Crooked indifferentiability of the Feistel Construction

arXiv:2404.09450v1 Announce Type: new
Abstract: 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 $2000n/\log(1/\epsilon)$ rounds can transform a subverted random function -- which disagrees with the original one at a small fraction (denoted by $\epsilon$) of …

adaptation adversarial algorithm arxiv attacks block building ciphers construction cs.cr functions simple subversion