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Modeling Linear and Non-linear Layers: An MILP Approach Towards Finding Differential and Impossible Differential Propagations

2024/05/01 by Debranjan Pal, Vishal Pankaj Chandratreya, Pal, Debranjan +5
Computer Science · Engineering · #Computational Physics and Python Applications #Cryptography and Security (cs.CR) #FOS: Computer and information sciences #Fault Detection and Control Systems

paper · pdf · doi:10.48550/arxiv.2405.00441

openalex publication_date 2024/05/01 · openalex created_date 2024/05/04 · openalex updated_date 2026/07/28

Abstract

Symmetric key cryptography stands as a fundamental cornerstone in ensuring security within contemporary electronic communication frameworks. The cryptanalysis of classical symmetric key ciphers involves traditional methods and techniques aimed at breaking or analyzing these cryptographic systems. In the evaluation of new ciphers, the resistance against linear and differential cryptanalysis is commonly a key design criterion. The wide trail design technique for block ciphers facilitates the demonstration of security against linear and differential cryptanalysis. Assessing the scheme's security against differential attacks often involves determining the minimum number of active SBoxes for all rounds of a cipher. The propagation characteristics of a cryptographic component, such as an SBox, can be expressed using Boolean functions. Mixed Integer Linear Programming (MILP) proves to be a valuable technique for solving Boolean functions. We formulate a set of inequalities to model a Boolean function, which is subsequently solved by an MILP solver. To efficiently model a Boolean function and select a minimal set of inequalities, two key challenges must be addressed. We propose algorithms to address the second challenge, aiming to find more optimized linear and non-linear components. Our approaches are applied to modeling SBoxes (up to six bits) and EXOR operations with any number of inputs. Additionally, we introduce an MILP-based automatic tool for exploring differential and impossible differential propagations within a cipher. The tool is successfully applied to five lightweight block ciphers: Lilliput, GIFT64, SKINNY64, Klein, and MIBS.

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