From 229148eb5a7566e1af3cef1891a3a2f5776b2232 Mon Sep 17 00:00:00 2001
From: zhenfei <zhenfei.zhang@hotmail.com>
Date: Tue, 26 Jul 2022 11:34:47 -0400
Subject: [PATCH] move transcript to trait (#46)

---
 Cargo.toml                                    |  3 +-
 pcs/Cargo.toml                                |  5 +-
 pcs/src/errors.rs                             | 12 ++--
 pcs/src/multilinear_kzg/batching.rs           |  6 +-
 pcs/src/multilinear_kzg/util.rs               | 13 ++++-
 poly-iop/Cargo.toml                           |  3 +-
 poly-iop/src/errors.rs                        | 13 ++++-
 poly-iop/src/hyperplonk/mod.rs                |  6 +-
 poly-iop/src/lib.rs                           |  2 -
 poly-iop/src/perm_check/mod.rs                | 11 ++--
 poly-iop/src/prod_check/mod.rs                |  3 +-
 poly-iop/src/structs.rs                       |  5 +-
 poly-iop/src/sum_check/mod.rs                 | 10 ++--
 poly-iop/src/sum_check/verifier.rs            |  2 +-
 poly-iop/src/virtual_poly.rs                  |  3 +-
 poly-iop/src/zero_check/mod.rs                |  3 +-
 transcript/Cargo.toml                         | 17 ++++++
 transcript/src/errors.rs                      | 19 ++++++
 .../transcript.rs => transcript/src/lib.rs    | 58 +++++++++----------
 19 files changed, 122 insertions(+), 72 deletions(-)
 create mode 100644 transcript/Cargo.toml
 create mode 100644 transcript/src/errors.rs
 rename poly-iop/src/transcript.rs => transcript/src/lib.rs (71%)

diff --git a/Cargo.toml b/Cargo.toml
index d841a62..2300049 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -2,5 +2,6 @@
 members = [
   "hyperplonk",
   "pcs",
-  "poly-iop"
+  "poly-iop",
+  "transcript",
 ]
diff --git a/pcs/Cargo.toml b/pcs/Cargo.toml
index 42929f5..e74ebc5 100644
--- a/pcs/Cargo.toml
+++ b/pcs/Cargo.toml
@@ -17,8 +17,7 @@ ark-bls12-381 = { version = "0.3.0", default-features = false, features = [ "cur
 
 displaydoc = { version = "0.2.3", default-features = false }
 
-poly-iop = { path = "../poly-iop" }
-
+transcript = { path = "../transcript" }
 
 # Benchmarks
 [[bench]]
@@ -34,9 +33,7 @@ parallel = [
     "ark-ff/parallel",  
     "ark-poly/parallel", 
     "ark-ec/parallel",
-    "poly-iop/parallel"
     ]
 print-trace = [ 
     "ark-std/print-trace",
-    "poly-iop/print-trace"
     ] 
\ No newline at end of file
diff --git a/pcs/src/errors.rs b/pcs/src/errors.rs
index 99d060d..804c8b9 100644
--- a/pcs/src/errors.rs
+++ b/pcs/src/errors.rs
@@ -3,7 +3,7 @@
 use ark_serialize::SerializationError;
 use ark_std::string::String;
 use displaydoc::Display;
-use poly_iop::PolyIOPErrors;
+use transcript::TranscriptErrors;
 
 /// A `enum` specifying the possible failure modes of the PCS.
 #[derive(Display, Debug)]
@@ -18,8 +18,8 @@ pub enum PCSErrors {
     InvalidParameters(String),
     /// An error during (de)serialization: {0}
     SerializationError(SerializationError),
-    /// PolyIOP error {0}
-    PolyIOPErrors(PolyIOPErrors),
+    /// Transcript error {0}
+    TranscriptError(TranscriptErrors),
 }
 
 impl From<SerializationError> for PCSErrors {
@@ -28,8 +28,8 @@ impl From<SerializationError> for PCSErrors {
     }
 }
 
