chore(rln): bring hash functions under a single module (#146)

rln/src/hashers.rs

@@ -1,7 +1,8 @@
 // This crate instantiate the Poseidon hash algorithm
 
-use crate::circuit::Fr;
+use crate::{circuit::Fr, utils::bytes_le_to_fr};
 use once_cell::sync::Lazy;
+use tiny_keccak::{Hasher, Keccak};
 use utils::poseidon::Poseidon;
 
 // These indexed constants hardcodes the supported round parameters tuples (t, RF, RN, SKIP_MATRICES) for the Bn254 scalar field
@@ -26,3 +27,17 @@ pub fn poseidon_hash(input: &[Fr]) -> Fr {
         .hash(input.to_vec())
         .expect("hash with fixed input size can't fail")
 }
+
+// Hashes arbitrary signal to the underlying prime field
+pub fn hash_to_field(signal: &[u8]) -> Fr {
+    // We hash the input signal using Keccak256
+    // (note that a bigger curve order might require a bigger hash blocksize)
+    let mut hash = [0; 32];
+    let mut hasher = Keccak::v256();
+    hasher.update(signal);
+    hasher.finalize(&mut hash);
+
+    // We export the hash as a field element
+    let (el, _) = bytes_le_to_fr(hash.as_ref());
+    el
+}

rln/src/lib.rs

@@ -1,7 +1,7 @@
 #![allow(dead_code)]
 
 pub mod circuit;
-pub mod poseidon_hash;
+pub mod hashers;
 pub mod poseidon_tree;
 pub mod protocol;
 pub mod public;

rln/src/poseidon_tree.rs

@@ -3,7 +3,7 @@
 // Implementation inspired by https://github.com/worldcoin/semaphore-rs/blob/d462a4372f1fd9c27610f2acfe4841fab1d396aa/src/poseidon_tree.rs (no differences)
 
 use crate::circuit::Fr;
-use crate::poseidon_hash::poseidon_hash;
+use crate::hashers::poseidon_hash;
 use cfg_if::cfg_if;
 use utils::merkle_tree::*;
 

rln/src/protocol.rs

@@ -17,7 +17,8 @@ use thiserror::Error;
 use tiny_keccak::{Hasher as _, Keccak};
 
 use crate::circuit::{Curve, Fr};
-use crate::poseidon_hash::poseidon_hash;
+use crate::hashers::hash_to_field;
+use crate::hashers::poseidon_hash;
 use crate::poseidon_tree::*;
 use crate::public::RLN_IDENTIFIER;
 use crate::utils::*;
@@ -483,20 +484,6 @@ pub fn extended_seeded_keygen(signal: &[u8]) -> (Fr, Fr, Fr, Fr) {
     )
 }
 
-// Hashes arbitrary signal to the underlying prime field
-pub fn hash_to_field(signal: &[u8]) -> Fr {
-    // We hash the input signal using Keccak256
-    // (note that a bigger curve order might require a bigger hash blocksize)
-    let mut hash = [0; 32];
-    let mut hasher = Keccak::v256();
-    hasher.update(signal);
-    hasher.finalize(&mut hash);
-
-    // We export the hash as a field element
-    let (el, _) = bytes_le_to_fr(hash.as_ref());
-    el
-}
-
 pub fn compute_id_secret(
     share1: (Fr, Fr),
     share2: (Fr, Fr),

rln/src/public.rs

@@ -1,5 +1,5 @@
 use crate::circuit::{vk_from_raw, zkey_from_raw, Curve, Fr};
-use crate::poseidon_hash::poseidon_hash as utils_poseidon_hash;
+use crate::hashers::{hash_to_field, poseidon_hash as utils_poseidon_hash};
 use crate::poseidon_tree::PoseidonTree;
 use crate::protocol::*;
 use crate::utils::*;

rln/tests/ffi.rs

@@ -4,7 +4,7 @@ mod test {
     use rand::Rng;
     use rln::circuit::*;
     use rln::ffi::{hash as ffi_hash, poseidon_hash as ffi_poseidon_hash, *};
-    use rln::poseidon_hash::{poseidon_hash as utils_poseidon_hash, ROUND_PARAMS};
+    use rln::hashers::{hash_to_field, poseidon_hash as utils_poseidon_hash, ROUND_PARAMS};
     use rln::protocol::*;
     use rln::public::RLN;
     use rln::utils::*;

rln/tests/poseidon_tree.rs

@@ -88,7 +88,7 @@ mod pmtree_test {
 
     use pmtree::*;
     use rln::circuit::Fr;
-    use rln::poseidon_hash::poseidon_hash;
+    use rln::hashers::{hash_to_field, poseidon_hash};
     use rln::poseidon_tree::PoseidonHash;
     use rln::protocol::hash_to_field;
     use rln::utils::str_to_fr;

rln/tests/protocol.rs

@@ -4,7 +4,7 @@ mod test {
         circom_from_folder, vk_from_folder, zkey_from_folder, Fr, TEST_RESOURCES_FOLDER,
         TEST_TREE_HEIGHT,
     };
-    use rln::poseidon_hash::poseidon_hash;
+    use rln::hashers::{hash_to_field, poseidon_hash};
     use rln::poseidon_tree::PoseidonTree;
     use rln::protocol::*;
     use rln::utils::str_to_fr;

rln/tests/public.rs

@@ -3,8 +3,8 @@ mod test {
     use ark_std::{rand::thread_rng, UniformRand};
     use rand::Rng;
     use rln::circuit::{Fr, TEST_RESOURCES_FOLDER, TEST_TREE_HEIGHT};
-    use rln::poseidon_hash::{poseidon_hash as utils_poseidon_hash, ROUND_PARAMS};
+    use rln::hashers::{hash_to_field, poseidon_hash as utils_poseidon_hash, ROUND_PARAMS};
-    use rln::protocol::{compute_tree_root, deserialize_identity_tuple, hash_to_field};
+    use rln::protocol::{compute_tree_root, deserialize_identity_tuple};
     use rln::public::{hash as public_hash, poseidon_hash as public_poseidon_hash, RLN};
     use rln::utils::*;
     use std::io::Cursor;