light-poseidon

light-poseidon is a Poseidon hash implementation in Rust created for Light Protocol.

Parameters

The library provides pre-generated parameters over the BN254 curve, however it can work with any parameters provided as long as developers take care of generating the round constants.

Parameters provided by the library are:

x^5 S-boxes
t = 2 - 17 (for 1 to 16 inputs)
8 full rounds and partial rounds depending on t [56, 57, 56, 60, 60, 63, 64, 63, 60, 66, 60, 65, 70, 60, 64, 68]

The parameters can be generated with: `$ cargo xtask generate-poseidon-parameters

Output type

Poseidon type implements two traits which serve the purpose of returning the calculated hash in different representations:

PoseidonBytesHasher with the hash_bytes method which returns a byte array.
PoseidonHasher with the hash method which returns ark_ff::PrimeField. Might be useful if you want to immediately process the result with an another library which works with ark_ff::PrimeField types.

Examples

Example with two simple big-endian byte inputs (converted to field elements) and BN254-based parameters provided by the library, with PoseidonBytesHasher trait and a byte array result:

```rust use lightposeidon::{Poseidon, PoseidonBytesHasher, parameters::bn254x53::poseidonparameters}; use arkbn254::Fr; use arkff::{BigInteger, PrimeField};

let mut poseidon = Poseidon::::new_circom(2).unwrap();

let hash = poseidon.hash_bytes(&[&[1u8; 32], &[2u8; 32]]).unwrap();

println!("{:?}", hash); // Should print: // [ // 13, 84, 225, 147, 143, 138, 140, 28, 125, 235, 94, 3, 85, 242, 99, 25, 32, 123, 132, // 254, 156, 162, 206, 27, 38, 231, 53, 200, 41, 130, 25, 144 // ] ```

With [PoseidonHasher][crate::PoseidonHasher] trait and ark_ff::PrimeField result:

```rust use lightposeidon::{Poseidon, PoseidonHasher, parameters::bn254x5}; use arkbn254::Fr; use arkff::{BigInteger, PrimeField};

let mut poseidon = Poseidon::::new_circom(2);

let input1 = Fr::frombebytesmodorder(&[1u8; 32]); let input2 = Fr::frombebytesmodorder(&[2u8; 32]);

let hash = poseidon.hash(&[input1, input2]).unwrap();

// Do something with hash. ```

Implementation

The implementation is compatible with the original SageMath implementation, but it was also inspired by the following ones:

Performance

This repository contains a benchmark measuring the performance of this Poseidon implementation for given 1 - 16 random 32 bytes inputs.

To run them, simply use:

bash cargo bench

This is the result from a host with the following hardware:

12th Gen Intel® Core™ i7-1260P × 16

```norust poseidonbn254x5_1 time: [14.656 µs 14.740 µs 14.848 µs] Found 8 outliers among 100 measurements (8.00%) 4 (4.00%) high mild 4 (4.00%) high severe

poseidonbn254x5_2 time: [23.013 µs 24.307 µs 25.752 µs] Found 5 outliers among 100 measurements (5.00%) 2 (2.00%) high mild 3 (3.00%) high severe

poseidonbn254x5_3 time: [29.276 µs 29.325 µs 29.377 µs] Found 4 outliers among 100 measurements (4.00%) 4 (4.00%) high mild

poseidonbn254x5_4 time: [41.699 µs 41.856 µs 42.039 µs] Found 7 outliers among 100 measurements (7.00%) 6 (6.00%) high mild 1 (1.00%) high severe

poseidonbn254x5_5 time: [55.947 µs 57.883 µs 60.190 µs] Found 14 outliers among 100 measurements (14.00%) 1 (1.00%) high mild 13 (13.00%) high severe

poseidonbn254x5_6 time: [70.992 µs 71.327 µs 71.737 µs] Found 10 outliers among 100 measurements (10.00%) 4 (4.00%) high mild 6 (6.00%) high severe

poseidonbn254x5_7 time: [87.824 µs 88.174 µs 88.587 µs] Found 12 outliers among 100 measurements (12.00%) 5 (5.00%) high mild 7 (7.00%) high severe

poseidonbn254x5_8 time: [110.07 µs 111.22 µs 112.77 µs]

poseidonbn254x5_9 time: [131.48 µs 131.82 µs 132.24 µs] Found 9 outliers among 100 measurements (9.00%) 1 (1.00%) high mild 8 (8.00%) high severe

poseidonbn254x5_10 time: [176.36 µs 177.01 µs 177.80 µs] Found 8 outliers among 100 measurements (8.00%) 1 (1.00%) low mild 6 (6.00%) high mild 1 (1.00%) high severe

poseidonbn254x5_11 time: [191.53 µs 192.26 µs 193.20 µs] Found 14 outliers among 100 measurements (14.00%) 8 (8.00%) high mild 6 (6.00%) high severe

poseidonbn254x5_12 time: [259.56 µs 273.31 µs 287.16 µs] Found 15 outliers among 100 measurements (15.00%) 15 (15.00%) high severe

poseidonbn254x5_13 time: [307.41 µs 307.88 µs 308.38 µs] Found 5 outliers among 100 measurements (5.00%) 2 (2.00%) high mild 3 (3.00%) high severe

poseidonbn254x5_14 time: [309.65 µs 311.24 µs 313.54 µs] Found 4 outliers among 100 measurements (4.00%) 2 (2.00%) high mild 2 (2.00%) high severe

poseidonbn254x5_15 time: [383.48 µs 385.41 µs 387.49 µs] Found 2 outliers among 100 measurements (2.00%) 2 (2.00%) high mild ```

License

Licensed under Apache License, Version 2.0.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.