys, const std::vector<multisig_kLRki> *kLRki, multisig_out *msout, xmr_amount txnFee, unsigned int mixin);
+    rctSig genRctSimple(const key & message, const ctkeyV & inSk, const keyV & destinations, const std::vector<xmr_amount> & inamounts, const std::vector<xmr_amount> & outamounts, xmr_amount txnFee, const ctkeyM & mixRing, const keyV &amount_keys, const std::vector<multisig_kLRki> *kLRki, multisig_out *msout, const std::vector<unsigned int> & index, ctkeyV &outSk, bool bulletproof);
     bool verRct(const rctSig & rv, bool semantics);
     static inline bool verRct(const rctSig & rv) { return verRct(rv, true) && verRct(rv, false); }
     bool verRctSimple(const rctSig & rv, bool semantics);
@@ -130,6 +130,8 @@ namespace rct {
     xmr_amount decodeRct(const rctSig & rv, const key & sk, unsigned int i);
     xmr_amount decodeRctSimple(const rctSig & rv, const key & sk, unsigned int i, key & mask);
     xmr_amount decodeRctSimple(const rctSig & rv, const key & sk, unsigned int i);
+
+    bool signMultisig(rctSig &rv, const std::vector<unsigned int> &indices, const keyV &k, const multisig_out &msout, const key &secret_key);
 }
 #endif  /* RCTSIGS_H */
 
diff --git a/src/ringct/rctTypes.h b/src/ringct/rctTypes.h
index 50dfdb432..1f44c1a9e 100644
--- a/src/ringct/rctTypes.h
+++ b/src/ringct/rctTypes.h
@@ -99,6 +99,22 @@ namespace rct {
     typedef std::vector<ctkey> ctkeyV;
     typedef std::vector<ctkeyV> ctkeyM;
 
+    //used for multisig data
+    struct multisig_kLRki {
+        key k;
+        key L;
+        key R;
+        key ki;
+    };
+
+    struct multisig_out {
+        std::vector<key> c; // for all inputs
+
+        BEGIN_SERIALIZE_OBJECT()
+          FIELD(c)
+        END_SERIALIZE()
+    };
+
     //data for passing the amount to the receiver secretly
     // If the pedersen commitment to an amount is C = aG + bH,
     // "mask" contains a 32 byte key a
@@ -504,6 +520,7 @@ inline std::ostream &operator <<(std::ostream &o, const rct::key &v) {
 BLOB_SERIALIZER(rct::key);
 BLOB_SERIALIZER(rct::key64);
 BLOB_SERIALIZER(rct::ctkey);
+BLOB_SERIALIZER(rct::multisig_kLRki);
 BLOB_SERIALIZER(rct::boroSig);
 
 VARIANT_TAG(debug_archive, rct::key, "rct::key");
@@ -519,6 +536,8 @@ VARIANT_TAG(debug_archive, rct::rangeSig, "rct::rangeSig");
 VARIANT_TAG(debug_archive, rct::boroSig, "rct::boroSig");
 VARIANT_TAG(debug_archive, rct::rctSig, "rct::rctSig");
 VARIANT_TAG(debug_archive, rct::Bulletproof, "rct::bulletproof");
+VARIANT_TAG(debug_archive, rct::multisig_kLRki, "rct::multisig_kLRki");
+VARIANT_TAG(debug_archive, rct::multisig_out, "rct::multisig_out");
 
 VARIANT_TAG(binary_archive, rct::key, 0x90);
 VARIANT_TAG(binary_archive, rct::key64, 0x91);
@@ -533,6 +552,8 @@ VARIANT_TAG(binary_archive, rct::rangeSig, 0x99);
 VARIANT_TAG(binary_archive, rct::boroSig, 0x9a);
 VARIANT_TAG(binary_archive, rct::rctSig, 0x9b);
 VARIANT_TAG(binary_archive, rct::Bulletproof, 0x9c);
+VARIANT_TAG(binary_archive, rct::multisig_kLRki, 0x9d);
+VARIANT_TAG(binary_archive, rct::multisig_out, 0x9e);
 
 VARIANT_TAG(json_archive, rct::key, "rct_key");
 VARIANT_TAG(json_archive, rct::key64, "rct_key64");
@@ -547,5 +568,7 @@ VARIANT_TAG(json_archive, rct::rangeSig, "rct_rangeSig");
 VARIANT_TAG(json_archive, rct::boroSig, "rct_boroSig");
 VARIANT_TAG(json_archive, rct::rctSig, "rct_rctSig");
 VARIANT_TAG(json_archive, rct::Bulletproof, "rct_bulletproof");
+VARIANT_TAG(json_archive, rct::multisig_kLRki, "rct_multisig_kLR");
+VARIANT_TAG(json_archive, rct::multisig_out, "rct_multisig_out");
 
 #endif  /* RCTTYPES_H */
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);
diff --git a/src/wallet/api/wallet2_api.h b/src/wallet/api/wallet2_api.h
index b1f8369a3..8593bd1f9 100644
--- a/src/wallet/api/wallet2_api.h
+++ b/src/wallet/api/wallet2_api.h
@@ -812,10 +812,10 @@ struct WalletManager
      * @brief verifyWalletPassword - check if the given filename is the wallet
      * @param keys_file_name - location of keys file
      * @param password - password to verify
-     * @param watch_only - verify only view keys?
+     * @param no_spend_key - verify only view keys?
      * @return - true if password is correct
      */
-    virtual bool verifyWalletPassword(const std::string &keys_file_name, const std::string &password, bool watch_only) const = 0;
+    virtual bool verifyWalletPassword(const std::string &keys_file_name, const std::string &password, bool no_spend_key) const = 0;
 
     /*!
      * \brief findWallets - searches for the wallet files by given path name recursively
diff --git a/src/wallet/api/wallet_manager.cpp b/src/wallet/api/wallet_manager.cpp
index ee69ec028..a6e5e551e 100644
--- a/src/wallet/api/wallet_manager.cpp
+++ b/src/wallet/api/wallet_manager.cpp
@@ -127,9 +127,9 @@ bool WalletManagerImpl::walletExists(const std::string &path)
     return false;
 }
 
-bool WalletManagerImpl::verifyWalletPassword(const std::string &keys_file_name, const std::string &password, bool watch_only) const
+bool WalletManagerImpl::verifyWalletPassword(const std::string &keys_file_name, const std::string &password, bool no_spend_key) const
 {
-	    return tools::wallet2::verify_password(keys_file_name, password, watch_only);
+	    return tools::wallet2::verify_password(keys_file_name, password, no_spend_key);
 }
 
 std::vector<std::string> WalletManagerImpl::findWallets(const std::string &path)
diff --git a/src/wallet/api/wallet_manager.h b/src/wallet/api/wallet_manager.h
index 978a2d411..ef5b8f91b 100644
--- a/src/wallet/api/wallet_manager.h
+++ b/src/wallet/api/wallet_manager.h
@@ -50,7 +50,7 @@ public:
                                                     const std::string &spendKeyString = "");
     virtual bool closeWallet(Wallet *wallet, bool store = true);
     bool walletExists(const std::string &path);
-    bool verifyWalletPassword(const std::string &keys_file_name, const std::string &password, bool watch_only) const;
+    bool verifyWalletPassword(const std::string &keys_file_name, const std::string &password, bool no_spend_key) const;
     std::vector<std::string> findWallets(const std::string &path);
     std::string errorString() const;
     void setDaemonAddress(const std::string &address);
diff --git a/src/wallet/wallet2.cpp b/src/wallet/wallet2.cpp
index 4ad527423..af48e711e 100644
--- a/src/wallet/wallet2.cpp
+++ b/src/wallet/wallet2.cpp
@@ -56,6 +56,7 @@ using namespace epee;
 #include "mnemonics/electrum-words.h"
 #include "common/i18n.h"
 #include "common/util.h"
+#include "common/apply_permutation.h"
 #include "rapidjson/document.h"
 #include "rapidjson/writer.h"
 #include "rapidjson/stringbuffer.h"
@@ -87,6 +88,7 @@ using namespace cryptonote;
 
 #define UNSIGNED_TX_PREFIX "Monero unsigned tx set\004"
 #define SIGNED_TX_PREFIX "Monero signed tx set\004"
+#define MULTISIG_UNSIGNED_TX_PREFIX "Monero multisig unsigned tx set\001"
 
 #define RECENT_OUTPUT_RATIO (0.5) // 50% of outputs are from the recent zone
 #define RECENT_OUTPUT_ZONE ((time_t)(1.8 * 86400)) // last 1.8 day makes up the recent zone (taken from monerolink.pdf, Miller et al)
@@ -524,6 +526,69 @@ uint8_t get_bulletproof_fork(bool testnet)
     return 255; // TODO
 }
 
+bool generate_key_image_helper_old(const account_keys& ack, const crypto::public_key& tx_public_key, size_t real_output_index, keypair& in_ephemeral, crypto::key_image& ki)
+{
+  crypto::key_derivation recv_derivation = AUTO_VAL_INIT(recv_derivation);
+  bool r = crypto::generate_key_derivation(tx_public_key, ack.m_view_secret_key, recv_derivation);
+  CHECK_AND_ASSERT_MES(r, false, "key image helper: failed to generate_key_derivation(" << tx_public_key << ", " << ack.m_view_secret_key << ")");
+
+  r = crypto::derive_public_key(recv_derivation, real_output_index, ack.m_account_address.m_spend_public_key, in_ephemeral.pub);
+  CHECK_AND_ASSERT_MES(r, false, "key image helper: failed to derive_public_key(" << recv_derivation << ", " << real_output_index <<  ", " << ack.m_account_address.m_spend_public_key << ")");
+
+  crypto::derive_secret_key(recv_derivation, real_output_index, ack.m_spend_secret_key, in_ephemeral.sec);
+
+  crypto::generate_key_image(in_ephemeral.pub, in_ephemeral.sec, ki);
+  return true;
+}
+
+bool wallet_generate_key_image_helper_old(const cryptonote::account_keys& ack, const crypto::public_key& tx_public_key, size_t real_output_index, cryptonote::keypair& in_ephemeral, crypto::key_image& ki, bool multisig_export = false)
+{
+  if (!generate_key_image_helper_old(ack, tx_public_key, real_output_index, in_ephemeral, ki))
+    return false;
+  if (multisig_export)
+  {
+    // we got the ephemeral keypair, but the key image isn't right as it's done as per our private spend key, which is multisig
+    crypto::generate_key_image(in_ephemeral.pub, ack.m_spend_secret_key, ki);
+  }
+  return true;
+}
+
+crypto::hash8 get_short_payment_id(const tools::wallet2::pending_tx &ptx)
+{
+  crypto::hash8 payment_id8 = null_hash8;
+  std::vector<tx_extra_field> tx_extra_fields;
+  if(!parse_tx_extra(ptx.tx.extra, tx_extra_fields))
+    return payment_id8;
+  cryptonote::tx_extra_nonce extra_nonce;
+  if (find_tx_extra_field_by_type(tx_extra_fields, extra_nonce))
+  {
+    if(get_encrypted_payment_id_from_tx_extra_nonce(extra_nonce.nonce, payment_id8))
+    {
+      decrypt_payment_id(payment_id8, ptx.dests[0].addr.m_view_public_key, ptx.tx_key); 
+    }
+  }
+  return payment_id8;
+}
+
+tools::wallet2::tx_construction_data get_construction_data_with_decrypted_short_payment_id(const tools::wallet2::pending_tx &ptx)
+{
+  tools::wallet2::tx_construction_data construction_data = ptx.construction_data;
+  crypto::hash8 payment_id = get_short_payment_id(ptx);
+  if (payment_id != null_hash8)
+  {
+    // Remove encrypted
+    remove_field_from_tx_extra(construction_data.extra, typeid(cryptonote::tx_extra_nonce));
+    // Add decrypted
+    std::string extra_nonce;
+    set_encrypted_payment_id_to_tx_extra_nonce(extra_nonce, payment_id);
+    THROW_WALLET_EXCEPTION_IF(!add_extra_nonce_to_tx_extra(construction_data.extra, extra_nonce),
+        tools::error::wallet_internal_error, "Failed to add decrypted payment id to tx extra");
+    LOG_PRINT_L1("Decrypted payment ID: " << payment_id);
+  }
+  return construction_data;
+}
+
+  //-----------------------------------------------------------------
 } //namespace
 
