| 摘要 |
PROBLEM TO BE SOLVED: To provide a technology for continuing, in case one of two devices that perform common key encryption communications distributes an encryption key to the other, the communications in the midst of a distribution procedure and even in a case where the encryption key (a key distribution message) is discarded. SOLUTION: In a system for performing encryption communications using a common key updated at a predetermined timing between a key transmitting device and a key receiving device, the key transmitting device includes: a first retaining unit for retaining most recently updated encryption key and a one-generation-anterior encryption key as the common keys; and first setting unit for setting the one-generation-anterior encryption key for transmission and the most recently updated encryption key and the one-generation-anterior encryption key for reception. The key receiving device includes: a second retaining unit for retaining the most recently updated encryption key and the one-generation-anterior encryption key as the common keys; and a second setting unit for setting the most recently updated encryption key for transmission, and the most recently updated encryption key and the one-generation-anterior key for reception. COPYRIGHT: (C)2004,JPO&NCIPI
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