csprng/lib/csprng.js

Secure random numbers of any size in any base

var DEFAULT_BITS  = 128,
    DEFAULT_RADIX = 16,
    DIGITS        = '0123456789abcdefghijklmnopqrstuvwxyz'.split('');

var crypto = require('crypto'),
    Seq    = require('sequin');

var rand = function(bits, radix) {
  bits  = bits  || DEFAULT_BITS;
  radix = radix || DEFAULT_RADIX;

  if (radix < 2 || radix > 36)
    throw new Error('radix argument must be between 2 and 36');

  var length  = Math.ceil(bits * Math.log(2) / Math.log(radix)),
      entropy = crypto.randomBytes(bits),
      stream  = new Seq(entropy),
      string  = '';

  while (string.length < length)
    string += DIGITS[stream.generate(radix)];

  return string;
};

module.exports = rand;