3.3.3 (cont) Add a dedicated Participant type

coins/monero/src/ringct/clsag/multisig.rs

@@ -23,7 +23,7 @@ use dleq::DLEqProof;
 use frost::{
   dkg::lagrange,
   curve::Ed25519,
-  FrostError, ThresholdKeys, ThresholdView,
+  Participant, FrostError, ThresholdKeys, ThresholdView,
   algorithm::{WriteAddendum, Algorithm},
 };
 
@@ -146,8 +146,8 @@ pub(crate) fn add_key_image_share(
   image: &mut EdwardsPoint,
   generator: EdwardsPoint,
   offset: Scalar,
-  included: &[u16],
-  participant: u16,
+  included: &[Participant],
+  participant: Participant,
   share: EdwardsPoint,
 ) {
   if image.is_identity() {
@@ -203,7 +203,7 @@ impl Algorithm<Ed25519> for ClsagMultisig {
   fn process_addendum(
     &mut self,
     view: &ThresholdView<Ed25519>,
-    l: u16,
+    l: Participant,
     addendum: ClsagAddendum,
   ) -> Result<(), FrostError> {
     if self.image.is_identity() {
@@ -212,7 +212,7 @@ impl Algorithm<Ed25519> for ClsagMultisig {
       self.transcript.append_message(b"mask", self.mask().to_bytes());
     }
 
-    self.transcript.append_message(b"participant", l.to_be_bytes());
+    self.transcript.append_message(b"participant", l.to_bytes());
 
     addendum
       .dleq

coins/monero/src/tests/clsag.rs

@@ -24,7 +24,10 @@ use crate::{
 use crate::ringct::clsag::{ClsagDetails, ClsagMultisig};
 
 #[cfg(feature = "multisig")]
-use frost::tests::{key_gen, algorithm_machines, sign};
+use frost::{
+  Participant,
+  tests::{key_gen, algorithm_machines, sign},
+};
 
 const RING_LEN: u64 = 11;
 const AMOUNT: u64 = 1337;
@@ -93,7 +96,7 @@ fn clsag_multisig() {
       mask = random_scalar(&mut OsRng);
       amount = OsRng.next_u64();
     } else {
-      dest = keys[&1].group_key().0;
+      dest = keys[&Participant::new(1).unwrap()].group_key().0;
       mask = randomness;
       amount = AMOUNT;
     }
@@ -103,7 +106,7 @@ fn clsag_multisig() {
   let mask_sum = random_scalar(&mut OsRng);
   let algorithm = ClsagMultisig::new(
     RecommendedTranscript::new(b"Monero Serai CLSAG Test"),
-    keys[&1].group_key().0,
+    keys[&Participant::new(1).unwrap()].group_key().0,
     Arc::new(RwLock::new(Some(ClsagDetails::new(
       ClsagInput::new(
         Commitment::new(randomness, AMOUNT),

coins/monero/src/wallet/send/multisig.rs

@@ -14,7 +14,7 @@ use dalek_ff_group as dfg;
 use transcript::{Transcript, RecommendedTranscript};
 use frost::{
   curve::Ed25519,
-  FrostError, ThresholdKeys,
+  Participant, FrostError, ThresholdKeys,
   sign::{
     Writable, Preprocess, CachedPreprocess, SignatureShare, PreprocessMachine, SignMachine,
     SignatureMachine, AlgorithmMachine, AlgorithmSignMachine, AlgorithmSignatureMachine,
@@ -35,7 +35,7 @@ use crate::{
 /// FROST signing machine to produce a signed transaction.
 pub struct TransactionMachine {
   signable: SignableTransaction,
-  i: u16,
+  i: Participant,
   transcript: RecommendedTranscript,
 
   decoys: Vec<Decoys>,
@@ -48,7 +48,7 @@ pub struct TransactionMachine {
 
 pub struct TransactionSignMachine {
   signable: SignableTransaction,
-  i: u16,
+  i: Participant,
   transcript: RecommendedTranscript,
 
   decoys: Vec<Decoys>,
@@ -236,7 +236,7 @@ impl SignMachine<Transaction> for TransactionSignMachine {
 
   fn sign(
     mut self,
-    mut commitments: HashMap<u16, Self::Preprocess>,
+    mut commitments: HashMap<Participant, Self::Preprocess>,
     msg: &[u8],
   ) -> Result<(TransactionSignatureMachine, Self::SignatureShare), FrostError> {
     if !msg.is_empty() {
@@ -263,7 +263,7 @@ impl SignMachine<Transaction> for TransactionSignMachine {
             // While each CLSAG will do this as they need to for security, they have their own
             // transcripts cloned from this TX's initial premise's transcript. For our TX
             // transcript to have the CLSAG data for entropy, it'll have to be added ourselves here
-            self.transcript.append_message(b"participant", (*l).to_be_bytes());
+            self.transcript.append_message(b"participant", (*l).to_bytes());
 
             let preprocess = if *l == self.i {
               self.our_preprocess[c].clone()
@@ -389,7 +389,7 @@ impl SignatureMachine<Transaction> for TransactionSignatureMachine {
 
   fn complete(
     mut self,
-    shares: HashMap<u16, Self::SignatureShare>,
+    shares: HashMap<Participant, Self::SignatureShare>,
   ) -> Result<Transaction, FrostError> {
     let mut tx = self.tx;
     match tx.rct_signatures.prunable {

coins/monero/tests/runner.rs

@@ -131,6 +131,7 @@ macro_rules! test {
         #[cfg(feature = "multisig")]
         use frost::{
           curve::Ed25519,
+          Participant,
           tests::{THRESHOLD, key_gen},
         };
 
@@ -165,7 +166,7 @@ macro_rules! test {
             #[cfg(not(feature = "multisig"))]
             panic!("Multisig branch called without the multisig feature");
             #[cfg(feature = "multisig")]
-            keys[&1].group_key().0
+            keys[&Participant::new(1).unwrap()].group_key().0
           };
 
           let view = ViewPair::new(spend_pub, Zeroizing::new(random_scalar(&mut OsRng)));
@@ -211,7 +212,7 @@ macro_rules! test {
                 #[cfg(feature = "multisig")]
                 {
                   let mut machines = HashMap::new();
-                  for i in 1 ..= THRESHOLD {
+                  for i in (1 ..= THRESHOLD).map(|i| Participant::new(i).unwrap()) {
                     machines.insert(
                       i,
                       tx