Solve #39

Test values were taken from <./javascript/test/signals.test.ts> line 86
and further.

.gitignore

@@ -5,8 +5,9 @@
 debug/
 target/
 
-# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
-# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
+# Remove Cargo.lock from gitignore if creating an executable, leave it for 
+# libraries. More information at 
+# <https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html>
 Cargo.lock
 
 # These are backup files generated by rustfmt
@@ -34,3 +35,5 @@ Sessionx.vim
 tags
 # Persistent undo
 [._]*.un~
+#______________________
+commit_message_draft.md

rust-arkworks/src/lib.rs

@@ -14,7 +14,8 @@ pub mod sig {
     };
     use ark_std::{marker::PhantomData, rand::Rng, UniformRand};
     use secp256k1::sec1::Sec1EncodePoint;
-    use sha2::{Digest, Sha512};
+    use sha2::digest::Output;
+    use sha2::{Digest, Sha256};
 
     pub enum PlumeVersion {
         V1,
@@ -48,16 +49,14 @@ pub mod sig {
         Ok(hash_to_curve::hash_to_curve::<Fq, P>(message, pk))
     }
 
-    // TODO [replace SHA-512](https://github.com/plume-sig/zk-nullifier-sig/issues/39#issuecomment-1732497672)
     fn compute_c_v1<P: SWModelParameters>(
         g: &GroupAffine<P>,
         pk: &GroupAffine<P>,
         h: &GroupAffine<P>,
         nul: &GroupAffine<P>,
         g_r: &GroupAffine<P>,
         z: &GroupAffine<P>,
-    // should be `Output<Sha256>` when tests are fixed <https://github.com/plume-sig/zk-nullifier-sig/issues/39#issuecomment-1732538695>
-    ) -> Vec<u8> {
+    ) -> Output<Sha256> {
         // Compute c = sha512([g, pk, h, nul, g^r, z])
         let g_bytes = affine_to_bytes::<P>(g);
         let pk_bytes = affine_to_bytes::<P>(pk);
@@ -68,28 +67,22 @@ pub mod sig {
 
         let c_preimage_vec = [g_bytes, pk_bytes, h_bytes, nul_bytes, g_r_bytes, z_bytes].concat();
 
-        let mut sha512_hasher = Sha512::new();
-        sha512_hasher.update(c_preimage_vec.as_slice());
-        sha512_hasher.finalize()[0..32].to_owned()
+        Sha256::digest(c_preimage_vec.as_slice())
     }
 
-    // TODO [replace SHA-512](https://github.com/plume-sig/zk-nullifier-sig/issues/39#issuecomment-1732497672)
     fn compute_c_v2<P: SWModelParameters>(
         nul: &GroupAffine<P>,
         g_r: &GroupAffine<P>,
         z: &GroupAffine<P>,
-    // should be `Output<Sha256>` when tests are fixed <https://github.com/plume-sig/zk-nullifier-sig/issues/39#issuecomment-1732538695>
-    ) -> Vec<u8> {
+    ) -> Output<Sha256> {
         // Compute c = sha512([nul, g^r, z])
         let nul_bytes = affine_to_bytes::<P>(nul);
         let g_r_bytes = affine_to_bytes::<P>(g_r);
         let z_bytes = affine_to_bytes::<P>(z);
 
         let c_preimage_vec = [nul_bytes, g_r_bytes, z_bytes].concat();
 
-        let mut sha512_hasher = Sha512::new();
-        sha512_hasher.update(c_preimage_vec.as_slice());
-        sha512_hasher.finalize()[0..32].to_owned()
+        Sha256::digest(c_preimage_vec.as_slice())
     }
 
     pub trait VerifiableUnpredictableFunction {

rust-arkworks/src/tests.rs

@@ -231,8 +231,8 @@ pub fn test_against_zk_nullifier_sig_c_and_s() {
         PlumeVersion::V1
     ).unwrap();
 
-    assert_eq!(coord_to_hex(sig.c.into()), "00000000000000007da1ad3f63c6180beefd0d6a8e3c87620b54f1b1d2c8287d104da9e53b6b5524");
-    assert_eq!(coord_to_hex(sig.s.into()), "0000000000000000638330fea277e97ad407b32c9dc4d522454f5483abd903e6710a59d14f6fbdf2");
+    assert_eq!(coord_to_hex(sig.c.into()), "0000000000000000c6a7fc2c926ddbaf20731a479fb6566f2daa5514baae5223fe3b32edbce83254");
+    assert_eq!(coord_to_hex(sig.s.into()), "0000000000000000e69f027d84cb6fe5f761e333d12e975fb190d163e8ea132d7de0bd6079ba28ca");
 
     let sig = Scheme::sign_with_r(
         &pp,
@@ -242,7 +242,7 @@ pub fn test_against_zk_nullifier_sig_c_and_s() {
         PlumeVersion::V2
     ).unwrap();
 
-    assert_eq!(coord_to_hex(sig.c.into()), "0000000000000000d898f5fa7e4af2d694cb948cfe3226aebd602852beb7b32f5e9225a10c2bc925");
-    assert_eq!(coord_to_hex(sig.s.into()), "00000000000000009231fa7cc28765f013def6b24310f09c8c25cb276b461d22162da027c90e348c");
+    assert_eq!(coord_to_hex(sig.c.into()), "00000000000000003dbfb717705010d4f44a70720c95e74b475bd3a783ab0b9e8a6b3b363434eb96");
+    assert_eq!(coord_to_hex(sig.s.into()), "0000000000000000528e8fbb6452f82200797b1a73b2947a92524bd611085a920f1177cb8098136b");
 
 }