-impl From<PolyIOPErrors> for PCSErrors {
-    fn from(e: PolyIOPErrors) -> Self {
-        Self::PolyIOPErrors(e)
+impl From<TranscriptErrors> for PCSErrors {
+    fn from(e: TranscriptErrors) -> Self {
+        Self::TranscriptError(e)
     }
 }
diff --git a/pcs/src/multilinear_kzg/batching.rs b/pcs/src/multilinear_kzg/batching.rs
index 875eb89..de26eef 100644
--- a/pcs/src/multilinear_kzg/batching.rs
+++ b/pcs/src/multilinear_kzg/batching.rs
@@ -13,7 +13,7 @@ use crate::{
 use ark_ec::PairingEngine;
 use ark_poly::{DenseMultilinearExtension, EvaluationDomain, MultilinearExtension, Polynomial};
 use ark_std::{end_timer, start_timer, vec::Vec};
-use poly_iop::IOPTranscript;
+use transcript::IOPTranscript;
 
 /// Input
 /// - the prover parameters for univariate KZG,
@@ -237,12 +237,12 @@ pub(super) fn batch_verify_internal<E: PairingEngine>(
 
     // 3. check `q(r) == batch_proof.q_x_value.last` and `q(omega^i) =
     // batch_proof.q_x_value[i]`
-    for i in 0..points_len {
+    for (i, value) in values.iter().enumerate().take(points_len) {
         if !KZGUnivariatePCS::verify(
             uni_verifier_param,
             &batch_proof.q_x_commit,
             &domain.element(i),
-            &values[i],
+            &value,
             &batch_proof.q_x_opens[i],
         )? {
             #[cfg(debug_assertion)]
diff --git a/pcs/src/multilinear_kzg/util.rs b/pcs/src/multilinear_kzg/util.rs
index 1846a04..09d26de 100644
--- a/pcs/src/multilinear_kzg/util.rs
+++ b/pcs/src/multilinear_kzg/util.rs
@@ -7,9 +7,20 @@ use ark_poly::{
     MultilinearExtension, Polynomial, Radix2EvaluationDomain,
 };
 use ark_std::{end_timer, log2, start_timer};
-use poly_iop::bit_decompose;
 use std::cmp::max;
 
+/// Decompose an integer into a binary vector in little endian.
+#[allow(dead_code)]
+pub(crate) fn bit_decompose(input: u64, num_var: usize) -> Vec<bool> {
+    let mut res = Vec::with_capacity(num_var);
+    let mut i = input;
+    for _ in 0..num_var {
+        res.push(i & 1 == 1);
+        i >>= 1;
+    }
+    res
+}
+
 /// For an MLE w with `mle_num_vars` variables, and `point_len` number of
 /// points, compute the degree of the univariate polynomial `q(x):= w(l(x))`
 /// where l(x) is a list of polynomials that go through all points.
diff --git a/poly-iop/Cargo.toml b/poly-iop/Cargo.toml
index 3fcf4bd..f90f2dc 100644
--- a/poly-iop/Cargo.toml
+++ b/poly-iop/Cargo.toml
@@ -14,11 +14,12 @@ ark-serialize =  { version = "^0.3.0", default-features = false }
 ark-bls12-381 = { version = "0.3.0", default-features = false, features = [ "curve" ] }
 
 rand_chacha = { version = "0.3.0", default-features = false }
-merlin = { version = "3.0.0", default-features = false }
 displaydoc = { version = "0.2.3", default-features = false }
 
 rayon = { version = "1.5.2", default-features = false, optional = true }
 
+transcript = { path = "../transcript" }
+
 # Benchmarks
 [[bench]]
 name = "poly-iop-benches"
diff --git a/poly-iop/src/errors.rs b/poly-iop/src/errors.rs
index 748cfbe..60ecdcd 100644
--- a/poly-iop/src/errors.rs
+++ b/poly-iop/src/errors.rs
@@ -2,6 +2,7 @@
 
 use ark_std::string::String;
 use displaydoc::Display;
+use transcript::TranscriptErrors;
 
