circomlib/src/poseidon_gencontract.js

// Copyright (c) 2018 Jordi Baylina
// License: LGPL-3.0+
//

const Poseidon = require("./poseidon.js");

const Contract = require("./evmasm");

const SEED = "poseidon";
const NROUNDSF = 8;
const NROUNDSP = 57;
const T = 6;

function toHex256(a) {
    let S = a.toString(16);
    while (S.length < 64) S="0"+S;
    return "0x" + S;
}

function createCode(t, nRoundsF, nRoundsP, seed) {
    if (typeof seed === "undefined") seed = SEED;
    if (typeof nRoundsF === "undefined") nRoundsF = NROUNDSF;
    if (typeof nRoundsP === "undefined") nRoundsP = NROUNDSP;
    if (typeof t === "undefined") t = T;

    const K = Poseidon.getConstants(t, seed, nRoundsP + nRoundsF);
    const M = Poseidon.getMatrix(t, seed, nRoundsP + nRoundsF);

    const C = new Contract();

    function saveM() {
        for (let i=0; i<t; i++) {
            for (let j=0; j<t; j++) {
                C.push(toHex256(M[i][j]));
                C.push((1+i*t+j)*32);
                C.mstore();
            }
        }
    }

    function ark(r) {
        C.push(toHex256(K[r])); // K, st, q
        for (let i=0; i<t; i++) {
            C.dup(1+t); // q, K, st, q
            C.dup(1);   // K, q, K, st, q
            C.dup(3+i); // st[i], K, q, K, st, q
            C.addmod(); // newSt[i], K, st, q
            C.swap(2 + i); // xx, K, st, q
            C.pop();
        }
        C.pop();
    }

    function sigma(p) {
        // sq, q
        C.dup(t);   // q, st, q
        C.dup(1+p); // st[p] , q , st, q
        C.dup(1);   // q, st[p] , q , st, q
        C.dup(0);   // q, q, st[p] , q , st, q
        C.dup(2);   // st[p] , q, q, st[p] , q , st, q
        C.dup(0);   // st[p] , st[p] , q, q, st[p] , q , st, q
        C.mulmod(); // st2[p], q, st[p] , q , st, q
        C.dup(0);   // st2[p], st2[p], q, st[p] , q , st, q
        C.mulmod(); // st4[p], st[p] , q , st, q
        C.mulmod(); // st5[p], st, q
        C.swap(1+p);
        C.pop();      // newst, q
    }

    function mix() {
        C.label("mix");
        for (let i=0; i<t; i++) {
            for (let j=0; j<t; j++) {
                if (j==0) {
                    C.dup(i+t);      // q, newSt, oldSt, q
                    C.push((1+i*t+j)*32);
                    C.mload();      // M, q, newSt, oldSt, q
                    C.dup(2+i+j);    // oldSt[j], M, q, newSt, oldSt, q
                    C.mulmod();      // acc, newSt, oldSt, q
                } else {
                    C.dup(1+i+t);    // q, acc, newSt, oldSt, q
                    C.push((1+i*t+j)*32);
                    C.mload();      // M, q, acc, newSt, oldSt, q
                    C.dup(3+i+j);    // oldSt[j], M, q, acc, newSt, oldSt, q
                    C.mulmod();      // aux, acc, newSt, oldSt, q
                    C.dup(2+i+t);    // q, aux, acc, newSt, oldSt, q
                    C.swap(2);       // acc, aux, q, newSt, oldSt, q
                    C.addmod();      // acc, newSt, oldSt, q
                }
            }
        }
        for (let i=0; i<t; i++) {
            C.swap((t -i) + (t -i-1));
            C.pop();
        }
        C.push(0);
        C.mload();
        C.jmp();
    }


    // Check selector
    C.push("0x0100000000000000000000000000000000000000000000000000000000");
    C.push(0);
    C.calldataload();
    C.div();
    C.push("0xc4420fb4"); // poseidon(uint256[])
    C.eq();
    C.jmpi("start");
    C.invalid();

    C.label("start");

    saveM();

    C.push("0x30644e72e131a029b85045b68181585d2833e84879b9709143e1f593f0000001");  // q

    // Load 6 values from the call data.
    // The function has a single array param param
    // [Selector (4)] [Pointer (32)][Length (32)] [data1 (32)] ....
    // We ignore the pointer and the length and just load 6 values to the state
    // (Stack positions 0-5) If the array is shorter, we just set zeros.
    for (let i=0; i<t; i++) {
        C.push(0x44+(0x20*(5-i)));
        C.calldataload();
    }

    for (let i=0; i<nRoundsF+nRoundsP; i++) {
        ark(i);
        if ((i<nRoundsF/2) || (i>=nRoundsP+nRoundsF/2)) {
            for (let j=0; j<t; j++) {
                sigma(j);
            }
        } else {
            sigma(0);
        }
        const strLabel = "aferMix"+i;
        C._pushLabel(strLabel);
        C.push(0);
        C.mstore();
        C.jmp("mix");
        C.label(strLabel);
    }

    C.push("0x00");
    C.mstore();     // Save it to pos 0;
    C.push("0x20");
    C.push("0x00");
    C.return();

    mix();

    return C.createTxData();
}

module.exports.abi = [
    {
        "constant": true,
        "inputs": [
            {
                "name": "input",
                "type": "uint256[]"
            }
        ],
        "name": "poseidon",
        "outputs": [
            {
                "name": "",
                "type": "uint256"
            }
        ],
        "payable": false,
        "stateMutability": "pure",
        "type": "function"
    }
];

module.exports.createCode = createCode;