From 39d4ee327418e3be94e8da73f2973efcd8acb4a3 Mon Sep 17 00:00:00 2001
From: CPerezz <c.perezbaro@gmail.com>
Date: Tue, 15 Oct 2024 17:32:07 +0200
Subject: [PATCH 01/12] feat: Enable load_witness functionallity within
 FCircuit

Since the witness is generated in the browser we need a way to store it
such that it can flow from `prove_step` into `generate_constraints` due
to the API restrictions.
---
 folding-schemes/src/folding/nova/circuits.rs | 3 +++
 folding-schemes/src/frontend/mod.rs          | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/folding-schemes/src/folding/nova/circuits.rs b/folding-schemes/src/folding/nova/circuits.rs
index b657b61e..6778a4c5 100644
--- a/folding-schemes/src/folding/nova/circuits.rs
+++ b/folding-schemes/src/folding/nova/circuits.rs
@@ -410,6 +410,9 @@ where
 
         // get z_{i+1} from the F circuit
         let i_usize = self.i_usize.unwrap_or(0);
+
+        // If we are in the browser-frontend case. The witness is already loaded within
+        // self.F.witness. This was done at `self.prove_step()` fn.
         let z_i1 = self
             .F
             .generate_step_constraints(cs.clone(), i_usize, z_i, external_inputs)?;
diff --git a/folding-schemes/src/frontend/mod.rs b/folding-schemes/src/frontend/mod.rs
index 7cf9e432..adffe409 100644
--- a/folding-schemes/src/frontend/mod.rs
+++ b/folding-schemes/src/frontend/mod.rs
@@ -48,6 +48,13 @@ pub trait FCircuit<F: PrimeField>: Clone + Debug {
         z_i: Vec<FpVar<F>>,
         external_inputs: Vec<FpVar<F>>, // inputs that are not part of the state
     ) -> Result<Vec<FpVar<F>>, SynthesisError>;
+
+    /// Allows to load pre-generated witness into the FCircuit implementor.
+    /// This is only needed by the browser use cases where we have already computed our
+    /// witness there. And we need a way to load it into the FCircuit since it's already computed.
+    ///
+    /// By default this method will simply do nothing. Only in the browser FCircuit implementors this will have usage.
+    fn load_witness(&mut self, _witness: Vec<F>) {}
 }
 
 #[cfg(test)]

From 039a40035e32c8958cc9a09064ea24b7008f1fe7 Mon Sep 17 00:00:00 2001
From: CPerezz <c.perezbaro@gmail.com>
Date: Tue, 15 Oct 2024 17:41:55 +0200
Subject: [PATCH 02/12] feat: Enable browser-folding with passed-in witness

This commit introduces CircomFCircuitBrowser, a structure that facilitates folding of
Circom-generated circuits in the browser via WASM. It loads R1CS data,
handles witness inputs, and generates constraints for the folding process.

Resolves: #155
---
 folding-schemes/src/folding/nova/mod.rs       |  21 +++
 .../src/frontend/circom/browser.rs            | 177 ++++++++++++++++++
 folding-schemes/src/frontend/circom/mod.rs    |   6 +-
 3 files changed, 203 insertions(+), 1 deletion(-)
 create mode 100644 folding-schemes/src/frontend/circom/browser.rs

