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Energy-efficient Masking of the Trivium Stream Cipher

The widespread development of the Internet of Things (IoT) increases the amount of data exchanged through easily observable communication channels like wireless transmissions. Encryption is a tool commonly used to guarantee the confidentiality of those data. Unfortunately, traditional encryption methods (AES for eg.) hardly meet the constraints imposed on resource usage and power consumption. New cryptographic schemes that are more lightweight and better suited to such constrained targets have been proposed. A flagship representative of the lightweight cryptography portfolio is the Trivium stream cipher, one of the three finalists of the eStream competition. Despite the fact that no significant algebraic attacks against Trivium have been found since its first publication in 2008, many side-channel attacks have been proposed and implemented. However, the addition of countermeasures against such attacks has a significant impact on the energy consumption of hardware implementations of Trivium. In this work, we propose an energy-efficient implementation of the Trivium cipher provably protected against such leakages based on a Threshold Implementation (TI) masking scheme. Our energy-efficient approach takes advantage of the fact that the target for side-channel attacks is the initialization phase of Trivium, and consumes approximately 29.4% less power than a standard TI scheme.