| 摘要 |
PROBLEM TO BE SOLVED: To improve security of a common key system relating to an expanded key generation device for generating an expanded key from a ciphered key by generating intermediate data from the ciphered key at a 1st step, selecting an arbitrary data from the intermediate data at a 2nd step to process it by a irreversible conversion and generating an expanded key of the arbitrary number of steps, and speedily generating expanded key of the arbitrary steps through the irreversible conversion. SOLUTION: This device is configured so as to be provided with an intermediate data generating means for dividing a bit string of an inputted cryptographic key into plural groups, generating an operation result of a plural number i by processing these divided groups of the bit strings each by arithmetic operation plural (i) times, performing an arithmetic operation for gathering the operation results together respectively among the plural groups concerning the operation results of the plural number i of each of these generated groups, and generating the plural number (i) of the intermediate data, and an expanded key generation for selecting one of the plural number (i) of the intermediate data based on the number of steps r of a specified expanded key, and processing the selected intermediate data by the irreversible conversion to generate the expanded key of the number of steps r.
|
