silasrebecca / poseidon252

Reference implementation for the Poseidon Snark-friendly Hash algorithm.

Dusk-Poseidon

Reference implementation for the Poseidon Hashing algorithm.

Reference: Starkad and Poseidon: New Hash Functions for Zero Knowledge Proof Systems

This repository has been created so there's a unique library that holds the tools & functions required to perform Poseidon Hashes on field elements of the bls12-381 elliptic curve.

The hash uses the Hades design for its inner permutation and the SAFE framework for contstructing the sponge.

The library provides the two hashing techniques of Poseidon:

• The 'normal' hashing functionalities operating on BlsScalar.
• The 'gadget' hashing functionalities that build a circuit which outputs the hash.

Examples

Hash

use rand::rngs::StdRng;
use rand::SeedableRng;

use dusk_poseidon::{Domain, Hash};
use dusk_bls12_381::BlsScalar;
use ff::Field;

// generate random input
let mut rng = StdRng::seed_from_u64(0xbeef);
let mut input = [BlsScalar::zero(); 42];
for scalar in input.iter_mut() {
    *scalar = BlsScalar::random(&mut rng);
}

// digest the input all at once
let hash = Hash::digest(Domain::Other, &input);

// update the input gradually
let mut hasher = Hash::new(Domain::Other);
hasher.update(&input[..3]);
hasher.update(&input[3..]);
assert_eq!(hash, hasher.finalize());

// create a hash used for merkle tree hashing with arity = 4
let merkle_hash = Hash::digest(Domain::Merkle4, &input[..4]);

// which is different when another domain is used
assert_ne!(merkle_hash, Hash::digest(Domain::Other, &input[..4]));

Encryption

#![cfg(feature = "encryption")]

use dusk_bls12_381::BlsScalar;
use dusk_jubjub::{JubJubScalar, GENERATOR_EXTENDED, dhke};
use dusk_poseidon::{decrypt, encrypt, Error};
use ff::Field;
use rand::rngs::StdRng;
use rand::SeedableRng;

// generate the keys and nonce needed for the encryption
let mut rng = StdRng::seed_from_u64(0x42424242);
let alice_secret = JubJubScalar::random(&mut rng);
let alice_public = GENERATOR_EXTENDED * &alice_secret;
let bob_secret = JubJubScalar::random(&mut rng);
let bob_public = GENERATOR_EXTENDED * &bob_secret;
let nonce = BlsScalar::random(&mut rng);

// Alice encrypts a message of 3 BlsScalar using Diffie-Hellman key exchange
// with Bob's public key
let message = vec![BlsScalar::from(10), BlsScalar::from(20), BlsScalar::from(30)];
let shared_secret = dhke(&alice_secret, &bob_public);
let cipher = encrypt(&message, &shared_secret, &nonce)
    .expect("Encryption should pass");

// Bob decrypts the cipher using Diffie-Hellman key exchange with Alice's public key
let shared_secret = dhke(&bob_secret, &alice_public);
let decrypted_message = decrypt(&cipher, &shared_secret, &nonce)
    .expect("Decryption should pass");

assert_eq!(decrypted_message, message);

Benchmarks

There are benchmarks for hashing, encrypting and decrypting in their native form, operating on Scalar, and for a zero-knowledge circuit proof generation and verification.

To run all benchmarks on your machine, run

cargo bench --features=zk,encryption

in the repository.

Licensing

This code is licensed under Mozilla Public License Version 2.0 (MPL-2.0). Please see LICENSE for further info.

About

Implementation designed by the dusk team.

Contributing

• If you want to contribute to this repository/project please, check CONTRIBUTING.md
• If you want to report a bug or request a new feature addition, please open an issue on this repository.