| 摘要 |
PROBLEM TO BE SOLVED: To easily and positively prevent a transmitter side from independently encrypting confidential information for unauthorized purposes and transmitting the information as double encryption even if the transmitter side does so, even in an electronic mail is encrypted. SOLUTION: This method has a step in which a mail server M<SB>A</SB>takes a common key K from a common key P<SB>MA</SB>(K) encrypted with its own public key by using its own secret key S<SB>MA</SB>, and decrypts the encrypted electronic mail K(M) by using the common key K; a step for checking the propriety of transmission of an electronic mail M; and a step in which the mail server M<SB>A</SB>erases the encrypted common key P<SB>MA</SB>(K) when it is judged that the electronic mail M may be transmitted after checking by the mail server M<SB>A</SB>, and transmits a common key P<SB>B</SB>(K) encrypted with a public key P<SB>B</SB>of a client B and the electronic mail K(M) encrypted with the common key K to a terminal B' of the client B. COPYRIGHT: (C)2005,JPO&NCIPI
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