k256: impl Eq/PartialEq/ConstantTimeEq for SigningKey (#359)

The `Eq`/`PartialEq` impls use `ConstantTimeEq` internally. This is useful for writing tests that need to compare keys.
RustCrypto · Jun 14, 2021 · 4fa72c0 · 4fa72c0
1 parent 08a3f6f
commit 4fa72c0
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Showing 3 changed files with 18 additions and 3 deletions.
diff --git a/Cargo.lock b/Cargo.lock
diff --git a/k256/Cargo.toml b/k256/Cargo.toml
@@ -18,7 +18,7 @@ keywords = ["bitcoin", "crypto", "ecc", "ethereum", "secp256k1"]
 
 [dependencies]
 cfg-if = "1.0"
-elliptic-curve = { version = "0.10", default-features = false, features = ["hazmat"] }
+elliptic-curve = { version = "0.10.2", default-features = false, features = ["hazmat"] }
 
 # optional dependencies
 hex-literal = { version = "0.3", optional = true }

diff --git a/k256/src/ecdsa/sign.rs b/k256/src/ecdsa/sign.rs
@@ -18,6 +18,7 @@ use elliptic_curve::{
     consts::U32,
     ops::Invert,
     rand_core::{CryptoRng, RngCore},
+    subtle::{Choice, ConstantTimeEq},
 };
 
 #[cfg(any(feature = "keccak256", feature = "sha256"))]
@@ -189,13 +190,27 @@ impl RecoverableSignPrimitive<Secp256k1> for Scalar {
     }
 }
 
+impl ConstantTimeEq for SigningKey {
+    fn ct_eq(&self, other: &Self) -> Choice {
+        self.inner.ct_eq(&other.inner)
+    }
+}
+
 impl Debug for SigningKey {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // TODO(tarcieri): use `finish_non_exhaustive` when stable
         f.debug_tuple("SigningKey").field(&"...").finish()
     }
 }
 
+impl Eq for SigningKey {}
+
+impl PartialEq for SigningKey {
+    fn eq(&self, other: &SigningKey) -> bool {
+        self.ct_eq(other).into()
+    }
+}
+
 impl From<SecretKey> for SigningKey {
     fn from(secret_key: SecretKey) -> SigningKey {
         Self::from(&secret_key)