code: function xor(buffer1, buffer2) {
      var length = Math.min(buffer1.length, buffer2.length);
      var retBuffer = new Buffer(length);
      for (var i = 0; i < length; i++) {
          retBuffer[i] = buffer1[i] ^ buffer2[i];
      }
      return retBuffer;
  }
docs: Xor op on buffers