| 摘要 |
PROBLEM TO BE SOLVED: To provide a technology capable of decrypting past encrypted texts and enhancing security against key leakage. SOLUTION: A reception terminal 20 includes: an update section 22 for updating an FSE decryption key; a discrimination section 27 for discriminating whether or not encryption timing for an encryption text encrypted from a plain text by using the FSE public key and time and a PKE second public key is coincident with update timing of the FSE decryption key; and a decryption section 23 that decrypts the encrypted text by using the FSE decryption key before the update and the PKE decryption key corresponding to the encryption timing generated through the use of a master key, when the discrimination section 27 discriminates non-coincidence or decrypts the encryption text by using the FSE decryption key before the update and the PKE decryption key, when the discrimination section 27 discriminates coincidence. COPYRIGHT: (C)2007,JPO&INPIT
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