Add sr25519 signature scheme

CODING.md

@@ -61,6 +61,7 @@ The `bc-ur` crate is also in this workspace and provides the UR serialization/de
 | `SymmetricKey`, `EncryptedMessage` | Types for symmetric encryption |
 | `ECPrivateKey`, `ECPublicKey` | Elliptic curve cryptography keys |
 | `Ed25519PrivateKey`, `Ed25519PublicKey` | Ed25519 cryptographic keys |
+| `Sr25519PrivateKey`, `Sr25519PublicKey` | SR25519 (Schnorr-Ristretto) cryptographic keys |
 | `X25519PrivateKey`, `X25519PublicKey` | X25519 key agreement keys |
 | `SigningPrivateKey`, `SigningPublicKey` | Keys for digital signatures |
 | `MLDSAPrivateKey`, `MLDSAPublicKey` | Post-quantum digital signature keys |
@@ -154,10 +155,11 @@ This section inventories all public API items that need documentation, ordered f
 2. **✅ `AuthenticationTag`** (`symmetric/authentication_tag.rs`) - Authentication tag for authenticated encryption
 3. **✅ `EncryptedMessage`** (`symmetric/encrypted_message.rs`) - A symmetrically-encrypted message
 
-#### Ed25519 and X25519
+#### Ed25519, SR25519, and X25519
 
 1. **✅ `Ed25519PrivateKey`**, **✅ `Ed25519PublicKey`** (`ed25519/ed25519_private_key.rs`, `ed25519/ed25519_public_key.rs`) - Ed25519 keys
-2. **✅ `X25519PrivateKey`**, **✅ `X25519PublicKey`** (`x25519/x25519_private_key.rs`, `x25519/x25519_public_key.rs`) - X25519 keys
+2. **✅ `Sr25519PrivateKey`**, **✅ `Sr25519PublicKey`** (`sr25519/sr25519_private_key.rs`, `sr25519/sr25519_public_key.rs`) - SR25519 keys
+3. **✅ `X25519PrivateKey`**, **✅ `X25519PublicKey`** (`x25519/x25519_private_key.rs`, `x25519/x25519_public_key.rs`) - X25519 keys
 
 #### ECDSA
 

Cargo.toml

@@ -35,6 +35,8 @@ zeroize = { version = "1.8.1", default-features = false, features = [
     "zeroize_derive",
 ] }
 rand_core = "^0.9.3"
+schnorrkel = { version = "0.11.5", optional = true }
+blake2 = { version = "0.10", optional = true }
 pqcrypto-mlkem = { version = "^0.1.0", optional = true }
 pqcrypto-mldsa = { version = "^0.1.1", optional = true }
 pqcrypto-traits = { version = "^0.3.5", optional = true }
@@ -46,9 +48,10 @@ indoc = "^2.0.0"
 version-sync = "^0.9.0"
 
 [features]
-default = ["secp256k1", "ed25519", "pqcrypto", "ssh"]
+default = ["secp256k1", "ed25519", "sr25519", "pqcrypto", "ssh"]
 secp256k1 = ["bc-crypto/secp256k1"]
 ed25519 = ["bc-crypto/ed25519"]
+sr25519 = ["dep:schnorrkel", "dep:blake2"]
 pqcrypto = ["dep:pqcrypto-mlkem", "dep:pqcrypto-mldsa", "dep:pqcrypto-traits"]
 ssh = ["dep:ssh-key"]
 ssh-agent = ["dep:ssh-agent-client-rs"]

README.md

@@ -65,6 +65,8 @@ The library is organized into several categories of cryptographic primitives and
 | `SchnorrPublicKey`        | A Schnorr (x-only) elliptic curve public key (BIP-340)          |
 | `Ed25519PrivateKey`       | An Edwards curve (Ed25519) private key for signatures           |
 | `Ed25519PublicKey`        | An Edwards curve (Ed25519) public key                           |
+| `Sr25519PrivateKey`       | A Schnorr-Ristretto (SR25519) private key for signatures        |
+| `Sr25519PublicKey`        | A Schnorr-Ristretto (SR25519) public key                        |
 | `X25519PrivateKey`        | A Curve25519 private key used for key agreement                 |
 | `X25519PublicKey`         | A Curve25519 public key used for key agreement                  |
 
@@ -81,14 +83,14 @@ The library is organized into several categories of cryptographic primitives and
 
