post-e-voting/source-code/scytl-cryptolib/cryptolib-js-zkproof/lib/pre-computation.js

/*
 * Copyright 2018 Scytl Secure Electronic Voting SA
 *
 * All rights reserved
 *
 * See our extended copyright notice in *file 'Copyright.txt' which is part of this source code package
 */
/* jshint node:true */
'use strict';

var codec = require('scytl-codec');

module.exports = ZeroKnowledgeProofPreComputation;

/**
 * @class ZeroKnowledgeProofPreComputation
 * @classdesc Encapsulates a zero-knowledge proof of knowledge pre-computation.
 *            This object is instantiated by the method {@link
 *            ZeroKnowledgeProofService.newPreComputation} or internally by the
 *            <code>preCompute</code> method of any zero-knowledge proof of
 *            knowledge prover object.
 * @property {Exponent[]} exponents The array of randomly generated exponents
 *           that comprise the pre-computation.
 * @property {ZpGroupElement[]} phiOutputs The array of PHI function output
 *           elements that comprise the pre-computation.
 */
function ZeroKnowledgeProofPreComputation(exponents, phiOutputs) {
  Object.freeze(this.exponents = exponents);
  Object.freeze(this.phiOutputs = phiOutputs);

  Object.freeze(this);
}

ZeroKnowledgeProofPreComputation.prototype = {
  /**
   * Serializes this object into a JSON string representation.
   * <p>
   * <b>IMPORTANT:</b> This serialization must be exactly the same as the
   * corresponding serialization in the library <code>cryptoLib</code>,
   * implemented in Java, since the two libraries are expected to communicates
   * with each other via these serializations.
   *
   * @function toJson
   * @memberof ZeroKnowledgeProofPreComputation
   * @returns {string} The JSON string representation of this object.
   */
  toJson: function() {
    var pB64 = codec.base64Encode(this.phiOutputs[0].p);
    var qB64 = codec.base64Encode(this.phiOutputs[0].q);
    var exponentValuesB64 = [];
    for (var i = 0; i < this.exponents.length; i++) {
      exponentValuesB64[i] = codec.base64Encode(this.exponents[i].value);
    }
    var phiOutputValuesB64 = [];
    for (var j = 0; j < this.phiOutputs.length; j++) {
      phiOutputValuesB64[j] = codec.base64Encode(this.phiOutputs[j].value);
    }

    return JSON.stringify({
      preComputed: {
        p: pB64,
        q: qB64,
        exponents: exponentValuesB64,
        phiOutputs: phiOutputValuesB64
      }
    });
  }
};