 namespace tools
@@ -846,7 +911,15 @@ static uint64_t decodeRct(const rct::rctSig & rv, const crypto::key_derivation &
 //----------------------------------------------------------------------------------------------------
 void wallet2::scan_output(const cryptonote::account_keys &keys, const cryptonote::transaction &tx, const crypto::public_key &tx_pub_key, size_t i, tx_scan_info_t &tx_scan_info, int &num_vouts_received, std::unordered_map<cryptonote::subaddress_index, uint64_t> &tx_money_got_in_outs, std::vector<size_t> &outs)
 {
-  bool r = cryptonote::generate_key_image_helper_precomp(keys, boost::get<cryptonote::txout_to_key>(tx.vout[i].target).key, tx_scan_info.received->derivation, i, tx_scan_info.received->index, tx_scan_info.in_ephemeral, tx_scan_info.ki);
+  bool r;
+  if (m_multisig)
+  {
+    r = wallet_generate_key_image_helper_old(keys, tx_pub_key, i, tx_scan_info.in_ephemeral, tx_scan_info.ki);
+  }
+  else
+  {
+    r = cryptonote::generate_key_image_helper_precomp(keys, boost::get<cryptonote::txout_to_key>(tx.vout[i].target).key, tx_scan_info.received->derivation, i, tx_scan_info.received->index, tx_scan_info.in_ephemeral, tx_scan_info.ki);
+  }
   THROW_WALLET_EXCEPTION_IF(!r, error::wallet_internal_error, "Failed to generate key image");
   THROW_WALLET_EXCEPTION_IF(tx_scan_info.in_ephemeral.pub != boost::get<cryptonote::txout_to_key>(tx.vout[i].target).key,
       error::wallet_internal_error, "key_image generated ephemeral public key not matched with output_key");
@@ -1018,7 +1091,8 @@ void wallet2::process_new_transaction(const crypto::hash &txid, const cryptonote
 	    td.m_tx = (const cryptonote::transaction_prefix&)tx;
 	    td.m_txid = txid;
             td.m_key_image = tx_scan_info[o].ki;
-            td.m_key_image_known = !m_watch_only;
+            td.m_key_image_known = !m_watch_only && !m_multisig;
+            td.m_key_image_partial = m_multisig;
             td.m_amount = tx.vout[o].amount;
             td.m_pk_index = pk_index - 1;
             td.m_subaddr_index = tx_scan_info[o].received->index;
@@ -1040,8 +1114,18 @@ void wallet2::process_new_transaction(const crypto::hash &txid, const cryptonote
               td.m_rct = false;
             }
 	    set_unspent(m_transfers.size()-1);
-	    m_key_images[td.m_key_image] = m_transfers.size()-1;
+            if (!m_multisig)
+	      m_key_images[td.m_key_image] = m_transfers.size()-1;
 	    m_pub_keys[tx_scan_info[o].in_ephemeral.pub] = m_transfers.size()-1;
+            if (m_multisig)
+            {
+              THROW_WALLET_EXCEPTION_IF(!m_multisig_rescan_k && m_multisig_rescan_info,
+                  error::wallet_internal_error, "NULL m_multisig_rescan_k");
+              if (m_multisig_rescan_info && m_multisig_rescan_info->front().size() >= m_transfers.size())
+                update_multisig_rescan_info(*m_multisig_rescan_k, *m_multisig_rescan_info, m_transfers.size() - 1);
+              else
+                td.m_multisig_k = rct::skGen();
+            }
 	    LOG_PRINT_L0("Received money: " << print_money(td.amount()) << ", with tx: " << txid);
 	    if (0 != m_callback)
 	      m_callback->on_money_received(height, txid, tx, td.m_amount, td.m_subaddr_index);
@@ -1090,6 +1174,15 @@ void wallet2::process_new_transaction(const crypto::hash &txid, const cryptonote
               td.m_mask = rct::identity();
               td.m_rct = false;
             }
+            if (m_multisig)
+            {
+              THROW_WALLET_EXCEPTION_IF(!m_multisig_rescan_k && m_multisig_rescan_info,
+                  error::wallet_internal_error, "NULL m_multisig_rescan_k");
+              if (m_multisig_rescan_info && m_multisig_rescan_info->front().size() >= m_transfers.size())
+                update_multisig_rescan_info(*m_multisig_rescan_k, *m_multisig_rescan_info, m_transfers.size() - 1);
+              else
+                td.m_multisig_k = rct::skGen();
+            }
             THROW_WALLET_EXCEPTION_IF(td.get_public_key() != tx_scan_info[o].in_ephemeral.pub, error::wallet_internal_error, "Inconsistent public keys");
 	    THROW_WALLET_EXCEPTION_IF(td.m_spent, error::wallet_internal_error, "Inconsistent spent status");
 
@@ -2083,8 +2176,10 @@ void wallet2::detach_blockchain(uint64_t height)
 
   for(size_t i = i_start; i!= m_transfers.size();i++)
   {
+    if (!m_transfers[i].m_key_image_known || m_transfers[i].m_key_image_partial)
+      continue;
     auto it_ki = m_key_images.find(m_transfers[i].m_key_image);
-    THROW_WALLET_EXCEPTION_IF(it_ki == m_key_images.end(), error::wallet_internal_error, "key image not found");
+    THROW_WALLET_EXCEPTION_IF(it_ki == m_key_images.end(), error::wallet_internal_error, "key image not found: index " + std::to_string(i) + ", ki " + epee::string_tools::pod_to_hex(m_transfers[i].m_key_image) + ", " + std::to_string(m_key_images.size()) + " key images known");
     m_key_images.erase(it_ki);
   }
 
@@ -2437,7 +2532,7 @@ bool wallet2::verify_password(const epee::wipeable_string& password) const
  * \brief verify password for specified wallet keys file.
  * \param keys_file_name  Keys file to verify password for
  * \param password        Password to verify
- * \param watch_only      If set = only verify view keys, otherwise also spend keys
+ * \param no_spend_key    If set = only verify view keys, otherwise also spend keys
  * \return                true if password is correct
  *
  * for verification only
@@ -2653,8 +2748,8 @@ void wallet2::make_multisig(const epee::wipeable_string &password,
 {
   CHECK_AND_ASSERT_THROW_MES(!view_keys.empty(), "empty view keys");
   CHECK_AND_ASSERT_THROW_MES(view_keys.size() == spend_keys.size(), "Mismatched view/spend key sizes");
-  CHECK_AND_ASSERT_THROW_MES(threshold > 0 && threshold <= spend_keys.size() + 1, "Invalid threshold");
-  CHECK_AND_ASSERT_THROW_MES(threshold == spend_keys.size() || threshold == spend_keys.size() + 1, "Unsupported threshold case");
+  CHECK_AND_ASSERT_THROW_MES(threshold > 1 && threshold <= spend_keys.size() + 1, "Invalid threshold");
+  CHECK_AND_ASSERT_THROW_MES(/*threshold == spend_keys.size() ||*/ threshold == spend_keys.size() + 1, "Unsupported threshold case");
 
   clear();
 
@@ -2669,19 +2764,20 @@ void wallet2::make_multisig(const epee::wipeable_string &password,
   else
   {
     // the multisig spend public key is the sum of keys derived from all spend public keys
-    const rct::key spend_skey = rct::sk2rct(get_account().get_keys().m_spend_secret_key);
+    const rct::key spend_skey = rct::sk2rct(get_account().get_keys().m_spend_secret_key); // WRONG
     for (const auto &k: spend_keys)
     {
-      rct::addKeys(spend_pkey, spend_pkey, rct::scalarmultBase(rct::cn_fast_hash(rct::scalarmultKey(rct::pk2rct(k), spend_skey))));
+      rct::addKeys(spend_pkey, spend_pkey, rct::scalarmultBase(rct::hash_to_scalar(rct::scalarmultKey(rct::pk2rct(k), spend_skey))));
     }
   }
 
   // the multisig view key is shared by all, make one all can derive
   MINFO("Creating view key...");
-  rct::key view_skey = rct::sk2rct(get_account().get_keys().m_view_secret_key);
+  crypto::hash hash;
+  crypto::cn_fast_hash(&get_account().get_keys().m_view_secret_key, sizeof(crypto::secret_key), hash);
+  rct::key view_skey = rct::hash2rct(hash);
   for (const auto &k: view_keys)
     sc_add(view_skey.bytes, view_skey.bytes, rct::sk2rct(k).bytes);
-  sc_reduce32(view_skey.bytes);
 
