Welcome to the resource topic for 2025/102
Title:
A practical distinguisher on the full Skyscraper permutation
Authors: Antoine Bak
Abstract:Skyscraper is a cryptographic permutation published in TCHES 2025, optimized for use in proof systems such as PlonK. This primitive is based on a 10-round Feistel network combining x^2 monomials and lookup-based functions to achieve competitive plain performances and efficiency in proof systems supporting lookups. In terms of security, the x^2 monomials are supposed to provide security against statistical attacks, while lookups are supposed to provide security against algebraic attacks.
In this note, we show that this primitive has a much lower security margin than expected. Using a rebound attack, we find practical truncated differentials on the full permutation. As a corollary, we also find a practical collision attack on the compression function based on a 9-round Skyscraper permutation, which significantly reduces the security margin of the primitive. All of these attacks have been implemented and work in practice.
ePrint: https://eprint.iacr.org/2025/102
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