From 75ff8797709c7caad17dac9fd4efec343e6b92fb Mon Sep 17 00:00:00 2001
From: David Rusu <davidrusu.me@gmail.com>
Date: Sat, 17 Aug 2024 15:17:09 +0400
Subject: [PATCH] goas: nullifier does not need to re-commit to nonce

since it's included in note commitment
---
 goas/cl/cl/src/input.rs     |  2 +-
 goas/cl/cl/src/note.rs      |  7 -------
 goas/cl/cl/src/nullifier.rs | 24 +++++++++++++++---------
 goas/cl/ledger/src/input.rs |  1 -
 4 files changed, 16 insertions(+), 18 deletions(-)

diff --git a/goas/cl/cl/src/input.rs b/goas/cl/cl/src/input.rs
index c2a4ff2..718b1bd 100644
--- a/goas/cl/cl/src/input.rs
+++ b/goas/cl/cl/src/input.rs
@@ -66,7 +66,7 @@ impl InputWitness {
     }
 
     pub fn nullifier(&self) -> Nullifier {
-        Nullifier::new(self.nf_sk, self.nonce, self.note_commitment())
+        Nullifier::new(self.nf_sk, self.note_commitment())
     }
 
     pub fn commit(&self) -> Input {
diff --git a/goas/cl/cl/src/note.rs b/goas/cl/cl/src/note.rs
index da8d520..2e70d67 100644
--- a/goas/cl/cl/src/note.rs
+++ b/goas/cl/cl/src/note.rs
@@ -1,4 +1,3 @@
-use rand_core::CryptoRngCore;
 use serde::{Deserialize, Serialize};
 use sha2::{Digest, Sha256};
 
@@ -27,12 +26,6 @@ pub fn unit_point(unit: &str) -> Unit {
 pub struct NoteCommitment(pub [u8; 32]);
 
 impl NoteCommitment {
-    pub fn random(mut rng: impl CryptoRngCore) -> Self {
-        let mut cm = [0u8; 32];
-        rng.fill_bytes(&mut cm);
-        Self(cm)
-    }
-
     pub fn as_bytes(&self) -> &[u8; 32] {
         &self.0
     }
diff --git a/goas/cl/cl/src/nullifier.rs b/goas/cl/cl/src/nullifier.rs
index 0f06476..4b8c59b 100644
--- a/goas/cl/cl/src/nullifier.rs
+++ b/goas/cl/cl/src/nullifier.rs
@@ -104,11 +104,10 @@ impl NullifierNonce {
 }
 
 impl Nullifier {
-    pub fn new(sk: NullifierSecret, nonce: NullifierNonce, note_cm: NoteCommitment) -> Self {
+    pub fn new(sk: NullifierSecret, note_cm: NoteCommitment) -> Self {
         let mut hasher = Sha256::new();
         hasher.update(b"NOMOS_CL_NULLIFIER");
         hasher.update(sk.0);
-        hasher.update(nonce.0);
         hasher.update(note_cm.0);
 
         let nf_bytes: [u8; 32] = hasher.finalize().into();
@@ -122,6 +121,8 @@ impl Nullifier {
 
 #[cfg(test)]
 mod test {
+    use crate::{note::unit_point, NoteWitness};
+
     use super::*;
 
     #[ignore = "nullifier test vectors not stable yet"]
@@ -145,12 +146,15 @@ mod test {
     fn test_nullifier_same_sk_different_nonce() {
         let mut rng = rand::thread_rng();
         let sk = NullifierSecret::random(&mut rng);
+        let note = NoteWitness::basic(1, unit_point("NMO"));
+
         let nonce_1 = NullifierNonce::random(&mut rng);
         let nonce_2 = NullifierNonce::random(&mut rng);
-        let note_cm = NoteCommitment::random(&mut rng);
+        let note_cm_1 = note.commit(sk.commit(), nonce_1);
+        let note_cm_2 = note.commit(sk.commit(), nonce_2);
 
-        let nf_1 = Nullifier::new(sk, nonce_1, note_cm);
-        let nf_2 = Nullifier::new(sk, nonce_2, note_cm);
+        let nf_1 = Nullifier::new(sk, note_cm_1);
+        let nf_2 = Nullifier::new(sk, note_cm_2);
 
         assert_ne!(nf_1, nf_2);
     }
@@ -159,12 +163,14 @@ mod test {
     fn test_same_sk_same_nonce_different_note() {
         let mut rng = rand::thread_rng();
         let sk = NullifierSecret::random(&mut rng);
+        let note_1 = NoteWitness::basic(1, unit_point("NMO"));
+        let note_2 = NoteWitness::basic(1, unit_point("ETH"));
         let nonce = NullifierNonce::random(&mut rng);
-        let note_cm_1 = NoteCommitment::random(&mut rng);
-        let note_cm_2 = NoteCommitment::random(&mut rng);
+        let note_cm_1 = note_1.commit(sk.commit(), nonce);
+        let note_cm_2 = note_2.commit(sk.commit(), nonce);
 
-        let nf_1 = Nullifier::new(sk, nonce, note_cm_1);
-        let nf_2 = Nullifier::new(sk, nonce, note_cm_2);
+        let nf_1 = Nullifier::new(sk, note_cm_1);
+        let nf_2 = Nullifier::new(sk, note_cm_2);
 
         assert_ne!(nf_1, nf_2);
     }
diff --git a/goas/cl/ledger/src/input.rs b/goas/cl/ledger/src/input.rs
index b0c3498..f1ea9ee 100644
--- a/goas/cl/ledger/src/input.rs
+++ b/goas/cl/ledger/src/input.rs
@@ -127,7 +127,6 @@ mod test {
                 input: cl::Input {
                     nullifier: cl::Nullifier::new(
                         cl::NullifierSecret::random(&mut rng),
-                        cl::NullifierNonce::random(&mut rng),
                         input.note_commitment(),
                     ),
                     ..expected_public_inputs.input