| 摘要 |
<p>PROBLEM TO BE SOLVED: To simply supply an ID and a cryptographic piece by recording information on the recording layer of a first recording area with a first modulation system and reproducing disk identification information which are recorded in a second recording area with a second modulation system and generating a second encryption information inherent to an optical disk while using cryptographic keys, the disk identification information and the first modulation system. SOLUTION: In a first computer 909, the distributed disk 801 provided with a write-one area BCA in which bar codes are overwritten is reproduced with a reproducer 819, the disk ID 815, a first cryptographic key 816, a second cryptographic key 817 and the data of a connection address 818 are reproduced by a BCA reproducing part 820 including a PE-RZ decoding part. A cipher which is ciphered by a first ciphering encoder 827 in which a public key being the first cryptographic key 816 is used and which is consisting of a public key cipher function is transmitted to the side of a second computer 812a. Then, in the side of the second computer 812a, the computer 821a retrieves a first decoding key 825 to know the decoding key and then it makes the received cipher a flat text surely.</p> |
