From 1d013b95ddfb02519c75cc8d5e3f64684a79b269 Mon Sep 17 00:00:00 2001
From: wborgeaud <williamborgeaud@gmail.com>
Date: Fri, 11 Feb 2022 16:22:57 +0100
Subject: [PATCH 1/4] Fix `hash_or_noop` in Merkle proof.

---
 plonky2/src/hash/merkle_proofs.rs |  2 +-
 plonky2/src/plonk/config.rs       | 11 +++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/plonky2/src/hash/merkle_proofs.rs b/plonky2/src/hash/merkle_proofs.rs
index f90f0657..7ef81570 100644
--- a/plonky2/src/hash/merkle_proofs.rs
+++ b/plonky2/src/hash/merkle_proofs.rs
@@ -32,7 +32,7 @@ pub(crate) fn verify_merkle_proof<F: RichField, H: Hasher<F>>(
     proof: &MerkleProof<F, H>,
 ) -> Result<()> {
     let mut index = leaf_index;
-    let mut current_digest = H::hash_no_pad(&leaf_data);
+    let mut current_digest = H::hash_or_noop(&leaf_data);
     for &sibling_digest in proof.siblings.iter() {
         let bit = index & 1;
         index >>= 1;
diff --git a/plonky2/src/plonk/config.rs b/plonky2/src/plonk/config.rs
index fdca7037..76891240 100644
--- a/plonky2/src/plonk/config.rs
+++ b/plonky2/src/plonk/config.rs
@@ -46,6 +46,17 @@ pub trait Hasher<F: RichField>: Sized + Clone + Debug + Eq + PartialEq {
         Self::hash_no_pad(&padded_input)
     }
 
+    /// Hash the slice if necessary to reduce its length to ~256 bits. If it already fits, this is a
+    /// no-op.
+    fn hash_or_noop(inputs: &[F]) -> Self::Hash {
+        if inputs.len() <= 4 {
+            let inputs_bytes = HashOut::from_partial(inputs).to_bytes();
+            Self::Hash::from_bytes(&inputs_bytes)
+        } else {
+            Self::hash_no_pad(inputs)
+        }
+    }
+
     fn two_to_one(left: Self::Hash, right: Self::Hash) -> Self::Hash;
 }
 

From f7256a6efc361d206879b65c5240ba7fe25d7a3c Mon Sep 17 00:00:00 2001
From: wborgeaud <williamborgeaud@gmail.com>
Date: Fri, 11 Feb 2022 16:41:44 +0100
Subject: [PATCH 2/4] Other fixes

---
 plonky2/src/hash/merkle_tree.rs      | 4 ++--
 plonky2/src/hash/path_compression.rs | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/plonky2/src/hash/merkle_tree.rs b/plonky2/src/hash/merkle_tree.rs
index e9460c14..f9890aa5 100644
--- a/plonky2/src/hash/merkle_tree.rs
+++ b/plonky2/src/hash/merkle_tree.rs
@@ -63,7 +63,7 @@ fn fill_subtree<F: RichField, H: Hasher<F>>(
 ) -> H::Hash {
     assert_eq!(leaves.len(), digests_buf.len() / 2 + 1);
     if digests_buf.is_empty() {
-        H::hash_no_pad(&leaves[0])
+        H::hash_or_noop(&leaves[0])
     } else {
         // Layout is: left recursive output || left child digest
         //             || right child digest || right recursive output.
@@ -99,7 +99,7 @@ fn fill_digests_buf<F: RichField, H: Hasher<F>>(
             .par_iter_mut()
             .zip(leaves)
             .for_each(|(cap_buf, leaf)| {
-                cap_buf.write(H::hash_no_pad(leaf));
+                cap_buf.write(H::hash_or_noop(leaf));
             });
         return;
     }
diff --git a/plonky2/src/hash/path_compression.rs b/plonky2/src/hash/path_compression.rs
index 56c355fd..fe7850f4 100644
--- a/plonky2/src/hash/path_compression.rs
+++ b/plonky2/src/hash/path_compression.rs
@@ -66,7 +66,7 @@ pub(crate) fn decompress_merkle_proofs<F: RichField, H: Hasher<F>>(
 
     for (&i, v) in leaves_indices.iter().zip(leaves_data) {
         // Observe the leaves.
-        seen.insert(i + num_leaves, H::hash_no_pad(v));
+        seen.insert(i + num_leaves, H::hash_or_noop(v));
     }
 
     // Iterators over the siblings.

