Paper 2024/1926 Original: eprint.iacr.org/2024/1926 ↗

Cryptanalysis of BAKSHEESH Block Cipher

Abstract

BAKSHEESH is a lightweight block cipher following up the well-known cipher GIFT-128, which uses a 4-bit SBox that has a non-trivial Linear Structure (LS). Also, the Sbox requires a low number of AND gates that makes BAKSHEESH stronger to resist the side channel attacks compared to GIFT-128. In this paper, we give the first third-party security analysis of BAKSHEESH from the traditional attacks perspective: integral, differential and linear attacks. Firstly, we propose a framework for integral attacks based on the properties of BAKSHEESH's Sbox and its inverse. By this, we achieve the 9- and 10-round practical key-recovery attacks, and give a 15-round theoretical attack. Secondly, we re-evaluate the security bound against differential cryptanalysis, correcting two errors from the original paper and presenting a key-recovery attack for 19 rounds. At last, for linear cryptanalysis, we develop an automated model for key-recovery attacks and then demonstrate a key-recovery attack for 21 rounds. We stress that our attacks cannot threaten the full-round BAKSHEESH, but give a deep understanding on its security.