Abstract: A semiconductor device that functions as a key to control access to a software program resident in a computer. The device includes a continuously running pulse generator that produces an output representative of real time, a shift register permanently storing a unique number and circuitry for executing an algorithm that combines real time and the permanently stored unique number to produce a password. The password is input to the computer. The computer is coded to execute an equivalent algorithm to produce a password within the computer. The two passwords are compared and access to the computer program is afforded only if they bear a prescribed relationship. The computer can be coded to produce on the video display thereof a timespace pattern on the computer video display, circuitry for deriving the stimulus number therefrom, and circuitry for processing the stimulus number so that the password displayed by the key is a function of the value of the stimulus number.

Abstract: A semiconductor device that functions as a key to control access to a software program resident in a computer. The device includes a continuously running pulse generator that produces an output representative of real time, a shift register permanently storing a unique number and circuitry for executing an algorithm that combines real time and the permanently stored unique number to produce a password. The password is input to the computer. The computer is coded to execute an equivalent algorithm to produce a password within the computer. The two passwords are compared and access to the computer program is afforded only if they bear a prescribed relationship. The computer can be coded to produce on the video display thereof a time-space pattern on the computer video display, circuitry for deriving the stimulus number therefrom, and circuitry for processing the stimulus number so that the password displayed by the key is a function of the value of the stimulus number.