feat: add sum for schnorr signature and capk signature (#231)

Adds sum for schnorr signature and capk signature as a features
new version

Cargo.toml

@@ -7,7 +7,7 @@ categories = ["cryptography"]
 homepage = "https://tari.com"
 readme = "README.md"
 license = "BSD-3-Clause"
-version = "0.20.2"
+version = "0.20.3"
 edition = "2018"
 
 [dependencies]

changelog.md

@@ -1,15 +1,22 @@
 # Changelog
 
 All notable changes to this project will be documented in this file. See [standard-version](https://github.com/conventional-changelog/standard-version) for commit guidelines.
-### [0.21.2](https://github.com/tari-project/tari-crypto/compare/v0.21.1...v0.21.2) (2024-06-28)
+### [0.20.3](https://github.com/tari-project/tari-crypto/compare/v0.20.1...v0.20.3) (2024-07-02)
+
+
+### Features
+
+* Include Add CAPK and Schnorr signatures together
+
+### [0.20.2](https://github.com/tari-project/tari-crypto/compare/v0.20.1...v0.20.2) (2024-06-28)
 
 
 ### Features
 
 * Adds public constructor for DHKE
 
 
-### [0.21.1](https://github.com/tari-project/tari-crypto/compare/v0.20.0...v0.21.1) (2024-05-09)
+### [0.20.1](https://github.com/tari-project/tari-crypto/compare/v0.20.0...v0.20.1) (2024-05-09)
 
 
 ### Features

src/ristretto/ristretto_com_and_pub_sig.rs

@@ -92,6 +92,7 @@ mod test {
             pedersen::{commitment_factory::PedersenCommitmentFactory, PedersenCommitment},
             RistrettoComAndPubSig,
             RistrettoPublicKey,
+            RistrettoSchnorr,
             RistrettoSecretKey,
         },
     };
@@ -265,6 +266,62 @@ mod test {
         assert!(sig_p_total.verify_challenge(&commitment, &pubkey, &challenge, &factory, &mut rng));
     }
 
+    /// Create a schnorr and RistrettoComAndPubSig adding them together and testing if they still valid.
+    #[test]
+    fn sign_and_verify_combined_schnorr() {
+        let mut rng = rand::thread_rng();
+
+        // Challenge; doesn't use proper Fiat-Shamir, so it's for testing only!
+        let challenge = Blake2b::<U64>::new().chain_update(b"Small Gods").finalize();
+
+        // Witness data
+        let a_value = RistrettoSecretKey::random(&mut rng);
+        let x_value = RistrettoSecretKey::random(&mut rng);
+        let y_value = RistrettoSecretKey::random(&mut rng);
+
+        // Statement data
+        let factory = PedersenCommitmentFactory::default();
+        let commitment = factory.commit(&x_value, &a_value);
+        let pubkey = RistrettoPublicKey::from_secret_key(&y_value);
+
+        // Nonce data
+        let r_a = RistrettoSecretKey::random(&mut rng);
+        let r_x = RistrettoSecretKey::random(&mut rng);
+        let r_y = RistrettoSecretKey::random(&mut rng);
+
+        let sig_capk =
+            RistrettoComAndPubSig::sign(&a_value, &x_value, &y_value, &r_a, &r_x, &r_y, &challenge, &factory).unwrap();
+        assert!(sig_capk.verify_challenge(&commitment, &pubkey, &challenge, &factory, &mut rng));
+
+        let (k, pub_k) = RistrettoPublicKey::random_keypair(&mut rng);
+        let r = RistrettoSecretKey::random(&mut rng);
+
+        let total_y_value = &y_value + &k;
+        let total_r_y = &r_y + &r;
+
+        let sig = RistrettoSchnorr::sign_raw_uniform(&k, r, &challenge).unwrap();
+        assert!(sig.verify_raw_uniform(&pub_k, &challenge));
+
+        let total_pubkey = RistrettoPublicKey::from_secret_key(&total_y_value);
+
+        let total_sig_capk = RistrettoComAndPubSig::sign(
+            &a_value,
+            &x_value,
+            &total_y_value,
+            &r_a,
+            &r_x,
+            &total_r_y,
+            &challenge,
+            &factory,
+        )
+        .unwrap();
+        assert!(total_sig_capk.verify_challenge(&commitment, &total_pubkey, &challenge, &factory, &mut rng));
+
+        let agg_sig = &sig_capk + &sig;
+        assert!(agg_sig.verify_challenge(&commitment, &total_pubkey, &challenge, &factory, &mut rng));
+        assert_eq!(agg_sig, total_sig_capk);
+    }
+
     /// Test that commitment signatures are linear, as in a multisignature construction
     #[test]
     fn test_signature_addition() {

