However, such attacks are certainly feasible, Anderson contends. Anderson's own studies have revealed that smart cards are not always as tamper-resistant as their manufacturers claim, and criminals have already taken advantage of such weaknesses. Indeed, the technology required to implement an attack based on causing a smart card to decode instructions incorrectly isn't much more complicated than that used to pirate TV signals. Anderson and Kuhn delayed publishing their findings on breaking tamper-resistant processors until last November in order to give developers of banking systems time to adopt some countermeasures. Calif. Manufacturers of smart cards have been aware for some time of the importance of protecting against physical intrusions involving abrupt temperature changes, voltage spikes, and radiation bursts.
Many devices already have circuitry to detect such abnormalities.
Moreover, simple procedures such as repeating calculations and checking to make sure the same answer comes out each time can provide additional safeguards, though they often slow smart-card operation unacceptably. Bellcore and other organizations have developed alternative strategies to circumvent the problem. In spite of these security concerns, the popularity of smart cards for a variety of applications continues to grow. Just as people don't hesitate to write checks even though checks are easy to forge or continue to give credit card numbers over the telephone without worrying about being overheard, they readily use smart cards because of the convenience they offer.