PROBLEM TO BE SOLVED: To provide a method for assuring electronic information assuring that the content of electronic information generated in the past is not altered. ;SOLUTION: Electronic information in which a user electronically signed is deposited to an assuring server. The assuring server H100 adds assuring information such as time stamps, etc., to the information in which the user signed electronically. The method for ciphering is changed as necessary. Later, the user requests the assuring server H10 for a delivery of the electronic information. The assuring server H100 reads, decodes, and delivers the electronic information from a data base. Thus, it is assured by double electronic signatures of the user and the assuring server that the content is not changed.;COPYRIGHT: (C)1998,JPO
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