Abstract

A portable hand held computing and indicating device for use in a verification system of the type wherein a first non-predictable code is generated at a first mechanism in accordance with a predetermined algorithm in response to both a unique static variable and a dynamic variable and a second non-predictable code is generated at a second mechanism in accordance with the predetermined algorithm in response to both the unique static variable and a second dynamic variable which corresponds to the first variable. The non-predictable codes are compared at the second mechanism to effect verification. The device forms the first mechanism and includes a processor having the algorithm preprogrammed therein and a means for storing a static variable which is unique for each device. The device also includes a means for generating a time varying dynamic variable which is substantially the same as that generated at the second mechanism at a given instant of time. The stored unique variable and the currently generated dynamic variable are applied to the processor and the resultant non-predictable code is visually displayed. The program for executing the algorithm and the static variable are preferably stored in volatile memory which causes the program and the static variable to be erased if any effort is made to gain access thereto. All or a portion of the static variable may appear in visually perceptible form on the device.