New differential cryptanalysis results for the lightweight block cipher BORON

BORON is a 64-bit lightweight block cipher based on the substitution–permutation network that supports an 80-bit (BORON-80) and 128-bit (BORON-128) secret key. In this paper, we revisit the use of differential cryptanalysis on BORON in the single-key model. Using an SAT/SMT approach, we look for differentials that consist of multiple differential characteristics with the same input and output differences. Each characteristic that conforms to a given differential improves its overall probability. We also implemented the same search using Matsui's algorithm for verification and performance comparison purposes. We identified high-probability differentials which were then used in key recovery attacks against BORON-80/128. We used 8-round differentials with a probability of 2^−58.16 and 2^−62.42 in key recovery attacks against 9 and 10 rounds of BORON-80 and BORON-128 with time/data/memory complexities of 2^59.18/2^59.16/2²⁴ and 2^111.34/2^63.42/2⁷¹ respectively. Our key recovery framework provides a more accurate estimate of the attack complexity as compared to previous work. The attacks proposed in this paper are the best differential attacks against BORON-80/128 in the single-key model to date.