ecdsa: provide a SigningKey::try_from_rng

Cargo.toml

@@ -35,15 +35,19 @@ sha3 = { git = "https://github.com/RustCrypto/hashes.git" }
 
 # https://github.com/RustCrypto/traits/pull/1751
 # https://github.com/RustCrypto/traits/pull/1767
-elliptic-curve = { git = "https://github.com/RustCrypto/traits.git" }
+# https://github.com/RustCrypto/traits/pull/1774
+elliptic-curve = { git = "https://github.com/baloo/traits.git", branch = "baloo/elliptic-curve/scalar-try-from-rng" }
 signature      = { git = "https://github.com/RustCrypto/traits.git" }
 
 # https://github.com/RustCrypto/crypto-bigint/pull/762
 # https://github.com/RustCrypto/crypto-bigint/pull/765
 crypto-bigint = { git = "https://github.com/RustCrypto/crypto-bigint.git" }
 
 # https://github.com/zkcrypto/ff/pull/122
-ff = { git = "https://github.com/pinkforest/ff.git", branch = "bump-rand-core" }
+# https://github.com/zkcrypto/ff/pull/126
+# https://github.com/zkcrypto/ff/pull/127
+ff = { git = "https://github.com/baloo/ff.git", branch = "baloo/try_from_rng" }
+
 # https://github.com/zkcrypto/group/pull/56
 group = { git = "https://github.com/pinkforest/group.git", branch = "bump-rand-0.9" }
 

ecdsa/src/signing.rs

@@ -85,6 +85,13 @@ where
         NonZeroScalar::<C>::random(rng).into()
     }
 
+    /// Generate a cryptographically random [`SigningKey`].
+    pub fn try_from_rng<R: TryCryptoRng + ?Sized>(
+        rng: &mut R,
+    ) -> core::result::Result<Self, R::Error> {
+        Ok(NonZeroScalar::<C>::try_from_rng(rng)?.into())
+    }
+
     /// Initialize signing key from a raw scalar serialized as a byte array.
     pub fn from_bytes(bytes: &FieldBytes<C>) -> Result<Self> {
         SecretKey::<C>::from_bytes(bytes)