Welcome to the resource topic for 2025/1601
Title:
Meet-in-the-Middle Attacks on Full ChiLow-32
Authors: Eran Lambooij, Patrick Neumann, Michiel Verbauwhede
Abstract:This work present attacks on full ChiLow-32, a tweakable block cipher presented at EUROCRYPT’25. We first show that an attack on full ChiLow-32 is possible with a straight forward Meet-in-the-Middle attack on the data path. Here, we introduce a method based on linear structures of the round functions to optimally select the meeting point in our attack.
Then, we improve this attack using novel high correlation non-linear approximations of the inverse of the \chi map. This results in a drastic reduction in the time complexity of the attack, in exchange for a reduced success probability. The final attack has a time complexity of 2^{111}, a success probability of 7% and requires 165 messages encrypted under the same tweak.
Application of the same techniques to ChiLow-40 results in a deterministic attack on 7 rounds with a time complexity of 2^{125} and 29 messages, and a probabilistic attack on 6 rounds with a time complexity of 2^{95}, a 14% success probability and 128 messages encrypted under the same tweak.
ePrint: https://eprint.iacr.org/2025/1601
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