| 摘要 |
PROBLEM TO BE SOLVED: To facilitate the change of a decoding algorithm to prevent illicit copying by recording source data ciphered by using identification information recorded in a part outside the recording area of a recording medium as key information in the recording area together with the decoding algorithm. SOLUTION: Identification information 1a is recorded in a part outside a recording area of an optical disk opened to a user, e.g. a jacket surface or the like, by a method such as marking, printing or the like. In a data recording device 2, a reading means 3 reads the identification information 1a, and a ciphering means 4 ciphers input source data by using the identification information 1a as key information according to the ciphering algorithm of a first storage device 6. A recording means 5 records the decoding algorithm of a second storage device 7 in the recording area of the optical disk 1 together with ciphering data. If decoding algorithm is decoded, the decoding algorithm of an optical disk 1 distributed thereafter is changed. |
