Oracle-Based Multistep Strategy for Solving Polynomial Systems Over Finite Fields and Algebraic Cryptanalysis of the Aradi Cipher

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Autori principali: La Scala, Roberto, Tiwari, Sharwan Kumar
Natura: Preprint
Pubblicazione: 2025
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author La Scala, Roberto
Tiwari, Sharwan Kumar
author_facet La Scala, Roberto
Tiwari, Sharwan Kumar
contents The multistep solving strategy consists in a divide-and-conquer approach: when a multivariate polynomial system is computationally infeasible to solve directly, one variable is assigned over the elements of the base finite field, and the procedure is recursively applied to the resulting simplified systems. In a previous work by the same authors (among others), this approach proved effective in the algebraic cryptanalysis of the Trivium cipher. In this paper, we present a new formulation of the corresponding algorithm based on a Depth-First Search strategy, along with a novel complexity analysis leveraging tree structures. We also introduce the notion of an ``oracle function'', which is intended to determine whether evaluating a new variable is required to simplify the current polynomial system. This notion allows us to unify all previously proposed variants of the multistep strategy, including the classical hybrid approach, by appropriately selecting the oracle function. Finally, we employ the multistep solving strategy in the cryptanalysis of the NSA's recently introduced low-latency block cipher Aradi, achieving a first full-round algebraic attack that exposes structural features in its symbolic model.
format Preprint
id arxiv_https___arxiv_org_abs_2506_09950
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Oracle-Based Multistep Strategy for Solving Polynomial Systems Over Finite Fields and Algebraic Cryptanalysis of the Aradi Cipher
La Scala, Roberto
Tiwari, Sharwan Kumar
Cryptography and Security
Symbolic Computation
Commutative Algebra
The multistep solving strategy consists in a divide-and-conquer approach: when a multivariate polynomial system is computationally infeasible to solve directly, one variable is assigned over the elements of the base finite field, and the procedure is recursively applied to the resulting simplified systems. In a previous work by the same authors (among others), this approach proved effective in the algebraic cryptanalysis of the Trivium cipher. In this paper, we present a new formulation of the corresponding algorithm based on a Depth-First Search strategy, along with a novel complexity analysis leveraging tree structures. We also introduce the notion of an ``oracle function'', which is intended to determine whether evaluating a new variable is required to simplify the current polynomial system. This notion allows us to unify all previously proposed variants of the multistep strategy, including the classical hybrid approach, by appropriately selecting the oracle function. Finally, we employ the multistep solving strategy in the cryptanalysis of the NSA's recently introduced low-latency block cipher Aradi, achieving a first full-round algebraic attack that exposes structural features in its symbolic model.
title Oracle-Based Multistep Strategy for Solving Polynomial Systems Over Finite Fields and Algebraic Cryptanalysis of the Aradi Cipher
topic Cryptography and Security
Symbolic Computation
Commutative Algebra
url https://arxiv.org/abs/2506.09950