poseidon2 for evm

implementations of poseidon2 hash function (https://eprint.iacr.org/2023/323.pdf) in solidity, yul and huff.

attention: code in this repository has not been reviewed for security

install

forge install zemse/poseidon2-evm
npm install poseidon2-evm

usage

contracts:

• solidity: Poseidon2.sol
• yul: Poseidon2Yul.sol
• huff: Poseidon2.huff

any of the above contracts needs to be deployed on the network and then you can make calls to it. here is an example to hash two field elements:

contract MyContract {
    function myFunction() external returns (uint256) {
        uint256 result = 0xPoseidon2ContractAddress.call(
            abi.encode(
                0x1762d324c2db6a912e607fd09664aaa02dfe45b90711c0dae9627d62a4207788,
                0x1047bd52da536f6bdd26dfe642d25d9092c458e64a78211298648e81414cbf35
            )
        );
        return result;
    }
}

notes

solidity code is inefficient due to lot of memory usage and functions.

yul is generated using yul-generator.ts file and provides an inlined implementation that simply mutates 4 stack variables, uses no memory, which brings a lot of gas savings.

huff uses a dirty approach where SWAPs are avoided which leaves unused elements on stack. EVM allows the stack to grow upto 1024 until we run into stack overflow. for parameters (t=4, rf=8, rp=56), we would leave 4*(8+56) = 256 garbage elements on stack which is much lower than 1024 limit.

benchmarks

huff

gas cost for hashing one, two or three elements: 14934

yul benchmarks

gas cost for hasing one, two or three elements: 27517

solidity benchmarks

| num elements | est gas | |--------------|-----------| | hash_1 | 219544 | | hash_2 | 220018 | | hash_3 | 220641 | | hash 4 | 416486 | | hash 5 | 417197 | | hash 6 | 417952 | | hash 7 | 604599 | | hash 8 | 605311 | | hash 9 | 606064 | | hash 10 | 792604 |