diff --git a/folding-schemes/src/folding/nova/mod.rs b/folding-schemes/src/folding/nova/mod.rs
index d67c33b9..dea5bd85 100644
--- a/folding-schemes/src/folding/nova/mod.rs
+++ b/folding-schemes/src/folding/nova/mod.rs
@@ -642,10 +642,31 @@ where
     fn prove_step(
         &mut self,
         mut rng: impl RngCore,
+        // This contains the full witness when we're in the browser-frontend case
         external_inputs: Vec<C1::ScalarField>,
         // Nova does not support multi-instances folding
         _other_instances: Option<Self::MultiCommittedInstanceWithWitness>,
     ) -> Result<(), Error> {
+        // Slice and separate between external inputs and frontend witness.
+        let (frontend_witness, external_inputs) =
+            if external_inputs.len() > self.F.external_inputs_len() {
+                (
+                    // Full circom witness trace
+                    Some(external_inputs[..].to_vec()),
+                    // Extracted external inputs from circom trace
+                    external_inputs[1 + self.F.state_len() * 2
+                        ..1 + self.F.state_len() * 2 + self.F.external_inputs_len()]
+                        .to_vec(),
+                )
+            } else {
+                (None, external_inputs)
+            };
+
+        // If we are in the browser-case (frontend_witness = Some(witness)) then we load the witness into the FCircuit.
+        if let Some(witness) = frontend_witness {
+            self.F.load_witness(witness)
+        };
+
         // ensure that commitments are blinding if user has specified so.
         if H && self.i >= C1::ScalarField::one() {
             let blinding_commitments = if self.i == C1::ScalarField::one() {
diff --git a/folding-schemes/src/frontend/circom/browser.rs b/folding-schemes/src/frontend/circom/browser.rs
new file mode 100644
index 00000000..7ee29c77
--- /dev/null
+++ b/folding-schemes/src/frontend/circom/browser.rs
@@ -0,0 +1,177 @@
+use crate::frontend::FCircuit;
+use crate::frontend::FpVar::Var;
+use crate::Error;
+use ark_circom::circom::{CircomCircuit, R1CS as CircomR1CS};
+use ark_circom::circom::{R1CSFile, R1CS};
+use ark_ff::{BigInteger, PrimeField};
+use ark_r1cs_std::alloc::AllocVar;
+use ark_r1cs_std::fields::fp::FpVar;
+use ark_relations::r1cs::{ConstraintSynthesizer, ConstraintSystemRef, SynthesisError};
+use ark_std::fmt::Debug;
+use byteorder::{LittleEndian, ReadBytesExt};
+use std::io::{BufReader, Cursor, Read};
+use std::usize;
+
+/// This circuit is the one we will use in order to fold from the browser.
+///
+/// A clear example on how to do all of this can be seen at:
+/// <https://github.com/CPerezz/wasm-sonobe-integration>
+#[derive(Clone, Debug)]
+pub struct CircomFCircuitBrowser<F: PrimeField> {
+    pub state_len: usize,
+    pub external_inputs_len: usize,
+    pub witness: Vec<F>,
+    pub r1cs: CircomR1CS<F>,
+}
+
+impl<F: PrimeField> FCircuit<F> for CircomFCircuitBrowser<F> {
+    /// (r1cs_file_bytes,  state_len, external_inputs_len)
+    type Params = (Vec<u8>, usize, usize);
+
+    fn new(params: Self::Params) -> Result<Self, Error> {
+        let (r1cs_bytes, state_len, external_inputs_len) = params;
+        let reader = BufReader::new(Cursor::new(&r1cs_bytes[..]));
+
+        let mut r1cs: R1CS<F> = R1CSFile::<F>::new(reader)
+            .expect("Error reading R1cs")
+            .into();
+
+        // That's some weird magic. Ask @dmpierre
+        r1cs.wire_mapping = None;
+
+        Ok(Self {
+            state_len,
+            external_inputs_len,
+            witness: vec![F::zero(); r1cs.num_variables],
+            r1cs,
+        })
+    }
+
+    fn state_len(&self) -> usize {
+        self.state_len
+    }
+    fn external_inputs_len(&self) -> usize {
+        self.external_inputs_len
+    }
+
+    fn step_native(
+        &self,
+        _i: usize,
+        z_i: Vec<F>,
+        external_inputs: Vec<F>,
+    ) -> Result<Vec<F>, Error> {
+        // Should we keep these?
+        assert_eq!(z_i.len(), self.state_len());
+        assert_eq!(external_inputs.len(), self.external_inputs_len());
+
+        // Extracts the z_i1(next state) from the witness vector and external inputs.
+        let z_i1 = z_i[..self.state_len()].to_vec();
+        Ok(z_i1)
+    }
+
+    fn generate_step_constraints(
+        &self,
+        cs: ConstraintSystemRef<F>,
+        _i: usize,
+        z_i: Vec<FpVar<F>>,
+        // This in reality contains the `witness` passed from the `prove_step` call from the
+        // browser.
+        _external_inputs: Vec<FpVar<F>>,
+    ) -> Result<Vec<FpVar<F>>, SynthesisError> {
+        // Since public inputs are already allocated variables, we will tell `circom-compat` to not re-allocate those
+        let mut already_allocated_public_inputs = vec![];
+        for var in z_i.iter() {
+            match var {
+                Var(var) => already_allocated_public_inputs.push(var.variable),
+                _ => return Err(SynthesisError::Unsatisfiable), // allocated z_i should be Var
+            }
+        }
+
+        // Initializes the CircomCircuit.
+        let circom_circuit = CircomCircuit {
+            r1cs: self.r1cs.clone(),
+            witness: Some(self.witness.clone()),
+            public_inputs_indexes: already_allocated_public_inputs,
+            // Since public inputs are already allocated variables, we will tell `circom-compat` to not re-allocate those
+            allocate_inputs_as_witnesses: true,
+        };
+
+        // Generates the constraints for the circom_circuit.
+        circom_circuit.generate_constraints(cs.clone())?;
+
+        // Extracts the z_i1(next state) from the witness vector.
+        let z_i1: Vec<FpVar<F>> = Vec::<FpVar<F>>::new_witness(cs.clone(), || {
+            Ok(self.witness[1..1 + self.state_len()].to_vec())
+        })?;
+
+        Ok(z_i1)
+    }
+
+    fn load_witness(&mut self, witness: Vec<F>) {
+        self.witness = witness;
+    }
+}
+
+/// Load Circom-generated witness from u8 array by a reader.
+///
+/// This fn has been taken from <https://github.com/nalinbhardwaj/Nova-Scotia/blob/main/src/circom/file.rs>
+pub fn load_witness_from_bin_reader<R: Read, F: PrimeField>(mut reader: R) -> Vec<F> {
+    let mut wtns_header = [0u8; 4];
+    reader.read_exact(&mut wtns_header).expect("read_error");
+    if wtns_header != [119, 116, 110, 115] {
+        // ruby -e 'p "wtns".bytes' => [119, 116, 110, 115]
+        panic!("invalid file header");
+    }
+    let version = reader.read_u32::<LittleEndian>().expect("read_error");
+    // println!("wtns version {}", version);
+    if version > 2 {
+        panic!("unsupported file version");
+    }
+    let num_sections = reader.read_u32::<LittleEndian>().expect("read_error");
+    if num_sections != 2 {
+        panic!("invalid num sections");
+    }
+    // read the first section
+    let sec_type = reader.read_u32::<LittleEndian>().expect("read_error");
+    if sec_type != 1 {
+        panic!("invalid section type");
+    }
+    let sec_size = reader.read_u64::<LittleEndian>().expect("read_error");
+    if sec_size != 4 + 32 + 4 {
+        panic!("invalid section len")
+    }
+    let field_size: u32 = reader.read_u32::<LittleEndian>().expect("read_error");
+    if field_size != 32 {
+        panic!("invalid field byte size");
+    }
+    let mut prime = vec![0u8; field_size as usize];
+    reader.read_exact(&mut prime).expect("read_error");
+    // if prime != hex!("010000f093f5e1439170b97948e833285d588181b64550b829a031e1724e6430") {
+    //     panic!("invalid curve prime {:?}", prime);
+    // }
+    let witness_len: u32 = reader.read_u32::<LittleEndian>().expect("read_error");
+    // println!("witness len {}", witness_len);
+    let sec_type = reader.read_u32::<LittleEndian>().expect("read_error");
+    if sec_type != 2 {
+        panic!("invalid section type");
+    }
+    let sec_size = reader.read_u64::<LittleEndian>().expect("read_error");
+    if sec_size != (witness_len * field_size) as u64 {
+        panic!("invalid witness section size");
+    }
+    let mut result = Vec::with_capacity(witness_len as usize);
+    for _ in 0..witness_len {
+        result.push(read_field::<&mut R, F>(&mut reader).expect("read_error"));
+    }
+    result
+}
+
+fn read_field<R: Read, F: PrimeField>(
+    mut reader: R,
+) -> Result<F, ark_serialize::SerializationError> {
+    let mut repr: Vec<u8> = F::ZERO.into_bigint().to_bytes_le();
+    for digit in repr.iter_mut() {
+        *digit = reader.read_u8()?;
+    }
+    Ok(F::from_le_bytes_mod_order(&repr[..]))
+}
diff --git a/folding-schemes/src/frontend/circom/mod.rs b/folding-schemes/src/frontend/circom/mod.rs
index a261f722..00473e43 100644
--- a/folding-schemes/src/frontend/circom/mod.rs
+++ b/folding-schemes/src/frontend/circom/mod.rs
@@ -13,7 +13,10 @@ use num_bigint::BigInt;
 use std::rc::Rc;
 use std::{fmt, usize};
 