   MINFO("Creating multisig address...");
   CHECK_AND_ASSERT_THROW_MES(m_account.make_multisig(rct::rct2sk(view_skey), rct::rct2pk(spend_pkey)),
@@ -2712,13 +2808,14 @@ std::string wallet2::get_multisig_info() const
   // It's a signed package of private view key and public spend key
   const crypto::secret_key &skey = get_account().get_keys().m_view_secret_key;
   const crypto::public_key &pkey = get_account().get_keys().m_account_address.m_spend_public_key;
+  crypto::hash hash;
 
   std::string data;
-  data += std::string((const char *)&skey, sizeof(crypto::secret_key));
+  crypto::cn_fast_hash(&skey, sizeof(crypto::secret_key), hash);
+  data += std::string((const char *)&hash, sizeof(crypto::hash));
   data += std::string((const char *)&pkey, sizeof(crypto::public_key));
 
   data.resize(data.size() + sizeof(crypto::signature));
-  crypto::hash hash;
   crypto::cn_fast_hash(data.data(), data.size() - sizeof(signature), hash);
   crypto::signature &signature = *(crypto::signature*)&data[data.size() - sizeof(crypto::signature)];
   crypto::generate_signature(hash, pkey, get_account().get_keys().m_spend_secret_key, signature);
@@ -2775,6 +2872,16 @@ bool wallet2::multisig(uint32_t *threshold, uint32_t *total) const
   return true;
 }
 
+bool wallet2::has_multisig_partial_key_images() const
+{
+  if (!m_multisig)
+    return false;
+  for (const auto &td: m_transfers)
+    if (td.m_key_image_partial)
+      return true;
+  return false;
+}
+
 /*!
  * \brief Rewrites to the wallet file for wallet upgrade (doesn't generate key, assumes it's already there)
  * \param wallet_name Name of wallet file (should exist)
@@ -3355,7 +3462,7 @@ void wallet2::rescan_spent()
   {
     transfer_details& td = m_transfers[i];
     // a view wallet may not know about key images
-    if (!td.m_key_image_known)
+    if (!td.m_key_image_known || td.m_key_image_partial)
       continue;
     if (td.m_spent != (spent_status[i] != COMMAND_RPC_IS_KEY_IMAGE_SPENT::UNSPENT))
     {
@@ -3695,23 +3802,6 @@ crypto::hash wallet2::get_payment_id(const pending_tx &ptx) const
   return payment_id;
 }
 
-crypto::hash8 wallet2::get_short_payment_id(const pending_tx &ptx) const
-{
-  crypto::hash8 payment_id8 = null_hash8;
-  std::vector<tx_extra_field> tx_extra_fields;
-  if(!parse_tx_extra(ptx.tx.extra, tx_extra_fields))
-    return payment_id8;
-  cryptonote::tx_extra_nonce extra_nonce;
-  if (find_tx_extra_field_by_type(tx_extra_fields, extra_nonce))
-  {
-    if(get_encrypted_payment_id_from_tx_extra_nonce(extra_nonce.nonce, payment_id8))
-    {
-      decrypt_payment_id(payment_id8, ptx.dests[0].addr.m_view_public_key, ptx.tx_key); 
-    }
-  }
-  return payment_id8;
-}
-
 //----------------------------------------------------------------------------------------------------
 // take a pending tx and actually send it to the daemon
 void wallet2::commit_tx(pending_tx& ptx)
@@ -3779,6 +3869,10 @@ void wallet2::commit_tx(pending_tx& ptx)
     set_spent(idx, 0);
   }
 
+  // tx generated, get rid of used k values
+  for (size_t idx: ptx.selected_transfers)
+    m_transfers[idx].m_multisig_k = rct::zero();
+
   //fee includes dust if dust policy specified it.
   LOG_PRINT_L1("Transaction successfully sent. <" << txid << ">" << ENDL
             << "Commission: " << print_money(ptx.fee) << " (dust sent to dust addr: " << print_money((ptx.dust_added_to_fee ? 0 : ptx.dust)) << ")" << ENDL
@@ -3801,27 +3895,10 @@ bool wallet2::save_tx(const std::vector<pending_tx>& ptx_vector, const std::stri
   unsigned_tx_set txs;
   for (auto &tx: ptx_vector)
   {
-    tx_construction_data construction_data = tx.construction_data;
     // Short payment id is encrypted with tx_key. 
     // Since sign_tx() generates new tx_keys and encrypts the payment id, we need to save the decrypted payment ID
-    // Get decrypted payment id from pending_tx
-    crypto::hash8 payment_id = get_short_payment_id(tx);
-    if (payment_id != null_hash8)
-    {
-      // Remove encrypted
-      remove_field_from_tx_extra(construction_data.extra, typeid(cryptonote::tx_extra_nonce));
-      // Add decrypted
-      std::string extra_nonce;
-      set_encrypted_payment_id_to_tx_extra_nonce(extra_nonce, payment_id);
-      if (!add_extra_nonce_to_tx_extra(construction_data.extra, extra_nonce))
-      {
-        LOG_ERROR("Failed to add decrypted payment id to tx extra");
-        return false;
-      }
-      LOG_PRINT_L1("Decrypted payment ID: " << payment_id);       
-    }
     // Save tx construction_data to unsigned_tx_set
-    txs.txes.push_back(construction_data);      
+    txs.txes.push_back(get_construction_data_with_decrypted_short_payment_id(tx));
   }
   
   txs.transfers = m_transfers;
@@ -3942,7 +4019,8 @@ bool wallet2::sign_tx(unsigned_tx_set &exported_txs, const std::string &signed_f
     bool bulletproof = sd.use_rct && !ptx.tx.rct_signatures.p.bulletproofs.empty();
     crypto::secret_key tx_key;
     std::vector<crypto::secret_key> additional_tx_keys;
-    bool r = cryptonote::construct_tx_and_get_tx_key(m_account.get_keys(), m_subaddresses, sd.sources, sd.splitted_dsts, sd.change_dts.addr, sd.extra, ptx.tx, sd.unlock_time, tx_key, additional_tx_keys, sd.use_rct, bulletproof);
+    rct::multisig_out msout;
+    bool r = cryptonote::construct_tx_and_get_tx_key(m_account.get_keys(), m_subaddresses, sd.sources, sd.splitted_dsts, sd.change_dts.addr, sd.extra, ptx.tx, sd.unlock_time, tx_key, additional_tx_keys, sd.use_rct, bulletproof, m_multisig ? &msout : NULL);
     THROW_WALLET_EXCEPTION_IF(!r, error::tx_not_constructed, sd.sources, sd.splitted_dsts, sd.unlock_time, m_testnet);
     // we don't test tx size, because we don't know the current limit, due to not having a blockchain,
     // and it's a bit pointless to fail there anyway, since it'd be a (good) guess only. We sign anyway,
@@ -3978,6 +4056,7 @@ bool wallet2::sign_tx(unsigned_tx_set &exported_txs, const std::string &signed_f
     ptx.selected_transfers = sd.selected_transfers;
     ptx.tx_key = rct::rct2sk(rct::identity()); // don't send it back to the untrusted view wallet
     ptx.dests = sd.dests;
+    ptx.msout = msout;
     ptx.construction_data = sd;
 
     txs.push_back(ptx);
@@ -3987,7 +4066,7 @@ bool wallet2::sign_tx(unsigned_tx_set &exported_txs, const std::string &signed_f
   signed_txes.key_images.resize(m_transfers.size());
   for (size_t i = 0; i < m_transfers.size(); ++i)
   {
-    if (!m_transfers[i].m_key_image_known)
+    if (!m_transfers[i].m_key_image_known || m_transfers[i].m_key_image_partial)
       LOG_PRINT_L0("WARNING: key image not known in signing wallet at index " << i);
     signed_txes.key_images[i] = m_transfers[i].m_key_image;
   }
@@ -4113,11 +4192,12 @@ bool wallet2::load_tx(const std::string &signed_filename, std::vector<tools::wal
   for (size_t i = 0; i < signed_txs.key_images.size(); ++i)
   {
     transfer_details &td = m_transfers[i];
-    if (td.m_key_image_known && td.m_key_image != signed_txs.key_images[i])
+    if (td.m_key_image_known && !td.m_key_image_partial && td.m_key_image != signed_txs.key_images[i])
       LOG_PRINT_L0("WARNING: imported key image differs from previously known key image at index " << i << ": trusting imported one");
     td.m_key_image = signed_txs.key_images[i];
     m_key_images[m_transfers[i].m_key_image] = i;
     td.m_key_image_known = true;
+    td.m_key_image_partial = false;
     m_pub_keys[m_transfers[i].get_public_key()] = i;
   }
 
