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Adaptive Masking: a Dynamic Trade-off between Energy Consumption and Hardware Security

As the Internet of Things (IoT) devices process and communicate an increasing amount of sensitive data, the confidentiality of these data is a growing concern. Hardware side-channel attacks pose a threat against the physical implementation of encryption, which is commonly used to ensure this confidentiality. Traditional hardware countermeasures against such side-channel attacks, like masking, usually introduce a high energy overhead. However, IoT devices are typically resource-constrained and have a small energy budget. Furthermore, the energy or security constraints may vary between devices or over time, depending on, e.g., the remaining battery level or data sensitivity. Therefore, a dynamic trade-off has to be found between security, power consumption and performance. In this paper, we introduce a new paradigm whereby hardware masking is applied on demand to increase the energy efficiency. We illustrate this concept by applying it to the stream cipher Trivium. We demonstrate that compared to a reference masked implementation, this solution ensures a high level of security when necessary while significantly reducing the power consumption (by up to 76.2%) the rest of the time, with a small area overhead (13.5%) and no impact on the performance.