+pub mod browser;
 pub mod utils;
+
+pub use browser::{load_witness_from_bin_reader, CircomFCircuitBrowser};
 use utils::CircomWrapper;
 
 type ClosurePointer<F> = Rc<dyn Fn(usize, Vec<F>, Vec<F>) -> Result<Vec<F>, Error>>;
@@ -33,7 +36,8 @@ impl<F: PrimeField> fmt::Debug for CustomStepNative<F> {
     }
 }
 
-/// Define CircomFCircuit
+/// This circuit is the one we will use in order to fold circom circuits
+/// from a non-browser environment.
 #[derive(Clone, Debug)]
 pub struct CircomFCircuit<F: PrimeField> {
     circom_wrapper: CircomWrapper<F>,

From 67a066dee59721d5d81468045f837e69eaa563d5 Mon Sep 17 00:00:00 2001
From: CPerezz <c.perezbaro@gmail.com>
Date: Tue, 15 Oct 2024 17:52:31 +0200
Subject: [PATCH 03/12] chore: Add "browser" feature and leave
 CircomFCircuitBrowser under it

---
 folding-schemes/Cargo.toml                 | 66 +++++++++++++++-------
 folding-schemes/src/frontend/circom/mod.rs |  2 +
 2 files changed, 49 insertions(+), 19 deletions(-)

