snarkjs/src/futils.js

/*
    Copyright 2018 0kims association.

    This file is part of zksnark JavaScript library.

    zksnark JavaScript library 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.

    zksnark JavaScript library 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 
    zksnark JavaScript library. If not, see <https://www.gnu.org/licenses/>.
*/

const bigInt = require("./bigint.js");

exports.mulScalar = (F, base, e) =>{
    let res = F.zero;
    let rem = bigInt(e);
    let exp = base;

    while (! rem.isZero()) {
        if (rem.isOdd()) {
            res = F.add(res, exp);
        }
        exp = F.double(exp);
        rem = rem.shr(1);
    }

    return res;
};


exports.exp = (F, base, e) =>{
    let res = F.one;
    let rem = bigInt(e);
    let exp = base;

    while (! rem.isZero()) {
        if (rem.isOdd()) {
            res = F.mul(res, exp);
        }
        exp = F.square(exp);
        rem = rem.shr(1);
    }

    return res;
};