| 摘要 |
PROBLEM TO BE SOLVED: To realize encryption corresponding to multi-cast for changing a cryptographic key in every second order, and for facilitating countermeasures to terminal equipment whose processing capability is low in distributing the contents of an IP stream or the like. SOLUTION: An encrypting server 2 encrypts and transmits a cryptographic key (key array) Kcn for encrypting the IP stream to a terminal 3 in each transmission interval of a prescribed cryptographic key, and encrypts and transmits the packet of the IP stream by using one cryptographic key Kcn in each prescribed encryption interval. Also, the encrypting server 2 encrypts and transmits the updated new cryptographic key (key array) Kcn to the terminal 3 in each update interval of the prescribed cryptographic key. When the received packet are data, the terminal 3 decodes the packet by one cryptographic key (key array) Kcn, and when the packet are associated with the cryptographic key, the terminal 3 decodes and stores the packet. COPYRIGHT: (C)2003,JPO
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