diff --git a/folding-schemes/Cargo.toml b/folding-schemes/Cargo.toml
index d7c45482..d0773bf8 100644
--- a/folding-schemes/Cargo.toml
+++ b/folding-schemes/Cargo.toml
@@ -4,20 +4,40 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
-ark-ec = { version = "^0.4.0", default-features = false, features = ["parallel"] }
-ark-ff = { version = "^0.4.0", default-features = false, features = ["parallel", "asm"] }
-ark-poly = { version = "^0.4.0", default-features = false, features = ["parallel"] }
-ark-std = { version = "^0.4.0", default-features = false, features = ["parallel"] }
-ark-crypto-primitives = { version = "^0.4.0", default-features = false, features = ["r1cs", "sponge", "crh", "parallel"] }
+ark-ec = { version = "^0.4.0", default-features = false, features = [
+    "parallel",
+] }
+ark-ff = { version = "^0.4.0", default-features = false, features = [
+    "parallel",
+    "asm",
+] }
+ark-poly = { version = "^0.4.0", default-features = false, features = [
+    "parallel",
+] }
+ark-std = { version = "^0.4.0", default-features = false, features = [
+    "parallel",
+] }
+ark-crypto-primitives = { version = "^0.4.0", default-features = false, features = [
+    "r1cs",
+    "sponge",
+    "crh",
+    "parallel",
+] }
 ark-grumpkin = { version = "0.4.0", default-features = false }
-ark-poly-commit = { version = "^0.4.0", default-features = false, features = ["parallel"] }
+ark-poly-commit = { version = "^0.4.0", default-features = false, features = [
+    "parallel",
+] }
 ark-relations = { version = "^0.4.0", default-features = false }
 # this is patched at the workspace level
-ark-r1cs-std = { version = "0.4.0", default-features = false, features = ["parallel"] }
+ark-r1cs-std = { version = "0.4.0", default-features = false, features = [
+    "parallel",
+] }
 ark-snark = { version = "^0.4.0", default-features = false }
 ark-serialize = { version = "^0.4.0", default-features = false }
 ark-circom = { git = "https://github.com/arnaucube/circom-compat", default-features = false }
-ark-groth16 = { version = "^0.4.0", default-features = false, features = ["parallel"]}
+ark-groth16 = { version = "^0.4.0", default-features = false, features = [
+    "parallel",
+] }
 ark-bn254 = { version = "^0.4.0", default-features = false }
 thiserror = "1.0"
 rayon = "1"
@@ -27,26 +47,30 @@ color-eyre = "=0.6.2"
 sha3 = "0.10"
 ark-noname = { git = "https://github.com/dmpierre/ark-noname", branch = "feat/sonobe-integration" }
 noname = { git = "https://github.com/dmpierre/noname" }
-serde_json = "1.0.85"                                                                # to (de)serialize JSON
+serde_json = "1.0.85" # to (de)serialize JSON
 serde = "1.0.203"
-acvm = { git = "https://github.com/noir-lang/noir", rev="2b4853e", default-features = false }
-noir_arkworks_backend = { package="arkworks_backend", git = "https://github.com/dmpierre/arkworks_backend", branch = "feat/sonobe-integration" }
+acvm = { git = "https://github.com/noir-lang/noir", rev = "2b4853e", default-features = false }
+noir_arkworks_backend = { package = "arkworks_backend", git = "https://github.com/dmpierre/arkworks_backend", branch = "feat/sonobe-integration" }
 log = "0.4"
 
 # tmp import for espresso's sumcheck
-espresso_subroutines = {git="https://github.com/EspressoSystems/hyperplonk", package="subroutines"}
+espresso_subroutines = { git = "https://github.com/EspressoSystems/hyperplonk", package = "subroutines" }
+# Dependencies needed for browser folding
+byteorder = { version = "1.4.3", optional = true }
 
 [dev-dependencies]
-ark-pallas = {version="0.4.0", features=["r1cs"]}
-ark-vesta = {version="0.4.0", features=["r1cs"]}
-ark-bn254 = {version="0.4.0", features=["r1cs"]}
-ark-grumpkin = {version="0.4.0", features=["r1cs"]}
+ark-pallas = { version = "0.4.0", features = ["r1cs"] }
+ark-vesta = { version = "0.4.0", features = ["r1cs"] }
+ark-bn254 = { version = "0.4.0", features = ["r1cs"] }
+ark-grumpkin = { version = "0.4.0", features = ["r1cs"] }
 # Note: do not use the MNTx_298 curves in practice due security reasons, here
 # we only use them in the tests.
-ark-mnt4-298 = {version="0.4.0", features=["r1cs"]}
-ark-mnt6-298 = {version="0.4.0", features=["r1cs"]}
+ark-mnt4-298 = { version = "0.4.0", features = ["r1cs"] }
+ark-mnt6-298 = { version = "0.4.0", features = ["r1cs"] }
 rand = "0.8.5"
-tracing = { version = "0.1", default-features = false, features = [ "attributes" ] }
+tracing = { version = "0.1", default-features = false, features = [
+    "attributes",
+] }
 tracing-subscriber = { version = "0.2" }
 
 # This allows the crate to be built when targeting WASM.
@@ -58,6 +82,7 @@ getrandom = { version = "0.2", features = ["js"] }
 default = ["ark-circom/default", "parallel"]
 parallel = []
 wasm = ["ark-circom/wasm"]
+browser = ["wasm", "byteorder"]
 light-test = []
 
 
@@ -72,3 +97,6 @@ path = "../examples/multi_inputs.rs"
 [[example]]
 name = "external_inputs"
 path = "../examples/external_inputs.rs"
+
+[lib]
+crate-type = ["cdylib", "rlib"]
diff --git a/folding-schemes/src/frontend/circom/mod.rs b/folding-schemes/src/frontend/circom/mod.rs
index 00473e43..cb70eb43 100644
--- a/folding-schemes/src/frontend/circom/mod.rs
+++ b/folding-schemes/src/frontend/circom/mod.rs
@@ -13,9 +13,11 @@ use num_bigint::BigInt;
 use std::rc::Rc;
 use std::{fmt, usize};
 
+#[cfg(feature = "browser")]
 pub mod browser;
 pub mod utils;
 
+#[cfg(feature = "browser")]
 pub use browser::{load_witness_from_bin_reader, CircomFCircuitBrowser};
 use utils::CircomWrapper;
 

