Support ark-bls12-381

[piotr-roslaniec]

Exploratory integration with Arkworks crates as described in #15, and similar to previous https://github.com/arkworks-rs/spartan integration.

This is a pretty rough, initial draft that broke several things (traits, conventions, crate::providers, tests), to enable prototyping with Sonobe.

I decided to make a draft PR to gain some feedback and pointers from maintainers, and eventually contribute if it is well-received and accepted.

[Autoparallel]

I'm so excited to see this and demo it!

Great work so far!

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[srinathsetty]

This is great! Will review in greater detail soon. Please let us know if you need any specific inputs.

Also, if we switch to arkworks for curves, do we still need dependency on halo2curves?

[piotr-roslaniec]

Hi @srinathsetty, thank you for looking into this.

At this point, I'm trying to fix a broken test which throws an InvalidSumcheckProof error.

In the meantime, here is a list of things that may benefit from your input:

• ConstraintSystem and Circuit have been replaced by ark-relations::r1cs::{ConstraintSystem, ConstraintSynthesizer}. It wasn't clear to me how to integrate with SpartanShape, so I removed it. Some utilities (like namespaces, or utils in shape_cs.rs) are not completely supported in Arkworks.
• I don't feel confident about this conversion from ark-relations::r1cs::ConstraintMatrices and R1CSShape
• Some provider modules have been commented out. I want to address them later but if it turns out that maintaining compatibility with Arkworks is an issue, perhaps this PR should function as a fork instead (similar to arkworks-rs/spartan)

On halo2curves: I think we can replace it with other Arkworks crates. Some (commented out) providers still use it. I will remove unused dependencies and clean this PR up before requesting a review.

Copilot reviewed 14 out of 29 changed files in this pull request and generated no comments.

Files not reviewed (15)

• benches/bench.rs: Evaluated as low risk
• src/provider/mod.rs: Evaluated as low risk
• src/bellpepper/solver.rs: Evaluated as low risk
• src/bellpepper/r1cs.rs: Evaluated as low risk
• src/bellpepper/shape_cs.rs: Evaluated as low risk
• src/bellpepper/test_shape_cs.rs: Evaluated as low risk
• src/provider/bn256_grumpkin.rs: Evaluated as low risk
• src/provider/pedersen.rs: Evaluated as low risk
• src/digest.rs: Evaluated as low risk
• src/provider/keccak.rs: Evaluated as low risk
• src/provider/secp_secq.rs: Evaluated as low risk
• src/bellpepper/mod.rs: Evaluated as low risk
• src/provider/ipa_pc.rs: Evaluated as low risk
• src/lib.rs: Evaluated as low risk
• examples/less_than.rs: Evaluated as low risk

Comments suppressed due to low confidence (4)

src/r1cs.rs:361

• The word 'accomodate' is misspelled. It should be 'accommodate'.

/// Renumbers variables to accomodate padded variables

src/r1cs.rs:435

• The word 'consitituent' is misspelled. It should be 'constituent'.

/// A method to create an instance object using consitituent elements

src/r1cs.rs:362

• The pad method should be reviewed to ensure it correctly handles the padding logic for R1CSShape.

pub fn pad(&self) -> Self {

src/provider/ark.rs:139

• Handle potential errors more gracefully when reading bytes from the XOF.

reader.read_exact(&mut uniform_bytes).expect("Failed to read bytes from XOF");

[srinathsetty]

I don't feel confident about this conversion from ark-relations::r1cs::ConstraintMatrices and R1CSShape

The bellpepper module we had turns bellpepper circuits into R1CS matrices. Doesn't arkworks provide similar functionality to extract R1CS matrices from arkworks circuit code?

Some provider modules have been commented out. I want to address them later but if it turns out that maintaining compatibility with Arkworks is an issue, perhaps this PR should function as a fork instead (similar to arkworks-rs/spartan)

I didn't follow the point about fork. When this PR is merged, we would be using arkworks for all curves. Can you clarify what you mean by fork?