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const bn128 = require("snarkjs").bn128; const bigInt = require("snarkjs").bigInt; const Web3 = require("web3"); const F = bn128.Fr;
const SEED = "mimc"; const NROUNDS = 91;
exports.getIV = (seed) => { if (typeof seed === "undefined") seed = SEED; const c = Web3.utils.keccak256(seed+"_iv"); const cn = bigInt(Web3.utils.toBN(c).toString()); const iv = cn.mod(F.q); return iv; };
exports.getConstants = (seed, nRounds) => { if (typeof seed === "undefined") seed = SEED; if (typeof nRounds === "undefined") nRounds = NROUNDS; const cts = new Array(nRounds); let c = Web3.utils.keccak256(SEED); for (let i=1; i<nRounds; i++) { c = Web3.utils.keccak256(c);
const n1 = Web3.utils.toBN(c).mod(Web3.utils.toBN(F.q.toString())); const c2 = Web3.utils.padLeft(Web3.utils.toHex(n1), 64); cts[i] = bigInt(Web3.utils.toBN(c2).toString()); } cts[0] = bigInt(0); return cts; };
const cts = exports.getConstants(SEED, 91);
exports.hash = (_x_in, _k) =>{ const x_in = bigInt(_x_in); const k = bigInt(_k); let r; for (let i=0; i<NROUNDS; i++) { const c = cts[i]; const t = (i==0) ? F.add(x_in, k) : F.add(F.add(r, k), c); r = F.exp(t, 7); } return F.affine(F.add(r, k)); };
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