 /// A `enum` specifying the possible failure modes of the PolyIOP.
 #[derive(Display, Debug)]
@@ -14,12 +15,14 @@ pub enum PolyIOPErrors {
     InvalidProof(String),
     /// Invalid parameters: {0}
     InvalidParameters(String),
-    /// Invalid Transcript: {0}
-    InvalidTranscript(String),
+    /// Invalid challenge: {0}
+    InvalidChallenge(String),
     /// Should not arrive to this point
     ShouldNotArrive,
     /// An error during (de)serialization: {0}
     SerializationError(ark_serialize::SerializationError),
+    /// Transcript Error: {0}
+    TranscriptError(TranscriptErrors),
 }
 
 impl From<ark_serialize::SerializationError> for PolyIOPErrors {
@@ -27,3 +30,9 @@ impl From<ark_serialize::SerializationError> for PolyIOPErrors {
         Self::SerializationError(e)
     }
 }
+
+impl From<TranscriptErrors> for PolyIOPErrors {
+    fn from(e: TranscriptErrors) -> Self {
+        Self::TranscriptError(e)
+    }
+}
diff --git a/poly-iop/src/hyperplonk/mod.rs b/poly-iop/src/hyperplonk/mod.rs
index 2401adc..4eb3846 100644
--- a/poly-iop/src/hyperplonk/mod.rs
+++ b/poly-iop/src/hyperplonk/mod.rs
@@ -1,12 +1,10 @@
 //! Main module for the HyperPlonk PolyIOP.
 
-use crate::{
-    errors::PolyIOPErrors, perm_check::PermutationCheck, transcript::IOPTranscript,
-    zero_check::ZeroCheck,
-};
+use crate::{errors::PolyIOPErrors, perm_check::PermutationCheck, zero_check::ZeroCheck};
 use ark_ff::PrimeField;
 use ark_poly::DenseMultilinearExtension;
 use std::rc::Rc;
+use transcript::IOPTranscript;
 
 /// A trait for HyperPlonk Poly-IOPs
 pub trait HyperPlonkPIOP<F: PrimeField> {
diff --git a/poly-iop/src/lib.rs b/poly-iop/src/lib.rs
index 57f83f5..117f7c0 100644
--- a/poly-iop/src/lib.rs
+++ b/poly-iop/src/lib.rs
@@ -7,7 +7,6 @@ mod perm_check;
 mod prod_check;
 mod structs;
 mod sum_check;
-mod transcript;
 mod utils;
 mod virtual_poly;
 mod zero_check;
@@ -20,7 +19,6 @@ pub use perm_check::{
 };
 pub use prod_check::ProductCheck;
 pub use sum_check::SumCheck;
-pub use transcript::IOPTranscript;
 pub use utils::*;
 pub use virtual_poly::{VPAuxInfo, VirtualPolynomial};
 pub use zero_check::ZeroCheck;
diff --git a/poly-iop/src/perm_check/mod.rs b/poly-iop/src/perm_check/mod.rs
index d6c33e8..1eb9399 100644
--- a/poly-iop/src/perm_check/mod.rs
+++ b/poly-iop/src/perm_check/mod.rs
@@ -1,13 +1,14 @@
 //! Main module for the Permutation Check protocol
 
 use crate::{
-    errors::PolyIOPErrors, perm_check::util::compute_prod_0, structs::IOPProof,
-    transcript::IOPTranscript, utils::get_index, PolyIOP, VirtualPolynomial, ZeroCheck,
+    errors::PolyIOPErrors, perm_check::util::compute_prod_0, structs::IOPProof, utils::get_index,
+    PolyIOP, VirtualPolynomial, ZeroCheck,
 };
 use ark_ff::PrimeField;
 use ark_poly::DenseMultilinearExtension;
 use ark_std::{end_timer, start_timer};
 use std::rc::Rc;
+use transcript::IOPTranscript;
 
 pub mod util;
 
