Reinforcement of a system renewability is realized skillfully utilizing properties peculiar to a system. As a result, there is produced such a new effect as to similarly reinforce required specification with respect to copyright protection of a content recorded in a medium for exclusive use in reproduction and a recordable medium. In a system which encrypts information such as a content to record/reproduce the information, design is made so that encryption/decryption processing information differs for a device (software (S/W) main body device) whose main body is software constituted of a recording/reproducing drive of a recording medium and a personal computer (PC), a device (hardware (H/W) main body device) whose main body is hardware integrally containing a drive and data coding/demodulation processing, and the medium for exclusive use in reproduction and the recording medium.