A security device, a key device and a program protection system and method
capable of coping with copy protection evading software or the
modification of a board. A comparison is made between a security code
unique to a game program which is obtained from a prestored key code and
a security code obtained by generating a random number by using a game
program stored in a storage device as an initial value. When they
disagree, the operation of the function module is stopped. The copy
protection is executed by hardware. By integrally forming the hardware
and the function module, it is possible to cope with copy protection
evading software or the modification of a board.