MuSig2

docs/limitations.md

@@ -77,6 +77,7 @@
 - derivation path for each cosigner must be known and consistent with PSBT
 - XFP values (fingerprints) MUST be unique for each of the co-signers
 - multisig wallet `name` can only contain printable ASCII characters `range(32, 127)`
+- for taproot multisig (musig) limitations check musig.md
 
 ### BIP-67
 

docs/miniscript.md

@@ -1,7 +1,6 @@
 # Miniscript
 
-**COLDCARD<sup>&reg;</sup>** Mk4 experimental `EDGE` versions
-support Miniscript and MiniTapscript.
+**COLDCARD<sup>&reg;</sup>** `EDGE` versions support Miniscript and MiniTapscript.
 
 ## Import/Export
 

docs/musig.md

@@ -0,0 +1,25 @@
+# MuSig2
+
+**COLDCARD<sup>&reg;</sup>** `EDGE` versions support [MuSig2](https://github.com/bitcoin/bips/blob/master/bip-0327.mediawiki) from version `6.4.2X` & `6.4.2QX`.
+
+COLDCARD implements all following BIPs, further restricting their scope (read more in Limitations section):
+* PSBT fields [BIP-373](https://github.com/bitcoin/bips/blob/master/bip-0373.mediawiki)
+* `musig()` descriptor key expression [BIP-390](https://github.com/bitcoin/bips/blob/master/bip-0390.mediawiki)
+* Derivation Scheme for MuSig2 Aggregate Keys [BIP-328](https://github.com/bitcoin/bips/blob/master/bip-0328.mediawiki)
+
+### Limitations:
+* COLDCARD must stay powered up between 1st and 2nd round as necessary musig session data are stored in volatile memory only
+* `musig()` can only be used inside `tr()` expression as key expression
+* cannot be nested within another `musig()` expression
+* only one own key in `musig()` expression
+* `musig(KEY, KEY, ..., KEY)/<NUM;NUM;...>/*`
+  * all `KEY`s MUST be unique - no repeated keys
+  * `KEY` expression MUST be extended key (not plain pubkey)
+  * `KEY` expression cannot contain child derivation, only `musig()` expression can contain derivation steps 
+  * `KEY`s are sorted prior to aggregation
+  * hardened derivation not allowed for `musig()` expression
+  * derivation must end with `*` - only ranged `musig()` expression allowed, if `musig()` derivation is omitted, `/<0;1>/*` is implied
+* PSBT must contain all the data required by BIP-373
+* COLDCARD strictly differentiate between 1st & 2nd MuSig2 round. If COLDCARD provides nonce, it will not attempt to sign even if it could (a.k.a enough nonces from cosigners are available).
+  To provide both nonce(s) & signature(s) signing needs to be preformed twice.
+* keys from WIF Store cannot be used for MuSig2 signing

releases/EdgeChangeLog.md

@@ -13,24 +13,22 @@ This lists the changes in the most recent EDGE firmware, for each hardware platf
 
 # Shared Improvements - Both Mk4 and Q
 
-- New Feature: Support for v3 transactions
-- New Feature: Send keystrokes with all derived BIP-85 secrets
-- Enhancement: CCC allow to reset block height
+- New Feature: Ability to sign MuSig2 UTXOs. Read more [here](docs/musig.md)  TODO proper link
 - Bugfix: PSBT global XPUBs validation when signing with specific wallet
 - Bugfix: Do not allow sighash DEFAULT outside taproot context
 
 # Mk4 Specific Changes
 
-## 6.4.1X - 2026-xx-xx
+## 6.5.0X - 2026-03-24
 
-- todo
+- synced with master up to `5.5.0`
 
 
 # Q Specific Changes
 
-## 6.4.0QX - 2026-xx-xx
+## 6.5.0QX - 2026-03-24
 
-- todo
+- synced with master up to `1.4.0Q`
 
 
 # Release History

shared/auth.py

@@ -8,6 +8,7 @@
 from ubinascii import hexlify as b2a_hex
 from ubinascii import unhexlify as a2b_hex
 from uhashlib import sha256
+from ustruct import pack
 from public_constants import AFC_SCRIPT, AF_CLASSIC, AFC_BECH32, SUPPORTED_ADDR_FORMATS, AF_P2TR
 from public_constants import STXN_FINALIZE, STXN_VISUALIZE, STXN_SIGNED, AF_P2SH, AF_P2WPKH_P2SH
 from sffile import SFFile
@@ -275,8 +276,10 @@ async def try_push_tx(data, txid, txn_sha=None):
 
 class ApproveTransaction(UserAuthorizedAction):
     def __init__(self, psbt_len, flags=None, psbt_sha=None, input_method=None,
-                 output_encoder=None, filename=None, miniscript_wallet=None):
+                 output_encoder=None, filename=None, miniscript_wallet=None,
+                 offset=TXN_INPUT_OFFSET):
         super().__init__()
+        self.offset = offset
         self.psbt_len = psbt_len
 