From 9bcf84c30f90fffa0a7459182ed5a9895c370949 Mon Sep 17 00:00:00 2001
From: CPerezz <c.perezbaro@gmail.com>
Date: Wed, 16 Oct 2024 16:12:41 +0200
Subject: [PATCH 04/12] chore: Address review leftovers

---
 folding-schemes/src/frontend/circom/browser.rs | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/folding-schemes/src/frontend/circom/browser.rs b/folding-schemes/src/frontend/circom/browser.rs
index 7ee29c77..3817f8b0 100644
--- a/folding-schemes/src/frontend/circom/browser.rs
+++ b/folding-schemes/src/frontend/circom/browser.rs
@@ -119,11 +119,9 @@ pub fn load_witness_from_bin_reader<R: Read, F: PrimeField>(mut reader: R) -> Ve
     let mut wtns_header = [0u8; 4];
     reader.read_exact(&mut wtns_header).expect("read_error");
     if wtns_header != [119, 116, 110, 115] {
-        // ruby -e 'p "wtns".bytes' => [119, 116, 110, 115]
         panic!("invalid file header");
     }
     let version = reader.read_u32::<LittleEndian>().expect("read_error");
-    // println!("wtns version {}", version);
     if version > 2 {
         panic!("unsupported file version");
     }
@@ -146,11 +144,7 @@ pub fn load_witness_from_bin_reader<R: Read, F: PrimeField>(mut reader: R) -> Ve
     }
     let mut prime = vec![0u8; field_size as usize];
     reader.read_exact(&mut prime).expect("read_error");
-    // if prime != hex!("010000f093f5e1439170b97948e833285d588181b64550b829a031e1724e6430") {
-    //     panic!("invalid curve prime {:?}", prime);
-    // }
     let witness_len: u32 = reader.read_u32::<LittleEndian>().expect("read_error");
-    // println!("witness len {}", witness_len);
     let sec_type = reader.read_u32::<LittleEndian>().expect("read_error");
     if sec_type != 2 {
         panic!("invalid section type");

From 206984cd9ec5e548eaaa24d9f06dff533c94d5d4 Mon Sep 17 00:00:00 2001
From: CPerezz <c.perezbaro@gmail.com>
Date: Thu, 17 Oct 2024 12:26:59 +0200
Subject: [PATCH 05/12] chore: Ammend review comments

---
 folding-schemes/src/folding/nova/mod.rs       | 39 ++++++++++---------
 .../src/frontend/circom/browser.rs            |  2 -
 2 files changed, 21 insertions(+), 20 deletions(-)

diff --git a/folding-schemes/src/folding/nova/mod.rs b/folding-schemes/src/folding/nova/mod.rs
index dea5bd85..dcb3e46d 100644
--- a/folding-schemes/src/folding/nova/mod.rs
+++ b/folding-schemes/src/folding/nova/mod.rs
@@ -647,25 +647,28 @@ where
         // Nova does not support multi-instances folding
         _other_instances: Option<Self::MultiCommittedInstanceWithWitness>,
     ) -> Result<(), Error> {
-        // Slice and separate between external inputs and frontend witness.
-        let (frontend_witness, external_inputs) =
-            if external_inputs.len() > self.F.external_inputs_len() {
-                (
-                    // Full circom witness trace
-                    Some(external_inputs[..].to_vec()),
-                    // Extracted external inputs from circom trace
-                    external_inputs[1 + self.F.state_len() * 2
-                        ..1 + self.F.state_len() * 2 + self.F.external_inputs_len()]
-                        .to_vec(),
-                )
-            } else {
-                (None, external_inputs)
+        #[cfg(feature = "browser")]
+        {
+            // Slice and separate between external inputs and frontend witness.
+            let (frontend_witness, external_inputs) =
+                if external_inputs.len() > self.F.external_inputs_len() {
+                    (
+                        // Full circom witness trace
+                        Some(external_inputs[..].to_vec()),
+                        // Extracted external inputs from circom trace
+                        external_inputs[1 + self.F.state_len() * 2
+                            ..1 + self.F.state_len() * 2 + self.F.external_inputs_len()]
+                            .to_vec(),
+                    )
+                } else {
+                    (None, external_inputs)
+                };
+
+            // If we are in the browser-case (frontend_witness = Some(witness)) then we load the witness into the FCircuit.
+            if let Some(witness) = frontend_witness {
+                self.F.load_witness(witness)
             };
-
-        // If we are in the browser-case (frontend_witness = Some(witness)) then we load the witness into the FCircuit.
-        if let Some(witness) = frontend_witness {
-            self.F.load_witness(witness)
-        };
+        }
 
         // ensure that commitments are blinding if user has specified so.
         if H && self.i >= C1::ScalarField::one() {
diff --git a/folding-schemes/src/frontend/circom/browser.rs b/folding-schemes/src/frontend/circom/browser.rs
index 3817f8b0..8185200a 100644
--- a/folding-schemes/src/frontend/circom/browser.rs
+++ b/folding-schemes/src/frontend/circom/browser.rs
@@ -74,8 +74,6 @@ impl<F: PrimeField> FCircuit<F> for CircomFCircuitBrowser<F> {
         cs: ConstraintSystemRef<F>,
         _i: usize,
         z_i: Vec<FpVar<F>>,
-        // This in reality contains the `witness` passed from the `prove_step` call from the
-        // browser.
         _external_inputs: Vec<FpVar<F>>,
     ) -> Result<Vec<FpVar<F>>, SynthesisError> {
         // Since public inputs are already allocated variables, we will tell `circom-compat` to not re-allocate those

