poseidon-solidity 

Poseidon implementation in Solidity over alt_bn128 (aka BN254).

This implementation has not been audited.

Benchmark

``yaml
T2 hash
- poseidon-solidity: 13,488 gas
- circomlibjs: 19,395 gas
- address: 0x22233340039aAB0C858bc6086f508d9A4f2fA4db

T3 hash
- poseidon-solidity: 21,124 gas
- circomlibjs: 32,173 gas
- address: 0x3333333C0A88F9BE4fd23ed0536F9B6c427e3B93

T4 hash
- poseidon-solidity: 37,617 gas
- circomlibjs: 48,267 gas
- address: 0x4443338EF595F44e0121df4C21102677B142ECF0

T5 hash
- poseidon-solidity: 54,326 gas
- circomlibjs: 73,307 gas
- address: 0x555333f3f677Ca3930Bf7c56ffc75144c51D9767

T6 hash
- poseidon-solidity: 74,039 gas
- circomlibjs: 100,197 gas
- address: 0x666333F371685334CdD69bdDdaFBABc87CE7c7Db

---

Deploy cost (T3)
- poseidon-solidity: 5,129,638 gas
- circomlibjs: 2,156,516 gas
`

Use

`sh
npm i poseidon-solidity
`

`solidity
import "poseidon-solidity/PoseidonT3.sol";

contract Example {

function combine(uint input0, uint input1) public {
uint out = PoseidonT3.hash([input0, input1]);
}

}
`

Deploy

This package includes config info for deploying with a deterministic proxy. The proxy itself is deployed using Nick's method with a pre-signed transaction from a keyless address. The poseidon contracts are deployed through this proxy to get the same address in any evm.

To deploy in a hardhat/ethers type environment:

`js
const { proxy, PoseidonT3 } = require('poseidon-solidity')

const [sender] = await ethers.getSigners()

// First check if the proxy exists
if (await ethers.provider.getCode(proxy.address) === '0x') {
// fund the keyless account
await sender.sendTransaction({
to: proxy.from,
value: proxy.gas,
})

// then send the presigned transaction deploying the proxy
await ethers.provider.sendTransaction(proxy.tx)
}

// Then deploy the hasher, if needed
if (await ethers.provider.getCode(PoseidonT3.address) === '0x') {
await send.sendTransaction({
to: proxy.address,
data: PoseidonT3.data
})
}

console.log(PoseidonT3 deployed to: ${PoseidonT3.address})
`

Testing

`sh
npm install
npm test
``