Fflonk Verifier

settlementFflonkPallet

Statement hash components

• context: keccak256(b"fflonk")
• vk: keccak256(vk.encode())
• pubs: keccak256(pubs)

Verifier implementation

• verify_proof() uses fflonk_verifier crate to deserialize the proof and public inputs and then verify them against the given verification key.

• Define the following types:

  pub type Pubs = [u8; 32];
  pub type Proof = [u8; 768];
  pub struct Vk {
      power: u8,
      k1: Fr,
      k2: Fr,
      w: Fr,
      w3: Fr,
      w4: Fr,
      w8: Fr,
      wr: Fr,
      x2: G2,
      c0: G1, 
  }
  
  pub struct Fr(U256)
  pub struct Fq(U256)
  pub struct Fq2(Fq, Fq)
  pub struct G1(Fq, Fq, Fq)
  pub struct G2(Fq2, Fq2, Fq2)

• hash context data is b"fflonk"

• the pubs bytes are the input ones

• validate_vk checks the fields value and curve points.

You can fill all the fields with both hex or decimal string: an example from Polkadot.js interface follows:

Result

The pallet's verification duties are summarized in the following code snippet:

let proof = Proof::try_from(&proof_data).unwrap();
let pubs = pubs_data.into();
let vk = vk.into();

fflonk_verifier::verify(vk, &proof, &pubs)

The submitProof exstrinsic can fail both if it's not possible to deserialize the proof (InvalidProofData) or if the proof doesn't verify (VerifyError).