Add hash_be and poseidon_hash_be functions

rln/src/public.rs

@@ -7,8 +7,8 @@ use crate::protocol::{
     serialize_proof_values, serialize_witness, verify_proof,
 };
 use crate::utils::{
-    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, vec_fr_to_bytes_le, vec_u8_to_bytes_le,
+    bytes_be_to_vec_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, vec_fr_to_bytes_le, vec_u8_to_bytes_le,
 };
 #[cfg(not(target_arch = "wasm32"))]
 use {
@@ -1493,6 +1493,20 @@ pub fn hash<R: Read, W: Write>(
     Ok(())
 }
 
+/// same as hash function but in BE format
+pub fn hash_be<R: Read, W: Write>(
+    mut input_data: R,
+    mut output_data: W,
+) -> Result<(), std::io::Error> {
+    let mut serialized: Vec<u8> = Vec::new();
+    input_data.read_to_end(&mut serialized)?;
+
+    let hash = hash_to_field(&serialized);
+    output_data.write_all(&fr_to_bytes_be(&hash))?;
+
+    Ok(())
+}
+
 /// Hashes a set of elements to a single element in the working prime field, using Poseidon.
 ///
 /// The result is computed as the Poseidon Hash of the input signal.
@@ -1529,3 +1543,18 @@ pub fn poseidon_hash<R: Read, W: Write>(
 
     Ok(())
 }
+
+/// same as poseidon_hash function but in BE format. Note that input is expected in BE format too.
+pub fn poseidon_hash_be<R: Read, W: Write>(
+    mut input_data: R,
+    mut output_data: W,
+) -> Result<(), RLNError> {
+    let mut serialized: Vec<u8> = Vec::new();
+    input_data.read_to_end(&mut serialized)?;
+
+    let (inputs, _) = bytes_be_to_vec_fr(&serialized)?;
+    let hash = utils_poseidon_hash(inputs.as_ref());
+    output_data.write_all(&fr_to_bytes_be(&hash))?;
+
+    Ok(())
+}

rln/src/utils.rs

@@ -138,6 +138,24 @@ pub fn bytes_le_to_vec_fr(input: &[u8]) -> Result<(Vec<Fr>, usize), ConversionEr
     Ok((res, read))
 }
 
+#[inline(always)]
+pub fn bytes_be_to_vec_fr(input: &[u8]) -> Result<(Vec<Fr>, usize), ConversionError> {
+    let mut read: usize = 0;
+    let mut res: Vec<Fr> = Vec::new();
+
+    let len = usize::try_from(u64::from_be_bytes(input[0..8].try_into()?))?;
+    read += 8;
+
+    let el_size = fr_byte_size();
+    for i in 0..len {
+        let (curr_el, _) = bytes_be_to_fr(&input[8 + el_size * i..8 + el_size * (i + 1)]);
+        res.push(curr_el);
+        read += el_size;
+    }
+
+    Ok((res, read))
+}
+
 #[inline(always)]
 pub fn bytes_le_to_vec_usize(input: &[u8]) -> Result<Vec<usize>, ConversionError> {
     let nof_elem = usize::try_from(u64::from_le_bytes(input[0..8].try_into()?))?;