A data recording and/or reproducing device is provided having a deciphering circuit, a detection circuit, a data processing unit, a recording unit and a controller. The deciphering processing unit deciphers and/or decompresses input encrypted and/or compressed data. The detection circuit detects whether or not watermark signals are contained in output data of the deciphering processing unit. The data processing unit is supplied at least with output signals from the deciphering processing unit and applies signal processing for recording on the supplied data. The recording unit records output data from the data processing unit on a recording medium. If the watermark signals are detected to be contained by the detection unit, the controller controls the operation of the data processing unit based on the detected watermark signals.