Security Analysis of Lightweight Block Ciphers ANU-II and LiCi

Résumé

ANU-II is a lightweight encryption design with 64-bit block and 80/128 bits key size which is proposed
as smallest lightweight design. LiCi is a low-power lightweight block cipher with a 64-bit block and
128-bit key size. Designers have provided a proof of security for differential attack on these ciphers. In
this paper, we analyse the security of ANU-II and LiCi to provide the accurate bounds for differential
attack. We apply branch-and-bound-based algorithm to search the differential trail. We construct
the optimal differential trails for 12 rounds and RK differential trails for 13 rounds of ANU-II that
require 262 and 263 chosen plaintext pairs respectively. We also search for the differential trail of
LiCi up to 11 rounds with probability 2−67 to give accurate security bounds for this attack. Our
results are better than the security bounds claimed by the designers. Our analysis provides the best
results available so far for a differential attack on ANU-II and differential cryptanalysis of LiCi.