Against Double Fault Attacks: Injection Effort Model, Space and Time Randomization Based Countermeasures for Reconfigurable Array Architecture

With the increasing accuracy of fault injections, it has become possible to inject two faults into specific circuit regions precisely at a certain time. Unfortunately, most existing fault attack countermeasures are based on the single fault assumption, and it is, therefore, very difficult to resist double fault attacks. Reconfigurable array architecture (RAA) has the ability to introduce spatial and time randomness by dynamic reconfiguration, which can alleviate the threat of double fault attacks. This paper, for the first time, analyzes the double fault attack issues in the fault injection phase systematically. An evaluation model, named injection effort model (IEM), is proposed to quantify the efforts of a successful fault injection. In IEM, the real injection process is described mathematically using the probability method, so that a theoretical basis can be provided for the corresponding countermeasure design. Based on the concept of spatial and time randomization, three countermeasures are implemented on RAA for the purpose of decreasing the implementation overhead under the premise of ensuring the security. When these countermeasures are adopted, tradeoffs can be made between the double fault resistance and the extra overhead through changing the degree of randomness. Experiments are carried out to analyze the relationship between the resistance and the overhead using Advanced Encryption Standard (AES), Data Encryption Standard (DES), and Camellia. When the overhead constraints in terms of throughput, hardware resources, and energy are 5%, 35%, and 10% respectively, the double fault resistance can increase by two to four orders of magnitude (ranging from 824 to 10 149 for different algorithms).