Replace Digest-related blanket impls with methods

signature-crate/src/signature.rs

@@ -22,19 +22,3 @@ pub trait Signature: AsRef<[u8]> + Debug + Sized {
         self.as_slice().into()
     }
 }
-
-/// Marker trait for `Signature` types computable as `S(H(m))`
-///
-/// - `S`: signature algorithm
-/// - `H`: hash (a.k.a. digest) function
-/// - `m`: message
-///
-/// For signature types that implement this trait, a blanket impl of
-/// `Signer` will be provided for all types that `impl DigestSigner`
-/// along with a corresponding impl of `Verifier` for all types that
-/// `impl DigestVerifier`.
-#[cfg(feature = "digest")]
-pub trait DigestSignature: Signature {
-    /// Preferred `Digest` algorithm to use when computing this signature type.
-    type Digest: digest::Digest;
-}

signature-crate/src/signer.rs

@@ -1,10 +1,7 @@
 //! Traits for generating digital signatures
 
 #[cfg(feature = "digest")]
-use crate::{
-    digest::{generic_array::GenericArray, Digest},
-    signature::DigestSignature,
-};
+use crate::digest::{generic_array::GenericArray, Digest};
 use crate::{error::Error, Signature};
 
 /// Sign the provided message bytestring using `Self` (e.g. a cryptographic key
@@ -30,7 +27,22 @@ where
     D: Digest,
     S: Signature,
 {
+    /// Sign the computed digest of the given message.
+    ///
+    /// Panics in the event of a signing error.
+    fn sign_msg_digest(&self, msg: &[u8]) -> S {
+        self.try_sign_msg_digest(msg)
+            .expect("signature operation failed")
+    }
+
+    /// Attempt to sign the computed digest of the given message.
+    fn try_sign_msg_digest(&self, msg: &[u8]) -> Result<S, Error> {
+        self.try_sign_digest(D::digest(msg))
+    }
+
     /// Sign the given prehashed message `Digest`, returning a signature.
+    ///
+    /// Panics in the event of a signing error.
     fn sign_digest(&self, digest: GenericArray<u8, D::OutputSize>) -> S {
         self.try_sign_digest(digest)
             .expect("signature operation failed")
@@ -40,14 +52,3 @@ where
     /// digital signature on success, or an error if something went wrong.
     fn try_sign_digest(&self, digest: GenericArray<u8, D::OutputSize>) -> Result<S, Error>;
 }
-
-#[cfg(feature = "digest")]
-impl<S, T> Signer<S> for T
-where
-    S: DigestSignature,
-    T: DigestSigner<S::Digest, S>,
-{
-    fn try_sign(&self, msg: &[u8]) -> Result<S, Error> {
-        self.try_sign_digest(S::Digest::digest(msg))
-    }
-}

signature-crate/src/verifier.rs

@@ -1,10 +1,7 @@
 //! Trait for verifying digital signatures
 
 #[cfg(feature = "digest")]
-use crate::{
-    digest::{generic_array::GenericArray, Digest},
-    signature::DigestSignature,
-};
+use crate::digest::{generic_array::GenericArray, Digest};
 use crate::{error::Error, Signature};
 
 /// Verify the provided message bytestring using `Self` (e.g. a public key)
@@ -24,21 +21,15 @@ where
     D: Digest,
     S: Signature,
 {
-    /// Verify the signature against the given `Digest`
+    /// Verify the signature against the computed `Digest` output.
+    fn verify_msg_digest(&self, msg: &[u8], signature: &S) -> Result<(), Error> {
+        self.verify_digest(D::digest(msg), signature)
+    }
+
+    /// Verify the signature against the given `Digest` output.
     fn verify_digest(
         &self,
         digest: GenericArray<u8, D::OutputSize>,
         signature: &S,
     ) -> Result<(), Error>;
 }
-
-#[cfg(feature = "digest")]
-impl<S, T> Verifier<S> for T
-where
-    S: DigestSignature,
-    T: DigestVerifier<S::Digest, S>,
-{
-    fn verify(&self, msg: &[u8], signature: &S) -> Result<(), Error> {
-        self.verify_digest(S::Digest::digest(msg), signature)
-    }
-}