@toruslabs/ffjavascript/build/lib.cjs/src/futils.js

Finite Field Library in Javascript

'use strict';

var scalar = require('./scalar.js');

/*
    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/>.
*/


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

    while (! rem.eq(bigInt.zero)) {
        if (rem.and(bigInt.one).eq(bigInt.one)) {
            res = F.add(res, exp);
        }
        exp = F.double(exp);
        rem = rem.shiftRight(1);
    }

    return res;
};
*/

function exp(F, base, e) {
  if (scalar.isZero(e)) return F.one;

  const n = scalar.bits(e);

  if (n.length == 0) return F.one;

  let res = base;

  for (let i = n.length - 2; i >= 0; i--) {
    res = F.square(res);

    if (n[i]) {
      res = F.mul(res, base);
    }
  }

  return res;
}

exports.exp = exp;