From 0cf1aaeaf4978df56c6ae48286e63639afa76800 Mon Sep 17 00:00:00 2001
From: CPerezz <c.perezbaro@gmail.com>
Date: Fri, 18 Oct 2024 11:19:29 +0200
Subject: [PATCH 06/12] fix: leftover `parallel` feature code

---
 .../src/utils/espresso/sum_check/prover.rs            | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/folding-schemes/src/utils/espresso/sum_check/prover.rs b/folding-schemes/src/utils/espresso/sum_check/prover.rs
index 24440d24..007a1cc4 100644
--- a/folding-schemes/src/utils/espresso/sum_check/prover.rs
+++ b/folding-schemes/src/utils/espresso/sum_check/prover.rs
@@ -102,14 +102,15 @@ impl<F: PrimeField> SumCheckProver<F> for IOPProverState<F> {
             self.challenges.push(*chal);
 
             let r = self.challenges[self.round - 1];
-            // #[cfg(feature = "parallel")]
+            #[cfg(feature = "parallel")]
             flattened_ml_extensions
                 .par_iter_mut()
                 .for_each(|mle| *mle = fix_variables(mle, &[r]));
-            // #[cfg(not(feature = "parallel"))]
-            // flattened_ml_extensions
-            //     .iter_mut()
-            //     .for_each(|mle| *mle = fix_variables(mle, &[r]));
+
+            #[cfg(not(feature = "parallel"))]
+            flattened_ml_extensions
+                .iter_mut()
+                .for_each(|mle| *mle = fix_variables(mle, &[r]));
         } else if self.round > 0 {
             return Err(PolyIOPErrors::InvalidProver(
                 "verifier message is empty".to_string(),

From 47d908a749331f837afcf583e9ef353535e05cc4 Mon Sep 17 00:00:00 2001
From: CPerezz <c.perezbaro@gmail.com>
Date: Fri, 18 Oct 2024 11:22:16 +0200
Subject: [PATCH 07/12] update: Remove `wasm` feature

As @arnaucube correctly suggested to me, the `wasm` feature can be omitted as the `wasmer` loader does not require it.

Therefore, feature set, CI and code has been updated accordingly.
Also, the browser feature has been renamed to `circom-browser`.
---
 .github/scripts/wasm-target-test-build.sh    |  2 +-
 .github/workflows/ci.yml                     | 12 ++++++------
 folding-schemes/Cargo.toml                   |  3 +--
 folding-schemes/src/folding/nova/circuits.rs |  2 +-
 folding-schemes/src/folding/nova/mod.rs      |  6 +++---
 folding-schemes/src/frontend/circom/mod.rs   |  6 +++---
 folding-schemes/src/frontend/mod.rs          |  4 ++--
 7 files changed, 17 insertions(+), 18 deletions(-)

diff --git a/.github/scripts/wasm-target-test-build.sh b/.github/scripts/wasm-target-test-build.sh
index e86ef832..026fac82 100644
--- a/.github/scripts/wasm-target-test-build.sh
+++ b/.github/scripts/wasm-target-test-build.sh
@@ -15,7 +15,7 @@ cp "${GIT_ROOT}/rust-toolchain" .
 rustup target add wasm32-unknown-unknown wasm32-wasi 
 
 # add dependencies
-cargo add --path "${GIT_ROOT}/folding-schemes" --features wasm, parallel
+cargo add --path "${GIT_ROOT}/folding-schemes" --features circom-browser
 cargo add getrandom --features js --target wasm32-unknown-unknown
 
 # test build for wasm32-* targets
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b7ef464e..d731e6c5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -43,7 +43,7 @@ jobs:
         feature_set: [basic]
         include:
           - feature_set: basic
-            features: --features default,light-test
+            features: --features default, light-test
     steps:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1
@@ -99,7 +99,7 @@ jobs:
         uses: actions-rs/cargo@v1
         with:
           command: build
-          args: -p folding-schemes --no-default-features --target ${{ matrix.target }} --features "wasm, parallel"
+          args: -p folding-schemes --target ${{ matrix.target }} --features circom-frontend
       - name: Run wasm-compat script
         run: |
           chmod +x .github/scripts/wasm-target-test-build.sh
@@ -156,13 +156,13 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        feature_set: [basic, wasm]
+        feature_set: [basic, circom-browser]
         include:
           - feature_set: basic
             features: --features default,light-test
-            # We only want to test `folding-schemes` package with `wasm` feature.
-          - feature_set: wasm
-            features: -p folding-schemes --features wasm,parallel --target wasm32-unknown-unknown
+            # We only want to test `folding-schemes` package with `circom-browser` feature.
+          - feature_set: circom-browser
+            features: -p folding-schemes --features circom-browser, parallel --target wasm32-unknown-unknown
     steps:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1
diff --git a/folding-schemes/Cargo.toml b/folding-schemes/Cargo.toml
index d0773bf8..470df177 100644
--- a/folding-schemes/Cargo.toml
+++ b/folding-schemes/Cargo.toml
@@ -81,8 +81,7 @@ getrandom = { version = "0.2", features = ["js"] }
 [features]
 default = ["ark-circom/default", "parallel"]
 parallel = []
-wasm = ["ark-circom/wasm"]
-browser = ["wasm", "byteorder"]
+circom-browser = ["ark-circom/wasm", "byteorder"]
 light-test = []
 
