Poseidon2 for EVM

Gas-optimized implementations of the Poseidon2 hash function for the EVM. Updates on TG

Implementation Details

See impl-specific documentation:

• BN254 (Rf=8, Rp=56)

Goldilocks support is planned.

Gas Costs

Implementation	hash_1	hash_2	hash_3	Notes
Solidity	264,090	264,836	265,733	Reference implementation
Yul	20,304	20,304	20,304	Recommended optimised
Huff	14,845	14,845	14,845	Heavy optimised

It is recommended to use yul implementation.

Usage example

Recommended: Helper Library

1. Install the dependency.

# Foundry
forge install zemse/poseidon2-evm

# npm
npm install poseidon2-evm

2. Import the file

import {Poseidon2} from "poseidon2-evm/src/bn254/Poseidon2.sol";

contract MyContract {
    function someWork() external {
        uint left;
        uint right;

        // Default: calls the globally deployed Yul contract with checked input
        uint result = Poseidon2.hash_2(left, right);
    }

    function someExperiment() external pure returns (uint256) {
        uint left;
        uint right;

        // Explicitly use Huff contract (lowest gas, unchecked)
        uint result = Poseidon2.hash_2_huff_unchecked(secret, nullifier);
    }
}

Alternative: Direct Interface

Copy the interface into your project IPoseidon2.sol and use it.

interface IPoseidon2 {
    function hash_2(uint256 x, uint256 y) external pure returns (uint256);
}

contract MyContract {
    function someWork() external {
        uint left;
        uint right;

        // Makes direct call to the contract. But you need to make sure inputs i.e.
        // left & right are valid field elements (< PRIME).
        uint result = IPoseidon2(0xDeployedAddress).hash_2(left, right);
    }
}

Deployed Contracts

Contracts are deployed with same address on all EVM networks.

BN254 (Rf=8, Rp=56)

Implementation	Address
Yul	TODO
Huff	TODO

Development

• Run tests: forge test
• Generate gas report: ./gas-report.sh
• Generate yul code: npm run generate:yul
• Generare huff code: npm run generate:huff

Tests include correctness vectors, fuzz testing against the reference Solidity implementation, and overflow safety checks for the ADDMOD optimization.

Security

Not yet audited. These implementations have not undergone a formal third-party security audit. Review the code before using in production. Also see SECURITY.md.

License

MIT