post-e-voting/source-code/scytl-cryptolib/cryptolib-js-zkproof/lib/proof.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 = ZeroKnowledgeProof;

/**
 * @class ZeroKnowledgeProof
 * @classdesc Encapsulates a zero-knowledge proof of knowledge. This object is
 *            instantiated by the method
 *            {@link ZeroKnowledgeProofService.newProof} or internally by the
 *            <code>prove</code> method of any zero-knowledge proof of
 *            knowledge prover object.
 * @property {Exponent} hash The hash of the zero-knowledge proof of knowledge.
 * @property {Exponent[]} values The values of the zero-knowledge proof of
 *           knowledge.
 */
function ZeroKnowledgeProof(hash, values) {
  this.hash = hash;
  Object.freeze(this.values = values);

  Object.freeze(this);
}

ZeroKnowledgeProof.prototype = {
  /**
   * Checks if this zero-knowledge proof of knowledge is equal to the
   * zero-knowledge proof of knowledge provided as input.
   *
   * @function equals
   * @memberof ZeroKnowledgeProof
   * @param {ZeroKnowledgeProof}
   *            proof The zero-knowledge proof of knowledge that should be
   *            checked against this zero-knowledge proof of knowledge for
   *            equality.
   * @returns {boolean} <code>true</code> if the equality holds,
   *          <code>false</code> otherwise.
   */
  equals: function(proof) {
    return proof.hash.equals(this.hash && proof.values.equals(this.values));
  },

  /**
   * 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 ZeroKnowledgeProof
   * @returns {string} The JSON string representation of this object.
   */
  toJson: function() {
    var qB64 = codec.base64Encode(this.hash.q);
    var hashB64 = codec.base64Encode(this.hash.value);
    var valuesB64 = [];
    for (var i = 0; i < this.values.length; i++) {
      valuesB64[i] = codec.base64Encode(this.values[i].value);
    }

    return JSON.stringify(
        {zkProof: {q: qB64, hash: hashB64, values: valuesB64}});
  }
};