@@ -221,7 +222,7 @@ impl<F: PrimeField> PermutationCheck<F> for PolyIOP<F> {
         prod_x_binding: &F,
     ) -> Result<(), PolyIOPErrors> {
         if challenge.alpha.is_some() {
-            return Err(PolyIOPErrors::InvalidTranscript(
+            return Err(PolyIOPErrors::InvalidChallenge(
                 "alpha should not be sampled at the current stage".to_string(),
             ));
         }
@@ -268,7 +269,7 @@ impl<F: PrimeField> PermutationCheck<F> for PolyIOP<F> {
         let start = start_timer!(|| "compute all prod polynomial");
 
         if challenge.alpha.is_some() {
-            return Err(PolyIOPErrors::InvalidTranscript(
+            return Err(PolyIOPErrors::InvalidChallenge(
                 "alpha is already sampled".to_string(),
             ));
         }
@@ -372,7 +373,7 @@ impl<F: PrimeField> PermutationCheck<F> for PolyIOP<F> {
         let alpha = match challenge.alpha {
             Some(p) => p,
             None => {
-                return Err(PolyIOPErrors::InvalidTranscript(
+                return Err(PolyIOPErrors::InvalidChallenge(
                     "alpha is not sampled yet".to_string(),
                 ))
             },
diff --git a/poly-iop/src/prod_check/mod.rs b/poly-iop/src/prod_check/mod.rs
index 7f3ff33..8fd377f 100644
--- a/poly-iop/src/prod_check/mod.rs
+++ b/poly-iop/src/prod_check/mod.rs
@@ -1,8 +1,9 @@
 //! Main module for the Permutation Check protocol
 
-use crate::{errors::PolyIOPErrors, transcript::IOPTranscript, VirtualPolynomial, ZeroCheck};
+use crate::{errors::PolyIOPErrors, VirtualPolynomial, ZeroCheck};
 use ark_ff::PrimeField;
 use ark_poly::DenseMultilinearExtension;
+use transcript::IOPTranscript;
 
 /// A ProductCheck is derived from ZeroCheck.
 ///
diff --git a/poly-iop/src/structs.rs b/poly-iop/src/structs.rs
index ecccfc8..459a30e 100644
--- a/poly-iop/src/structs.rs
+++ b/poly-iop/src/structs.rs
@@ -2,17 +2,18 @@
 
 use crate::VirtualPolynomial;
 use ark_ff::PrimeField;
+use ark_serialize::{CanonicalSerialize, SerializationError, Write};
 
 /// An IOP proof is a collections of messages from prover to verifier at each
 /// round through the interactive protocol.
-#[derive(Clone, Debug, Default, PartialEq)]
+#[derive(Clone, Debug, Default, PartialEq, CanonicalSerialize)]
 pub struct IOPProof<F: PrimeField> {
     pub proofs: Vec<IOPProverMessage<F>>,
 }
 
 /// A message from the prover to the verifier at a given round
 /// is a list of evaluations.
-#[derive(Clone, Debug, Default, PartialEq)]
+#[derive(Clone, Debug, Default, PartialEq, CanonicalSerialize)]
 pub struct IOPProverMessage<F: PrimeField> {
     pub(crate) evaluations: Vec<F>,
 }
diff --git a/poly-iop/src/sum_check/mod.rs b/poly-iop/src/sum_check/mod.rs
index ebd036e..a8f7d5b 100644
--- a/poly-iop/src/sum_check/mod.rs
+++ b/poly-iop/src/sum_check/mod.rs
@@ -3,13 +3,13 @@
 use crate::{
     errors::PolyIOPErrors,
     structs::{IOPProof, IOPProverState, IOPVerifierState},
-    transcript::IOPTranscript,
     virtual_poly::{VPAuxInfo, VirtualPolynomial},
     PolyIOP,
 };
 use ark_ff::PrimeField;
 use ark_poly::DenseMultilinearExtension;
 use ark_std::{end_timer, start_timer};
+use transcript::IOPTranscript;
 
 mod prover;
 mod verifier;
@@ -160,7 +160,7 @@ impl<F: PrimeField> SumCheck<F> for PolyIOP<F> {
     ) -> Result<Self::Proof, PolyIOPErrors> {
         let start = start_timer!(|| "sum check prove");
 
-        transcript.append_aux_info(&poly.aux_info)?;
+        transcript.append_serializable_element(b"aux info", &poly.aux_info)?;
 
         let mut prover_state = IOPProverState::prover_init(poly)?;
         let mut challenge = None;
@@ -168,7 +168,7 @@ impl<F: PrimeField> SumCheck<F> for PolyIOP<F> {
         for _ in 0..poly.aux_info.num_variables {
             let prover_msg =
                 IOPProverState::prove_round_and_update_state(&mut prover_state, &challenge)?;
-            transcript.append_prover_message(&prover_msg)?;
+            transcript.append_serializable_element(b"prover msg", &prover_msg)?;
             prover_msgs.push(prover_msg);
             challenge = Some(transcript.get_and_append_challenge(b"Internal round")?);
         }
@@ -188,11 +188,11 @@ impl<F: PrimeField> SumCheck<F> for PolyIOP<F> {
     ) -> Result<Self::SumCheckSubClaim, PolyIOPErrors> {
         let start = start_timer!(|| "sum check verify");
 
-        transcript.append_aux_info(aux_info)?;
+        transcript.append_serializable_element(b"aux info", aux_info)?;
         let mut verifier_state = IOPVerifierState::verifier_init(aux_info);
         for i in 0..aux_info.num_variables {
             let prover_msg = proof.proofs.get(i).expect("proof is incomplete");
-            transcript.append_prover_message(prover_msg)?;
+            transcript.append_serializable_element(b"prover msg", prover_msg)?;
             IOPVerifierState::verify_round_and_update_state(
                 &mut verifier_state,
                 prover_msg,
diff --git a/poly-iop/src/sum_check/verifier.rs b/poly-iop/src/sum_check/verifier.rs
index 0e41269..24d90b7 100644
--- a/poly-iop/src/sum_check/verifier.rs
+++ b/poly-iop/src/sum_check/verifier.rs
@@ -4,11 +4,11 @@ use super::{SumCheckSubClaim, SumCheckVerifier};
 use crate::{
     errors::PolyIOPErrors,
     structs::{IOPProverMessage, IOPVerifierState},
-    transcript::IOPTranscript,
     virtual_poly::VPAuxInfo,
 };
 use ark_ff::PrimeField;
 use ark_std::{end_timer, start_timer};
+use transcript::IOPTranscript;
 
 #[cfg(feature = "parallel")]
 use rayon::iter::{IndexedParallelIterator, IntoParallelIterator, ParallelIterator};
diff --git a/poly-iop/src/virtual_poly.rs b/poly-iop/src/virtual_poly.rs
index 197b261..c16ced8 100644
--- a/poly-iop/src/virtual_poly.rs
+++ b/poly-iop/src/virtual_poly.rs
@@ -4,6 +4,7 @@
 use crate::errors::PolyIOPErrors;
 use ark_ff::PrimeField;
 use ark_poly::{DenseMultilinearExtension, MultilinearExtension};
+use ark_serialize::{CanonicalSerialize, SerializationError, Write};
 use ark_std::{
     end_timer,
     rand::{Rng, RngCore},
@@ -51,7 +52,7 @@ pub struct VirtualPolynomial<F: PrimeField> {
     raw_pointers_lookup_table: HashMap<*const DenseMultilinearExtension<F>, usize>,
 }
 
