From 23623f57ed26315834d6b2ab5b4901563e55105a Mon Sep 17 00:00:00 2001
From: Charles Edward Gagnon <76854355+carloskiki@users.noreply.github.com>
Date: Sun, 6 Jul 2025 11:02:27 -0400
Subject: [PATCH] ecdsa: remove implementations of `PrehashSignature` (#1007)

---
 ecdsa/CHANGELOG.md  |  5 +++++
 ecdsa/src/der.rs    | 10 ----------
 ecdsa/src/hazmat.rs | 25 ++-----------------------
 3 files changed, 7 insertions(+), 33 deletions(-)

diff --git a/ecdsa/CHANGELOG.md b/ecdsa/CHANGELOG.md
index 77609d8..e94b910 100644
--- a/ecdsa/CHANGELOG.md
+++ b/ecdsa/CHANGELOG.md
@@ -4,6 +4,11 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Removed
+- `signature::PrehashSignature` implementation for `Signature` ([#1007])
+
 ## 0.16.9 (2023-11-16)
 ### Changed
 - Loosen `signature` bound to `2.0, <2.3` ([#756])
diff --git a/ecdsa/src/der.rs b/ecdsa/src/der.rs
index a8d8cfa..89ca193 100644
--- a/ecdsa/src/der.rs
+++ b/ecdsa/src/der.rs
@@ -393,16 +393,6 @@ fn find_scalar_range(outer: &[u8], inner: &[u8]) -> Result<Range<usize>> {
     Ok(Range { start, end })
 }
 
-#[cfg(all(feature = "digest", feature = "hazmat"))]
-impl<C> signature::PrehashSignature for Signature<C>
-where
-    C: EcdsaCurve + crate::hazmat::DigestAlgorithm,
-    MaxSize<C>: ArraySize,
-    <FieldBytesSize<C> as Add>::Output: Add<MaxOverhead> + ArraySize,
-{
-    type Digest = C::Digest;
-}
-
 #[cfg(all(test, feature = "arithmetic"))]
 mod tests {
     use elliptic_curve::dev::MockCurve;
diff --git a/ecdsa/src/hazmat.rs b/ecdsa/src/hazmat.rs
index ad64400..d1f87f4 100644
--- a/ecdsa/src/hazmat.rs
+++ b/ecdsa/src/hazmat.rs
@@ -28,30 +28,18 @@ use {
 };
 
 #[cfg(feature = "digest")]
-use {
-    elliptic_curve::FieldBytesSize,
-    signature::{
-        PrehashSignature,
-        digest::{Digest, FixedOutput, FixedOutputReset, block_api::BlockSizeUser},
-    },
-};
+use signature::digest::{Digest, FixedOutput, FixedOutputReset, block_api::BlockSizeUser};
 
 #[cfg(feature = "rfc6979")]
 use elliptic_curve::FieldBytesEncoding;
 
-#[cfg(any(feature = "arithmetic", feature = "digest"))]
+#[cfg(any(feature = "arithmetic", feature = "rfc6979"))]
 use crate::{Signature, elliptic_curve::array::ArraySize};
 
 /// Bind a preferred [`Digest`] algorithm to an elliptic curve type.
 ///
 /// Generally there is a preferred variety of the SHA-2 family used with ECDSA
 /// for a particular elliptic curve.
-///
-/// This trait can be used to specify it, and with it receive a blanket impl of
-/// [`PrehashSignature`], used by [`signature_derive`][1]) for the [`Signature`]
-/// type for a particular elliptic curve.
-///
-/// [1]: https://github.com/RustCrypto/traits/tree/master/signature/derive
 #[cfg(feature = "digest")]
 pub trait DigestAlgorithm: EcdsaCurve {
     /// Preferred digest to use when computing ECDSA signatures for this
@@ -59,15 +47,6 @@ pub trait DigestAlgorithm: EcdsaCurve {
     type Digest: BlockSizeUser + Digest + FixedOutput + FixedOutputReset;
 }
 
-#[cfg(feature = "digest")]
-impl<C> PrehashSignature for Signature<C>
-where
-    C: DigestAlgorithm,
-    <FieldBytesSize<C> as core::ops::Add>::Output: ArraySize,
-{
-    type Digest = C::Digest;
-}
-
 /// Partial implementation of the `bits2int` function as defined in
 /// [RFC6979 § 2.3.2] as well as [SEC1] § 2.3.8.
 ///