From 736b65b0a7d595b0e1417bd08607edcda859e548 Mon Sep 17 00:00:00 2001
From: wborgeaud <williamborgeaud@gmail.com>
Date: Sat, 12 Feb 2022 15:18:20 +0100
Subject: [PATCH 3/4] PR feedback

---
 plonky2/src/hash/hashing.rs | 10 ----------
 plonky2/src/plonk/config.rs |  9 +++++++--
 2 files changed, 7 insertions(+), 12 deletions(-)

diff --git a/plonky2/src/hash/hashing.rs b/plonky2/src/hash/hashing.rs
index 468bd1b8..9d043ea3 100644
--- a/plonky2/src/hash/hashing.rs
+++ b/plonky2/src/hash/hashing.rs
@@ -12,16 +12,6 @@ pub(crate) const SPONGE_RATE: usize = 8;
 pub(crate) const SPONGE_CAPACITY: usize = 4;
 pub const SPONGE_WIDTH: usize = SPONGE_RATE + SPONGE_CAPACITY;
 
-/// Hash the slice if necessary to reduce its length to ~256 bits. If it already fits, this is a
-/// no-op.
-pub fn hash_or_noop<F: RichField, P: PlonkyPermutation<F>>(inputs: &[F]) -> HashOut<F> {
-    if inputs.len() <= 4 {
-        HashOut::from_partial(inputs)
-    } else {
-        hash_n_to_hash_no_pad::<F, P>(inputs)
-    }
-}
-
 impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
     pub fn hash_or_noop<H: AlgebraicHasher<F>>(&mut self, inputs: Vec<Target>) -> HashOutTarget {
         let zero = self.zero();
diff --git a/plonky2/src/plonk/config.rs b/plonky2/src/plonk/config.rs
index 76891240..40179c38 100644
--- a/plonky2/src/plonk/config.rs
+++ b/plonky2/src/plonk/config.rs
@@ -3,6 +3,7 @@ use std::fmt::Debug;
 use plonky2_field::extension_field::quadratic::QuadraticExtension;
 use plonky2_field::extension_field::{Extendable, FieldExtension};
 use plonky2_field::goldilocks_field::GoldilocksField;
+use plonky2_util::ceil_div_usize;
 use serde::{de::DeserializeOwned, Serialize};
 
 use crate::hash::hash_types::HashOut;
@@ -49,8 +50,12 @@ pub trait Hasher<F: RichField>: Sized + Clone + Debug + Eq + PartialEq {
     /// Hash the slice if necessary to reduce its length to ~256 bits. If it already fits, this is a
     /// no-op.
     fn hash_or_noop(inputs: &[F]) -> Self::Hash {
-        if inputs.len() <= 4 {
-            let inputs_bytes = HashOut::from_partial(inputs).to_bytes();
+        if inputs.len() * ceil_div_usize(F::BITS, 8) <= Self::HASH_SIZE {
+            let mut inputs_bytes = inputs
+                .iter()
+                .flat_map(|x| x.to_canonical_u64().to_le_bytes())
+                .collect::<Vec<_>>();
+            inputs_bytes.resize(Self::HASH_SIZE, 0);
             Self::Hash::from_bytes(&inputs_bytes)
         } else {
             Self::hash_no_pad(inputs)

From 7af2d05828240123e70f108dc0baf67a5338788c Mon Sep 17 00:00:00 2001
From: wborgeaud <williamborgeaud@gmail.com>
Date: Sun, 13 Feb 2022 15:04:40 +0100
Subject: [PATCH 4/4] Save allocation and add const generic bound

---
 plonky2/benches/merkle.rs               |  7 +++++-
 plonky2/src/fri/oracle.rs               | 17 ++++++++++----
 plonky2/src/fri/proof.rs                |  5 ++++-
 plonky2/src/fri/prover.rs               | 10 +++++++--
 plonky2/src/fri/verifier.rs             | 21 ++++++++++-------
 plonky2/src/gates/gate_testing.rs       |  7 ++++--
 plonky2/src/hash/merkle_proofs.rs       |  5 ++++-
 plonky2/src/hash/merkle_tree.rs         | 25 +++++++++++++--------
 plonky2/src/hash/path_compression.rs    |  5 ++++-
 plonky2/src/plonk/circuit_builder.rs    | 15 ++++++++++---
 plonky2/src/plonk/circuit_data.rs       | 30 ++++++++++++++++++++-----
 plonky2/src/plonk/config.rs             | 18 ++++++++-------
 plonky2/src/plonk/proof.rs              | 15 ++++++++++---
 plonky2/src/plonk/prover.rs             |  5 ++++-
 plonky2/src/plonk/recursive_verifier.rs | 15 ++++++++++---
 plonky2/src/plonk/verifier.rs           | 10 +++++++--
 starky/src/prover.rs                    |  3 ++-
 starky/src/verifier.rs                  |  4 +++-
 18 files changed, 160 insertions(+), 57 deletions(-)

