| 摘要 |
PROBLEM TO BE SOLVED: To secure a high confidentiality of an encryption key by increasing the number of kinds of encryption keys capable of being generated, with a limited memory capacity. SOLUTION: When encrypting transmission object information by using an effective encryption key and then transmitting the information, a transmission terminal 1 incorporates not encrypted plain text information into a transmission text. Identical fundamental encryption key tables formed from a plurality of fundamental encryption keys are stored in fundamental encryption key storage parts 12a and 12b. Fundamental encryption key selection parts 13a and 13b select one or more fundamental encryption keys from the fundamental encryption key tables in accordance with common plain text information. Effective encryption key generation parts 14a and 14b use the selected fundamental encryption keys to generate effective encryption keys in accordance with common plain text information. COPYRIGHT: (C)2008,JPO&INPIT
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