Add BE serialization for Fr and identity pair/tuple

rln/src/protocol.rs

@@ -19,10 +19,7 @@ use crate::error::{ComputeIdSecretError, ConversionError, ProofError, ProtocolEr
 use crate::hashers::{hash_to_field, poseidon_hash};
 use crate::poseidon_tree::{MerkleProof, PoseidonTree};
 use crate::public::RLN_IDENTIFIER;
-use crate::utils::{
-    bytes_le_to_fr, bytes_le_to_vec_fr, bytes_le_to_vec_u8, fr_byte_size, fr_to_bytes_le,
-    normalize_usize, to_bigint, vec_fr_to_bytes_le, vec_u8_to_bytes_le,
-};
+use crate::utils::{bytes_be_to_fr, bytes_le_to_fr, bytes_le_to_vec_fr, bytes_le_to_vec_u8, fr_byte_size, fr_to_bytes_be, fr_to_bytes_le, normalize_usize, to_bigint, vec_fr_to_bytes_le, vec_u8_to_bytes_le};
 use utils::{ZerokitMerkleProof, ZerokitMerkleTree};
 ///////////////////////////////////////////////////////
 // RLN Witness data structure and utility functions
@@ -60,9 +57,17 @@ pub fn serialize_field_element(element: Fr) -> Vec<u8> {
     fr_to_bytes_le(&element)
 }
 
+pub fn serialize_field_element_be(element: Fr) -> Vec<u8> {
+    fr_to_bytes_be(&element)
+}
+
 pub fn deserialize_field_element(serialized: Vec<u8>) -> Fr {
     let (element, _) = bytes_le_to_fr(&serialized);
+    element
+}
 
+pub fn deserialize_field_element_be(serialized: Vec<u8>) -> Fr {
+    let (element, _) = bytes_be_to_fr(&serialized);
     element
 }
 
@@ -73,6 +78,13 @@ pub fn deserialize_identity_pair(serialized: Vec<u8>) -> (Fr, Fr) {
     (identity_secret_hash, id_commitment)
 }
 
+pub fn deserialize_identity_pair_be(serialized: Vec<u8>) -> (Fr, Fr) {
+    let (identity_secret_hash, read) = bytes_be_to_fr(&serialized);
+    let (id_commitment, _) = bytes_be_to_fr(&serialized[read..]);
+
+    (identity_secret_hash, id_commitment)
+}
+
 pub fn deserialize_identity_tuple(serialized: Vec<u8>) -> (Fr, Fr, Fr, Fr) {
     let mut all_read = 0;
 
@@ -95,6 +107,28 @@ pub fn deserialize_identity_tuple(serialized: Vec<u8>) -> (Fr, Fr, Fr, Fr) {
     )
 }
 
+pub fn deserialize_identity_tuple_be(serialized: Vec<u8>) -> (Fr, Fr, Fr, Fr) {
+    let mut all_read = 0;
+
+    let (identity_trapdoor, read) = bytes_be_to_fr(&serialized[all_read..]);
+    all_read += read;
+
+    let (identity_nullifier, read) = bytes_be_to_fr(&serialized[all_read..]);
+    all_read += read;
+
+    let (identity_secret_hash, read) = bytes_be_to_fr(&serialized[all_read..]);
+    all_read += read;
+
+    let (identity_commitment, _) = bytes_be_to_fr(&serialized[all_read..]);
+
+    (
+        identity_trapdoor,
+        identity_nullifier,
+        identity_secret_hash,
+        identity_commitment,
+    )
+}
+
 /// Serializes witness
 ///
 /// # Errors

rln/src/utils.rs

@@ -47,6 +47,15 @@ pub fn bytes_le_to_fr(input: &[u8]) -> (Fr, usize) {
     )
 }
 
+#[inline(always)]
+pub fn bytes_be_to_fr(input: &[u8]) -> (Fr, usize) {
+    let el_size = fr_byte_size();
+    (
+        Fr::from(BigUint::from_bytes_be(&input[0..el_size])),
+        el_size,
+    )
+}
+
 #[inline(always)]
 pub fn fr_to_bytes_le(input: &Fr) -> Vec<u8> {
     let input_biguint: BigUint = (*input).into();
@@ -56,6 +65,15 @@ pub fn fr_to_bytes_le(input: &Fr) -> Vec<u8> {
     res
 }
 
+#[inline(always)]
+pub fn fr_to_bytes_be(input: &Fr) -> Vec<u8> {
+    let input_biguint: BigUint = (*input).into();
+    let mut res = input_biguint.to_bytes_be();
+    //BigUint conversion ignores most significant zero bytes. We restore them otherwise serialization will fail (length % 8 != 0)
+    res.resize(fr_byte_size(), 0);
+    res
+}
+
 #[inline(always)]
 pub fn vec_fr_to_bytes_le(input: &[Fr]) -> Vec<u8> {
     // Calculate capacity for Vec: