A upper bound of the tweak length in tweakable block cipher
Yitian Wang, Feng Yuan Β· 2025
In this paper, We analyze the upper bound of the tweak length in a specific Tweakable Block Cipher(TBC), which has been proven to achieve ππ security. The upper bound of the tweak length is determined by the number of times it is utilized in two distinct manners. In addition, it is also influenced by potential collisions between plaintext(or ciphertext) and key. The upper bound is proven to be ππ bits when the input and output of the underlying block cipher are of size π bits. Furthermore, we propose a TBC structure, called π΄π, with a tweak length of ππ bits, and prove that it achieves ππ security. Besides the increase in tweak length from ππ bits to ππ bits, the performance of π΄π is comparable with existing TBCs.