| 摘要 |
PURPOSE: To prevent the occurrence of illegal resending by a third person by storing a group of integers and an integer corresponding to a communicating party, generating an integer depending upon time, generating a certificate to be sent to the communicating party based upon the integer group and both the integers, and generating a key from the integers of the integer groups and both the integers. CONSTITUTION: A random number (r) is generated, x=α<er> (mod n) ins calculated from a group of integers (e), (n) read out from a user's card and C=hash (Time, x) is found out by using a previously determined hash function (hash). Where, Time is current time. Then y=S1 .α<cr> (mod d) is calculated based upon integers S1 , n obtained from the card and (x, y) is defined as a certificate. When an opposite user is a user (j), a key is generated by WK=Zij <r> (mod n). Then c= hash (Time, x) for the received certificate (x, y) is calculated based upon the hash function. Whether IDj =y<e> /x<c> (mod n) or not is judged by using the value (c) and the group of integers e, n read our from the card. Since a key on the transmitting side is equal to a key on the receiving side, cipher communication using the key can be executed.
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