snarkjs/src/powersoftau_truncate.js

zkSNARKs implementation in JavaScript

/*
    Copyright 2018 0KIMS association.

    This file is part of snarkJS.

    snarkJS is a free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    snarkJS is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
    License for more details.

    You should have received a copy of the GNU General Public License
    along with snarkJS. If not, see <https://www.gnu.org/licenses/>.
*/

import * as binFileUtils from "@iden3/binfileutils";
import * as utils from "./powersoftau_utils.js";

export default async function truncate(ptauFilename, template, logger) {

    const {fd: fdOld, sections} = await binFileUtils.readBinFile(ptauFilename, "ptau", 1);
    const {curve, power, ceremonyPower} = await utils.readPTauHeader(fdOld, sections);

    const sG1 = curve.G1.F.n8*2;
    const sG2 = curve.G2.F.n8*2;

    for (let p=1; p<power; p++) {
        await generateTruncate(p);
    }

    await fdOld.close();

    return true;

    async function generateTruncate(p) {

        let sP = p.toString();
        while (sP.length<2) sP = "0" + sP;

        if (logger) logger.debug("Writing Power: "+sP);

        const fdNew = await binFileUtils.createBinFile(template + sP + ".ptau", "ptau", 1, 11);
        await utils.writePTauHeader(fdNew, curve, p, ceremonyPower);

        await binFileUtils.copySection(fdOld, sections, fdNew, 2, ((2 ** p)*2-1) * sG1 ); // tagG1
        await binFileUtils.copySection(fdOld, sections, fdNew, 3, (2 ** p) * sG2); // tauG2
        await binFileUtils.copySection(fdOld, sections, fdNew, 4, (2 ** p) * sG1); // alfaTauG1
        await binFileUtils.copySection(fdOld, sections, fdNew, 5, (2 ** p) * sG1); // betaTauG1
        await binFileUtils.copySection(fdOld, sections, fdNew, 6,  sG2); // betaTauG2
        await binFileUtils.copySection(fdOld, sections, fdNew, 7); // contributions
        await binFileUtils.copySection(fdOld, sections, fdNew, 12, ((2 ** (p+1))*2 -1) * sG1); // L_tauG1
        await binFileUtils.copySection(fdOld, sections, fdNew, 13, ((2 ** p)*2 -1) * sG2); // L_tauG2
        await binFileUtils.copySection(fdOld, sections, fdNew, 14, ((2 ** p)*2 -1) * sG1); // L_alfaTauG1
        await binFileUtils.copySection(fdOld, sections, fdNew, 15, ((2 ** p)*2 -1) * sG1); // L_betaTauG1

        await fdNew.close();
    }


}