From 53916aab6baca6f2adf8cac55c3532a739003076 Mon Sep 17 00:00:00 2001
From: Thomas Eizinger <thomas@eizinger.io>
Date: Tue, 11 May 2021 12:47:20 +1000
Subject: [PATCH] Make `Ring` an implementation detail of clsag module

---
 monero-adaptor/src/clsag.rs | 17 +++++++++--------
 monero-adaptor/src/lib.rs   | 25 +++++++++----------------
 monero-adaptor/src/ring.rs  | 12 ++++++------
 3 files changed, 24 insertions(+), 30 deletions(-)

diff --git a/monero-adaptor/src/clsag.rs b/monero-adaptor/src/clsag.rs
index 32336e9f..db5e2e99 100644
--- a/monero-adaptor/src/clsag.rs
+++ b/monero-adaptor/src/clsag.rs
@@ -17,8 +17,8 @@ pub fn sign(
     signing_key: Scalar,
     H_p_pk: EdwardsPoint,
     alpha: Scalar,
-    ring: &Ring,
-    commitment_ring: &Ring,
+    ring: &[EdwardsPoint; RING_SIZE],
+    commitment_ring: &[EdwardsPoint; RING_SIZE],
     fake_responses: [Scalar; RING_SIZE - 1],
     z: Scalar,
     pseudo_output_commitment: EdwardsPoint,
@@ -28,6 +28,8 @@ pub fn sign(
 ) -> Signature {
     let D = z * H_p_pk;
     let D_inv_8 = D * INV_EIGHT;
+    let ring = Ring::new(ring);
+    let commitment_ring = Ring::new(commitment_ring);
 
     let mus = AggregationHashes::new(
         &ring,
@@ -92,11 +94,14 @@ pub fn sign(
 pub fn verify(
     sig: &Signature,
     msg: &[u8],
-    ring: &Ring,
-    commitment_ring: &Ring,
+    ring: &[EdwardsPoint; RING_SIZE],
+    commitment_ring: &[EdwardsPoint; RING_SIZE],
     pseudo_output_commitment: EdwardsPoint,
     H_p_pk: EdwardsPoint,
 ) -> bool {
+    let ring = Ring::new(ring);
+    let commitment_ring = Ring::new(commitment_ring);
+
     let mus = AggregationHashes::new(
         &ring,
         &commitment_ring,
@@ -312,8 +317,6 @@ mod tests {
             x * ED25519_BASEPOINT_POINT
         });
 
-        let ring = Ring::new(ring);
-
         let mut commitment_ring = [EdwardsPoint::default(); RING_SIZE];
 
         let real_commitment_blinding = Scalar::random(&mut OsRng);
@@ -323,8 +326,6 @@ mod tests {
             x * ED25519_BASEPOINT_POINT
         });
 
-        let commitment_ring = Ring::new(commitment_ring);
-
         // TODO: document
         let pseudo_output_commitment = commitment_ring[0];
 
diff --git a/monero-adaptor/src/lib.rs b/monero-adaptor/src/lib.rs
index 7f6e2bc1..8e70387f 100644
--- a/monero-adaptor/src/lib.rs
+++ b/monero-adaptor/src/lib.rs
@@ -14,7 +14,6 @@ use rand::{CryptoRng, Rng};
 use tiny_keccak::{Hasher, Keccak};
 
 use clsag::{Signature, RING_SIZE};
-use ring::Ring;
 
 mod clsag;
 mod ring;
@@ -83,9 +82,9 @@ impl AdaptorSignature {
 
 pub struct Alice0 {
     // secret index is always 0
-    ring: Ring,
+    ring: [EdwardsPoint; RING_SIZE],
     fake_responses: [Scalar; RING_SIZE - 1],
-    commitment_ring: Ring,
+    commitment_ring: [EdwardsPoint; RING_SIZE],
     pseudo_output_commitment: EdwardsPoint,
     msg: [u8; 32],
     // encryption key
@@ -113,9 +112,6 @@ impl Alice0 {
         s_prime_a: Scalar,
         rng: &mut (impl Rng + CryptoRng),
     ) -> Result<Self> {
-        let ring = Ring::new(ring);
-        let commitment_ring = Ring::new(commitment_ring);
-
         let mut fake_responses = [Scalar::zero(); RING_SIZE - 1];
         for response in fake_responses.iter_mut().take(RING_SIZE - 1) {
             *response = Scalar::random(rng);
@@ -226,9 +222,9 @@ pub struct Alice2 {
 }
 
 pub struct Bob0 {
-    ring: Ring,
+    ring: [EdwardsPoint; RING_SIZE],
     msg: [u8; 32],
-    commitment_ring: Ring,
+    commitment_ring: [EdwardsPoint; RING_SIZE],
     pseudo_output_commitment: EdwardsPoint,
     R_a: EdwardsPoint,
     R_prime_a: EdwardsPoint,
@@ -251,9 +247,6 @@ impl Bob0 {
         s_b: Scalar,
         rng: &mut (impl Rng + CryptoRng),
     ) -> Result<Self> {
-        let ring = Ring::new(ring);
-        let commitment_ring = Ring::new(commitment_ring);
-
         let alpha_b = Scalar::random(rng);
 
         let p_k = ring[0];
@@ -300,9 +293,9 @@ impl Bob0 {
 }
 
 pub struct Bob1 {
-    ring: Ring,
+    ring: [EdwardsPoint; RING_SIZE],
     msg: [u8; 32],
-    commitment_ring: Ring,
+    commitment_ring: [EdwardsPoint; RING_SIZE],
     pseudo_output_commitment: EdwardsPoint,
     R_a: EdwardsPoint,
     R_prime_a: EdwardsPoint,
@@ -634,9 +627,9 @@ mod tests {
         assert!(clsag::verify(
             &sig,
             msg_to_sign,
-            todo!(),
-            todo!(),
-            todo!(),
+            &ring,
+            &commitment_ring,
+            pseudo_output_commitment,
             todo!()
         ));
     }
diff --git a/monero-adaptor/src/ring.rs b/monero-adaptor/src/ring.rs
index d078c8ab..424db196 100644
--- a/monero-adaptor/src/ring.rs
+++ b/monero-adaptor/src/ring.rs
@@ -3,13 +3,13 @@ use std::ops::Index;
 use curve25519_dalek::edwards::EdwardsPoint;
 
 #[derive(Clone)]
-pub struct Ring {
-    elements: [EdwardsPoint; 11],
+pub struct Ring<'a> {
+    elements: &'a [EdwardsPoint; 11],
     bytes: [u8; 32 * 11],
 }
 
-impl Ring {
-    pub fn new(elements: [EdwardsPoint; 11]) -> Ring {
+impl<'a> Ring<'a> {
+    pub fn new(elements: &[EdwardsPoint; 11]) -> Ring<'_> {
         let mut bytes = [0u8; 32 * 11];
 
         for (i, element) in elements.iter().enumerate() {
@@ -23,13 +23,13 @@ impl Ring {
     }
 }
 
-impl AsRef<[u8]> for Ring {
+impl<'a> AsRef<[u8]> for Ring<'a> {
     fn as_ref(&self) -> &[u8] {
         self.bytes.as_ref()
     }
 }
 
-impl Index<usize> for Ring {
+impl<'a> Index<usize> for Ring<'a> {
     type Output = EdwardsPoint;
 
     fn index(&self, index: usize) -> &Self::Output {