@@ -4126,6 +4206,217 @@ bool wallet2::load_tx(const std::string &signed_filename, std::vector<tools::wal
   return true;
 }
 //----------------------------------------------------------------------------------------------------
+bool wallet2::save_multisig_tx(multisig_tx_set txs, const std::string &filename)
+{
+  LOG_PRINT_L0("saving " << txs.m_ptx.size() << " multisig transactions");
+
+  // txes generated, get rid of used k values
+  for (size_t n = 0; n < txs.m_ptx.size(); ++n)
+    for (size_t idx: txs.m_ptx[n].construction_data.selected_transfers)
+      m_transfers[idx].m_multisig_k = rct::zero();
+
+  // zero out some data we don't want to share
+  for (auto &ptx: txs.m_ptx)
+  {
+    for (auto &e: ptx.construction_data.sources)
+      e.multisig_kLRki.k = rct::zero();
+  }
+
+  for (auto &ptx: txs.m_ptx)
+  {
+    // Get decrypted payment id from pending_tx
+    ptx.construction_data = get_construction_data_with_decrypted_short_payment_id(ptx);
+  }
+
+  // save as binary
+  std::ostringstream oss;
+  boost::archive::portable_binary_oarchive ar(oss);
+  try
+  {
+    ar << txs;
+  }
+  catch (...)
+  {
+    return false;
+  }
+  LOG_PRINT_L2("Saving multisig unsigned tx data: " << oss.str());
+  std::string ciphertext = encrypt_with_view_secret_key(oss.str());
+  return epee::file_io_utils::save_string_to_file(filename, std::string(MULTISIG_UNSIGNED_TX_PREFIX) + ciphertext);  
+}
+//----------------------------------------------------------------------------------------------------
+bool wallet2::save_multisig_tx(const std::vector<pending_tx>& ptx_vector, const std::string &filename)
+{
+  multisig_tx_set txs;
+  txs.m_ptx = ptx_vector;
+  crypto::hash hash;
+  cn_fast_hash(&get_account().get_keys().m_spend_secret_key, sizeof(crypto::secret_key), (char*)&hash);
+  txs.m_signers.insert(hash);
+  return save_multisig_tx(txs, filename);
+}
+//----------------------------------------------------------------------------------------------------
+bool wallet2::load_multisig_tx_from_file(const std::string &filename, multisig_tx_set &exported_txs, std::function<bool(const multisig_tx_set&)> accept_func)
+{
+  std::string s;
+  boost::system::error_code errcode;
+
+  if (!boost::filesystem::exists(filename, errcode))
+  {
+    LOG_PRINT_L0("File " << filename << " does not exist: " << errcode);
+    return false;
+  }
+  if (!epee::file_io_utils::load_file_to_string(filename.c_str(), s))
+  {
+    LOG_PRINT_L0("Failed to load from " << filename);
+    return false;
+  }
+  const size_t magiclen = strlen(MULTISIG_UNSIGNED_TX_PREFIX);
+  if (strncmp(s.c_str(), MULTISIG_UNSIGNED_TX_PREFIX, magiclen))
+  {
+    LOG_PRINT_L0("Bad magic from " << filename);
+    return false;
+  }
+  try
+  {
+    s = decrypt_with_view_secret_key(std::string(s, magiclen));
+  }
+  catch (const std::exception &e)
+  {
+    LOG_PRINT_L0("Failed to decrypt " << filename << ": " << e.what());
+    return 0;
+  }
+  try
+  {
+    std::istringstream iss(s);
+    boost::archive::portable_binary_iarchive ar(iss);
+    ar >> exported_txs;
+  }
+  catch (...)
+  {
+    LOG_PRINT_L0("Failed to parse data from " << filename);
+    return false;
+  }
+
+  // sanity checks
+  for (const auto &ptx: exported_txs.m_ptx)
+  {
+    CHECK_AND_ASSERT_MES(ptx.selected_transfers.size() == ptx.tx.vin.size(), false, "Mismatched selected_transfers/vin sizes");
+    for (size_t idx: ptx.selected_transfers)
+      CHECK_AND_ASSERT_MES(idx < m_transfers.size(), false, "Transfer index out of range");
+    CHECK_AND_ASSERT_MES(ptx.construction_data.selected_transfers.size() == ptx.tx.vin.size(), false, "Mismatched cd selected_transfers/vin sizes");
+    for (size_t idx: ptx.construction_data.selected_transfers)
+      CHECK_AND_ASSERT_MES(idx < m_transfers.size(), false, "Transfer index out of range");
+    CHECK_AND_ASSERT_MES(ptx.construction_data.sources.size() == ptx.tx.vin.size(), false, "Mismatched sources/vin sizes");
+  }
+
+  LOG_PRINT_L1("Loaded multisig tx unsigned data from binary: " << exported_txs.m_ptx.size() << " transactions");
+  for (auto &ptx: exported_txs.m_ptx) LOG_PRINT_L0(cryptonote::obj_to_json_str(ptx.tx));
+
+  if (accept_func && !accept_func(exported_txs))
+  {
+    LOG_PRINT_L1("Transactions rejected by callback");
+    return false;
+  }
+
+  const bool is_signed = exported_txs.m_signers.size() >= m_multisig_threshold;
+  if (is_signed)
+  {
+    for (const auto &ptx: exported_txs.m_ptx)
+    {
+      const crypto::hash txid = get_transaction_hash(ptx.tx);
+      if (store_tx_info())
+      {
+        m_tx_keys.insert(std::make_pair(txid, ptx.tx_key));
+        m_additional_tx_keys.insert(std::make_pair(txid, ptx.additional_tx_keys));
+      }
+    }
+  }
+
+  return true;
+}
+//----------------------------------------------------------------------------------------------------
+bool wallet2::sign_multisig_tx(multisig_tx_set &exported_txs, const std::string &filename, std::vector<crypto::hash> &txids)
+{
+  THROW_WALLET_EXCEPTION_IF(exported_txs.m_ptx.empty(), error::wallet_internal_error, "No tx found");
+
+  txids.clear();
+
+  // sign the transactions
+  for (size_t n = 0; n < exported_txs.m_ptx.size(); ++n)
+  {
+    tools::wallet2::pending_tx &ptx = exported_txs.m_ptx[n];
+    tools::wallet2::tx_construction_data &sd = ptx.construction_data;
+    LOG_PRINT_L1(" " << (n+1) << ": " << sd.sources.size() << " inputs, mixin " << (sd.sources[0].outputs.size()-1) <<
+        ", signed by " << exported_txs.m_signers.size() << "/" << m_multisig_threshold);
+    cryptonote::transaction tx;
+    rct::multisig_out msout = ptx.msout;
+    auto sources = sd.sources;
+    const bool bulletproof = sd.use_rct && (ptx.tx.rct_signatures.type == rct::RCTTypeFullBulletproof || ptx.tx.rct_signatures.type == rct::RCTTypeSimpleBulletproof);
+    bool r = cryptonote::construct_tx_with_tx_key(m_account.get_keys(), m_subaddresses, sources, sd.splitted_dsts, ptx.change_dts.addr, sd.extra, tx, sd.unlock_time, ptx.tx_key, ptx.additional_tx_keys, sd.use_rct, bulletproof, &msout);
+    THROW_WALLET_EXCEPTION_IF(!r, error::tx_not_constructed, sd.sources, sd.splitted_dsts, sd.unlock_time, m_testnet);
+
+    THROW_WALLET_EXCEPTION_IF(get_transaction_prefix_hash (tx) != get_transaction_prefix_hash(ptx.tx),
+        error::wallet_internal_error, "Transaction prefix does not match data");
+
+    // Tests passed, sign
+    std::vector<unsigned int> indices;
+    for (const auto &source: sources)
+      indices.push_back(source.real_output);
+
+    rct::keyV k;
+    for (size_t idx: sd.selected_transfers)
+      k.push_back(get_multisig_k(idx));
+
+    THROW_WALLET_EXCEPTION_IF(!rct::signMultisig(ptx.tx.rct_signatures, indices, k, ptx.msout, rct::sk2rct(get_account().get_keys().m_spend_secret_key)),
+        error::wallet_internal_error, "Failed signing, transaction likely malformed");
+
+    const bool is_last = exported_txs.m_signers.size() + 1 >= m_multisig_threshold;
+    if (is_last)
+    {
+      const crypto::hash txid = get_transaction_hash(ptx.tx);
+      if (store_tx_info())
+      {
+        m_tx_keys.insert(std::make_pair(txid, ptx.tx_key));
+        m_additional_tx_keys.insert(std::make_pair(txid, ptx.additional_tx_keys));
+      }
+      txids.push_back(txid);
+    }
+  }
+
+  // txes generated, get rid of used k values
+  for (size_t n = 0; n < exported_txs.m_ptx.size(); ++n)
+    for (size_t idx: exported_txs.m_ptx[n].construction_data.selected_transfers)
+      m_transfers[idx].m_multisig_k = rct::zero();
+
+  crypto::hash hash;
+  cn_fast_hash(&get_account().get_keys().m_spend_secret_key, sizeof(crypto::secret_key), (char*)&hash);
+  exported_txs.m_signers.insert(hash);
+
+  return save_multisig_tx(exported_txs, filename);
+}
+//----------------------------------------------------------------------------------------------------
+bool wallet2::sign_multisig_tx_from_file(const std::string &filename, std::vector<crypto::hash> &txids, std::function<bool(const multisig_tx_set&)> accept_func)
+{
+  multisig_tx_set exported_txs;
+  if(!load_multisig_tx_from_file(filename, exported_txs))
+    return false;
+
+  crypto::hash hash;
+  cn_fast_hash(&get_account().get_keys().m_spend_secret_key, sizeof(crypto::secret_key), (char*)&hash);
+  THROW_WALLET_EXCEPTION_IF(exported_txs.m_signers.find(hash) != exported_txs.m_signers.end(),
+      error::wallet_internal_error, "Transaction already signed by this private key");
+  THROW_WALLET_EXCEPTION_IF(exported_txs.m_signers.size() > m_multisig_threshold,
+      error::wallet_internal_error, "Transaction was signed by too many signers");
+  THROW_WALLET_EXCEPTION_IF(exported_txs.m_signers.size() == m_multisig_threshold,
+      error::wallet_internal_error, "Transaction is already fully signed");
+
+  if (accept_func && !accept_func(exported_txs))
+  {
+    LOG_PRINT_L1("Transactions rejected by callback");
+    return false;
+  }
+  return sign_multisig_tx(exported_txs, filename, txids);
+}
+//----------------------------------------------------------------------------------------------------
 uint64_t wallet2::get_fee_multiplier(uint32_t priority, int fee_algorithm)
 {
   static const uint64_t old_multipliers[3] = {1, 2, 3};
@@ -4749,6 +5040,10 @@ void wallet2::transfer_selected(const std::vector<cryptonote::tx_destination_ent
     src.real_out_additional_tx_keys = get_additional_tx_pub_keys_from_extra(td.m_tx);
     src.real_output = it_to_replace - src.outputs.begin();
     src.real_output_in_tx_index = td.m_internal_output_index;
+    if (m_multisig)
+      src.multisig_kLRki = get_multisig_composite_LRki(idx, get_multisig_k(idx));
+    else
+      src.multisig_kLRki = rct::multisig_kLRki({rct::zero(), rct::zero(), rct::zero(), rct::zero()});
     detail::print_source_entry(src);
     ++out_index;
   }
@@ -4776,8 +5071,9 @@ void wallet2::transfer_selected(const std::vector<cryptonote::tx_destination_ent
 
   crypto::secret_key tx_key;
   std::vector<crypto::secret_key> additional_tx_keys;
+  rct::multisig_out msout;
   LOG_PRINT_L2("constructing tx");
-  bool r = cryptonote::construct_tx_and_get_tx_key(m_account.get_keys(), m_subaddresses, sources, splitted_dsts, change_dts.addr, extra, tx, unlock_time, tx_key, additional_tx_keys);
+  bool r = cryptonote::construct_tx_and_get_tx_key(m_account.get_keys(), m_subaddresses, sources, splitted_dsts, change_dts.addr, extra, tx, unlock_time, tx_key, additional_tx_keys, false, false, m_multisig ? &msout : NULL);
   LOG_PRINT_L2("constructed tx, r="<<r);
   THROW_WALLET_EXCEPTION_IF(!r, error::tx_not_constructed, sources, splitted_dsts, unlock_time, m_testnet);
   THROW_WALLET_EXCEPTION_IF(upper_transaction_size_limit <= get_object_blobsize(tx), error::tx_too_big, tx, upper_transaction_size_limit);
@@ -4807,6 +5103,7 @@ void wallet2::transfer_selected(const std::vector<cryptonote::tx_destination_ent
   ptx.tx_key = tx_key;
   ptx.additional_tx_keys = additional_tx_keys;
   ptx.dests = dsts;
+  ptx.msout = msout;
   ptx.construction_data.sources = sources;
   ptx.construction_data.change_dts = change_dts;
   ptx.construction_data.splitted_dsts = splitted_dsts;
@@ -4907,6 +5204,10 @@ void wallet2::transfer_selected_rct(std::vector<cryptonote::tx_destination_entry
     src.real_output = it_to_replace - src.outputs.begin();
     src.real_output_in_tx_index = td.m_internal_output_index;
     src.mask = td.m_mask;
+    if (m_multisig)
+      src.multisig_kLRki = get_multisig_composite_LRki(idx, get_multisig_k(idx));
+    else
+      src.multisig_kLRki = rct::multisig_kLRki({rct::zero(), rct::zero(), rct::zero(), rct::zero()});
     detail::print_source_entry(src);
     ++out_index;
   }
@@ -4940,12 +5241,28 @@ void wallet2::transfer_selected_rct(std::vector<cryptonote::tx_destination_entry
 