 
diff --git a/folding-schemes/src/folding/nova/circuits.rs b/folding-schemes/src/folding/nova/circuits.rs
index 6778a4c5..2697d95f 100644
--- a/folding-schemes/src/folding/nova/circuits.rs
+++ b/folding-schemes/src/folding/nova/circuits.rs
@@ -411,7 +411,7 @@ where
         // get z_{i+1} from the F circuit
         let i_usize = self.i_usize.unwrap_or(0);
 
-        // If we are in the browser-frontend case. The witness is already loaded within
+        // If we are in the circom-browser-frontend case. The witness is already loaded within
         // self.F.witness. This was done at `self.prove_step()` fn.
         let z_i1 = self
             .F
diff --git a/folding-schemes/src/folding/nova/mod.rs b/folding-schemes/src/folding/nova/mod.rs
index dcb3e46d..62c9d913 100644
--- a/folding-schemes/src/folding/nova/mod.rs
+++ b/folding-schemes/src/folding/nova/mod.rs
@@ -642,12 +642,12 @@ where
     fn prove_step(
         &mut self,
         mut rng: impl RngCore,
-        // This contains the full witness when we're in the browser-frontend case
+        // This contains the full witness when we're in the circom-browser-frontend case
         external_inputs: Vec<C1::ScalarField>,
         // Nova does not support multi-instances folding
         _other_instances: Option<Self::MultiCommittedInstanceWithWitness>,
     ) -> Result<(), Error> {
-        #[cfg(feature = "browser")]
+        #[cfg(feature = "circom-browser")]
         {
             // Slice and separate between external inputs and frontend witness.
             let (frontend_witness, external_inputs) =
@@ -664,7 +664,7 @@ where
                     (None, external_inputs)
                 };
 
-            // If we are in the browser-case (frontend_witness = Some(witness)) then we load the witness into the FCircuit.
+            // If we are in the circom-browser-case (frontend_witness = Some(witness)) then we load the witness into the FCircuit.
             if let Some(witness) = frontend_witness {
                 self.F.load_witness(witness)
             };
diff --git a/folding-schemes/src/frontend/circom/mod.rs b/folding-schemes/src/frontend/circom/mod.rs
index cb70eb43..8b9982a0 100644
--- a/folding-schemes/src/frontend/circom/mod.rs
+++ b/folding-schemes/src/frontend/circom/mod.rs
@@ -13,11 +13,11 @@ use num_bigint::BigInt;
 use std::rc::Rc;
 use std::{fmt, usize};
 
-#[cfg(feature = "browser")]
+#[cfg(feature = "circom-browser")]
 pub mod browser;
 pub mod utils;
 
-#[cfg(feature = "browser")]
+#[cfg(feature = "circom-browser")]
 pub use browser::{load_witness_from_bin_reader, CircomFCircuitBrowser};
 use utils::CircomWrapper;
 
@@ -38,7 +38,7 @@ impl<F: PrimeField> fmt::Debug for CustomStepNative<F> {
     }
 }
 
-/// This circuit is the one we will use in order to fold circom circuits
+/// This circuit is the one we will use in order to fold Circom circuits
 /// from a non-browser environment.
 #[derive(Clone, Debug)]
 pub struct CircomFCircuit<F: PrimeField> {
diff --git a/folding-schemes/src/frontend/mod.rs b/folding-schemes/src/frontend/mod.rs
index adffe409..e68c971f 100644
--- a/folding-schemes/src/frontend/mod.rs
+++ b/folding-schemes/src/frontend/mod.rs
@@ -50,10 +50,10 @@ pub trait FCircuit<F: PrimeField>: Clone + Debug {
     ) -> Result<Vec<FpVar<F>>, SynthesisError>;
 
     /// Allows to load pre-generated witness into the FCircuit implementor.
-    /// This is only needed by the browser use cases where we have already computed our
+    /// This is only needed by the circom-browser use cases where we have already computed our
     /// witness there. And we need a way to load it into the FCircuit since it's already computed.
     ///
-    /// By default this method will simply do nothing. Only in the browser FCircuit implementors this will have usage.
+    /// By default this method will simply do nothing. Only in the circom-browser FCircuit implementors this will have usage.
     fn load_witness(&mut self, _witness: Vec<F>) {}
 }
 

From 5c678493efa6be5071316c5d484a08a30bf75bb1 Mon Sep 17 00:00:00 2001
From: CPerezz <c.perezbaro@gmail.com>
Date: Fri, 18 Oct 2024 11:34:27 +0200
Subject: [PATCH 08/12] fix: Exclude constant 1 from zi_1 returned in
 browser::step_native

---
 folding-schemes/src/frontend/circom/browser.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/folding-schemes/src/frontend/circom/browser.rs b/folding-schemes/src/frontend/circom/browser.rs
index 8185200a..9c3ac20f 100644
--- a/folding-schemes/src/frontend/circom/browser.rs
+++ b/folding-schemes/src/frontend/circom/browser.rs
@@ -65,7 +65,7 @@ impl<F: PrimeField> FCircuit<F> for CircomFCircuitBrowser<F> {
         assert_eq!(external_inputs.len(), self.external_inputs_len());
 
