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
• 3 prime fields (one zero prime field and two inputs from the caller)
• 8 full rounds and 57 partial rounds

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 prime fields) 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::Fq; use arkff::{BigInteger, PrimeField};

let params = poseidon_parameters(); let mut poseidon = Poseidon::new(params);

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

println!("{:?}", hash); // Should print: // [ // 40, 7, 251, 60, 51, 30, 115, 141, 251, 200, 13, 46, 134, 91, 113, 170, 131, 90, 53, // 175, 9, 61, 242, 164, 127, 33, 249, 65, 253, 131, 35, 116 // ] ```

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

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

let params = poseidon_parameters(); let mut poseidon = Poseidon::new(params);

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

• circomlibjs
• zero-knowledge-gadgets

Performance

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

To run them, simply use:

bash cargo bench

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

• AMD Ryzen 9 5950x (base clock: 3.4 GHz, up to: 4.9 GHz)
• 4 x Corsair Vengeance DDR4 32GB 3600 MHz

norust poseidon_bn254_x5_3 time: [21.980 µs 21.997 µs 22.017 µs] Found 9 outliers among 100 measurements (9.00%) 4 (4.00%) high mild 5 (5.00%) high severe

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.