Protection circuit for personal identification number key=pad - uses number of keys to enter PIN value, with indicated values varying in pseudo-random manner

摘要

The circuit is used in conjunction with a keyboard entry pad (b) of the type used to enter personal identification numbers in associated with a bank cash card. Keys can be assigned different values. When a specific credit card is entered, an input unit (a) generates an output to a micro-processor (C). Depending upon the specific data obtained from the card, the microprocessor activates a generator (d) to reassign the display values to the keys in a pseudo random process. A similar process may be used to vary the sequence of input values assigned to a single input key. ADVANTAGE - Allows number values assigned to keys to be varied to reduce possibility of entered numbers being observed.