Has anyone successfully used Arkworks with Spartan?

[ihyunnam]

Hi, I'm a student trying to write zkSNARKs for a project of mine. I just learned about Arkworks -- thanks for the very cool stuff -- and would like to use it with Spartan (https://github.com/microsoft/Spartan) to produce and verify zkSNARKS.

However, it seems like Arkworks doesn't readily interface with Spartan. I explored the spartan repository in arkworks-rs but it didn't seem too integrated with Arkworks.

Does anyone have more insight on using Arkworks with Spartan? In particular, after writing R1CS constraints using crypto-primitives, I don't know how to turn these constraints into an R1CS instance that interface with Spartan's API like verify or prove.

For example, from Spartan's README, this is how to use libspartan to create and verify a SNARK proof. How can I turn an Arkworks R1CS constraints into the (inst, vars, inputs) that Spartan seems to require?

# extern crate libspartan;
# extern crate merlin;
# use libspartan::{Instance, SNARKGens, SNARK};
# use merlin::Transcript;
# use ark_bls12_381::{G1Projective, Fr};
#
# fn main() {
    // specify the size of an R1CS instance
    let num_vars = 1024;
    let num_cons = 1024;
    let num_inputs = 10;
    let num_non_zero_entries = 1024;

    // produce public parameters
    let gens = SNARKGens::<G1Projective>::new(num_cons, num_vars, num_inputs, num_non_zero_entries);

    // ask the library to produce a synthentic R1CS instance
    let (inst, vars, inputs) = Instance::produce_synthetic_r1cs(num_cons, num_vars, num_inputs);

    // create a commitment to the R1CS instance
    let (comm, decomm) = SNARK::encode(&inst, &gens);

    // produce a proof of satisfiability
    let mut prover_transcript = Transcript::new(b"snark_example");
    let proof = SNARK::prove(&inst, &comm, &decomm, vars, &inputs, &gens, &mut prover_transcript);

    // verify the proof of satisfiability
    let mut verifier_transcript = Transcript::new(b"snark_example");
    assert!(proof
      .verify(&comm, &inputs, &mut verifier_transcript, &gens)
      .is_ok());
    println!("proof verification successful!");
# }

What are some detailed steps or caveats if anyone has tried wiring these up before?

Thank you!