code: function(data) {
        var bytesToPad, padding;
        bytesToPad = BLOCKSIZE - (data.length % BLOCKSIZE);
        padding = this.randomBytes(bytesToPad);
        return this.concat([padding, data]);
      }
docs: Prepend padding to data to make it fill the blocksize.
  @param {Buffer} data The data to pad.
  @return {Buffer} The data with padding added.