   crypto::secret_key tx_key;
   std::vector<crypto::secret_key> additional_tx_keys;
+  rct::multisig_out msout;
   LOG_PRINT_L2("constructing tx");
-  bool r = cryptonote::construct_tx_and_get_tx_key(m_account.get_keys(), m_subaddresses, sources, splitted_dsts, change_dts.addr, extra, tx, unlock_time, tx_key, additional_tx_keys, true, bulletproof);
+  auto sources_copy = sources;
+  bool r = cryptonote::construct_tx_and_get_tx_key(m_account.get_keys(), m_subaddresses, sources, splitted_dsts, change_dts.addr, extra, tx, unlock_time, tx_key, additional_tx_keys, true, bulletproof, m_multisig ? &msout : NULL);
   LOG_PRINT_L2("constructed tx, r="<<r);
   THROW_WALLET_EXCEPTION_IF(!r, error::tx_not_constructed, sources, dsts, unlock_time, m_testnet);
   THROW_WALLET_EXCEPTION_IF(upper_transaction_size_limit <= get_object_blobsize(tx), error::tx_too_big, tx, upper_transaction_size_limit);
 
+  // work out the permutation done on sources
+  std::vector<size_t> ins_order;
+  for (size_t n = 0; n < sources.size(); ++n)
+  {
+    for (size_t idx = 0; idx < sources_copy.size(); ++idx)
+    {
+      THROW_WALLET_EXCEPTION_IF((size_t)sources_copy[idx].real_output >= sources_copy[idx].outputs.size(),
+          error::wallet_internal_error, "Invalid real_output");
+      if (sources_copy[idx].outputs[sources_copy[idx].real_output].second.dest == sources[n].outputs[sources[n].real_output].second.dest)
+        ins_order.push_back(idx);
+    }
+  }
+  THROW_WALLET_EXCEPTION_IF(ins_order.size() != sources.size(), error::wallet_internal_error, "Failed to work out sources permutation");
+
   LOG_PRINT_L2("gathering key images");
   std::string key_images;
   bool all_are_txin_to_key = std::all_of(tx.vin.begin(), tx.vin.end(), [&](const txin_v& s_e) -> bool
@@ -4964,13 +5281,15 @@ void wallet2::transfer_selected_rct(std::vector<cryptonote::tx_destination_entry
   ptx.tx = tx;
   ptx.change_dts = change_dts;
   ptx.selected_transfers = selected_transfers;
+  tools::apply_permutation(ins_order, ptx.selected_transfers);
   ptx.tx_key = tx_key;
   ptx.additional_tx_keys = additional_tx_keys;
   ptx.dests = dsts;
+  ptx.msout = msout;
   ptx.construction_data.sources = sources;
   ptx.construction_data.change_dts = change_dts;
   ptx.construction_data.splitted_dsts = splitted_dsts;
-  ptx.construction_data.selected_transfers = selected_transfers;
+  ptx.construction_data.selected_transfers = ptx.selected_transfers;
   ptx.construction_data.extra = tx.extra;
   ptx.construction_data.unlock_time = unlock_time;
   ptx.construction_data.use_rct = true;
@@ -4997,13 +5316,13 @@ std::vector<size_t> wallet2::pick_preferred_rct_inputs(uint64_t needed_money, ui
   for (size_t i = 0; i < m_transfers.size(); ++i)
   {
     const transfer_details& td = m_transfers[i];
-    if (!td.m_spent && td.is_rct() && is_transfer_unlocked(td) && td.m_subaddr_index.major == subaddr_account && subaddr_indices.count(td.m_subaddr_index.minor) == 1)
+    if (!td.m_spent && !td.m_key_image_partial && td.is_rct() && is_transfer_unlocked(td) && td.m_subaddr_index.major == subaddr_account && subaddr_indices.count(td.m_subaddr_index.minor) == 1)
     {
       LOG_PRINT_L2("Considering input " << i << ", " << print_money(td.amount()));
       for (size_t j = i + 1; j < m_transfers.size(); ++j)
       {
         const transfer_details& td2 = m_transfers[j];
-        if (!td2.m_spent && td2.is_rct() && td.amount() + td2.amount() >= needed_money && is_transfer_unlocked(td2) && td2.m_subaddr_index == td.m_subaddr_index)
+        if (!td2.m_spent && !td.m_key_image_partial && td2.is_rct() && td.amount() + td2.amount() >= needed_money && is_transfer_unlocked(td2) && td2.m_subaddr_index == td.m_subaddr_index)
         {
           // update our picks if those outputs are less related than any we
           // already found. If the same, don't update, and oldest suitable outputs
@@ -5665,7 +5984,7 @@ std::vector<wallet2::pending_tx> wallet2::create_transactions_2(std::vector<cryp
   for (size_t i = 0; i < m_transfers.size(); ++i)
   {
     const transfer_details& td = m_transfers[i];
-    if (!td.m_spent && (use_rct ? true : !td.is_rct()) && is_transfer_unlocked(td) && td.m_subaddr_index.major == subaddr_account && subaddr_indices.count(td.m_subaddr_index.minor) == 1)
+    if (!td.m_spent && !td.m_key_image_partial && (use_rct ? true : !td.is_rct()) && is_transfer_unlocked(td) && td.m_subaddr_index.major == subaddr_account && subaddr_indices.count(td.m_subaddr_index.minor) == 1)
     {
       const uint32_t index_minor = td.m_subaddr_index.minor;
       auto find_predicate = [&index_minor](const std::pair<uint32_t, std::vector<size_t>>& x) { return x.first == index_minor; };
@@ -6041,7 +6360,7 @@ std::vector<wallet2::pending_tx> wallet2::create_transactions_all(uint64_t below
   for (size_t i = 0; i < m_transfers.size(); ++i)
   {
     const transfer_details& td = m_transfers[i];
-    if (!td.m_spent && (use_rct ? true : !td.is_rct()) && is_transfer_unlocked(td) && td.m_subaddr_index.major == subaddr_account && subaddr_indices.count(td.m_subaddr_index.minor) == 1)
+    if (!td.m_spent && !td.m_key_image_partial && (use_rct ? true : !td.is_rct()) && is_transfer_unlocked(td) && td.m_subaddr_index.major == subaddr_account && subaddr_indices.count(td.m_subaddr_index.minor) == 1)
     {
       if (below == 0 || td.amount() < below)
       {
@@ -6255,6 +6574,8 @@ std::vector<size_t> wallet2::select_available_outputs(const std::function<bool(c
   {
     if (i->m_spent)
       continue;
+    if (i->m_key_image_partial)
+      continue;
     if (!is_transfer_unlocked(*i))
       continue;
     if (f(*i))
@@ -7235,7 +7556,7 @@ std::vector<std::pair<crypto::key_image, crypto::signature>> wallet2::export_key
     bool r = cryptonote::generate_key_image_helper(m_account.get_keys(), m_subaddresses, pkey, tx_pub_key, additional_tx_pub_keys, td.m_internal_output_index, in_ephemeral, ki);
     THROW_WALLET_EXCEPTION_IF(!r, error::wallet_internal_error, "Failed to generate key image");
 
-    THROW_WALLET_EXCEPTION_IF(td.m_key_image_known && ki != td.m_key_image,
+    THROW_WALLET_EXCEPTION_IF(td.m_key_image_known && !td.m_key_image_partial && ki != td.m_key_image,
         error::wallet_internal_error, "key_image generated not matched with cached key image");
     THROW_WALLET_EXCEPTION_IF(in_ephemeral.pub != pkey,
         error::wallet_internal_error, "key_image generated ephemeral public key not matched with output_key");
@@ -7350,6 +7671,7 @@ uint64_t wallet2::import_key_images(const std::vector<std::pair<crypto::key_imag
     m_transfers[n].m_key_image = signed_key_images[n].first;
     m_key_images[m_transfers[n].m_key_image] = n;
     m_transfers[n].m_key_image_known = true;
+    m_transfers[n].m_key_image_partial = false;
   }
 
   if(check_spent)
@@ -7634,6 +7956,7 @@ size_t wallet2::import_outputs(const std::vector<tools::wallet2::transfer_detail
     THROW_WALLET_EXCEPTION_IF(!r, error::wallet_internal_error, "Failed to generate key image");
     expand_subaddresses(td.m_subaddr_index);
     td.m_key_image_known = true;
+    td.m_key_image_partial = false;
     THROW_WALLET_EXCEPTION_IF(in_ephemeral.pub != boost::get<cryptonote::txout_to_key>(td.m_tx.vout[td.m_internal_output_index].target).key,
         error::wallet_internal_error, "key_image generated ephemeral public key not matched with output_key at index " + boost::lexical_cast<std::string>(i));
 