 ### Digital Signatures
 
-| Name                | Description                                                                   |
-| ------------------- | ----------------------------------------------------------------------------- |
-| `SigningPrivateKey` | A private key for digital signatures (Schnorr, ECDSA, Ed25519, MLDSA, or SSH) |
-| `SigningPublicKey`  | A public key for signature verification                                       |
-| `Signature`         | A digital signature supporting multiple algorithms                            |
-| `SignatureScheme`   | Enumeration of supported signature schemes                                    |
-| `Signer`            | A trait for types that can create signatures                                  |
-| `Verifier`          | A trait for types that can verify signatures                                  |
+| Name                | Description                                                                            |
+| ------------------- | -------------------------------------------------------------------------------------- |
+| `SigningPrivateKey` | A private key for digital signatures (Schnorr, ECDSA, Ed25519, Sr25519, MLDSA, or SSH) |
+| `SigningPublicKey`  | A public key for signature verification                                                |
+| `Signature`         | A digital signature supporting multiple algorithms                                     |
+| `SignatureScheme`   | Enumeration of supported signature schemes                                             |
+| `Signer`            | A trait for types that can create signatures                                           |
+| `Verifier`          | A trait for types that can verify signatures                                           |
 
 ### Key Encapsulation and Encryption
 

run_tests.sh

@@ -40,11 +40,14 @@ cargo test --lib --bins --tests --benches --no-default-features > /dev/null
 test_only_features "pqcrypto"
 test_only_features "secp256k1"
 test_only_features "ed25519"
+test_only_features "sr25519"
 test_only_features "ssh"
 
 test_only_features "ssh,ed25519"
 test_only_features "secp256k1,ed25519,pqcrypto"
 test_only_features "secp256k1,pqcrypto,ssh"
+test_only_features "sr25519,ed25519"
+test_only_features "sr25519,secp256k1"
 
 test_additional_features "ssh-agent"
 test_additional_features "ssh-agent-tests"

src/keypair.rs

@@ -111,6 +111,7 @@ pub fn keypair_opt(
     #[cfg(any(
         feature = "secp256k1",
         feature = "ed25519",
+        feature = "sr25519",
         feature = "ssh",
         feature = "pqcrypto"
     ))]
@@ -130,6 +131,7 @@ pub fn keypair_opt(
     #[cfg(not(any(
         feature = "secp256k1",
         feature = "ed25519",
+        feature = "sr25519",
         feature = "ssh",
         feature = "pqcrypto"
     )))]

src/lib.rs

@@ -57,6 +57,11 @@ mod ed25519;
 #[cfg(feature = "ed25519")]
 pub use ed25519::{Ed25519PrivateKey, Ed25519PublicKey};
 
+#[cfg(feature = "sr25519")]
+mod sr25519;
+#[cfg(feature = "sr25519")]
+pub use sr25519::{Sr25519PrivateKey, Sr25519PublicKey};
+
 mod seed;
 pub use seed::Seed;
 

src/private_keys.rs

@@ -156,6 +156,7 @@ impl CBORTaggedEncodable for PrivateKeys {
         #[cfg(any(
             feature = "secp256k1",
             feature = "ed25519",
+            feature = "sr25519",
             feature = "ssh",
             feature = "pqcrypto"
         ))]
@@ -169,6 +170,7 @@ impl CBORTaggedEncodable for PrivateKeys {
         #[cfg(not(any(
             feature = "secp256k1",
             feature = "ed25519",
+            feature = "sr25519",
             feature = "ssh",
             feature = "pqcrypto"
         )))]

src/public_keys.rs

@@ -150,6 +150,7 @@ impl CBORTaggedEncodable for PublicKeys {
         #[cfg(any(
             feature = "secp256k1",
             feature = "ed25519",
+            feature = "sr25519",
             feature = "ssh",
             feature = "pqcrypto"
         ))]
@@ -163,6 +164,7 @@ impl CBORTaggedEncodable for PublicKeys {
         #[cfg(not(any(
             feature = "secp256k1",
             feature = "ed25519",
+            feature = "sr25519",
             feature = "ssh",
             feature = "pqcrypto"
         )))]

src/signing/mod.rs

@@ -90,7 +90,7 @@ mod tests {
     use bc_rand::make_fake_random_number_generator;
     #[cfg(any(feature = "secp256k1", feature = "pqcrypto"))]
     use dcbor::prelude::*;
-    #[cfg(any(feature = "secp256k1", feature = "ed25519"))]
+    #[cfg(any(feature = "secp256k1", feature = "ed25519", feature = "sr25519"))]
     use hex_literal::hex;
     #[cfg(feature = "secp256k1")]
     use indoc::indoc;
@@ -100,6 +100,7 @@ mod tests {
     #[cfg(any(
         feature = "secp256k1",
         feature = "ed25519",
+        feature = "sr25519",
         feature = "ssh"
     ))]
     use super::SignatureScheme;
@@ -110,17 +111,22 @@ mod tests {
     #[cfg(any(
         feature = "secp256k1",
         feature = "ed25519",
+        feature = "sr25519",
         feature = "ssh"
     ))]
     use crate::SigningOptions;
     #[cfg(all(feature = "secp256k1", not(feature = "ed25519")))]
     use crate::SigningPrivateKey;
     #[cfg(feature = "ed25519")]
-    use crate::{Ed25519PrivateKey, Signer, SigningPrivateKey, Verifier};
+    use crate::Ed25519PrivateKey;
+    #[cfg(feature = "sr25519")]
+    use crate::Sr25519PrivateKey;
+    #[cfg(any(feature = "ed25519", feature = "sr25519"))]
+    use crate::{Signer, SigningPrivateKey, Verifier};
     #[cfg(feature = "pqcrypto")]
     use crate::{MLDSA, MLDSASignature};
     #[cfg(all(
-        not(feature = "ed25519"),
+        not(any(feature = "ed25519", feature = "sr25519")),
         any(feature = "secp256k1", feature = "ssh")
     ))]
     use crate::{Signer, Verifier};
@@ -142,9 +148,17 @@ mod tests {
             "322b5c1dd5a17c3481c2297990c85c232ed3c17b52ce9905c6ec5193ad132c36"
         )));
 
