A data reproducing apparatus and method is provided for reproducing data that was ciphered during recording in one or more of sector forming, header appending, error correction coding, modulation, and synchronization appending operations used for processing input data to form a recording signal. Thus, deciphering requires knowledge of both the ciphering key and the aspect(s) of the recording operation in which the ciphering took place. The deciphering may also include a descrambling operation in which an initial value and/or a generating polynomial is varied in accordance with ciphering key information.