@@ -7645,6 +7968,138 @@ size_t wallet2::import_outputs(const std::vector<tools::wallet2::transfer_detail
   return m_transfers.size();
 }
 //----------------------------------------------------------------------------------------------------
+rct::key wallet2::get_multisig_k(size_t idx) const
+{
+  CHECK_AND_ASSERT_THROW_MES(m_multisig, "Wallet is not multisig");
+  CHECK_AND_ASSERT_THROW_MES(idx < m_transfers.size(), "Index out of range");
+  THROW_WALLET_EXCEPTION_IF(m_transfers[idx].m_multisig_k == rct::zero(), error::multisig_export_needed);
+  return m_transfers[idx].m_multisig_k;
+}
+//----------------------------------------------------------------------------------------------------
+rct::multisig_kLRki wallet2::get_multisig_LRki(size_t n, const rct::key &k) const
+{
+  rct::multisig_kLRki kLRki;
+  kLRki.k = k;
+  rct::scalarmultBase(kLRki.L, kLRki.k);
+  crypto::generate_key_image(m_transfers[n].get_public_key(), rct::rct2sk(kLRki.k), (crypto::key_image&)kLRki.R);
+  kLRki.ki = rct::ki2rct(m_transfers[n].m_key_image);
+  return kLRki;
+}
+//----------------------------------------------------------------------------------------------------
+rct::multisig_kLRki wallet2::get_multisig_composite_LRki(size_t n, const rct::key &k) const
+{
+  rct::multisig_kLRki kLRki = get_multisig_LRki(n, k);
+  const transfer_details &td = m_transfers[n];
+  crypto::public_key tx_key = get_tx_pub_key_from_received_outs(td);
+  cryptonote::keypair in_ephemeral;
+  bool r = wallet_generate_key_image_helper_old(get_account().get_keys(), tx_key, td.m_internal_output_index, in_ephemeral, (crypto::key_image&)kLRki.ki);
+  CHECK_AND_ASSERT_THROW_MES(r, "Failed to generate key image");
+  for (const auto &info: td.m_multisig_info)
+  {
+    rct::addKeys(kLRki.ki, kLRki.ki, rct::ki2rct(info.m_partial_key_image));
+    rct::addKeys(kLRki.L, kLRki.L, info.m_L);
+    rct::addKeys(kLRki.R, kLRki.R, info.m_R);
+  }
+  return kLRki;
+}
+//----------------------------------------------------------------------------------------------------
+std::vector<tools::wallet2::multisig_info> wallet2::export_multisig()
+{
+  std::vector<tools::wallet2::multisig_info> info;
+
+  info.resize(m_transfers.size());
+  for (size_t n = 0; n < m_transfers.size(); ++n)
+  {
+    transfer_details &td = m_transfers[n];
+    crypto::public_key tx_key = get_tx_pub_key_from_received_outs(td);
+    cryptonote::keypair in_ephemeral;
+    crypto::key_image ki;
+    td.m_multisig_k = rct::skGen();
+    const rct::multisig_kLRki kLRki = get_multisig_LRki(n, td.m_multisig_k);
+    const std::vector<crypto::public_key> additional_tx_pub_keys = get_additional_tx_pub_keys_from_extra(td.m_tx);
+    // we want to export the partial key image, not the full one, so we can't use td.m_key_image
+    bool r = wallet_generate_key_image_helper_old(get_account().get_keys(), tx_key, td.m_internal_output_index, in_ephemeral, ki, true);
+    CHECK_AND_ASSERT_THROW_MES(r, "Failed to generate key image");
+    // we got the ephemeral keypair, but the key image isn't right as it's done as per our private spend key, which is multisig
+    crypto::generate_key_image(in_ephemeral.pub, get_account().get_keys().m_spend_secret_key, ki);
+    info[n] = multisig_info({ki, kLRki.L, kLRki.R});
+  }
+
+  return info;
+}
+//----------------------------------------------------------------------------------------------------
+void wallet2::update_multisig_rescan_info(const std::vector<rct::key> &multisig_k, const std::vector<std::vector<tools::wallet2::multisig_info>> &info, size_t n)
+{
+  CHECK_AND_ASSERT_THROW_MES(n < m_transfers.size(), "Bad index in update_multisig_info");
+  CHECK_AND_ASSERT_THROW_MES(multisig_k.size() >= m_transfers.size(), "Mismatched sizes of multisig_k and info");
+
+  MDEBUG("update_multisig_rescan_info: updating index " << n);
+  transfer_details &td = m_transfers[n];
+  td.m_multisig_info.clear();
+  for (const auto &pi: info)
+  {
+    CHECK_AND_ASSERT_THROW_MES(n < pi.size(), "Bad pi size");
+    td.m_multisig_info.push_back(pi[n]);
+  }
+  m_key_images.erase(td.m_key_image);
+  td.m_key_image = rct::rct2ki(get_multisig_composite_LRki(n, rct::skGen()).ki);
+  td.m_key_image_known = true;
+  td.m_key_image_partial = false;
+  td.m_multisig_k = multisig_k[n];
+  m_key_images[td.m_key_image] = n;
+}
+//----------------------------------------------------------------------------------------------------
+size_t wallet2::import_multisig(std::vector<std::vector<tools::wallet2::multisig_info>> info)
+{
+  CHECK_AND_ASSERT_THROW_MES(m_multisig, "Wallet is not multisig");
+  CHECK_AND_ASSERT_THROW_MES(info.size() + 1 == m_multisig_total, "Wrong number of multisig sources");
+
+  std::vector<rct::key> k;
+  k.reserve(m_transfers.size());
+  for (const auto &td: m_transfers)
+    k.push_back(td.m_multisig_k);
+
+  // how many outputs we're going to update
+  size_t n_outputs = m_transfers.size();
+  for (const auto &pi: info)
+    if (pi.size() < n_outputs)
+      n_outputs = pi.size();
+
+  // trim data we don't have info for from all participants
+  for (auto &pi: info)
+    pi.resize(n_outputs);
+
+  // first pass to determine where to detach the blockchain
+  for (size_t n = 0; n < n_outputs; ++n)
+  {
+    const transfer_details &td = m_transfers[n];
+    if (!td.m_key_image_partial)
+      continue;
+    MINFO("Multisig info importing from block height " << td.m_block_height);
+    detach_blockchain(td.m_block_height);
+    break;
+  }
+
+  MFATAL("import_multisig: updating from import");
+  for (size_t n = 0; n < n_outputs && n < m_transfers.size(); ++n)
+  {
+    update_multisig_rescan_info(k, info, n);
+  }
+
+  m_multisig_rescan_k = &k;
+  m_multisig_rescan_info = &info;
+  try
+  {
+    MFATAL("import_multisig: refreshing");
+    refresh();
+  }
+  catch (...) {}
+  m_multisig_rescan_info = NULL;
+  m_multisig_rescan_k = NULL;
+
+  return n_outputs;
+}
+//----------------------------------------------------------------------------------------------------
 std::string wallet2::encrypt(const std::string &plaintext, const crypto::secret_key &skey, bool authenticated) const
 {
   crypto::chacha8_key key;
diff --git a/src/wallet/wallet2.h b/src/wallet/wallet2.h
index 9b068df3c..97abb1476 100644
--- a/src/wallet/wallet2.h
+++ b/src/wallet/wallet2.h
@@ -145,7 +145,7 @@ namespace tools
     };
 
   private:
-    wallet2(const wallet2&) : m_run(true), m_callback(0), m_testnet(false), m_always_confirm_transfers(true), m_print_ring_members(false), m_store_tx_info(true), m_default_mixin(0), m_default_priority(0), m_refresh_type(RefreshDefault), m_auto_refresh(true), m_refresh_from_block_height(0), m_confirm_missing_payment_id(true), m_ask_password(true), m_min_output_count(0), m_min_output_value(0), m_merge_destinations(false), m_confirm_backlog(true), m_is_initialized(false),m_node_rpc_proxy(m_http_client, m_daemon_rpc_mutex) {}
+    wallet2(const wallet2&) : m_multisig_rescan_info(NULL), m_multisig_rescan_k(NULL), m_run(true), m_callback(0), m_testnet(false), m_always_confirm_transfers(true), m_print_ring_members(false), m_store_tx_info(true), m_default_mixin(0), m_default_priority(0), m_refresh_type(RefreshDefault), m_auto_refresh(true), m_refresh_from_block_height(0), m_confirm_missing_payment_id(true), m_ask_password(true), m_min_output_count(0), m_min_output_value(0), m_merge_destinations(false), m_confirm_backlog(true), m_is_initialized(false),m_node_rpc_proxy(m_http_client, m_daemon_rpc_mutex) {}
 
   public:
     static const char* tr(const char* str);
@@ -168,7 +168,20 @@ namespace tools
 
     static bool verify_password(const std::string& keys_file_name, const epee::wipeable_string& password, bool no_spend_key);
 
-    wallet2(bool testnet = false, bool restricted = false) : m_run(true), m_callback(0), m_testnet(testnet), m_always_confirm_transfers(true), m_print_ring_members(false), m_store_tx_info(true), m_default_mixin(0), m_default_priority(0), m_refresh_type(RefreshDefault), m_auto_refresh(true), m_refresh_from_block_height(0), m_confirm_missing_payment_id(true), m_ask_password(true), m_min_output_count(0), m_min_output_value(0), m_merge_destinations(false), m_confirm_backlog(true), m_is_initialized(false), m_restricted(restricted), is_old_file_format(false), m_node_rpc_proxy(m_http_client, m_daemon_rpc_mutex), m_light_wallet(false), m_light_wallet_scanned_block_height(0), m_light_wallet_blockchain_height(0), m_light_wallet_connected(false), m_light_wallet_balance(0), m_light_wallet_unlocked_balance(0) {}
+    wallet2(bool testnet = false, bool restricted = false) : m_multisig_rescan_info(NULL), m_multisig_rescan_k(NULL), m_run(true), m_callback(0), m_testnet(testnet), m_always_confirm_transfers(true), m_print_ring_members(false), m_store_tx_info(true), m_default_mixin(0), m_default_priority(0), m_refresh_type(RefreshDefault), m_auto_refresh(true), m_refresh_from_block_height(0), m_confirm_missing_payment_id(true), m_ask_password(true), m_min_output_count(0), m_min_output_value(0), m_merge_destinations(false), m_confirm_backlog(true), m_is_initialized(false), m_restricted(restricted), is_old_file_format(false), m_node_rpc_proxy(m_http_client, m_daemon_rpc_mutex), m_light_wallet(false), m_light_wallet_scanned_block_height(0), m_light_wallet_blockchain_height(0), m_light_wallet_connected(false), m_light_wallet_balance(0), m_light_wallet_unlocked_balance(0) {}
+
+    struct multisig_info
+    {
+      crypto::key_image m_partial_key_image;
+      rct::key m_L;
+      rct::key m_R;
+
+      BEGIN_SERIALIZE_OBJECT()
+        FIELD(m_partial_key_image)
+        FIELD(m_L)
+        FIELD(m_R)
+      END_SERIALIZE()
+    };
 
     struct tx_scan_info_t
     {
@@ -199,6 +212,9 @@ namespace tools
       bool m_key_image_known;
       size_t m_pk_index;
       cryptonote::subaddress_index m_subaddr_index;
+      bool m_key_image_partial;
+      rct::key m_multisig_k;
+      std::vector<multisig_info> m_multisig_info;
 
       bool is_rct() const { return m_rct; }
       uint64_t amount() const { return m_amount; }
@@ -219,6 +235,9 @@ namespace tools
         FIELD(m_key_image_known)
         FIELD(m_pk_index)
         FIELD(m_subaddr_index)
+        FIELD(m_key_image_partial)
+        FIELD(m_multisig_k)
+        FIELD(m_multisig_info)
       END_SERIALIZE()
     };
 