diff --git a/plonky2/benches/merkle.rs b/plonky2/benches/merkle.rs
index 7445682b..8bc43730 100644
--- a/plonky2/benches/merkle.rs
+++ b/plonky2/benches/merkle.rs
@@ -1,3 +1,5 @@
+#![feature(generic_const_exprs)]
+
 use criterion::{criterion_group, criterion_main, BenchmarkId, Criterion};
 use plonky2::field::goldilocks_field::GoldilocksField;
 use plonky2::hash::hash_types::RichField;
@@ -9,7 +11,10 @@ use tynm::type_name;
 
 const ELEMS_PER_LEAF: usize = 135;
 
-pub(crate) fn bench_merkle_tree<F: RichField, H: Hasher<F>>(c: &mut Criterion) {
+pub(crate) fn bench_merkle_tree<F: RichField, H: Hasher<F>>(c: &mut Criterion)
+where
+    [(); H::HASH_SIZE]:,
+{
     let mut group = c.benchmark_group(&format!(
         "merkle-tree<{}, {}>",
         type_name::<F>(),
diff --git a/plonky2/src/fri/oracle.rs b/plonky2/src/fri/oracle.rs
index 0922962a..bd1e9ac5 100644
--- a/plonky2/src/fri/oracle.rs
+++ b/plonky2/src/fri/oracle.rs
@@ -12,7 +12,7 @@ use crate::fri::FriParams;
 use crate::hash::hash_types::RichField;
 use crate::hash::merkle_tree::MerkleTree;
 use crate::iop::challenger::Challenger;
-use crate::plonk::config::GenericConfig;
+use crate::plonk::config::{GenericConfig, Hasher};
 use crate::timed;
 use crate::util::reducing::ReducingFactor;
 use crate::util::reverse_bits;
@@ -43,7 +43,10 @@ impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>
         cap_height: usize,
         timing: &mut TimingTree,
         fft_root_table: Option<&FftRootTable<F>>,
-    ) -> Self {
+    ) -> Self
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         let coeffs = timed!(
             timing,
             "IFFT",
@@ -68,7 +71,10 @@ impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>
         cap_height: usize,
         timing: &mut TimingTree,
         fft_root_table: Option<&FftRootTable<F>>,
-    ) -> Self {
+    ) -> Self
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         let degree = polynomials[0].len();
         let lde_values = timed!(
             timing,
@@ -133,7 +139,10 @@ impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>
         challenger: &mut Challenger<F, C::Hasher>,
         fri_params: &FriParams,
         timing: &mut TimingTree,
-    ) -> FriProof<F, C::Hasher, D> {
+    ) -> FriProof<F, C::Hasher, D>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         assert!(D > 1, "Not implemented for D=1.");
         let alpha = challenger.get_extension_challenge::<D>();
         let mut alpha = ReducingFactor::new(alpha);
diff --git a/plonky2/src/fri/proof.rs b/plonky2/src/fri/proof.rs
index 44f74cba..9c6961a4 100644
--- a/plonky2/src/fri/proof.rs
+++ b/plonky2/src/fri/proof.rs
@@ -245,7 +245,10 @@ impl<F: RichField + Extendable<D>, H: Hasher<F>, const D: usize> CompressedFriPr
         challenges: &ProofChallenges<F, D>,
         fri_inferred_elements: FriInferredElements<F, D>,
         params: &FriParams,
-    ) -> FriProof<F, H, D> {
+    ) -> FriProof<F, H, D>
+    where
+        [(); H::HASH_SIZE]:,
+    {
         let CompressedFriProof {
             commit_phase_merkle_caps,
             query_round_proofs,
diff --git a/plonky2/src/fri/prover.rs b/plonky2/src/fri/prover.rs
index 5cd5fdf1..5a20ab9d 100644
--- a/plonky2/src/fri/prover.rs
+++ b/plonky2/src/fri/prover.rs
@@ -24,7 +24,10 @@ pub fn fri_proof<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const
     challenger: &mut Challenger<F, C::Hasher>,
     fri_params: &FriParams,
     timing: &mut TimingTree,
-) -> FriProof<F, C::Hasher, D> {
+) -> FriProof<F, C::Hasher, D>
+where
+    [(); C::Hasher::HASH_SIZE]:,
+{
     let n = lde_polynomial_values.len();
     assert_eq!(lde_polynomial_coeffs.len(), n);
 
