| 摘要 |
The invention relates to a method of distributing a key for enciphering an unenciphered or plaintext message and for deciphering the enciphered message. A prior art key distribution system has disadvantages in that since it needs a large amount of public information corresponding to respective conversers, the amount of the public information increases as the number of conversers increases. Further, strict control of such information becomes necessary to prevent the information from being tampered. A key distribution method according to the invention is free from the above-mentioned disadvantages of the prior art system. According to an aspect of the invention, there is provided a method which comprises the following steps: generating a first random number in a first system; generating first key distribution information in the first system by applying a predetermined first transformation to the first random number on the basis of first secret information known only by the first system; transmitting the first key distribution information to a second system via a communication channel; receiving the first key distribution information in the second system; generating a second random number in the second system; generating second key distribution information by applying the predetermined first transformation to the second random number on the basis of second secret information known only by the second system; transmitting the second key distribution information to the first system via the channel; receiving the second key distribution information in the first system; and generating an enciphering key in the first system by applying a predetermined second transformation to the second key distribution information on the basis of the first random number and identification information of the second system which is not secret. |
