Synthesis of Fault-Attack Countermeasures for Cryptographic Circuits

Fault sensitivity analysis (FSA) is a side-channel attack method that injects faults to cryptographic circuits through clock glitching and applies statistical analysis to deduce sensitive data such as the cryptographic key. It exploits the correlation between the circuit’s signal path delays and sensitive data. A countermeasure, in this case, is an alternative implementation of the circuit where signal path delays are made independent of the sensitive data. However, manually developing such countermeasure is tedious and error prone. In this paper, we propose a method for synthesizing the countermeasure automatically to defend against FSA attacks. Our method uses a syntax-guided inductive synthesis procedure combined with a light-weight static analysis. Given a circuit and a set of sensitive signals as input, it returns a functionally-equivalent and FSA-resistant circuit as output, where all path delays are made independent of the sensitive signals. We have implemented our method and evaluated it on a set of cryptographic circuits. Our experiments show that the method is both scalable and effective in eliminating FSA vulnerabilities.