Switch to Ceno field element and transcript

Author: darth-cy

circ_blocks/examples/zxc.rs

@@ -31,7 +31,6 @@ use std::path::PathBuf;
 use libspartan::{
     instance::Instance, Assignment, InputsAssignment, MemsAssignment, VarsAssignment, SNARK,
 };
-use merlin::Transcript;
 use serde::{Deserialize, Serialize};
 use std::time::*;
 

spartan_parallel/examples/interface.rs

@@ -7,7 +7,7 @@ use std::{fs::File, io::BufReader};
 
 use libspartan::scalar::{ScalarExt2, SpartanExtensionField};
 use libspartan::{instance::Instance, InputsAssignment, MemsAssignment, VarsAssignment, SNARK};
-use merlin::Transcript;
+use transcript::BasicTranscript as Transcript;
 use serde::{Deserialize, Serialize};
 use std::time::*;
 

spartan_parallel/src/bytes.rs

@@ -0,0 +1,30 @@
+use ff_ext::ExtensionField;
+use subtle::{Choice, CtOption};
+
+/// Attempts to convert a little-endian byte representation of
+/// a field element into an `ExtensionField`, failing if the input is not canonical.
+pub fn from_bytes<E: ExtensionField>(bytes: &[u8; 32]) -> CtOption<E> {
+    let mut padded = [0u8; 64];
+    padded[..32].copy_from_slice(bytes);
+
+    CtOption::new(
+        E::from_uniform_bytes(&padded),
+        Choice::from(1u8),
+    )
+}
+
+/// Converts an element of `ExtensionField` into a byte representation in
+/// little-endian byte order.
+pub fn to_bytes<E: ExtensionField>(num: E) -> [u8; 32] {
+    let mut res = [0; 32];
+    let els = num.to_canonical_u64_vec();
+    res[..8].copy_from_slice(&els[0].to_le_bytes());
+    res[8..16].copy_from_slice(&els[1].to_le_bytes());
+    res
+}
+
+/// Converts a 512-bit little endian integer into
+/// an `ExtensionField` element by reducing by the modulus.
+pub fn from_bytes_wide<E: ExtensionField>(bytes: &[u8; 64]) -> E {
+    E::from_uniform_bytes(bytes).into()
+}