CIPHER COMMUNICATION DEVICE

摘要

PROBLEM TO BE SOLVED: To unnecessitate operation only for generating random numbers and to prevent an excess load from being applied to a user by generating the random numbers based on a read time of information recorded on an information recording medium. SOLUTION: A data code 4-n printed on a data sheet is scanned by a data code scanner 5, and read time information (t) is generated. A one-directional function operation part 6a of a user terminal 6 generates the random numbers a based on the primitive root (α), the prime number (q) of the data code 4-n. A remainder system operation part 6b calculates R2 =α<2> mod q to transmit it to a center 3. The remainder system operation part 3d of the center 3 calculates R3 =α mod q by using temporary secret data (b), and simultaneously calculates beforehand K=R2 mod q. The remainder system operation part 6c of the user terminal 6 calculates K=R3 mod q by using the received R3 . The user and the center 3 generate a random numbers line from a temporary common key K by a common procedure.