Fix warnings (ZcashFoundation#578)

* Use from_coefficients() instead of evaluate_polynomial() when computing a signing_share (ZcashFoundation#576)

* Refactor BindingFactor::deserialize into from_hex as it's only used for testing (ZcashFoundation#576)

* Remove BindingFactorList::iter() and use directly in vector test (ZcashFoundation#576)

book/src/dev/developer-guide.md

@@ -11,4 +11,4 @@
 Test coverage checks are performed in the pipeline. This is cofigured here: `.github/workflows/coverage.yaml`
 To run these locally:
 1. Install coverage tool by running `cargo install cargo-llvm-cov`
-2. Run `cargo llvm-cov --ignore-filename-regex '.*(tests).*|benches.rs|gencode|helpers.rs` (you may be asked if you want to install `llvm-tools-preview`, if so type `Y`)
+2. Run `cargo llvm-cov --ignore-filename-regex '.*(tests).*|benches.rs|gencode|helpers.rs'` (you may be asked if you want to install `llvm-tools-preview`, if so type `Y`)

frost-core/src/keys.rs

@@ -894,12 +894,12 @@ pub(crate) fn generate_secret_shares<C: Ciphersuite>(
     }
 
     for id in identifiers {
-        let value = evaluate_polynomial(*id, &coefficients);
+        let signing_share = SigningShare::from_coefficients(&coefficients, *id);
 
         secret_shares.push(SecretShare {
             header: Header::default(),
             identifier: *id,
-            signing_share: SigningShare(value),
+            signing_share,
             commitment: commitment.clone(),
         });
     }

frost-core/src/keys/dkg.rs

@@ -421,13 +421,13 @@ pub fn part2<C: Ciphersuite>(
         // > Each P_i securely sends to each other participant P_ℓ a secret share (ℓ, f_i(ℓ)),
         // > deleting f_i and each share afterward except for (i, f_i(i)),
         // > which they keep for themselves.
-        let value = evaluate_polynomial(ell, &secret_package.coefficients);
+        let signing_share = SigningShare::from_coefficients(&secret_package.coefficients, ell);
 
         round2_packages.insert(
             ell,
             round2::Package {
                 header: Header::default(),
-                signing_share: SigningShare(value),
+                signing_share,
             },
         );
     }

frost-core/src/lib.rs

@@ -185,15 +185,6 @@ impl<C> BindingFactor<C>
 where
     C: Ciphersuite,
 {
-    /// Deserializes [`BindingFactor`] from bytes.
-    pub fn deserialize(
-        bytes: <<C::Group as Group>::Field as Field>::Serialization,
-    ) -> Result<Self, Error<C>> {
-        <<C::Group as Group>::Field>::deserialize(&bytes)
-            .map(|scalar| Self(scalar))
-            .map_err(|e| e.into())
-    }
-
     /// Serializes [`BindingFactor`] to bytes.
     pub fn serialize(&self) -> <<C::Group as Group>::Field as Field>::Serialization {
         <<C::Group as Group>::Field>::serialize(&self.0)
@@ -227,11 +218,6 @@ where
         Self(binding_factors)
     }
 
-    /// Return iterator through all factors.
-    pub fn iter(&self) -> impl Iterator<Item = (&Identifier<C>, &BindingFactor<C>)> {
-        self.0.iter()
-    }
-
     /// Get the [`BindingFactor`] for the given identifier, or None if not found.
     pub fn get(&self, key: &Identifier<C>) -> Option<&BindingFactor<C>> {
         self.0.get(key)
@@ -273,8 +259,11 @@ where
 
     fn from_hex<T: AsRef<[u8]>>(hex: T) -> Result<Self, Self::Error> {
         let v: Vec<u8> = FromHex::from_hex(hex).map_err(|_| "invalid hex")?;
+
         match v.try_into() {
-            Ok(bytes) => Self::deserialize(bytes).map_err(|_| "malformed scalar encoding"),
+            Ok(bytes) => <<C::Group as Group>::Field>::deserialize(&bytes)
+                .map(|scalar| Self(scalar))
+                .map_err(|_| "malformed scalar encoding"),
             Err(_) => Err("malformed scalar encoding"),
         }
     }

frost-core/src/tests/vectors.rs

@@ -271,7 +271,7 @@ pub fn check_sign_with_test_vectors<C: Ciphersuite>(json_vectors: &Value) {
     let binding_factor_list: frost::BindingFactorList<C> =
         compute_binding_factor_list(&signing_package, &verifying_key, &[]);
 
-    for (identifier, binding_factor) in binding_factor_list.iter() {
+    for (identifier, binding_factor) in binding_factor_list.0.iter() {
         assert_eq!(*binding_factor, binding_factors[identifier]);
     }