Decider

Decider prove

Two options:

• onchain (Ethereum's EVM) mode
• offchain mode

Once we have been folding our circuit instances, we can generate the "final proof", the Decider proof.

Onchain Decider

Generating the final proof (decider), to be able to verify it in Ethereum's EVM:

#![allow(unused)]
fn main() {
type DECIDER = Decider<
    Projective,
    Projective2,
    CubicFCircuit<Fr>,
    KZG<'static, Bn254>,
    Pedersen<Projective2>,
    Groth16<Bn254>, // here we define the Snark to use in the decider
    NOVA,              // here we define the FoldingScheme to use
>;

let mut rng = rand::rngs::OsRng;

// prepare the Decider prover & verifier params for the given nova_params and nova instance. This involves generating the Groth16 and KZG10 setup
let (decider_pp, decider_vp) = DECIDER::preprocess(&mut rng, &nova_params, nova.clone()).unwrap();

// decider proof generation
let proof = DECIDER::prove(rng, decider_pp, nova.clone()).unwrap();

}

As in the previous sections, you can find a full examples with all the code at sonobe/examples.

Decider verify

We can now verify the Decider proof

#![allow(unused)]
fn main() {
// this is the same that we defined for the prover
type DECIDER = Decider<
    Projective,
    Projective2,
    CubicFCircuit<Fr>,
    KZG<'static, Bn254>,
    Pedersen<Projective2>,
    Groth16<Bn254>,
    NOVA,
>;

let verified = DECIDER::verify(
    decider_vp, nova.i, nova.z_0, nova.z_i, &nova.U_i, &nova.u_i, proof,
)
.unwrap();
assert!(verified);
}

In the Ethereum Decider case, we can generate a Solidity smart contract that verifies the proofs onchain. More details in the next section.