Recover the Secret Components in a ForkCipher
Tao Hou, Jiyan Zhang, Ting Cui · Chinese Journal of Electronics · 2023
Recently, a new cryptographic primitive has been proposed called ForkCiphers. This paper aims at proposing new generic cryptanalysis against such constructions. We give a generic method to apply existing decompositions againt the underlying block cipher$\mathcal{E}^{r}$on the forking variant$\text{Fork}\mathcal{E}-(r-1)-r_{0}-(r+1-r_{0})$. As application, we consider the security of ForkSPN and ForkFN with secret inner functions. We provide a generic attack against$\text{ForkSPN}-2-r_{0}-(4-r_{0})$based on the decomposition of SASAS. And also we extend the decomposition of Biryukov et al. against Feistel networks in SAC 2015 to get all the unknown round functions in$\text{ForkFN}-r-r_{0}-r_{1}$for$r\leq 6$and$r_{0}+r_{1}\leq 8$. Therefore, compared with the original block cipher, the forking version requires more iteration rounds to resist the recovery attack.