[TASK] VAnchor API

[lazovicff]

To make the API more configurable and more stable, I propose the following struct:

struct VAnchorR1CSProver<
    E: PairingEngine,
    H: FieldHasher<E::Fr>,
    const HEIGHT: usize,
    const BRIDGE_SIZE: usize,
    const INS: usize,
    const OUTS: usize,
> {
    engine: PhantomData<E>,
    hasher: PhantomData<H>,
}

Which will be defined as:

type VAnchorR1CSProver_Bn254_Poseidon_30_2_2_2 = VAnchorR1CSProver<Bn254, Poseidon<Bn254Fr>, 30, 2, 2, 2>;

With the name convention: [prover name]_[ec]_[hasher]_[tree height]_[bridge size]_[num inputs]_[num outputs]

With interface:

trait VAnchorProver<
    F: PrimeField,
    H: HasherGadget,
    const HEIGHT: usize,
    const BRIDGE_SIZE: usize,
    const INS: usize,
    const OUTS: usize,
> {
    // For creating fresh utxo, or create a new one by passing values for secret key and blinding
    pub fn create_utxo<R: RngCore>(
        chain_id: u128,
        amount: u128,
        index: Option<u64>,
        secret_key: Option<Vec<u8>>,
        blinding: Option<Vec<u8>>,
        rng: &mut R,
    ) -> Result<Leaf, Error>;
    // For making proofs
    pub fn create_proof<R: RngCore + CryptoRng>(
        curve: Curve,
        // External data
        public_amount: Vec<u8>,
        ext_data_hash: Vec<u8>,
        in_root_set: [Vec<u8>; M],
        in_indices: [u64; INS],
        in_leaves: [Vec<Vec<u8>>; INS],
        // Input transactions
        in_utxos: [Utxo<F>; INS],
        // Output transactions
        out_utxos: [Utxo<F>; OUTS],
        rng: &mut R,
    ) -> Result<VAnchorProof, Error>;
}

NOTE: This interface can be implemented for both R1CS and PLONK systems

• Update R1CS circuit API
• Update PLONK circuit API