@@ -68,7 +71,10 @@ fn fri_committed_trees<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>,
 ) -> (
     Vec<MerkleTree<F, C::Hasher>>,
     PolynomialCoeffs<F::Extension>,
-) {
+)
+where
+    [(); C::Hasher::HASH_SIZE]:,
+{
     let mut trees = Vec::new();
 
     let mut shift = F::MULTIPLICATIVE_GROUP_GENERATOR;
diff --git a/plonky2/src/fri/verifier.rs b/plonky2/src/fri/verifier.rs
index 49cfa053..2607ab0d 100644
--- a/plonky2/src/fri/verifier.rs
+++ b/plonky2/src/fri/verifier.rs
@@ -56,18 +56,17 @@ pub(crate) fn fri_verify_proof_of_work<F: RichField + Extendable<D>, const D: us
     Ok(())
 }
 
-pub fn verify_fri_proof<
-    F: RichField + Extendable<D>,
-    C: GenericConfig<D, F = F>,
-    const D: usize,
->(
+pub fn verify_fri_proof<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>(
     instance: &FriInstanceInfo<F, D>,
     openings: &FriOpenings<F, D>,
     challenges: &FriChallenges<F, D>,
     initial_merkle_caps: &[MerkleCap<F, C::Hasher>],
     proof: &FriProof<F, C::Hasher, D>,
     params: &FriParams,
-) -> Result<()> {
+) -> Result<()>
+where
+    [(); C::Hasher::HASH_SIZE]:,
+{
     ensure!(
         params.final_poly_len() == proof.final_poly.len(),
         "Final polynomial has wrong degree."
@@ -112,7 +111,10 @@ fn fri_verify_initial_proof<F: RichField, H: Hasher<F>>(
     x_index: usize,
     proof: &FriInitialTreeProof<F, H>,
     initial_merkle_caps: &[MerkleCap<F, H>],
-) -> Result<()> {
+) -> Result<()>
+where
+    [(); H::HASH_SIZE]:,
+{
     for ((evals, merkle_proof), cap) in proof.evals_proofs.iter().zip(initial_merkle_caps) {
         verify_merkle_proof::<F, H>(evals.clone(), x_index, cap, merkle_proof)?;
     }
@@ -177,7 +179,10 @@ fn fri_verifier_query_round<
     n: usize,
     round_proof: &FriQueryRound<F, C::Hasher, D>,
     params: &FriParams,
-) -> Result<()> {
+) -> Result<()>
+where
+    [(); C::Hasher::HASH_SIZE]:,
+{
     fri_verify_initial_proof::<F, C::Hasher>(
         x_index,
         &round_proof.initial_trees_proof,
diff --git a/plonky2/src/gates/gate_testing.rs b/plonky2/src/gates/gate_testing.rs
index ea1ef9a4..51768ba8 100644
--- a/plonky2/src/gates/gate_testing.rs
+++ b/plonky2/src/gates/gate_testing.rs
@@ -10,7 +10,7 @@ use crate::hash::hash_types::RichField;
 use crate::iop::witness::{PartialWitness, Witness};
 use crate::plonk::circuit_builder::CircuitBuilder;
 use crate::plonk::circuit_data::CircuitConfig;
-use crate::plonk::config::GenericConfig;
+use crate::plonk::config::{GenericConfig, Hasher};
 use crate::plonk::vars::{EvaluationTargets, EvaluationVars, EvaluationVarsBaseBatch};
 use crate::plonk::verifier::verify;
 use crate::util::transpose;
@@ -92,7 +92,10 @@ pub fn test_eval_fns<
     const D: usize,
 >(
     gate: G,
-) -> Result<()> {
+) -> Result<()>
+where
+    [(); C::Hasher::HASH_SIZE]:,
+{
     // Test that `eval_unfiltered` and `eval_unfiltered_base` are coherent.
     let wires_base = F::rand_vec(gate.num_wires());
     let constants_base = F::rand_vec(gate.num_constants());
diff --git a/plonky2/src/hash/merkle_proofs.rs b/plonky2/src/hash/merkle_proofs.rs
index 7ef81570..c3ebf406 100644
--- a/plonky2/src/hash/merkle_proofs.rs
+++ b/plonky2/src/hash/merkle_proofs.rs
@@ -30,7 +30,10 @@ pub(crate) fn verify_merkle_proof<F: RichField, H: Hasher<F>>(
     leaf_index: usize,
     merkle_cap: &MerkleCap<F, H>,
     proof: &MerkleProof<F, H>,
-) -> Result<()> {
+) -> Result<()>
+where
+    [(); H::HASH_SIZE]:,
+{
     let mut index = leaf_index;
     let mut current_digest = H::hash_or_noop(&leaf_data);
     for &sibling_digest in proof.siblings.iter() {
diff --git a/plonky2/src/hash/merkle_tree.rs b/plonky2/src/hash/merkle_tree.rs
index f9890aa5..5fbc441c 100644
--- a/plonky2/src/hash/merkle_tree.rs
+++ b/plonky2/src/hash/merkle_tree.rs
@@ -60,7 +60,10 @@ fn capacity_up_to_mut<T>(v: &mut Vec<T>, len: usize) -> &mut [MaybeUninit<T>] {
 fn fill_subtree<F: RichField, H: Hasher<F>>(
     digests_buf: &mut [MaybeUninit<H::Hash>],
     leaves: &[Vec<F>],
-) -> H::Hash {
+) -> H::Hash
+where
+    [(); H::HASH_SIZE]:,
+{
     assert_eq!(leaves.len(), digests_buf.len() / 2 + 1);
     if digests_buf.is_empty() {
         H::hash_or_noop(&leaves[0])
@@ -89,7 +92,9 @@ fn fill_digests_buf<F: RichField, H: Hasher<F>>(
     cap_buf: &mut [MaybeUninit<H::Hash>],
     leaves: &[Vec<F>],
     cap_height: usize,
-) {
+) where
+    [(); H::HASH_SIZE]:,
+{
     // Special case of a tree that's all cap. The usual case will panic because we'll try to split
     // an empty slice into chunks of `0`. (We would not need this if there was a way to split into
     // `blah` chunks as opposed to chunks _of_ `blah`.)
@@ -121,7 +126,10 @@ fn fill_digests_buf<F: RichField, H: Hasher<F>>(
 }
 
