International Association for Cryptologic Research

International Association
for Cryptologic Research


Efficient Side-Channel Protections of ARX Ciphers

Bernhard Jungk , Fraunhofer Singapore
Richard Petri , Fraunhofer SIT
Marc Stöttinger , Continental Teves
DOI: 10.13154/tches.v2018.i3.627-653
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Abstract: The current state of the art of Boolean masking for the modular addition operation in software has a very high performance overhead. Firstly, the instruction count is very high compared to a normal addition operation. Secondly, until recently, the entropy consumed by such protections was also quite high. Our paper significantly improves both aspects, by applying the Threshold Implementation (TI) methodology with two shares and by reusing internal values as randomness source in such a way that the uniformity is always preserved. Our approach performs considerably faster compared to the previously known masked addition and subtraction algorithms by Coron et al. and Biryukov et al. improving the state of the art by 36%, if we only consider the number of ARM assembly instructions. Furthermore, similar to the masked adder from Biryukov et al. we reduce the amount of randomness and only require one bit additional entroy per addition, which is a good trade-off for the improved performance. We applied our improved masked adder to ChaCha20, for which we provide two new first-order protected implementations and achieve a 36% improvement over the best published result for ChaCha20 using an ARM Cortex-M4 microprocessor.
  title={Efficient Side-Channel Protections of ARX Ciphers},
  journal={IACR Trans. Cryptogr. Hardw. Embed. Syst.},
  publisher={Ruhr-Universität Bochum},
  volume={2018, Issue 3},
  author={Bernhard Jungk and Richard Petri and Marc Stöttinger},