101 lines
2.6 KiB
JavaScript
101 lines
2.6 KiB
JavaScript
import { Scalar, getCurveFromName } from "ffjavascript";
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import ethers from "ethers";
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const SEED = "mimcsponge";
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const NROUNDS = 220;
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export default async function buildMimcSponge() {
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const bn128 = await getCurveFromName("bn128");
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return new MimcSponge(bn128.Fr);
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}
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class MimcSponge {
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constructor (F) {
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this.F = F;
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this.cts = this.getConstants(SEED, NROUNDS);
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}
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getIV (seed) {
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const F = this.F;
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if (typeof seed === "undefined") seed = SEED;
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const c = ethers.utils.keccak256(ethers.utils.toUtf8Bytes(seed+"_iv"));
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const cn = Scalar.e(c);
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const iv = cn.mod(F.p);
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return iv;
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};
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getConstants (seed, nRounds) {
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const F = this.F;
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if (typeof seed === "undefined") seed = SEED;
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if (typeof nRounds === "undefined") nRounds = NROUNDS;
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const cts = new Array(nRounds);
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let c = ethers.utils.keccak256(ethers.utils.toUtf8Bytes(SEED));;
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for (let i=1; i<nRounds; i++) {
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c = ethers.utils.keccak256(c);
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cts[i] = F.e(c);
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}
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cts[0] = F.e(0);
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cts[cts.length - 1] = F.e(0);
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return cts;
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};
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hash(_xL_in, _xR_in, _k) {
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const F = this.F;
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let xL = F.e(_xL_in);
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let xR = F.e(_xR_in);
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const k = F.e(_k);
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for (let i=0; i<NROUNDS; i++) {
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const c = this.cts[i];
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const t = (i==0) ? F.add(xL, k) : F.add(F.add(xL, k), c);
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const t2 = F.square(t);
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const t4 = F.square(t2);
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const t5 = F.mul(t4, t);
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const xR_tmp = F.e(xR);
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if (i < (NROUNDS - 1)) {
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xR = xL;
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xL = F.add(xR_tmp, t5);
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} else {
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xR = F.add(xR_tmp, t5);
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}
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}
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return {
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xL: xL,
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xR: xR
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};
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}
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multiHash(arr, key, numOutputs) {
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const F = this.F;
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if (typeof(numOutputs) === "undefined") {
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numOutputs = 1;
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}
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if (typeof(key) === "undefined") {
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key = F.zero;
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}
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let R = F.zero;
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let C = F.zero;
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for (let i=0; i<arr.length; i++) {
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R = F.add(R, F.e(arr[i]));
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const S = this.hash(R, C, key);
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R = S.xL;
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C = S.xR;
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}
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let outputs = [R];
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for (let i=1; i < numOutputs; i++) {
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const S = this.hash(R, C, key);
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R = S.xL;
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C = S.xR;
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outputs.push(R);
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}
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if (numOutputs == 1) {
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return outputs[0];
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} else {
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return outputs;
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}
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}
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}
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