Abstract: A verifier for use in a personal identification system of the type in which a generator receives at least a personal account number (PAN) and a secret personal identification number (PIN) and based thereon produces digits A.sub.i 's which are present in a feedback shift register (FSR) A and digits C.sub.i 's present in a feedback shift register (FSR) C respectively. The A.sub.i 's and C.sub.i 's are mapped into D.sub.i 's which represent digits of an Offset Number which together with the PAN are recorded on the magnetic stripe of a card. To use the cards the Offset Number and the PAN are read off therefrom and an intended user enters a secret PIN. In the verifier, the PIN is operated upon to produce C.sub.i 's and the PAN is operated upon to produce A.sub.i 's. The latter together with the D.sub.i 's of the received Offset Number are mapped by a processer (201) to form C.sub.i.sup.c 's. These are compared with the C.sub.

Abstract: A personal identification system comprises a generator which generates an Offset Number which is recorded on the magnetic stripe of a card, together with the account number (PAN) of the person to whom the card is to be issued. The generator stores transformed digits of a sequence of digits (IN) which have been secretly entered by one or more officers of the card-issuing institution. To generate the Offset Number the PAN is entered and transformed before being stored to initialize a first feedback shift register. The person to whom the card is to be issued enters a chosen alphanumeric sequence (PIN) secretly known only to him. The PIN, after undergoing transformation is stored to initialize a second feedback shift register. When both registers have been initialized they are reinitialized by different parts of different digits of the transformed IN.