Remove poseidon_hash_mt

Author: sydhds

rln/src/hashers.rs

@@ -3,7 +3,6 @@ use crate::{circuit::Fr, utils::bytes_le_to_fr};
 use once_cell::sync::Lazy;
 use tiny_keccak::{Hasher, Keccak};
 use utils::poseidon::Poseidon;
-use zeroize::Zeroize;
 
 /// These indexed constants hardcode the supported round parameters tuples (t, RF, RN, SKIP_MATRICES) for the Bn254 scalar field.
 /// SKIP_MATRICES is the index of the randomly generated secure MDS matrix.
@@ -28,14 +27,6 @@ pub fn poseidon_hash(input: &[Fr]) -> Fr {
         .expect("hash with fixed input size can't fail")
 }
 
-pub fn poseidon_hash_mut(input: &mut [Fr]) -> Fr {
-    let result = POSEIDON
-        .hash(input)
-        .expect("hash with fixed input size can't fail");
-    input.into_iter().for_each(|i| i.zeroize());
-    result
-}
-
 /// The zerokit RLN Merkle tree Hasher.
 #[derive(Clone, Copy, PartialEq, Eq)]
 pub struct PoseidonHash;

rln/src/protocol.rs

@@ -2,7 +2,7 @@
 
 use crate::circuit::{calculate_rln_witness, qap::CircomReduction, Curve};
 use crate::error::{ComputeIdSecretError, ConversionError, ProofError, ProtocolError};
-use crate::hashers::{hash_to_field, poseidon_hash, poseidon_hash_mut};
+use crate::hashers::{hash_to_field, poseidon_hash};
 use crate::poseidon_tree::{MerkleProof, PoseidonTree};
 use crate::public::RLN_IDENTIFIER;
 use crate::utils::{
@@ -298,13 +298,14 @@ pub fn proof_values_from_witness(
     message_id_range_check(&rln_witness.message_id, &rln_witness.user_message_limit)?;
 
     // y share
-    let mut a_0: Fr = *rln_witness.identity_secret;
-    let a_1 = poseidon_hash(&[a_0, rln_witness.external_nullifier, rln_witness.message_id]);
-    let y = a_0 + rln_witness.x * a_1;
-    a_0.zeroize();
+    let a_0 = &rln_witness.identity_secret;
+    let mut to_hash = [*(a_0.clone()), rln_witness.external_nullifier, rln_witness.message_id];
+    let a_1 = poseidon_hash(&to_hash);
+    let y = *(a_0.clone()) + rln_witness.x * a_1;
 
     // Nullifier
     let nullifier = poseidon_hash(&[a_1]);
+    to_hash[0].zeroize();
 
     // Merkle tree root computations
     let root = compute_tree_root(
@@ -421,7 +422,10 @@ pub fn compute_tree_root(
     path_elements: &[Fr],
     identity_path_index: &[u8],
 ) -> Fr {
-    let id_commitment = poseidon_hash_mut(&mut [**identity_secret]);
+    let mut to_hash = [*identity_secret.clone()];
+    let id_commitment = poseidon_hash(&to_hash);
+    to_hash[0].zeroize();
+    
     let mut root = poseidon_hash(&[id_commitment, *user_message_limit]);
 
     for i in 0..identity_path_index.len() {
@@ -445,7 +449,9 @@ pub fn compute_tree_root(
 pub fn keygen() -> (IdSecret, Fr) {
     let mut rng = thread_rng();
     let identity_secret_hash = IdSecret::rand(&mut rng);
-    let id_commitment = poseidon_hash_mut(&mut [*identity_secret_hash]);
+    let mut to_hash = [*identity_secret_hash.clone()];
+    let id_commitment = poseidon_hash(&to_hash);
+    to_hash[0].zeroize();
     (identity_secret_hash, id_commitment)
 }
 

rln/src/utils.rs

@@ -190,11 +190,18 @@ impl IdSecret {
     pub(crate) fn to_bytes_le(&self) -> Zeroizing<Vec<u8>> {
         let input_biguint: BigUint = self.0.into();
         let mut res = input_biguint.to_bytes_le();
-        //BigUint conversion ignores most significant zero bytes. We restore them otherwise serialization will fail (length % 8 != 0)
         res.resize(fr_byte_size(), 0);
         Zeroizing::new(res)
     }
 
+    /*
+    pub(crate) fn to_fr(mut self) -> Zeroizing<Fr> {
+        let result = Zeroizing::new(self.0);
+        self.zeroize();
+        result
+    }
+    */
+    
 }
 
 impl From<&mut Fr> for IdSecret {