Computer Security and Cryptography

18.4 KEYED-ACCESS CARDS

The IBM Corporation decided in 1972 to offer customers a keyed regulated entrance system to control access into their facilities supported by an IBM Series/1 processing system. The Series/1 Controlled Access System is described in an IBM publication dated March 21, 1978. Each employee would possess a card on which an identifier would be magnetically recorded. The data on the card is the encipherment of the pair (ID,PW) of 5-digit decimal numbers. The ciphertext data on the card would be read at a card reader at an entry door, be deciphered, and (ID,PW) would be verified at the system's database. A single IBM Series/1 processor could handle 31 entry points.The design constraints of the system were these:

1. The data would be read by a card-reader – no user-entry of data at a key-pad would be provided;
2. The system database would not contain a listing of every valid employee;
3. The database would be able to maintain a list of lost/stolen and reported cards;
4. The card-readers would transmit the data read from the card to a shared processor;
5. The verification-processing needed to be simple and fast;
6. The fabrication of bogus cards had to be infeasible.

Although the copying of valid access cards existed, it seemed less of a problem for a company who could discharge an employee if it discovered the employee allowed the copying of the keyed-access card.

The keyed-access card of the IBM product contained the encipherment Y of two 16-bit numbers (ID,PW) – approximately two ...