 impl<F: RichField, H: Hasher<F>> MerkleTree<F, H> {
-    pub fn new(leaves: Vec<Vec<F>>, cap_height: usize) -> Self {
+    pub fn new(leaves: Vec<Vec<F>>, cap_height: usize) -> Self
+    where
+        [(); H::HASH_SIZE]:,
+    {
         let log2_leaves_len = log2_strict(leaves.len());
         assert!(
             cap_height <= log2_leaves_len,
@@ -208,14 +216,13 @@ mod tests {
         (0..n).map(|_| F::rand_vec(k)).collect()
     }
 
-    fn verify_all_leaves<
-        F: RichField + Extendable<D>,
-        C: GenericConfig<D, F = F>,
-        const D: usize,
-    >(
+    fn verify_all_leaves<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>(
         leaves: Vec<Vec<F>>,
         cap_height: usize,
-    ) -> Result<()> {
+    ) -> Result<()>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         let tree = MerkleTree::<F, C::Hasher>::new(leaves.clone(), cap_height);
         for (i, leaf) in leaves.into_iter().enumerate() {
             let proof = tree.prove(i);
diff --git a/plonky2/src/hash/path_compression.rs b/plonky2/src/hash/path_compression.rs
index fe7850f4..6dae3d94 100644
--- a/plonky2/src/hash/path_compression.rs
+++ b/plonky2/src/hash/path_compression.rs
@@ -57,7 +57,10 @@ pub(crate) fn decompress_merkle_proofs<F: RichField, H: Hasher<F>>(
     compressed_proofs: &[MerkleProof<F, H>],
     height: usize,
     cap_height: usize,
-) -> Vec<MerkleProof<F, H>> {
+) -> Vec<MerkleProof<F, H>>
+where
+    [(); H::HASH_SIZE]:,
+{
     let num_leaves = 1 << height;
     let compressed_proofs = compressed_proofs.to_vec();
     let mut decompressed_proofs = Vec::with_capacity(compressed_proofs.len());
diff --git a/plonky2/src/plonk/circuit_builder.rs b/plonky2/src/plonk/circuit_builder.rs
index cf89bf1a..7811c0db 100644
--- a/plonky2/src/plonk/circuit_builder.rs
+++ b/plonky2/src/plonk/circuit_builder.rs
@@ -610,7 +610,10 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
     }
 
     /// Builds a "full circuit", with both prover and verifier data.
-    pub fn build<C: GenericConfig<D, F = F>>(mut self) -> CircuitData<F, C, D> {
+    pub fn build<C: GenericConfig<D, F = F>>(mut self) -> CircuitData<F, C, D>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         let mut timing = TimingTree::new("preprocess", Level::Trace);
         let start = Instant::now();
         let rate_bits = self.config.fri_config.rate_bits;
@@ -776,7 +779,10 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
     }
 
