From 25debdc051ae38cbfe06a9be1ff0886e7fd18f8c Mon Sep 17 00:00:00 2001
From: Jazz Turner-Baggs <473256+jazzz@users.noreply.github.com>
Date: Mon, 27 Apr 2026 13:35:20 -0700
Subject: [PATCH] Add Signature + Verifying key types (#93)

---
 Cargo.lock                    |  1 +
 core/crypto/Cargo.toml        |  2 +-
 core/crypto/src/lib.rs        |  2 +
 core/crypto/src/signatures.rs | 83 +++++++++++++++++++++++++++++++++++
 4 files changed, 87 insertions(+), 1 deletion(-)
 create mode 100644 core/crypto/src/signatures.rs

diff --git a/Cargo.lock b/Cargo.lock
index e763180..c26b345 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -639,6 +639,7 @@ checksum = "70e796c081cee67dc755e1a36a0a172b897fab85fc3f6bc48307991f64e4eca9"
 dependencies = [
  "curve25519-dalek",
  "ed25519",
+ "rand_core 0.6.4",
  "serde",
  "sha2",
  "subtle",
diff --git a/core/crypto/Cargo.toml b/core/crypto/Cargo.toml
index 2c688f3..04100aa 100644
--- a/core/crypto/Cargo.toml
+++ b/core/crypto/Cargo.toml
@@ -8,7 +8,7 @@ x25519-dalek = { version = "2.0.1", features = ["static_secrets"] }
 hkdf = "0.12"
 sha2 = "0.10"
 rand_core = { version = "0.6", features = ["getrandom"] }
-ed25519-dalek = "2.2.0"
+ed25519-dalek = { version = "2.2.0", features = ["rand_core"] }
 xeddsa = "1.0.2"
 zeroize = {version = "1.8.2", features= ["derive"]}
 generic-array = "1.3.5"
diff --git a/core/crypto/src/lib.rs b/core/crypto/src/lib.rs
index fff9cd2..1759091 100644
--- a/core/crypto/src/lib.rs
+++ b/core/crypto/src/lib.rs
@@ -1,9 +1,11 @@
 mod identity;
 mod keys;
+mod signatures;
 mod x3dh;
 mod xeddsa_sign;
 
 pub use identity::Identity;
 pub use keys::{PrivateKey, PublicKey, SymmetricKey32};
+pub use signatures::{Ed25519SigningKey, Ed25519VerifyingKey};
 pub use x3dh::{DomainSeparator, PrekeyBundle, X3Handshake};
 pub use xeddsa_sign::{Ed25519Signature, SignatureError, xeddsa_sign, xeddsa_verify};
diff --git a/core/crypto/src/signatures.rs b/core/crypto/src/signatures.rs
new file mode 100644
index 0000000..28eb6dd
--- /dev/null
+++ b/core/crypto/src/signatures.rs
@@ -0,0 +1,83 @@
+use ed25519_dalek::{self, Signer};
+use rand_core::OsRng;
+use std::fmt::Debug;
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+#[error("verification failed of the Ed25519 Signature")]
+pub struct SignatureVerificationError {}
+
+/// A 64-byte XEdDSA signature over an Ed25519-compatible curve.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct Ed25519Signature([u8; 64]);
+
+impl Ed25519Signature {
+    pub fn empty() -> Self {
+        Self([0u8; 64])
+    }
+}
+
+impl AsRef<[u8; 64]> for Ed25519Signature {
+    fn as_ref(&self) -> &[u8; 64] {
+        &self.0
+    }
+}
+
+impl From<[u8; 64]> for Ed25519Signature {
+    fn from(bytes: [u8; 64]) -> Self {
+        Self(bytes)
+    }
+}
+
+#[derive(Clone)]
+pub struct Ed25519SigningKey(ed25519_dalek::SigningKey);
+
+impl Ed25519SigningKey {
+    pub fn generate() -> Self {
+        Self(ed25519_dalek::SigningKey::generate(&mut OsRng))
+    }
+
+    pub fn sign(&self, msg: &[u8]) -> Ed25519Signature {
+        self.0.sign(msg).to_bytes().into()
+    }
+
+    pub fn verifying_key(&self) -> Ed25519VerifyingKey {
+        self.0.verifying_key().into()
+    }
+}
+
+impl Debug for Ed25519SigningKey {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_tuple("Ed25519SigningKey")
+            .field(&"[redacted]")
+            .finish()
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Ed25519VerifyingKey(ed25519_dalek::VerifyingKey);
+
+impl Ed25519VerifyingKey {
+    pub fn verify(
+        &self,
+        msg: &[u8],
+        signature: &Ed25519Signature,
+    ) -> Result<(), SignatureVerificationError> {
+        let inner_signature = signature.0;
+        self.0
+            .verify_strict(msg, &ed25519_dalek::Signature::from_bytes(&inner_signature))
+            .map_err(|_| SignatureVerificationError {})
+    }
+}
+
+impl From<ed25519_dalek::VerifyingKey> for Ed25519VerifyingKey {
+    fn from(value: ed25519_dalek::VerifyingKey) -> Self {
+        Ed25519VerifyingKey(value)
+    }
+}
+
+impl AsRef<[u8]> for Ed25519VerifyingKey {
+    fn as_ref(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}