rng.js

// Original code adapted from Robert Kieffer.
// details at https://github.com/broofa/node-uuid
(function() {
  var _global = this;

  var mathRNG, whatwgRNG;

  // NOTE: Math.random() does not guarantee "cryptographic quality"
  mathRNG = function(size) {
    var bytes = new Array(size);
    var r;

    for (var i = 0, r; i < size; i++) {
      if ((i & 0x03) == 0) r = Math.random() * 0x100000000;
      bytes[i] = r >>> ((i & 0x03) << 3) & 0xff;
    }

    return bytes;
  }

  if (_global.crypto && crypto.getRandomValues) {
    var _rnds = new Uint32Array(4);
    whatwgRNG = function(size) {
      var bytes = new Array(size);
      crypto.getRandomValues(_rnds);

      for (var c = 0 ; c < size; c++) {
        bytes[c] = _rnds[c >> 2] >>> ((c & 0x03) * 8) & 0xff;
      }
      return bytes;
    }
  }

  module.exports = whatwgRNG || mathRNG;

}())