Related-Key Differential Cryptanalysis of the Reduced-Round Block Cipher GIFT

GIFT is a lightweight block cipher that was proposed by Banik et al. at CHES 2017, which is said to be a direct improvement over PRESENT since “that provides a much increased efficiency in all domains (smaller and faster)” and improves the security weaknesses of the latter. At Asiacrypt in 2014, Sun et al. introduced a bit-oriented mixed integer linear programming (MILP) method to search for the differential characteristics of block ciphers. In this paper, we use the differential cryptanalysis method based on this automated tool to analyse GIFT. We propose 12-round and 13-round related-key differential characteristics of GIFT- 64 and 7-round and 10-round related-key differential characteristics of GIFT- 128. By using them as distinguishers, we apply key recovery attacks on the 19-round and 20-round reduced GIFT-64 with data complexities of 2⁴⁷ and 2⁵⁶ plaintexts, respectively, which mean that the data complexities are lower. Furthermore, we improve the GIFT-64 key recovery attack using differential cryptanalysis by one round over the previous differential cryptanalysis.