Scan Based Side Channel Attacks on Stream Ciphers and Their Counter-Measures

Scan chain based attacks are a kind of side channel attack, which targets one of the most important feature of todays hardware the test circuitry. Design for Testability (DFT) is a design technique that adds certain testability features to a hardware design. On the other hand, this very feature opens up a side channel for cryptanalysis, rendering crypto-devices vulnerable to scan-based attack. Our work studies scan attack as a general threat to stream ciphers and arrives at a general relation between the design of stream ciphers and their vulnerability to scan attack. Finally, we propose a scheme which we show to thwart the attacks and is more secure than other contemporary strategies.