@@ -322,6 +341,7 @@ namespace tools
       crypto::secret_key tx_key;
       std::vector<crypto::secret_key> additional_tx_keys;
       std::vector<cryptonote::tx_destination_entry> dests;
+      rct::multisig_out msout;
 
       tx_construction_data construction_data;
 
@@ -354,6 +374,12 @@ namespace tools
       std::vector<crypto::key_image> key_images;
     };
 
+    struct multisig_tx_set
+    {
+      std::vector<pending_tx> m_ptx;
+      std::unordered_set<crypto::hash> m_signers;
+    };
+
     struct keys_file_data
     {
       crypto::chacha8_iv iv;
@@ -434,6 +460,16 @@ namespace tools
      */
     static bool verify_multisig_info(const std::string &data, crypto::secret_key &skey, crypto::public_key &pkey);
     /*!
+     * Export multisig info
+     * This will generate and remember new k values
+     */
+    std::vector<tools::wallet2::multisig_info> export_multisig();
+    /*!
+     * Import a set of multisig info from multisig partners
+     * \return the number of inputs which were imported
+     */
+    size_t import_multisig(std::vector<std::vector<tools::wallet2::multisig_info>> info);
+    /*!
      * \brief Rewrites to the wallet file for wallet upgrade (doesn't generate key, assumes it's already there)
      * \param wallet_name Name of wallet file (should exist)
      * \param password    Password for wallet file
@@ -528,6 +564,7 @@ namespace tools
     bool restricted() const { return m_restricted; }
     bool watch_only() const { return m_watch_only; }
     bool multisig(uint32_t *threshold = NULL, uint32_t *total = NULL) const;
+    bool has_multisig_partial_key_images() const;
 
     // locked & unlocked balance of given or current subaddress account
     uint64_t balance(uint32_t subaddr_index_major) const;
@@ -555,6 +592,8 @@ namespace tools
     void commit_tx(pending_tx& ptx_vector);
     void commit_tx(std::vector<pending_tx>& ptx_vector);
     bool save_tx(const std::vector<pending_tx>& ptx_vector, const std::string &filename);
+    bool save_multisig_tx(multisig_tx_set txs, const std::string &filename);
+    bool save_multisig_tx(const std::vector<pending_tx>& ptx_vector, const std::string &filename);
     // load unsigned tx from file and sign it. Takes confirmation callback as argument. Used by the cli wallet
     bool sign_tx(const std::string &unsigned_filename, const std::string &signed_filename, std::vector<wallet2::pending_tx> &ptx, std::function<bool(const unsigned_tx_set&)> accept_func = NULL, bool export_raw = false);
     // sign unsigned tx. Takes unsigned_tx_set as argument. Used by GUI
@@ -567,6 +606,9 @@ namespace tools
     std::vector<wallet2::pending_tx> create_transactions_all(uint64_t below, const cryptonote::account_public_address &address, bool is_subaddress, const size_t fake_outs_count, const uint64_t unlock_time, uint32_t priority, const std::vector<uint8_t>& extra, uint32_t subaddr_account, std::set<uint32_t> subaddr_indices, bool trusted_daemon);
     std::vector<wallet2::pending_tx> create_transactions_single(const crypto::key_image &ki, const cryptonote::account_public_address &address, bool is_subaddress, const size_t fake_outs_count, const uint64_t unlock_time, uint32_t priority, const std::vector<uint8_t>& extra, bool trusted_daemon);
     std::vector<wallet2::pending_tx> create_transactions_from(const cryptonote::account_public_address &address, bool is_subaddress, std::vector<size_t> unused_transfers_indices, std::vector<size_t> unused_dust_indices, const size_t fake_outs_count, const uint64_t unlock_time, uint32_t priority, const std::vector<uint8_t>& extra, bool trusted_daemon);
+    bool load_multisig_tx_from_file(const std::string &filename, multisig_tx_set &exported_txs, std::function<bool(const multisig_tx_set&)> accept_func = NULL);
+    bool sign_multisig_tx_from_file(const std::string &filename, std::vector<crypto::hash> &txids, std::function<bool(const multisig_tx_set&)> accept_func);
+    bool sign_multisig_tx(multisig_tx_set &exported_txs, const std::string &filename, std::vector<crypto::hash> &txids);
     std::vector<pending_tx> create_unmixable_sweep_transactions(bool trusted_daemon);
     bool check_connection(uint32_t *version = NULL, uint32_t timeout = 200000);
     void get_transfers(wallet2::transfer_container& incoming_transfers) const;
@@ -881,7 +923,6 @@ namespace tools
     void check_genesis(const crypto::hash& genesis_hash) const; //throws
     bool generate_chacha8_key_from_secret_keys(crypto::chacha8_key &key) const;
     crypto::hash get_payment_id(const pending_tx &ptx) const;
-    crypto::hash8 get_short_payment_id(const pending_tx &ptx) const;
     void check_acc_out_precomp(const cryptonote::tx_out &o, const crypto::key_derivation &derivation, const std::vector<crypto::key_derivation> &additional_derivations, size_t i, tx_scan_info_t &tx_scan_info) const;
     void parse_block_round(const cryptonote::blobdata &blob, cryptonote::block &bl, crypto::hash &bl_id, bool &error) const;
     uint64_t get_upper_transaction_size_limit();
@@ -893,12 +934,15 @@ namespace tools
     void set_unspent(size_t idx);
     void get_outs(std::vector<std::vector<get_outs_entry>> &outs, const std::vector<size_t> &selected_transfers, size_t fake_outputs_count);
     bool tx_add_fake_output(std::vector<std::vector<tools::wallet2::get_outs_entry>> &outs, uint64_t global_index, const crypto::public_key& tx_public_key, const rct::key& mask, uint64_t real_index, bool unlocked) const;
-    bool wallet_generate_key_image_helper(const cryptonote::account_keys& ack, const crypto::public_key& tx_public_key, size_t real_output_index, cryptonote::keypair& in_ephemeral, crypto::key_image& ki);
     crypto::public_key get_tx_pub_key_from_received_outs(const tools::wallet2::transfer_details &td) const;
     bool should_pick_a_second_output(bool use_rct, size_t n_transfers, const std::vector<size_t> &unused_transfers_indices, const std::vector<size_t> &unused_dust_indices) const;
     std::vector<size_t> get_only_rct(const std::vector<size_t> &unused_dust_indices, const std::vector<size_t> &unused_transfers_indices) const;
     void scan_output(const cryptonote::account_keys &keys, const cryptonote::transaction &tx, const crypto::public_key &tx_pub_key, size_t i, tx_scan_info_t &tx_scan_info, int &num_vouts_received, std::unordered_map<cryptonote::subaddress_index, uint64_t> &tx_money_got_in_outs, std::vector<size_t> &outs);
     void trim_hashchain();
+    rct::multisig_kLRki get_multisig_composite_LRki(size_t n, const rct::key &k) const;
+    rct::multisig_kLRki get_multisig_LRki(size_t n, const rct::key &k) const;
+    rct::key get_multisig_k(size_t idx) const;
+    void update_multisig_rescan_info(const std::vector<rct::key> &multisig_k, const std::vector<std::vector<tools::wallet2::multisig_info>> &info, size_t n);
 
     cryptonote::account_base m_account;
     boost::optional<epee::net_utils::http::login> m_daemon_login;
@@ -927,6 +971,8 @@ namespace tools
     std::unordered_map<std::string, std::string> m_attributes;
     std::vector<tools::wallet2::address_book_row> m_address_book;
     uint64_t m_upper_transaction_size_limit; //TODO: auto-calc this value or request from daemon, now use some fixed value
+    const std::vector<std::vector<tools::wallet2::multisig_info>> *m_multisig_rescan_info;
+    const std::vector<rct::key> *m_multisig_rescan_k;
 
     std::atomic<bool> m_run;
 
@@ -976,7 +1022,9 @@ namespace tools
   };
 }
 BOOST_CLASS_VERSION(tools::wallet2, 22)
-BOOST_CLASS_VERSION(tools::wallet2::transfer_details, 8)
+BOOST_CLASS_VERSION(tools::wallet2::transfer_details, 9)
+BOOST_CLASS_VERSION(tools::wallet2::multisig_info, 1)
+BOOST_CLASS_VERSION(tools::wallet2::multisig_tx_set, 1)
 BOOST_CLASS_VERSION(tools::wallet2::payment_details, 2)
 BOOST_CLASS_VERSION(tools::wallet2::pool_payment_details, 1)
 BOOST_CLASS_VERSION(tools::wallet2::unconfirmed_transfer_details, 7)
@@ -985,7 +1033,7 @@ BOOST_CLASS_VERSION(tools::wallet2::address_book_row, 17)
 BOOST_CLASS_VERSION(tools::wallet2::unsigned_tx_set, 0)
 BOOST_CLASS_VERSION(tools::wallet2::signed_tx_set, 0)
 BOOST_CLASS_VERSION(tools::wallet2::tx_construction_data, 2)
-BOOST_CLASS_VERSION(tools::wallet2::pending_tx, 2)
+BOOST_CLASS_VERSION(tools::wallet2::pending_tx, 3)
 
 namespace boost
 {
@@ -1023,6 +1071,12 @@ namespace boost
         {
           x.m_subaddr_index = {};
         }
+        if (ver < 9)
+        {
+          x.m_key_image_partial = false;
+          x.m_multisig_info.clear();
+          x.m_multisig_k = rct::zero();
+        }
     }
 
     template <class Archive>
@@ -1096,6 +1150,29 @@ namespace boost
         return;
       }
       a & x.m_subaddr_index;
+      if (ver < 9)
+      {
+        initialize_transfer_details(a, x, ver);
+        return;
+      }
+      a & x.m_multisig_info;
+      a & x.m_multisig_k;
+      a & x.m_key_image_partial;
+    }
+
+    template <class Archive>
+    inline void serialize(Archive &a, tools::wallet2::multisig_info &x, const boost::serialization::version_type ver)
+    {
+      a & x.m_partial_key_image;
+      a & x.m_L;
+      a & x.m_R;
+    }
+
+    template <class Archive>
+    inline void serialize(Archive &a, tools::wallet2::multisig_tx_set &x, const boost::serialization::version_type ver)
+    {
+      a & x.m_ptx;
+      a & x.m_signers;
     }
 