     /// Builds a "prover circuit", with data needed to generate proofs but not verify them.
-    pub fn build_prover<C: GenericConfig<D, F = F>>(self) -> ProverCircuitData<F, C, D> {
+    pub fn build_prover<C: GenericConfig<D, F = F>>(self) -> ProverCircuitData<F, C, D>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         // TODO: Can skip parts of this.
         let CircuitData {
             prover_only,
@@ -790,7 +796,10 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
     }
 
     /// Builds a "verifier circuit", with data needed to verify proofs but not generate them.
-    pub fn build_verifier<C: GenericConfig<D, F = F>>(self) -> VerifierCircuitData<F, C, D> {
+    pub fn build_verifier<C: GenericConfig<D, F = F>>(self) -> VerifierCircuitData<F, C, D>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         // TODO: Can skip parts of this.
         let CircuitData {
             verifier_only,
diff --git a/plonky2/src/plonk/circuit_data.rs b/plonky2/src/plonk/circuit_data.rs
index 7e667b8d..3d4ee2df 100644
--- a/plonky2/src/plonk/circuit_data.rs
+++ b/plonky2/src/plonk/circuit_data.rs
@@ -104,7 +104,10 @@ pub struct CircuitData<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>,
 impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>
     CircuitData<F, C, D>
 {
-    pub fn prove(&self, inputs: PartialWitness<F>) -> Result<ProofWithPublicInputs<F, C, D>> {
+    pub fn prove(&self, inputs: PartialWitness<F>) -> Result<ProofWithPublicInputs<F, C, D>>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         prove(
             &self.prover_only,
             &self.common,
@@ -113,14 +116,20 @@ impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>
         )
     }
 
-    pub fn verify(&self, proof_with_pis: ProofWithPublicInputs<F, C, D>) -> Result<()> {
+    pub fn verify(&self, proof_with_pis: ProofWithPublicInputs<F, C, D>) -> Result<()>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         verify(proof_with_pis, &self.verifier_only, &self.common)
     }
 
     pub fn verify_compressed(
         &self,
         compressed_proof_with_pis: CompressedProofWithPublicInputs<F, C, D>,
-    ) -> Result<()> {
+    ) -> Result<()>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         compressed_proof_with_pis.verify(&self.verifier_only, &self.common)
     }
 }
@@ -144,7 +153,10 @@ pub struct ProverCircuitData<
 impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>
     ProverCircuitData<F, C, D>
 {
-    pub fn prove(&self, inputs: PartialWitness<F>) -> Result<ProofWithPublicInputs<F, C, D>> {
+    pub fn prove(&self, inputs: PartialWitness<F>) -> Result<ProofWithPublicInputs<F, C, D>>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         prove(
             &self.prover_only,
             &self.common,
@@ -168,14 +180,20 @@ pub struct VerifierCircuitData<
 impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>
     VerifierCircuitData<F, C, D>
 {
-    pub fn verify(&self, proof_with_pis: ProofWithPublicInputs<F, C, D>) -> Result<()> {
+    pub fn verify(&self, proof_with_pis: ProofWithPublicInputs<F, C, D>) -> Result<()>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         verify(proof_with_pis, &self.verifier_only, &self.common)
     }
 
     pub fn verify_compressed(
         &self,
         compressed_proof_with_pis: CompressedProofWithPublicInputs<F, C, D>,
-    ) -> Result<()> {
+    ) -> Result<()>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         compressed_proof_with_pis.verify(&self.verifier_only, &self.common)
     }
 }
diff --git a/plonky2/src/plonk/config.rs b/plonky2/src/plonk/config.rs
index 40179c38..cb6d9a9b 100644
--- a/plonky2/src/plonk/config.rs
+++ b/plonky2/src/plonk/config.rs
@@ -3,7 +3,6 @@ use std::fmt::Debug;
 use plonky2_field::extension_field::quadratic::QuadraticExtension;
 use plonky2_field::extension_field::{Extendable, FieldExtension};
 use plonky2_field::goldilocks_field::GoldilocksField;
-use plonky2_util::ceil_div_usize;
 use serde::{de::DeserializeOwned, Serialize};
 
 use crate::hash::hash_types::HashOut;
@@ -49,13 +48,16 @@ pub trait Hasher<F: RichField>: Sized + Clone + Debug + Eq + PartialEq {
 
