Add BIP-373 PSBT_{IN,OUT}_MUSIG2_PARTICIPANT_PUBKEYS serialization and deserialization

Author: Ademan

bitcoin/src/psbt/map/input.rs

@@ -59,6 +59,8 @@ const PSBT_IN_TAP_BIP32_DERIVATION: u64 = 0x16;
 const PSBT_IN_TAP_INTERNAL_KEY: u64 = 0x17;
 /// Type: Taproot Merkle Root PSBT_IN_TAP_MERKLE_ROOT = 0x18
 const PSBT_IN_TAP_MERKLE_ROOT: u64 = 0x18;
+/// Type: MuSig2 Public Keys Participating in Aggregate Input PSBT_IN_MUSIG2_PARTICIPANT_PUBKEYS = 0x1a
+const PSBT_IN_MUSIG2_PARTICIPANT_PUBKEYS: u64 = 0x1a;
 /// Type: Proprietary Use Type PSBT_IN_PROPRIETARY = 0xFC
 const PSBT_IN_PROPRIETARY: u64 = 0xFC;
 
@@ -113,6 +115,8 @@ pub struct Input {
     pub tap_internal_key: Option<XOnlyPublicKey>,
     /// Taproot Merkle root.
     pub tap_merkle_root: Option<TapNodeHash>,
+    /// Mapping from MuSig2 aggregate keys to the participant keys from which they were aggregated.
+    pub musig2_participant_pubkeys: BTreeMap<secp256k1::PublicKey, Vec<secp256k1::PublicKey>>,
     /// Proprietary key-value pairs for this input.
     pub proprietary: BTreeMap<raw::ProprietaryKey, Vec<u8>>,
     /// Unknown key-value pairs for this input.
@@ -352,6 +356,11 @@ impl Input {
                     self.tap_merkle_root <= <raw_key: _>|< raw_value: TapNodeHash>
                 }
             }
+            PSBT_IN_MUSIG2_PARTICIPANT_PUBKEYS => {
+                impl_psbt_insert_pair! {
+                    self.musig2_participant_pubkeys <= <raw_key: secp256k1::PublicKey>|< raw_value: Vec<secp256k1::PublicKey> >
+                }
+            }
             PSBT_IN_PROPRIETARY => {
                 let key = raw::ProprietaryKey::try_from(raw_key.clone())?;
                 match self.proprietary.entry(key) {
@@ -390,6 +399,7 @@ impl Input {
         self.tap_script_sigs.extend(other.tap_script_sigs);
         self.tap_scripts.extend(other.tap_scripts);
         self.tap_key_origins.extend(other.tap_key_origins);
+        self.musig2_participant_pubkeys.extend(other.musig2_participant_pubkeys);
         self.proprietary.extend(other.proprietary);
         self.unknown.extend(other.unknown);
 
@@ -482,6 +492,11 @@ impl Map for Input {
         impl_psbt_get_pair! {
             rv.push(self.tap_merkle_root, PSBT_IN_TAP_MERKLE_ROOT)
         }
+
+        impl_psbt_get_pair! {
+            rv.push_map(self.musig2_participant_pubkeys, PSBT_IN_MUSIG2_PARTICIPANT_PUBKEYS)
+        }
+
         for (key, value) in self.proprietary.iter() {
             rv.push(raw::Pair { key: key.to_key(), value: value.clone() });
         }

bitcoin/src/psbt/map/output.rs

@@ -20,6 +20,8 @@ const PSBT_OUT_TAP_INTERNAL_KEY: u64 = 0x05;
 const PSBT_OUT_TAP_TREE: u64 = 0x06;
 /// Type: Taproot Key BIP 32 Derivation Path PSBT_OUT_TAP_BIP32_DERIVATION = 0x07
 const PSBT_OUT_TAP_BIP32_DERIVATION: u64 = 0x07;
+/// Type: MuSig2 Public Keys Participating in Aggregate Output PSBT_OUT_MUSIG2_PARTICIPANT_PUBKEYS = 0x08
+const PSBT_OUT_MUSIG2_PARTICIPANT_PUBKEYS: u64 = 0x08;
 /// Type: Proprietary Use Type PSBT_IN_PROPRIETARY = 0xFC
 const PSBT_OUT_PROPRIETARY: u64 = 0xFC;
 
@@ -40,6 +42,8 @@ pub struct Output {
     pub tap_tree: Option<TapTree>,
     /// Map of tap root x only keys to origin info and leaf hashes contained in it.
     pub tap_key_origins: BTreeMap<XOnlyPublicKey, (Vec<TapLeafHash>, KeySource)>,
+    /// Mapping from MuSig2 aggregate keys to the participant keys from which they were aggregated.
+    pub musig2_participant_pubkeys: BTreeMap<secp256k1::PublicKey, Vec<secp256k1::PublicKey>>,
     /// Proprietary key-value pairs for this output.
     pub proprietary: BTreeMap<raw::ProprietaryKey, Vec<u8>>,
     /// Unknown key-value pairs for this output.
@@ -90,6 +94,11 @@ impl Output {
                     self.tap_key_origins <= <raw_key: XOnlyPublicKey>|< raw_value: (Vec<TapLeafHash>, KeySource)>
                 }
             }
+            PSBT_OUT_MUSIG2_PARTICIPANT_PUBKEYS => {
+                impl_psbt_insert_pair! {
+                    self.musig2_participant_pubkeys <= <raw_key: secp256k1::PublicKey>|< raw_value: Vec<secp256k1::PublicKey> >
+                }
+            }
             _ => match self.unknown.entry(raw_key) {
                 btree_map::Entry::Vacant(empty_key) => {
                     empty_key.insert(raw_value);
@@ -107,6 +116,7 @@ impl Output {
         self.proprietary.extend(other.proprietary);
         self.unknown.extend(other.unknown);
         self.tap_key_origins.extend(other.tap_key_origins);
+        self.musig2_participant_pubkeys.extend(other.musig2_participant_pubkeys);
 
         combine!(redeem_script, self, other);
         combine!(witness_script, self, other);
@@ -143,6 +153,10 @@ impl Map for Output {
             rv.push_map(self.tap_key_origins, PSBT_OUT_TAP_BIP32_DERIVATION)
         }
 
+        impl_psbt_get_pair! {
+            rv.push_map(self.musig2_participant_pubkeys, PSBT_OUT_MUSIG2_PARTICIPANT_PUBKEYS)
+        }
+
         for (key, value) in self.proprietary.iter() {
             rv.push(raw::Pair { key: key.to_key(), value: value.clone() });
         }

bitcoin/src/psbt/serialize.rs

@@ -172,6 +172,28 @@ impl Deserialize for secp256k1::PublicKey {
     }
 }
 
+impl Serialize for Vec<secp256k1::PublicKey> {
+    fn serialize(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = Vec::with_capacity(secp256k1::constants::PUBLIC_KEY_SIZE * self.len());
+
+        for pubkey in self.iter() {
+            result.extend(Serialize::serialize(pubkey));
+        }
+
+        result
+    }
+}
+
+impl Deserialize for Vec<secp256k1::PublicKey> {
+    fn deserialize(bytes: &[u8]) -> Result<Self, Error> {
+        bytes.chunks(secp256k1::constants::PUBLIC_KEY_SIZE)
+            .map(|pubkey_bytes| {
+                secp256k1::PublicKey::deserialize(pubkey_bytes)
+            })
+            .collect()
+    }
+}
+
 impl Serialize for ecdsa::Signature {
     fn serialize(&self) -> Vec<u8> { self.to_vec() }
 }