src/signatures/commitment_and_public_key_signature.rs

@@ -16,6 +16,7 @@ use crate::{
     alloc::borrow::ToOwned,
     commitment::{HomomorphicCommitment, HomomorphicCommitmentFactory},
     keys::{PublicKey, SecretKey},
+    signatures::SchnorrSignature,
 };
 
 /// An error when creating a commitment signature
@@ -305,6 +306,60 @@ where
     }
 }
 
+impl<'a, 'b, P, K> Add<&'b SchnorrSignature<P, K>> for &'a CommitmentAndPublicKeySignature<P, K>
+where
+    P: PublicKey<K = K>,
+    &'a HomomorphicCommitment<P>: Add<&'b HomomorphicCommitment<P>, Output = HomomorphicCommitment<P>>,
+    &'a P: Add<&'b P, Output = P>,
+    K: SecretKey,
+    &'a K: Add<&'b K, Output = K>,
+{
+    type Output = CommitmentAndPublicKeySignature<P, K>;
+
+    fn add(self, rhs: &'b SchnorrSignature<P, K>) -> CommitmentAndPublicKeySignature<P, K> {
+        let ephemeral_commitment_sum = self.ephemeral_commitment().clone();
+        let ephemeral_pubkey_sum_sum = self.ephemeral_pubkey() + rhs.get_public_nonce();
+        let u_a_sum = self.u_a().clone();
+        let u_x_sum = self.u_x().clone();
+        let u_y_sum = self.u_y() + rhs.get_signature();
+
+        CommitmentAndPublicKeySignature::new(
+            ephemeral_commitment_sum,
+            ephemeral_pubkey_sum_sum,
+            u_a_sum,
+            u_x_sum,
+            u_y_sum,
+        )
+    }
+}
+
+impl<'a, P, K> Add<SchnorrSignature<P, K>> for &'a CommitmentAndPublicKeySignature<P, K>
+where
+    P: PublicKey<K = K>,
+    for<'b> &'a HomomorphicCommitment<P>: Add<&'b HomomorphicCommitment<P>, Output = HomomorphicCommitment<P>>,
+    for<'b> &'a P: Add<&'b P, Output = P>,
+    K: SecretKey,
+    for<'b> &'a K: Add<&'b K, Output = K>,
+{
+    type Output = CommitmentAndPublicKeySignature<P, K>;
+
+    fn add(self, rhs: SchnorrSignature<P, K>) -> CommitmentAndPublicKeySignature<P, K> {
+        let ephemeral_commitment_sum = self.ephemeral_commitment().clone();
+        let ephemeral_pubkey_sum_sum = self.ephemeral_pubkey() + rhs.get_public_nonce();
+        let u_a_sum = self.u_a().clone();
+        let u_x_sum = self.u_x().clone();
+        let u_y_sum = self.u_y() + rhs.get_signature();
+
+        CommitmentAndPublicKeySignature::new(
+            ephemeral_commitment_sum,
+            ephemeral_pubkey_sum_sum,
+            u_a_sum,
+            u_x_sum,
+            u_y_sum,
+        )
+    }
+}
+
 impl<P, K> Default for CommitmentAndPublicKeySignature<P, K>
 where
     P: PublicKey<K = K>,