International Association for Cryptologic Research

International Association
for Cryptologic Research


Optimizing Implementations of Lightweight Building Blocks

Jérémy Jean , ANSSI Crypto Lab, Paris
Thomas Peyrin , Nanyang Technological University
Siang Meng Sim , Nanyang Technological University
Jade Tourteaux , ANSSI Crypto Lab, Paris; Paris Diderot University
DOI: 10.13154/tosc.v2017.i4.130-168
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Abstract: We study the synthesis of small functions used as building blocks in lightweight cryptographic designs in terms of hardware implementations. This phase most notably appears during the ASIC implementation of cryptographic primitives. The quality of this step directly affects the output circuit, and while general tools exist to carry out this task, most of them belong to proprietary software suites and apply heuristics to any size of functions. In this work, we focus on small functions (4- and 8-bit mappings) and look for their optimal implementations on a specific weighted instructions set which allows fine tuning of the technology. We propose a tool named LIGHTER, based on two related algorithms, that produces optimized implementations of small functions. To demonstrate the validity and usefulness of our tool, we applied it to two practical cases: first, linear permutations that define diffusion in most of SPN ciphers; second, non-linear 4-bit permutations that are used in many lightweight block ciphers. For linear permutations, we exhibit several new MDS diffusion matrices lighter than the state-of-the-art, and we also decrease the implementation cost of several already known MDS matrices. As for non-linear permutations, LIGHTER outperforms the area-optimized synthesis of the state-of-the-art academic tool ABC. Smaller circuits can also be reached when ABC and LIGHTER are used jointly.
  title={Optimizing Implementations of Lightweight Building Blocks},
  journal={IACR Trans. Symmetric Cryptol.},
  publisher={Ruhr-Universität Bochum},
  volume={2017, Issue 4},
  author={Jérémy Jean and Thomas Peyrin and Siang Meng Sim and Jade Tourteaux},