| 摘要 |
<P>PROBLEM TO BE SOLVED: To improve processing efficiency, when encrypting and inputting/outputting data that should be confidential between a recording apparatus and a host device. <P>SOLUTION: Upon a license-data transmitter verifying a certificate C[KPdx] (the license-data receiver and the license-data transmitter are to be referred to as "x" and "y", respectively), the license-data transmitter transmits challenge information EP(KPdx, Kcy) to the license-data receiver. In response to the challenge information, the license-data receiver transmits session information Es(Kcy, Ksx/KPpy) to the license-data transmitter. The license-data transmitter provides encrypted license data Es(Ksx, Ep(KPpx, LIC)) in a form encrypted by using these two keys Ksx and KPpx thus received. With this cryptosystem according to the present invention employing EC-DH as the public key cryptosystem, the transmitter provides second or subsequent license data, without the transmission of the challenge information or updating of the shared key in the EC-DH. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
