Study of a Novel Software Constant Weight Implementation

While in the early 2000’s lots of research was focused on Differential Power Analysis of first and second-order, it seems the recent trend is of even higher-order. As this order grows, countermeasures such as masking need to be designed in a more generic way. In this paper, we introduce a new constant weight implementation of the AES extending the idea of the software dual-rail countermeasure proposed by Hoogvorst et al. at COSADE 2011. Notably, we illustrate its practicality on 16-bit microcontroller in terms of speed and complexity. This countermeasure applies to all devices that leak a function of the Hamming weight of the internal variables. Under this assumption, our constant weight implementation is theoretically inherently resistant to side-channel attacks of any order. A security evaluation is conducted to analyze its resistance when the leakage slightly deviates from the Hamming weight assumption. It reveals that the countermeasure remains as good as several well-known masking countermeasures. Moreover, the proposed countermeasure offers the possibility to detect some classes of faults.