     /// Hash the slice if necessary to reduce its length to ~256 bits. If it already fits, this is a
     /// no-op.
-    fn hash_or_noop(inputs: &[F]) -> Self::Hash {
-        if inputs.len() * ceil_div_usize(F::BITS, 8) <= Self::HASH_SIZE {
-            let mut inputs_bytes = inputs
-                .iter()
-                .flat_map(|x| x.to_canonical_u64().to_le_bytes())
-                .collect::<Vec<_>>();
-            inputs_bytes.resize(Self::HASH_SIZE, 0);
+    fn hash_or_noop(inputs: &[F]) -> Self::Hash
+    where
+        [(); Self::HASH_SIZE]:,
+    {
+        if inputs.len() <= 4 {
+            let mut inputs_bytes = [0u8; Self::HASH_SIZE];
+            for i in 0..inputs.len() {
+                inputs_bytes[i * 8..(i + 1) * 8]
+                    .copy_from_slice(&inputs[i].to_canonical_u64().to_le_bytes());
+            }
             Self::Hash::from_bytes(&inputs_bytes)
         } else {
             Self::hash_no_pad(inputs)
diff --git a/plonky2/src/plonk/proof.rs b/plonky2/src/plonk/proof.rs
index 3de608d4..145ef694 100644
--- a/plonky2/src/plonk/proof.rs
+++ b/plonky2/src/plonk/proof.rs
@@ -138,7 +138,10 @@ impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>
         challenges: &ProofChallenges<F, D>,
         fri_inferred_elements: FriInferredElements<F, D>,
         params: &FriParams,
-    ) -> Proof<F, C, D> {
+    ) -> Proof<F, C, D>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         let CompressedProof {
             wires_cap,
             plonk_zs_partial_products_cap,
@@ -174,7 +177,10 @@ impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>
     pub fn decompress(
         self,
         common_data: &CommonCircuitData<F, C, D>,
-    ) -> anyhow::Result<ProofWithPublicInputs<F, C, D>> {
+    ) -> anyhow::Result<ProofWithPublicInputs<F, C, D>>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         let challenges = self.get_challenges(self.get_public_inputs_hash(), common_data)?;
         let fri_inferred_elements = self.get_inferred_elements(&challenges, common_data);
         let decompressed_proof =
@@ -190,7 +196,10 @@ impl<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, const D: usize>
         self,
         verifier_data: &VerifierOnlyCircuitData<C, D>,
         common_data: &CommonCircuitData<F, C, D>,
-    ) -> anyhow::Result<()> {
+    ) -> anyhow::Result<()>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         ensure!(
             self.public_inputs.len() == common_data.num_public_inputs,
             "Number of public inputs doesn't match circuit data."
diff --git a/plonky2/src/plonk/prover.rs b/plonky2/src/plonk/prover.rs
index d49014f0..1d99b60a 100644
--- a/plonky2/src/plonk/prover.rs
+++ b/plonky2/src/plonk/prover.rs
@@ -31,7 +31,10 @@ pub(crate) fn prove<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, co
     common_data: &CommonCircuitData<F, C, D>,
     inputs: PartialWitness<F>,
     timing: &mut TimingTree,
-) -> Result<ProofWithPublicInputs<F, C, D>> {
+) -> Result<ProofWithPublicInputs<F, C, D>>
+where
+    [(); C::Hasher::HASH_SIZE]:,
+{
     let config = &common_data.config;
     let num_challenges = config.num_challenges;
     let quotient_degree = common_data.quotient_degree();
diff --git a/plonky2/src/plonk/recursive_verifier.rs b/plonky2/src/plonk/recursive_verifier.rs
index c91cbba2..6210bb29 100644
--- a/plonky2/src/plonk/recursive_verifier.rs
+++ b/plonky2/src/plonk/recursive_verifier.rs
@@ -187,7 +187,9 @@ mod tests {
     use crate::gates::noop::NoopGate;
     use crate::iop::witness::{PartialWitness, Witness};
     use crate::plonk::circuit_data::{CircuitConfig, VerifierOnlyCircuitData};
-    use crate::plonk::config::{GenericConfig, KeccakGoldilocksConfig, PoseidonGoldilocksConfig};
+    use crate::plonk::config::{
+        GenericConfig, Hasher, KeccakGoldilocksConfig, PoseidonGoldilocksConfig,
+    };
     use crate::plonk::proof::{CompressedProofWithPublicInputs, ProofWithPublicInputs};
