Robust FSMs for cryptographic devices resilient to strong fault injection attacks

The security of the cryptographic device may be compromised if the FSM of the system is not properly protected. FSM protection architectures based on linear codes cannot provide a guaranteed level of protection under the assumption of a strong attack model. In this paper, we propose secure FSM architectures based on the idea of randomly selecting one code from a set of codes for each encoding and decoding operation. Assuming that the attacker is able to inject specific error patterns, randomly selecting one code from L codes as described in the paper can reduce the chance for the attacker to conduct a successful attack by a factor of L. The proposed techniques can achieve much higher security level than architectures based on linear codes with reasonable hardware overhead for cryptography applications (120% - 130% for the protection of the FSM for the Montgomery ladder algorithm). The security level of the proposed architectures can be increased by increasing L and the number of information bits k of the codes.