-#[derive(Clone, Debug, Default, PartialEq)]
+#[derive(Clone, Debug, Default, PartialEq, CanonicalSerialize)]
 /// Auxiliary information about the multilinear polynomial
 pub struct VPAuxInfo<F: PrimeField> {
     /// max number of multiplicands in each product
diff --git a/poly-iop/src/zero_check/mod.rs b/poly-iop/src/zero_check/mod.rs
index eab9e65..56b77f0 100644
--- a/poly-iop/src/zero_check/mod.rs
+++ b/poly-iop/src/zero_check/mod.rs
@@ -1,8 +1,9 @@
 //! Main module for the ZeroCheck protocol.
 
-use crate::{errors::PolyIOPErrors, sum_check::SumCheck, transcript::IOPTranscript, PolyIOP};
+use crate::{errors::PolyIOPErrors, sum_check::SumCheck, PolyIOP};
 use ark_ff::PrimeField;
 use ark_std::{end_timer, start_timer};
+use transcript::IOPTranscript;
 
 /// A zero check IOP subclaim for \hat f(x) is 0, consists of the following:
 ///   - the SubClaim from the SumCheck
diff --git a/transcript/Cargo.toml b/transcript/Cargo.toml
new file mode 100644
index 0000000..91c7c2f
--- /dev/null
+++ b/transcript/Cargo.toml
@@ -0,0 +1,17 @@
+[package]
+name = "transcript"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+
+merlin = { version = "3.0.0", default-features = false }
+
+
+ark-ff = { version = "^0.3.0", default-features = false }
+ark-serialize =  { version = "^0.3.0", default-features = false }
+ark-std = { version = "^0.3.0", default-features = false }
+
+displaydoc = { version = "0.2.3", default-features = false }
diff --git a/transcript/src/errors.rs b/transcript/src/errors.rs
new file mode 100644
index 0000000..0886575
--- /dev/null
+++ b/transcript/src/errors.rs
@@ -0,0 +1,19 @@
+//! Error module.
+
+use ark_std::string::String;
+use displaydoc::Display;
+
+/// A `enum` specifying the possible failure modes of the Transcript.
+#[derive(Display, Debug)]
+pub enum TranscriptErrors {
+    /// Invalid Transcript: {0}
+    InvalidTranscript(String),
+    /// An error during (de)serialization: {0}
+    SerializationError(ark_serialize::SerializationError),
+}
+
+impl From<ark_serialize::SerializationError> for TranscriptErrors {
+    fn from(e: ark_serialize::SerializationError) -> Self {
+        Self::SerializationError(e)
+    }
+}
diff --git a/poly-iop/src/transcript.rs b/transcript/src/lib.rs
similarity index 71%
rename from poly-iop/src/transcript.rs
rename to transcript/src/lib.rs
index 7202379..63ad852 100644
--- a/poly-iop/src/transcript.rs
+++ b/transcript/src/lib.rs
@@ -3,13 +3,14 @@
 //! useful.
 //! TODO(ZZ): decide which APIs need to be public.
 
+mod errors;
+pub use errors::TranscriptErrors;
+
 use ark_ff::PrimeField;
 use ark_serialize::CanonicalSerialize;
 use merlin::Transcript;
 use std::marker::PhantomData;
 
-use crate::{errors::PolyIOPErrors, structs::IOPProverMessage, to_bytes, virtual_poly::VPAuxInfo};
-
 /// An IOP transcript consists of a Merlin transcript and a flag `is_empty` to
 /// indicate that if the transcript is empty.
 ///
@@ -27,6 +28,7 @@ pub struct IOPTranscript<F: PrimeField> {
     phantom: PhantomData<F>,
 }
 
