Errors caused by protocol violations should contain the misbehaving p… (#341)

Errors caused by protocol violations should contain the misbehaving party.

frost-core/src/error.rs

@@ -46,7 +46,10 @@ pub enum Error<C: Ciphersuite> {
     },
     /// Secret share verification failed.
     #[error("Invalid secret share.")]
-    InvalidSecretShare,
+    InvalidSecretShare {
+        /// The identifier of the signer whose share validation failed.
+        identifier: Identifier<C>,
+    },
     /// Round 1 package not found for Round 2 participant.
     #[error("Round 1 package not found for Round 2 participant.")]
     PackageNotFound,
@@ -61,7 +64,10 @@ pub enum Error<C: Ciphersuite> {
     DKGNotSupported,
     /// The proof of knowledge is not valid.
     #[error("The proof of knowledge is not valid.")]
-    InvalidProofOfKnowledge,
+    InvalidProofOfKnowledge {
+        /// The identifier of the signer whose share validation failed.
+        sender: Identifier<C>,
+    },
     /// Error in scalar Field.
     #[error("Error in scalar Field.")]
     FieldError(#[from] FieldError),

frost-core/src/frost/keys.rs

@@ -299,7 +299,9 @@ where
         let result = evaluate_vss(&self.commitment, self.identifier);
 
         if !(f_result == result) {
-            return Err(Error::InvalidSecretShare);
+            return Err(Error::InvalidSecretShare {
+                identifier: self.identifier,
+            });
         }
 
         let group_public = VerifyingKey {

frost-core/src/frost/keys/dkg.rs

@@ -197,7 +197,7 @@ pub fn part2<C: Ciphersuite>(
         let c_ell = challenge::<C>(ell, &R_ell, &phi_ell0).ok_or(Error::DKGNotSupported)?;
 
         if R_ell != <C::Group>::generator() * mu_ell - phi_ell0 * c_ell.0 {
-            return Err(Error::InvalidProofOfKnowledge);
+            return Err(Error::InvalidProofOfKnowledge { sender: ell });
         }
 
         // Round 2, Step 1