CARD TERMINAL SECURITY SYSTEM

摘要

PROBLEM TO BE SOLVED: To establish safer security in addition to satisfying a restriction condition of an authentication system of a terminal of a financial institution by making the numeral value of plural digits to be stored on a card the product of a prime number that corresponds to a password number notified from a user by a prime number selected by the financial institution. SOLUTION: A user U reports an optional integer as a user password number nU to a financial institution B. The institution B calculates a prime number pu =g (nu ) by using a prescribed function (g). Also, it randomly selects an optional prime number pc from (Np and Nx ), calculates nc =pu pc and destroys pc . And, a card C on which nc is stored is transferred to the user U. The user U inserts the card C into a terminal V and inputs the number nc . The terminal V calculates pu =g(nu ) and calculates y= /pu from nc and pu which are stored on the card C and when it is not divisible, when (y) is not a prime number and when it is not Np<=y<=Nx, it rejects it and returns the card C.