International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

jiadong zhu

Publications and invited talks

Year
Venue
Title
2024
ASIACRYPT
Crooked Indifferentiability of the Feistel Construction
The Feistel construction is a fundamental technique for building pseudorandom permutations and block ciphers. This paper shows that a simple adaptation of the construction is resistant, even to algorithm substitution attacks---that is, adversarial subversion---of the component round functions. Specifically, we establish that a Feistel-based construction with more than $337n/\log(1/\epsilon)$ rounds can transform a subverted random function---which disagrees with the original one at a small fraction (denoted by $\epsilon$) of inputs---into an object that is \emph{crooked-indifferentiable} from a random permutation, even if the adversary is aware of all the randomness used in the transformation. Here, $n$ denotes the length of both the input and output of the round functions that underlie the Feistel cipher. We also provide a lower bound showing that the construction cannot use fewer than $2n/\log(1/\epsilon)$ rounds to achieve crooked-indifferentiable security.

Coauthors

Alexander Russell (1)
Qiang Tang (1)
jiadong zhu (1)