METHOD, PROGRAM, AND SYSTEM FOR SIMULTANEOUS OR POST-ENCRYPTION DELIVERY OF SHARED KEY ENCRYPTION KEY DESIRED BY USER

摘要

The present invention addresses the problem of performing simultaneous or post-encryption delivery of an easy-to-remember shared key that is desired by a user. A base shared key is shared in advance between a sender and a receiver using the Diffie-Hellman key exchange method. The sender generates an easy-to-remember first shared key that said sender desires for the purpose of creating an encrypted text and encrypts plain text using the first shared key. The encrypted text and a second shared key that is generated by summing the first shared key and the base shared key are simultaneously delivered by the sender to the receiver, or the second shared key is delivered afterward. The receiver then subtracts the previously shared base shared key from the delivered second shared key in order to calculate the first shared key and decrypts the encrypted text using the first shared key.