+// TODO: Make this into a Trait
 impl<F: PrimeField> IOPTranscript<F> {
     /// Create a new IOP transcript.
     pub fn new(label: &'static [u8]) -> Self {
@@ -42,29 +44,18 @@ impl<F: PrimeField> IOPTranscript<F> {
         &mut self,
         label: &'static [u8],
         msg: &[u8],
-    ) -> Result<(), PolyIOPErrors> {
+    ) -> Result<(), TranscriptErrors> {
         self.transcript.append_message(label, msg);
         self.is_empty = false;
         Ok(())
     }
 
-    // Append the aux information for a virtual polynomial.
-    pub(crate) fn append_aux_info(&mut self, aux_info: &VPAuxInfo<F>) -> Result<(), PolyIOPErrors> {
-        let message = format!(
-            "max_mul {} num_var {}",
-            aux_info.max_degree, aux_info.num_variables
-        );
-        self.append_message(b"aux info", message.as_bytes())?;
-
-        Ok(())
-    }
-
     // Append the message to the transcript.
     pub fn append_field_element(
         &mut self,
         label: &'static [u8],
         field_elem: &F,
-    ) -> Result<(), PolyIOPErrors> {
+    ) -> Result<(), TranscriptErrors> {
         self.append_message(label, &to_bytes!(field_elem)?)
     }
 
@@ -73,30 +64,22 @@ impl<F: PrimeField> IOPTranscript<F> {
         &mut self,
         label: &'static [u8],
         group_elem: &S,
-    ) -> Result<(), PolyIOPErrors> {
+    ) -> Result<(), TranscriptErrors> {
         self.append_message(label, &to_bytes!(group_elem)?)
     }
 
-    // Append a prover message to the transcript.
-    pub(crate) fn append_prover_message(
-        &mut self,
-        prover_message: &IOPProverMessage<F>,
-    ) -> Result<(), PolyIOPErrors> {
-        for e in prover_message.evaluations.iter() {
-            self.append_field_element(b"prover_message", e)?;
-        }
-        Ok(())
-    }
-
     // Generate the challenge from the current transcript
     // and append it to the transcript.
     //
     // The output field element is statistical uniform as long
     // as the field has a size less than 2^384.
-    pub fn get_and_append_challenge(&mut self, label: &'static [u8]) -> Result<F, PolyIOPErrors> {
+    pub fn get_and_append_challenge(
+        &mut self,
+        label: &'static [u8],
+    ) -> Result<F, TranscriptErrors> {
         //  we need to reject when transcript is empty
         if self.is_empty {
-            return Err(PolyIOPErrors::InvalidTranscript(
+            return Err(TranscriptErrors::InvalidTranscript(
                 "transcript is empty".to_string(),
             ));
         }
@@ -114,14 +97,14 @@ impl<F: PrimeField> IOPTranscript<F> {
     //
     // The output field element are statistical uniform as long
     // as the field has a size less than 2^384.
-    pub(crate) fn get_and_append_challenge_vectors(
+    pub fn get_and_append_challenge_vectors(
         &mut self,
         label: &'static [u8],
         len: usize,
-    ) -> Result<Vec<F>, PolyIOPErrors> {
+    ) -> Result<Vec<F>, TranscriptErrors> {
         //  we need to reject when transcript is empty
         if self.is_empty {
-            return Err(PolyIOPErrors::InvalidTranscript(
+            return Err(TranscriptErrors::InvalidTranscript(
                 "transcript is empty".to_string(),
             ));
         }
@@ -133,3 +116,14 @@ impl<F: PrimeField> IOPTranscript<F> {
         Ok(res)
     }
 }
+
+/// Takes as input a struct, and converts them to a series of bytes. All traits
+/// that implement `CanonicalSerialize` can be automatically converted to bytes
+/// in this manner.
+#[macro_export]
+macro_rules! to_bytes {
+    ($x:expr) => {{
+        let mut buf = ark_std::vec![];
+        ark_serialize::CanonicalSerialize::serialize($x, &mut buf).map(|_| buf)
+    }};
+}