docs: function (data) {
      if (typeof data === "string") {
        data = sjcl.codec.utf8String.toBits(data);
      }
      var i, b = this._buffer = sjcl.bitArray.concat(this._buffer, data),
          ol = this._length,
          nl = this._length = ol + sjcl.bitArray.bitLength(data);
      for (i = 512+ol & -512; i <= nl; i+= 512) {
        this._block(b.splice(0,16));
      }
      return this;
    }