         # do finalize is None if not USB, None = decide based on is_complete
@@ -405,7 +408,7 @@ async def interact(self):
         # step 1: parse PSBT from PSRAM into in-memory objects.
 
         try:
-            with SFFile(TXN_INPUT_OFFSET, length=self.psbt_len, message='Reading...') as fd:
+            with SFFile(self.offset, length=self.psbt_len, message='Reading...') as fd:
                 # NOTE: psbtObject captures the file descriptor and uses it later
                 self.psbt = psbtObject.read_psbt(fd)
         except BaseException as exc:
@@ -433,6 +436,9 @@ async def interact(self):
             # which outputs are change
             self.psbt.consider_dangerous_sighash()
 
+            if self.psbt.session:
+                self.psbt.session.update(pack('<I', self.psbt.lock_time))
+
         except FraudulentChangeOutput as exc:
             # sys.print_exception(exc)
             #print('FraudulentChangeOutput: ' + exc.args[0])
@@ -769,13 +775,14 @@ def output_summary_text(self, msg):
                 msg.write('%s %s\n\n' % self.chain.render_value(total_change - visible_change_sum))
 
 
-def sign_transaction(psbt_len, flags=0x0, psbt_sha=None, miniscript_wallet=None):
+def sign_transaction(psbt_len, flags=0x0, psbt_sha=None, miniscript_wallet=None,
+                     offset=TXN_INPUT_OFFSET):
     # transaction (binary) loaded into PSRAM already, checksum checked
     # optional miniscript_wallet arg, choose particular enrolled wallet by name to sign
     UserAuthorizedAction.check_busy(ApproveTransaction)
     UserAuthorizedAction.active_request = ApproveTransaction(
         psbt_len, flags, psbt_sha=psbt_sha, input_method="usb",
-        miniscript_wallet=miniscript_wallet,
+        miniscript_wallet=miniscript_wallet, offset=offset
     )
 
     # kill any menu stack, and put our thing at the top
@@ -816,6 +823,7 @@ async def done_signing(psbt, tx_req, input_method=None, filename=None,
     first_time = True
     msg = None
     title = None
+    base_title = "PSBT " + ("Signed" if psbt.sig_added else "Updated")
 
     is_complete = psbt.is_complete()
     if finalize is not None:
@@ -849,7 +857,7 @@ async def done_signing(psbt, tx_req, input_method=None, filename=None,
 
         first_time = False
         msg = noun + " shared via USB."
-        title = "PSBT Signed"
+        title = base_title
 
     if txid and await try_push_tx(data_len, txid, data_sha2):
         # go directly to reexport menu after pushTX
@@ -929,8 +937,9 @@ async def done_signing(psbt, tx_req, input_method=None, filename=None,
         elif (ch == 't') and not is_complete:
             # they might want to teleport it, but only if we have PSBT
             # there is no need to teleport PSBT if txn is already complete & ready to be broadcast
+            # updated PSBT is at TXN_OUTPUT_OFFSET (at TXN_INPUT_OFFSET is PSBT that is NOT updated)
             from teleport import kt_send_psbt
-            ok = await kt_send_psbt(psbt, data_len)
+            ok = await kt_send_psbt(psbt, data_len, psbt_offset=TXN_OUTPUT_OFFSET)
             if ok:
                 title = "Sent by Teleport"
             else:
@@ -946,7 +955,7 @@ async def done_signing(psbt, tx_req, input_method=None, filename=None,
 
         input_method = None
         first_time = False
-        title = "PSBT Signed"
+        title = base_title
 
 async def _save_to_disk(psbt, txid, save_options, is_complete, data_len, output_encoder, filename=None):
     # Saving a PSBT from PSRAM to something disk-like.
@@ -1806,6 +1815,9 @@ def yield_item(self, offset, end, qr_items, change_idxs):
                     psbt_item += "Multisig: %dof%d\n\n" % (M, N)
                 except: pass
 
+        if inp.is_musig:
+            psbt_item += "MuSig2\n\n"
+
         if inp.part_sigs or inp.taproot_script_sigs:
             # do not show XFPs in case input is fully signed
             # only part_sig should be available, as we haven't signed yet so added_sigs empty

shared/bsms.py

@@ -17,7 +17,7 @@
 from files import CardSlot, CardMissingError, needs_microsd
 from ux import ux_show_story, ux_enter_number, restore_menu, ux_input_text
 from ux import the_ux, _import_prompt_builder, export_prompt_builder
-from descriptor import Descriptor, Key, append_checksum
+from descriptor import Descriptor, ExtendedKey, append_checksum
 from miniscript import Sortedmulti, Number
 from charcodes import KEY_NFC, KEY_QR
 
@@ -686,7 +686,7 @@ def get_token(index):
         )
         version, tok, key_exp, description, sig = data.strip().split("\n")
         assert tok == token, "Token mismatch saved %s, received from signer %s" % (token, tok)
-        key = Key.from_string(key_exp)
+        key = ExtendedKey.from_string(key_exp)
         dis.progress_bar_show(i_div_N / 4)
         msg = signer_data_round1(token, key_exp, description)
         digest = chain.hash_message(msg.encode())