Faultless to a Fault? The Case of Threshold Implementations of Crypto-systems vs Fault Template Attacks

The propagation of faults in hardware devices for a Boolean circuit leaves a distinct fault template which can be used as a signature to launch a new class of attacks called Fault Template Attacks (FTA). In this paper we present a systematic methodology to develop fault templates of Boolean circuits using a well known concept in design verification, namely positive Davio's decomposition. We use this improved template called FTA* to attack a popular defence against side channel analysis called Threshold Implementations (TI), which are based on computations using non-complete shares of the secret data to hide it. The paper tries to explore whether such shares can be still combined to reveal the secret quantities by inflicting carefully crafted faults in the registers storing the shares and observing the fault propagation templates. In particular, we show as a case study that a TI-protected S-Box of the PRESENT block cipher can be circumvented by considering Double Event Upset (DEU) faults in single registers storing targeted shared bits as suggested by the derived fault templates. This shows that the TI crypto-circuits are not naturally faultless to faults and needs further explorations to thwart such powerful attack vectors.