+    #[cfg(feature = "sr25519")]
+    fn sr25519_signing_private_key() -> SigningPrivateKey {
+        SigningPrivateKey::new_sr25519(Sr25519PrivateKey::from_seed(hex!(
+            "322b5c1dd5a17c3481c2297990c85c232ed3c17b52ce9905c6ec5193ad132c36"
+        )))
+    }
+
     #[cfg(any(
         feature = "secp256k1",
         feature = "ed25519",
+        feature = "sr25519",
         feature = "pqcrypto",
         feature = "ssh"
     ))]
@@ -227,6 +241,22 @@ mod tests {
         assert_eq!(signature, received_signature);
     }
 
+    #[test]
+    #[cfg(feature = "sr25519")]
+    fn test_sr25519_cbor() {
+        let private_key = sr25519_signing_private_key();
+        let signature = private_key.sign(MESSAGE).unwrap();
+        let signature_cbor: CBOR = signature.clone().into();
+        let tagged_cbor_data = signature_cbor.to_cbor_data();
+
+        let received_signature =
+            Signature::from_tagged_cbor_data(&tagged_cbor_data).unwrap();
+
+        let public_key = private_key.public_key().unwrap();
+        assert!(public_key.verify(&signature, MESSAGE));
+        assert!(public_key.verify(&received_signature, MESSAGE));
+    }
+
     #[test]
     #[cfg(feature = "ed25519")]
     fn test_ed25519_signing() {
@@ -242,6 +272,22 @@ mod tests {
         assert!(public_key.verify(&another_signature, MESSAGE));
     }
 
+    #[test]
+    #[cfg(feature = "sr25519")]
+    fn test_sr25519_signing() {
+        let private_key = sr25519_signing_private_key();
+        let public_key = private_key.public_key().unwrap();
+        let signature = private_key.sign(MESSAGE).unwrap();
+
+        assert!(public_key.verify(&signature, MESSAGE));
+        assert!(!public_key.verify(&signature, b"Wolf Mcnally"));
+
+        // SR25519 signatures include randomness, so they differ each time
+        let another_signature = private_key.sign(MESSAGE).unwrap();
+        assert_ne!(signature, another_signature);
+        assert!(public_key.verify(&another_signature, MESSAGE));
+    }
+
     #[test]
     #[cfg(feature = "pqcrypto")]
     fn test_mldsa_signing() {
@@ -268,7 +314,7 @@ mod tests {
         assert_eq!(signature, received_signature);
     }
 
-    #[cfg(any(feature = "secp256k1", feature = "ed25519", feature = "ssh"))]
+    #[cfg(any(feature = "secp256k1", feature = "ed25519", feature = "sr25519", feature = "ssh"))]
     fn test_keypair_signing(
         scheme: SignatureScheme,
         options: Option<SigningOptions>,
@@ -297,10 +343,16 @@ mod tests {
         test_keypair_signing(SignatureScheme::Ed25519, None);
     }
 
+    #[test]
+    #[cfg(feature = "sr25519")]
+    fn test_sr25519_keypair() {
+        test_keypair_signing(SignatureScheme::Sr25519, None);
+    }
+
     #[test]
     #[cfg(all(
         feature = "pqcrypto",
-        any(feature = "secp256k1", feature = "ed25519")
+        any(feature = "secp256k1", feature = "ed25519", feature = "sr25519")
     ))]
     fn test_mldsa44_keypair() {
         test_keypair_signing(SignatureScheme::MLDSA44, None);
@@ -309,7 +361,7 @@ mod tests {
     #[test]
     #[cfg(all(
         feature = "pqcrypto",
-        any(feature = "secp256k1", feature = "ed25519")
+        any(feature = "secp256k1", feature = "ed25519", feature = "sr25519")
     ))]
     fn test_mldsa65_keypair() {
         test_keypair_signing(SignatureScheme::MLDSA65, None);
@@ -318,7 +370,7 @@ mod tests {
     #[test]
     #[cfg(all(
         feature = "pqcrypto",
-        any(feature = "secp256k1", feature = "ed25519")
+        any(feature = "secp256k1", feature = "ed25519", feature = "sr25519")
     ))]
     fn test_mldsa87_keypair() {
         test_keypair_signing(SignatureScheme::MLDSA87, None);