| 摘要 |
PROBLEM TO BE SOLVED: To provide an encryption key update system that safely updates an encryption key used by a common key encryption system and reduces the amount of information needed to update the encryption key shared with a communication partner. SOLUTION: In the encryption key update system, an electronic key 12 and an onboard device 13 which perform encryption communication by a common key encryption system are made to previously share secret information K<SB>0</SB>for generating an encryption key to be shared by both. The electronic key 12 and onboard device 13 set, as a first encryption key K<SB>n</SB>, arithmetic results obtained by entering the arithmetic results of a hash function H() as an identical unidirectional function repeatedly as many times as predetermined for the function including an input of the secret information K<SB>0</SB>for the hash function H(). When the encryption key K<SB>n</SB>is updated, the electronic key 12 and onboard device 13 set, as a new encryption key, arithmetic results obtained by entering the arithmetic results of the function repeatedly as many time as the number of times which is one less than that when the encryption key is generated last including an input of the secret information K<SB>0</SB>for the function. COPYRIGHT: (C)2010,JPO&INPIT |