     use crate::plonk::prover::prove;
     use crate::util::timing::TimingTree;
@@ -322,7 +324,10 @@ mod tests {
         ProofWithPublicInputs<F, C, D>,
         VerifierOnlyCircuitData<C, D>,
         CommonCircuitData<F, C, D>,
-    )> {
+    )>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         let mut builder = CircuitBuilder::<F, D>::new(config.clone());
         for _ in 0..num_dummy_gates {
             builder.add_gate(NoopGate, vec![]);
@@ -356,6 +361,7 @@ mod tests {
     )>
     where
         InnerC::Hasher: AlgebraicHasher<F>,
+        [(); C::Hasher::HASH_SIZE]:,
     {
         let mut builder = CircuitBuilder::<F, D>::new(config.clone());
         let mut pw = PartialWitness::new();
@@ -407,7 +413,10 @@ mod tests {
     >(
         proof: &ProofWithPublicInputs<F, C, D>,
         cd: &CommonCircuitData<F, C, D>,
-    ) -> Result<()> {
+    ) -> Result<()>
+    where
+        [(); C::Hasher::HASH_SIZE]:,
+    {
         let proof_bytes = proof.to_bytes()?;
         info!("Proof length: {} bytes", proof_bytes.len());
         let proof_from_bytes = ProofWithPublicInputs::from_bytes(proof_bytes, cd)?;
diff --git a/plonky2/src/plonk/verifier.rs b/plonky2/src/plonk/verifier.rs
index 5d69dcb1..ee0e976f 100644
--- a/plonky2/src/plonk/verifier.rs
+++ b/plonky2/src/plonk/verifier.rs
@@ -15,7 +15,10 @@ pub(crate) fn verify<F: RichField + Extendable<D>, C: GenericConfig<D, F = F>, c
     proof_with_pis: ProofWithPublicInputs<F, C, D>,
     verifier_data: &VerifierOnlyCircuitData<C, D>,
     common_data: &CommonCircuitData<F, C, D>,
-) -> Result<()> {
+) -> Result<()>
+where
+    [(); C::Hasher::HASH_SIZE]:,
+{
     ensure!(
         proof_with_pis.public_inputs.len() == common_data.num_public_inputs,
         "Number of public inputs doesn't match circuit data."
@@ -42,7 +45,10 @@ pub(crate) fn verify_with_challenges<
     challenges: ProofChallenges<F, D>,
     verifier_data: &VerifierOnlyCircuitData<C, D>,
     common_data: &CommonCircuitData<F, C, D>,
-) -> Result<()> {
+) -> Result<()>
+where
+    [(); C::Hasher::HASH_SIZE]:,
+{
     let local_constants = &proof.openings.constants;
     let local_wires = &proof.openings.wires;
     let vars = EvaluationVars {
diff --git a/starky/src/prover.rs b/starky/src/prover.rs
index de97ecce..e88aa619 100644
--- a/starky/src/prover.rs
+++ b/starky/src/prover.rs
@@ -7,7 +7,7 @@ use plonky2::field::zero_poly_coset::ZeroPolyOnCoset;
 use plonky2::fri::oracle::PolynomialBatch;
 use plonky2::hash::hash_types::RichField;
 use plonky2::iop::challenger::Challenger;
-use plonky2::plonk::config::GenericConfig;
+use plonky2::plonk::config::{GenericConfig, Hasher};
 use plonky2::timed;
 use plonky2::util::timing::TimingTree;
 use plonky2::util::transpose;
@@ -33,6 +33,7 @@ where
     S: Stark<F, D>,
     [(); S::COLUMNS]:,
     [(); S::PUBLIC_INPUTS]:,
+    [(); C::Hasher::HASH_SIZE]:,
 {
     let degree = trace.len();
     let degree_bits = log2_strict(degree);
diff --git a/starky/src/verifier.rs b/starky/src/verifier.rs
index 91a51bed..8bf1faab 100644
--- a/starky/src/verifier.rs
+++ b/starky/src/verifier.rs
@@ -3,7 +3,7 @@ use plonky2::field::extension_field::{Extendable, FieldExtension};
 use plonky2::field::field_types::Field;
 use plonky2::fri::verifier::verify_fri_proof;
 use plonky2::hash::hash_types::RichField;
-use plonky2::plonk::config::GenericConfig;
+use plonky2::plonk::config::{GenericConfig, Hasher};
 use plonky2::plonk::plonk_common::reduce_with_powers;
 use plonky2_util::log2_strict;
 
@@ -26,6 +26,7 @@ pub fn verify<
 where
     [(); S::COLUMNS]:,
     [(); S::PUBLIC_INPUTS]:,
+    [(); C::Hasher::HASH_SIZE]:,
 {
     let degree_bits = log2_strict(recover_degree(&proof_with_pis.proof, config));
     let challenges = proof_with_pis.get_challenges(config, degree_bits)?;
@@ -47,6 +48,7 @@ pub(crate) fn verify_with_challenges<
 where
     [(); S::COLUMNS]:,
     [(); S::PUBLIC_INPUTS]:,
+    [(); C::Hasher::HASH_SIZE]:,
 {
     let StarkProofWithPublicInputs {
         proof,