Welcome to the resource topic for 2020/1582
Title:
A New Method for Designing Lightweight S-boxes with High Differential and Linear Branch Numbers, and Its Application
Authors: Hangi Kim, Yongjin Jeon, Giyoon Kim, Jongsung Kim, Bo-Yeon Sim, Dong-Guk Han, Hwajeong Seo, Seonggyeom Kim, Seokhie Hong, Jaechul Sung, Deukjo Hong
Abstract:Bit permutations are efficient linear functions often used for lightweight cipher designs. However, they have low diffusion effects, compared to word-oriented binary and MDS matrices. Thus, the security of bit permutation-based ciphers is significantly affected by differential and linear branch numbers (DBN and LBN) of nonlinear functions. In this paper, we introduce a widely applicable method for constructing S-boxes with high DBN and LBN. Our method exploits constructions of S-boxes from smaller S-boxes and it derives/proves the required conditions for smaller S-boxes so that the DBN and LBN of the constructed S-boxes are at least 3. These conditions enable us to significantly reduce the search space required to create such S-boxes. In order to make cryptographically good and efficient S-boxes, we propose a unbalanced-Bridge structure that accepts one 3-bit and two 5-bit S-boxes, and produces 8-bit S-boxes. Using the proposed structure, we develop a variety of new lightweight S-boxes that provide not only both DBN and LBN of at least 3 but also efficient bitsliced implementations including at most 11 nonlinear bitwise operations. The new S-boxes are the first that exhibit these characteristics. Moreover, we propose a block cipher PIPO based on one of the new S-boxes, which supports a 64-bit plaintext and a 128 or 256-bit key. Our implementations demonstrate that PIPO outperforms existing block ciphers (for the same block and key lengths) in both side-channel protected and unprotected environments, on an 8-bit AVR. The security of PIPO has been scrutinized with regards to state-of-the-art cryptanalysis.
ePrint: https://eprint.iacr.org/2020/1582
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