Out in Front: July 18, 1996

A new device from Exel Microelectronics provides a "challenge-and-response" protocol for authentication. In an electronic-key application (Figure 1), the XL107 SureLok die in the key receives power when you insert the key into the correct lock. The XL107 then alerts the lock host controller that the XL107 is present. The host, which has a corresponding XL107 programmed with an identical, secret 64-bit key, sends a 32-bit random number to the key device. The key-device XL107 then encrypts the 32-bit challenge using the 64-bit key, and the resulting 32-bit response returns to the host, which performs the same encryption. The host controller then compares the results for authentication.

The device needs no other components, because the host provides power. You can also use the XL107 to prevent unauthorized users from adding peripherals to any system, such as knockoff batteries to cellular phones or incompatible multiprocessor and video cards to workstations. The XL107 can hold as many as four 64-bit keys, providing access to four locks. The 64-bit keys are unreadable, thus guarding security. The XL107 is in production now and available in eight-pin plastic DIP and SOIC packages and as dice. The DIP costs $0.94 (1000).

—by Stephen Kempainen

Exel Microelectronics, San Jose, CA. (408) 432-0500, fax (408) 432-810, http://wwwexel.com.