         // Extracts the z_i1(next state) from the witness vector and external inputs.
-        let z_i1 = z_i[..self.state_len()].to_vec();
+        let z_i1 = z_i[1..1 + self.state_len()].to_vec();
         Ok(z_i1)
     }
 

From 29ba23e25ad895cf7f8dae9262cbb0f0fec8b48a Mon Sep 17 00:00:00 2001
From: CPerezz <c.perezbaro@gmail.com>
Date: Fri, 18 Oct 2024 11:36:19 +0200
Subject: [PATCH 09/12] fix: Avoid whitespaces within features passed to CLI
 commands

---
 .github/workflows/ci.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d731e6c5..1add8edc 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -43,7 +43,7 @@ jobs:
         feature_set: [basic]
         include:
           - feature_set: basic
-            features: --features default, light-test
+            features: --features default,light-test
     steps:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1
@@ -162,7 +162,7 @@ jobs:
             features: --features default,light-test
             # We only want to test `folding-schemes` package with `circom-browser` feature.
           - feature_set: circom-browser
-            features: -p folding-schemes --features circom-browser, parallel --target wasm32-unknown-unknown
+            features: -p folding-schemes --features circom-browser,parallel --target wasm32-unknown-unknown
     steps:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1

From 291082e1f68ca63de7639346701906eee44af64e Mon Sep 17 00:00:00 2001
From: CPerezz <c.perezbaro@gmail.com>
Date: Mon, 21 Oct 2024 15:28:17 +0200
Subject: [PATCH 10/12] fix: Clippy warns

---
 folding-schemes/src/folding/nova/mod.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/folding-schemes/src/folding/nova/mod.rs b/folding-schemes/src/folding/nova/mod.rs
index 62c9d913..1cb7b208 100644
--- a/folding-schemes/src/folding/nova/mod.rs
+++ b/folding-schemes/src/folding/nova/mod.rs
@@ -648,7 +648,7 @@ where
         _other_instances: Option<Self::MultiCommittedInstanceWithWitness>,
     ) -> Result<(), Error> {
         #[cfg(feature = "circom-browser")]
-        {
+        let external_inputs = {
             // Slice and separate between external inputs and frontend witness.
             let (frontend_witness, external_inputs) =
                 if external_inputs.len() > self.F.external_inputs_len() {
@@ -668,7 +668,9 @@ where
             if let Some(witness) = frontend_witness {
                 self.F.load_witness(witness)
             };
-        }
+
+            external_inputs
+        };
 
         // ensure that commitments are blinding if user has specified so.
         if H && self.i >= C1::ScalarField::one() {

From d2d543f9ca91c4d4a1d1d0bf82f2c89451cce62b Mon Sep 17 00:00:00 2001
From: CPerezz <c.perezbaro@gmail.com>
Date: Mon, 21 Oct 2024 15:33:42 +0200
Subject: [PATCH 11/12] fix: CI feature typo

---
 .github/workflows/ci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 1add8edc..64749770 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -99,7 +99,7 @@ jobs:
         uses: actions-rs/cargo@v1
         with:
           command: build
-          args: -p folding-schemes --target ${{ matrix.target }} --features circom-frontend
+          args: -p folding-schemes --target ${{ matrix.target }} --features circom-browser 
       - name: Run wasm-compat script
         run: |
           chmod +x .github/scripts/wasm-target-test-build.sh

From 63f599ece3943c11f47804429eb01eb84b7688b7 Mon Sep 17 00:00:00 2001
From: CPerezz <c.perezbaro@gmail.com>
Date: Mon, 21 Oct 2024 23:15:13 +0200
Subject: [PATCH 12/12] fix: Update CI package to test for WASM build to
 `frontends`

---
 .github/workflows/ci.yml | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 49eeef6f..92a4f44b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -99,7 +99,12 @@ jobs:
         uses: actions-rs/cargo@v1
         with:
           command: build
-          args: -p folding-schemes --target ${{ matrix.target }} --features circom-browser
+          args: -p frontends --no-default-features --target ${{ matrix.target }} --features "circom-browser, parallel"
+      - name: Wasm-compat folding-schemes build
+        uses: actions-rs/cargo@v1
+        with:
+          command: build
+          args: -p folding-schemes --no-default-features --target ${{ matrix.target }} --features "default,light-test"
       - name: Run wasm-compat script
         run: |
           chmod +x .github/scripts/wasm-target-test-build.sh
@@ -156,13 +161,13 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        feature_set: [basic, circom-browser]
+        feature_set: [basic, wasm]
         include:
           - feature_set: basic
             features: --features default,light-test
-            # We only want to test `folding-schemes` package with `circom-browser` feature.
-          - feature_set: circom-browser
-            features: -p folding-schemes --features circom-browser,parallel --target wasm32-unknown-unknown
+            # We only want to test `frontends` package with `wasm` feature.
+          - feature_set: wasm
+            features: -p frontends --features circom-browser,parallel --target wasm32-unknown-unknown
     steps:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1