From afddda0fa51da361216cd16a6380c2af6aaa3fcc Mon Sep 17 00:00:00 2001
From: Michael Rosenberg <michael@mrosenberg.pub>
Date: Sat, 4 Sep 2021 18:00:18 -0400
Subject: [PATCH 1/4] Wrote a stateful signer trait

---
 signature/src/signer.rs | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/signature/src/signer.rs b/signature/src/signer.rs
index 0031b73a7..1b079a467 100644
--- a/signature/src/signer.rs
+++ b/signature/src/signer.rs
@@ -24,6 +24,22 @@ pub trait Signer<S: Signature> {
     fn try_sign(&self, msg: &[u8]) -> Result<S, Error>;
 }
 
+/// Sign the provided message bytestring using `&mut Self` (e.g., an evolving
+/// cryptographic key), returning a digital signature.
+pub trait StatefulSigner<S: Signature> {
+    /// Sign the given message, update the state, and return a digital signature
+    fn sign(&mut self, msg: &[u8]) -> S {
+        self.try_sign(msg).expect("signature operation failed")
+    }
+
+    /// Attempt to sign the given message, updating the state, and returning a
+    /// digital signature on success, or an error if something went wrong.
+    ///
+    /// Signing can fail, e.g., if the number of time periods allowed by the
+    /// current key is exceeded.
+    fn try_sign(&mut self, msg: &[u8]) -> Result<S, Error>;
+}
+
 /// Sign the given prehashed message [`Digest`] using `Self`.
 ///
 /// ## Notes

From be3784d84e17268b85109f6c2ddc75e21f9eb4ec Mon Sep 17 00:00:00 2001
From: Michael Rosenberg <michael@mrosenberg.pub>
Date: Sat, 4 Sep 2021 18:01:08 -0400
Subject: [PATCH 2/4] Updated CHANGELOG

---
 signature/CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/signature/CHANGELOG.md b/signature/CHANGELOG.md
index 847134ef8..33982b4e4 100644
--- a/signature/CHANGELOG.md
+++ b/signature/CHANGELOG.md
@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Re-export `rand_core`. Emit compilation error if unstable functionality
 is enabled by bypassing the preview features. ([#683])
+- Defined the `StatefulSigner` trait
 
 [#683]: https://github.com/RustCrypto/traits/pull/683
 

From e0942e4e333f9f430f2b4ba26a10655ed63c8905 Mon Sep 17 00:00:00 2001
From: Michael Rosenberg <michael@mrosenberg.pub>
Date: Sat, 4 Sep 2021 22:21:32 -0400
Subject: [PATCH 3/4] Renamed StatefulSigner -> SignerMut

---
 signature/CHANGELOG.md  | 2 +-
 signature/src/signer.rs | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/signature/CHANGELOG.md b/signature/CHANGELOG.md
index 33982b4e4..b21101d9e 100644
--- a/signature/CHANGELOG.md
+++ b/signature/CHANGELOG.md
@@ -8,7 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Re-export `rand_core`. Emit compilation error if unstable functionality
 is enabled by bypassing the preview features. ([#683])
-- Defined the `StatefulSigner` trait
+- Defined the `SignerMut` trait
 
 [#683]: https://github.com/RustCrypto/traits/pull/683
 
diff --git a/signature/src/signer.rs b/signature/src/signer.rs
index 1b079a467..bbcce56c8 100644
--- a/signature/src/signer.rs
+++ b/signature/src/signer.rs
@@ -26,7 +26,7 @@ pub trait Signer<S: Signature> {
 
 /// Sign the provided message bytestring using `&mut Self` (e.g., an evolving
 /// cryptographic key), returning a digital signature.
-pub trait StatefulSigner<S: Signature> {
+pub trait SignerMut<S: Signature> {
     /// Sign the given message, update the state, and return a digital signature
     fn sign(&mut self, msg: &[u8]) -> S {
         self.try_sign(msg).expect("signature operation failed")

From ab016e02d1c3fbb56d1b1421e62572dd716a4c9a Mon Sep 17 00:00:00 2001
From: Michael Rosenberg <michael@mrosenberg.pub>
Date: Sun, 5 Sep 2021 10:29:15 -0400
Subject: [PATCH 4/4] Wrote blanket impl for SignerMut for all Signer types

---
 signature/src/signer.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/signature/src/signer.rs b/signature/src/signer.rs
index bbcce56c8..8ec1099c3 100644
--- a/signature/src/signer.rs
+++ b/signature/src/signer.rs
@@ -40,6 +40,17 @@ pub trait SignerMut<S: Signature> {
     fn try_sign(&mut self, msg: &[u8]) -> Result<S, Error>;
 }
 
+// Blanket impl of SignerMut for all Signer types
+impl<T, S> SignerMut<S> for T
+where
+    T: Signer<S>,
+    S: Signature,
+{
+    fn try_sign(&mut self, msg: &[u8]) -> Result<S, Error> {
+        T::try_sign(&self, msg)
+    }
+}
+
 /// Sign the given prehashed message [`Digest`] using `Self`.
 ///
 /// ## Notes