6. Physical Attack Countermeasures for Reconfigurable Cryptographic Processors

The physical attack countermeasures for reconfigurable cryptographic processors are mainly achieved in two ways. One way is to implement all the universal countermeasures to the reconfigurable architecture. Another way is to develop new countermeasures by using the characteristics of the reconfigurable computing. Traditional universal countermeasures do not take full advantage of the characteristics of reconfigurable computing and result in significant performance, area, and power overhead. In addition, new threatening attack methods such as the local electromagnetic attack with the attack precision of gate level, multiple fault attack which can introduce more than one fault in a single execution, and attacks based on ultra-low frequency (kHz level for instance) acoustic or electromagnetic signal continue to emerge. Various existing traditional countermeasures cannot be used to effectively resist these attacks. Compared with the direct application of traditional countermeasures, countermeasures designed based on the characteristics of reconfigurable cryptographic architecture can effectively reduce the performance, area, and power overhead caused by security improvement through resource reuse. What is more, the new countermeasures are expected to resist novel attack methods that have not been effectively overcome. On the one hand, the dynamic and partial reconfiguration feature can be fully exploited to develop countermeasures based on time and spatial randomization. When each execution of the cryptographic algorithm is performed at a different time and circuit region in the array, various precision attacks will not take effect. It just like that when an attacker wants to attack the backdoor of the cryptographic implementation, the randomization method keeps the position of the backdoor changing rapidly, making it difficult for the attacker to attack even when he or she has the key to the backdoor. On the other hand, we can make full use of the structural advantages of reconfigurable processors and fully combine the countermeasure design with the reconfigurable architecture, thus maximizing the advantages of reconfigurable computing. The rich array computing units and interconnection resources on the reconfigurable cryptographic processors can be used to resist physical attacks. With the resource reuse, the consumption caused by countermeasures can be significantly reduced. For example, a physically unclonable function (PUF) can be constructed based on array computing units, and lightweight authentication or security keys can be generated after the basic encryption/decryption operations are performed. The rich interconnection resources on the array can also be fully developed to resist attacks. When various topology attributes of interconnection network changed slightly and randomness was introduced, physical attack countermeasures can be implemented besides the normal data transmission.