     template <class Archive>
@@ -1301,6 +1378,9 @@ namespace boost
       if (ver < 2)
         return;
       a & x.selected_transfers;
+      if (ver < 3)
+        return;
+      a & x.msout;
     }
   }
 }
@@ -1478,6 +1558,10 @@ namespace tools
       src.real_out_tx_key = get_tx_pub_key_from_extra(td.m_tx);
       src.real_output = interted_it - src.outputs.begin();
       src.real_output_in_tx_index = td.m_internal_output_index;
+      if (m_multisig)
+        src.multisig_kLRki = get_multisig_composite_LRki(idx, get_multisig_k(idx));
+      else
+        src.multisig_kLRki = rct::multisig_kLRki({rct::zero(), rct::zero(), rct::zero(), rct::zero()});
       detail::print_source_entry(src);
       ++i;
     }
@@ -1504,7 +1588,8 @@ namespace tools
 
     crypto::secret_key tx_key;
     std::vector<crypto::secret_key> additional_tx_keys;
-    bool r = cryptonote::construct_tx_and_get_tx_key(m_account.get_keys(), m_subaddresses, sources, splitted_dsts, change_dts.addr, extra, tx, unlock_time, tx_key, additional_tx_keys);
+    rct::multisig_out msout;
+    bool r = cryptonote::construct_tx_and_get_tx_key(m_account.get_keys(), m_subaddresses, sources, splitted_dsts, change_dts.addr, extra, tx, unlock_time, tx_key, additional_tx_keys, false, false, m_multisig ? &msout : NULL);
     THROW_WALLET_EXCEPTION_IF(!r, error::tx_not_constructed, sources, splitted_dsts, unlock_time, m_testnet);
     THROW_WALLET_EXCEPTION_IF(upper_transaction_size_limit <= get_object_blobsize(tx), error::tx_too_big, tx, upper_transaction_size_limit);
 
@@ -1532,6 +1617,7 @@ namespace tools
     ptx.tx_key = tx_key;
     ptx.additional_tx_keys = additional_tx_keys;
     ptx.dests = dsts;
+    ptx.msout = msout;
     ptx.construction_data.sources = sources;
     ptx.construction_data.change_dts = change_dts;
     ptx.construction_data.splitted_dsts = splitted_dsts;
diff --git a/src/wallet/wallet_errors.h b/src/wallet/wallet_errors.h
index 48fce40dd..234c22d85 100644
--- a/src/wallet/wallet_errors.h
+++ b/src/wallet/wallet_errors.h
@@ -50,6 +50,8 @@ namespace tools
     //       wallet_internal_error
     //         unexpected_txin_type
     //         wallet_not_initialized
+    //       multisig_export_needed
+    //       multisig_import_needed
     //   std::logic_error
     //     wallet_logic_error *
     //       file_exists
@@ -186,7 +188,22 @@ namespace tools
       {
       }
     };
-
+    //----------------------------------------------------------------------------------------------------
+    struct multisig_export_needed : public wallet_runtime_error
+    {
+      explicit multisig_export_needed(std::string&& loc)
+        : wallet_runtime_error(std::move(loc), "This signature was made with stale data: export fresh multisig data, which other participants must then use")
+      {
+      }
+    };
+    //----------------------------------------------------------------------------------------------------
+    struct multisig_import_needed : public wallet_runtime_error
+    {
+      explicit multisig_import_needed(std::string&& loc)
+        : wallet_runtime_error(std::move(loc), "Not enough multisig data was found to sign: import multisig data from more other participants")
+      {
+      }
+    };
     //----------------------------------------------------------------------------------------------------
     const char* const file_error_messages[] = {
       "file already exists",
diff --git a/src/wallet/wallet_rpc_server.cpp b/src/wallet/wallet_rpc_server.cpp
index e790b9954..ab911d0ef 100644
--- a/src/wallet/wallet_rpc_server.cpp
+++ b/src/wallet/wallet_rpc_server.cpp
@@ -324,6 +324,7 @@ namespace tools
     {
       res.balance = m_wallet->balance(req.account_index);
       res.unlocked_balance = m_wallet->unlocked_balance(req.account_index);
+      res.multisig_import_needed = m_wallet->multisig() && m_wallet->has_multisig_partial_key_images();
       std::map<uint32_t, uint64_t> balance_per_subaddress = m_wallet->balance_per_subaddress(req.account_index);
       std::map<uint32_t, uint64_t> unlocked_balance_per_subaddress = m_wallet->unlocked_balance_per_subaddress(req.account_index);
       std::vector<tools::wallet2::transfer_details> transfers;
diff --git a/src/wallet/wallet_rpc_server_commands_defs.h b/src/wallet/wallet_rpc_server_commands_defs.h
index e084d9e6d..cf35cc48d 100644
--- a/src/wallet/wallet_rpc_server_commands_defs.h
+++ b/src/wallet/wallet_rpc_server_commands_defs.h
@@ -78,11 +78,13 @@ namespace wallet_rpc
     {
       uint64_t 	 balance;
       uint64_t 	 unlocked_balance;
+      bool       multisig_import_needed;
       std::vector<per_subaddress_info> per_subaddress;
 
       BEGIN_KV_SERIALIZE_MAP()
         KV_SERIALIZE(balance)
         KV_SERIALIZE(unlocked_balance)
+        KV_SERIALIZE(multisig_import_needed)
         KV_SERIALIZE(per_subaddress)
       END_KV_SERIALIZE_MAP()
     };
diff --git a/tests/unit_tests/ringct.cpp b/tests/unit_tests/ringct.cpp
index ef6151efb..6956179c1 100644
--- a/tests/unit_tests/ringct.cpp
+++ b/tests/unit_tests/ringct.cpp
@@ -111,7 +111,7 @@ TEST(ringct, MG_sigs)
             sk[j] = xm[ind][j];
         }
         key message = identity();
-        mgSig IIccss = MLSAG_Gen(message, P, sk, ind, R);
+        mgSig IIccss = MLSAG_Gen(message, P, sk, NULL, NULL, ind, R);
         ASSERT_TRUE(MLSAG_Ver(message, P, IIccss, R));
 
         //#MG sig: false one
@@ -132,7 +132,7 @@ TEST(ringct, MG_sigs)
             sk[j] = xx[ind][j];
         }
         sk[2] = skGen();//asume we don't know one of the private keys..
-        IIccss = MLSAG_Gen(message, P, sk, ind, R);
+        IIccss = MLSAG_Gen(message, P, sk, NULL, NULL, ind, R);
         ASSERT_FALSE(MLSAG_Ver(message, P, IIccss, R));
 }
 
@@ -171,7 +171,7 @@ TEST(ringct, range_proofs)
         destinations.push_back(Pk);
 
         //compute rct data with mixin 500
-        rctSig s = genRct(rct::zero(), sc, pc, destinations, amounts, amount_keys, 3);
+        rctSig s = genRct(rct::zero(), sc, pc, destinations, amounts, amount_keys, NULL, NULL, 3);
 
         //verify rct data
         ASSERT_TRUE(verRct(s));
@@ -188,7 +188,7 @@ TEST(ringct, range_proofs)
 
 
         //compute rct data with mixin 500
-        s = genRct(rct::zero(), sc, pc, destinations, amounts, amount_keys, 3);
+        s = genRct(rct::zero(), sc, pc, destinations, amounts, amount_keys, NULL, NULL, 3);
 
         //verify rct data
         ASSERT_FALSE(verRct(s));
@@ -235,7 +235,7 @@ TEST(ringct, range_proofs_with_fee)
         destinations.push_back(Pk);
 
         //compute rct data with mixin 500
-        rctSig s = genRct(rct::zero(), sc, pc, destinations, amounts, amount_keys, 3);
+        rctSig s = genRct(rct::zero(), sc, pc, destinations, amounts, amount_keys, NULL, NULL, 3);
 
         //verify rct data
         ASSERT_TRUE(verRct(s));
@@ -252,7 +252,7 @@ TEST(ringct, range_proofs_with_fee)
 
 
         //compute rct data with mixin 500
-        s = genRct(rct::zero(), sc, pc, destinations, amounts, amount_keys, 3);
+        s = genRct(rct::zero(), sc, pc, destinations, amounts, amount_keys, NULL, NULL, 3);
 
         //verify rct data
         ASSERT_FALSE(verRct(s));
@@ -310,7 +310,7 @@ TEST(ringct, simple)
         //compute sig with mixin 2
         xmr_amount txnfee = 1;
 
-        rctSig s = genRctSimple(message, sc, pc, destinations,inamounts, outamounts, amount_keys, txnfee, 2);
+        rctSig s = genRctSimple(message, sc, pc, destinations,inamounts, outamounts, amount_keys, NULL, NULL, txnfee, 2);
 
         //verify ring ct signature
         ASSERT_TRUE(verRctSimple(s));
@@ -344,7 +344,7 @@ static rct::rctSig make_sample_rct_sig(int n_inputs, const uint64_t input_amount
         }
     }
 
-    return genRct(rct::zero(), sc, pc, destinations, amounts, amount_keys, 3);;
+    return genRct(rct::zero(), sc, pc, destinations, amounts, amount_keys, NULL, NULL, 3);;
 }
 
 static rct::rctSig make_sample_simple_rct_sig(int n_inputs, const uint64_t input_amounts[], int n_outputs, const uint64_t output_amounts[], uint64_t fee)
@@ -370,7 +370,7 @@ static rct::rctSig make_sample_simple_rct_sig(int n_inputs, const uint64_t input
         destinations.push_back(Pk);
     }
 
-    return genRctSimple(rct::zero(), sc, pc, destinations, inamounts, outamounts, amount_keys, fee, 3);;
+    return genRctSimple(rct::zero(), sc, pc, destinations, inamounts, outamounts, amount_keys, NULL, NULL, fee, 3);;
 }
 
 static bool range_proof_test(bool expected_valid,
diff --git a/tests/unit_tests/serialization.cpp b/tests/unit_tests/serialization.cpp
index 0750ab7d1..9e76efadf 100644
--- a/tests/unit_tests/serialization.cpp
+++ b/tests/unit_tests/serialization.cpp
@@ -591,7 +591,7 @@ TEST(Serialization, serializes_ringct_types)
   rct::skpkGen(Sk, Pk);
   destinations.push_back(Pk);
   //compute rct data with mixin 500
-  s0 = rct::genRct(rct::zero(), sc, pc, destinations, amounts, amount_keys, 3);
+  s0 = rct::genRct(rct::zero(), sc, pc, destinations, amounts, amount_keys, NULL, NULL, 3);
 
   mg0 = s0.p.MGs[0];
   ASSERT_TRUE(serialization::dump_binary(mg0, blob));