| 摘要 |
PROBLEM TO BE SOLVED: To deliver a random number which causes problems in the case of using a vernum cipher which enables realizing high safety cipher communication, to as safe and efficient as possible. SOLUTION: A first random number r1 is generated using a random number generator R, and the number r1 is shared by both the transmission side and the receiving side of a cipher text C. Next, a second random number r2 is generated by using the generator R and the number r2 is made to be a common key Kc to be used for both of ciphering and deciphering. Next, the bit string of the first random number r1 is added to the second random number r2 by an exclusive-OR, to generate a third random number r3 which is delivered to an opposite party via a communication path. The opposite party receiving the third random number r3 adds the bit string of the first random number r1 to the number r3 by the exclusive-OR to restore the second random number r2. Next, in the case of cipher communication, the transmission side adds the bit string of the key Kc, delivered in advance to the bit stream of information (plaintext) M by the exclusive-OR, to prepare the cipher text C and transmits the cipher text C to the opposite party via the communication path. The receiving side adds the bit string of the key Kc received and restored in advance, to the bit stream of the cipher text C by the exclusive-OR to restore the original information (plaintext) M. |
