| 摘要 |
PROBLEM TO BE SOLVED: To protect the secrecy of ciphered data in a medium by deciphering data deciphering keys from medium ID read from the medium, permission information and its own device ID and deciphering ciphered data which is read from the medium through the use of the keys. SOLUTION: Permission information 22 obtained by cipherring data cipherring key 6 by an individual key which is generated from medium ID 21 read from the medium 1 and its own device ID 4 by an individual key generating means 5 is generated and written in the medium at the time of writing data. A ciphering means 8 also writes ciphering data 23 obtained by ciphering data by the data ciphering key 6 in the medium. Then, at the time of reading data, the individual key is generated by the individual key generating means 9 from medium ID 21 read from the medium 1 and its own device ID 4, a deciphering means 10 deciphers permission information 22 which is read by the generated individual key from the medium 1 so as to generate the data deciphering key 11 and a deciphering means 12 deciphers ciphering data 23 read by the generated data deciphering key 11 from the medium so as to generate data. |
