| 摘要 |
PROBLEM TO BE SOLVED: To improve safety of leakage of a decryption key, and to decrypt past encrypted sentences. SOLUTION: A receiving terminal 20 is provided with: an updating unit 22 for updating the decryption key; a communication unit 25 for using a public key to receive the encrypted encryption sentences; a determining unit 27 for determining whether an updating timing matches an encryption timing; and a decrypting unit 23 for generating a decryption key before updating corresponding to the encryption timing, if the determining unit 27 determines that the timing does not match, and using a decryption key after updating to decrypt the encrypted sentences, if the determining unit 27 determines that the timing matches. COPYRIGHT: (C)2006,JPO&NCIPI
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