| 摘要 |
PROBLEM TO BE SOLVED: To improve safety of leakage of a decryption key without complicating updating processing of the decryption key. SOLUTION: A receiving terminal 20 is provided with: an updating unit 22 for updating a decryption key using a decryption key before being updated, and updating a decryption key using an updating auxiliary key from an external auxiliary device 40; a communication unit 25 for receiving the encrypted sentences encrypted using an public key; and a decrypting unit 23 for decrypting the encrypted sentences using the decryption key. COPYRIGHT: (C)2006,JPO&NCIPI
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