论文标题

CDCL(加密)SAT求解器进行隐式分析

CDCL(Crypto) SAT Solvers for Cryptanalysis

论文作者

Nejati, Saeed, Ganesh, Vijay

论文摘要

在过去的二十年中,我们看到冲突驱动的子句学习布尔可满足性(CDCL SAT)关于来自各个领域的工业问题的效率的效率有了显着提高。这样强大的通用搜索工具的可用性导致许多研究人员提出了基于SAT的隐式分析方法,包括在哈希功能中查找碰撞和破坏对称的加密方案的技术。先前提出的基于SAT的密码分析方法是黑框技术,从某种意义上说,密码分析问题被编码为SAT实例,然后调用CDCL SAT求解器来解决该实例。这种方法的弱点是,因此生成的编码可能太大了,对于任何现代求解器而言,无法有效地解决。也许这种方法的一个更重要的弱点是,求解器绝不是专业或调整来解决给定实例的。为了解决这些问题,我们提出了一种称为CDCL(Crypto)的方法(受满意度理论求解器中的CDCL(t)范式的启发),以量身定制CDCL SAT求解器的内部子例程,并具有有关加密原始域的特定领域知识。具体而言,我们使用专门的代码扩展了CDCL求解器的传播和冲突分析子例程,这些代码对求解器分析的加密原始构图有所了解。我们在哈希函数的差分路径和代数断层分析中证明了这种方法的力量。我们的最初结果非常令人鼓舞,并加强了这种方法是基于黑盒SAT的隐底分析的重大改进的观念。

Over the last two decades, we have seen a dramatic improvement in the efficiency of conflict-driven clause-learning Boolean satisfiability (CDCL SAT) solvers on industrial problems from a variety of domains. The availability of such powerful general-purpose search tools as SAT solvers has led many researchers to propose SAT-based methods for cryptanalysis, including techniques for finding collisions in hash functions and breaking symmetric encryption schemes. Most of the previously proposed SAT-based cryptanalysis approaches are blackbox techniques, in the sense that the cryptanalysis problem is encoded as a SAT instance and then a CDCL SAT solver is invoked to solve the said instance. A weakness of this approach is that the encoding thus generated may be too large for any modern solver to solve efficiently. Perhaps a more important weakness of this approach is that the solver is in no way specialized or tuned to solve the given instance. To address these issues, we propose an approach called CDCL(Crypto) (inspired by the CDCL(T) paradigm in Satisfiability Modulo Theory solvers) to tailor the internal subroutines of the CDCL SAT solver with domain-specific knowledge about cryptographic primitives. Specifically, we extend the propagation and conflict analysis subroutines of CDCL solvers with specialized codes that have knowledge about the cryptographic primitive being analyzed by the solver. We demonstrate the power of this approach in the differential path and algebraic fault analysis of hash functions. Our initial results are very encouraging and reinforce the notion that this approach is a significant improvement over blackbox SAT-based cryptanalysis.

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