Explanation in Constraint Satisfaction: A Survey

Much of the focus on explanation in the field of artificial intelligence has focused on machine learning methods and, in particular, concepts produced by advanced methods such as neural networks and deep learning. However, there has been a long history of explanation generation in the general field of constraint satisfaction, one of the AI's most ubiquitous subfields. In this paper we survey the major seminal papers on the explanation and constraints, as well as some more recent works. The survey sets out to unify many disparate lines of work in areas such as model-based diagnosis, constraint programming, Boolean satisfiability, truth maintenance systems, quantified logics, and related areas.

Abstract Cores in Implicit Hitting Set MaxSat Solving (Extended Abstract)

Maximum satisfiability (MaxSat) solving is an active area of research motivated by numerous successful applications to solving NP-hard combinatorial optimization problems. One of the most successful approaches for solving MaxSat instances from real world domains are the so called implicit hitting set (IHS) solvers. IHS solvers decouple MaxSat solving into separate core-extraction (i.e. reasoning) and optimization steps which are tackled by a Boolean satisfiability (SAT) and an integer linear programming (IP) solver, respectively. While the approach shows state-of-the-art performance on many industrial instances, it is known that there exists instances on which IHS solvers need to extract an exponential number of cores before terminating. Motivated by the simplest of these problematic instances, we propose abstract cores, a compact representation for a potentially exponential number of regular cores. We demonstrate how to incorporate abstract core reasoning into the IHS algorithm and report on an empirical evaluation demonstrating, that including abstract cores into a state-of-the-art IHS solver improves its performance enough to surpass the best performing solvers of the 2019 MaxSat Evaluation.

Breaking CAS-Lock and Its Variants by Exploiting Structural Traces

Logic locking is a prominent solution to protect against design intellectual property theft. However, there has been a decade-long cat-and-mouse game between defenses and attacks. A turning point in logic locking was the development of miterbased Boolean satisfiability (SAT) attack that steered the research in the direction of developing SAT-resilient schemes. These schemes, however achieved SAT resilience at the cost of low output corruption. Recently, cascaded locking (CAS-Lock) [SXTF20a] was proposed that provides non-trivial output corruption all-the-while maintaining resilience to the SAT attack. Regardless of the theoretical properties, we revisit some of the assumptions made about its implementation, especially about security-unaware synthesis tools, and subsequently expose a set of structural vulnerabilities that can be exploited to break these schemes. We propose our attacks on baseline CAS-Lock as well as mirrored CAS (M-CAS), an improved version of CAS-Lock. We furnish extensive simulation results of our attacks on ISCAS’85 and ITC’99 benchmarks, where we show that CAS-Lock/M-CAS can be broken with ∼94% success rate. Further, we open-source all implementation scripts, locked circuits, and attack scripts for the community. Finally, we discuss the pitfalls of point function-based locking techniques including Anti-SAT [XS18] and Stripped Functionality Logic Locking(SFLL-HD) [YSN+17], which suffer from similar implementation issues.

Linear Cryptanalyses of Three AEADs with GIFT-128 as Underlying Primitives

This paper considers the linear cryptanalyses of Authenticated Encryptions with Associated Data (AEADs) GIFT-COFB, SUNDAE-GIFT, and HyENA. All of these proposals take GIFT-128 as underlying primitives. The automatic search with the Boolean satisfiability problem (SAT) method is implemented to search for linear approximations that match the attack settings concerning these primitives. With the newly identified approximations, we launch key-recovery attacks on GIFT-COFB, SUNDAE-GIFT, and HyENA when the underlying primitives are replaced with 16-round, 17-round, and 16-round versions of GIFT-128. The resistance of GIFT-128 against linear cryptanalysis is also evaluated. We present a 24-round key-recovery attack on GIFT-128 with a newly obtained 19-round linear approximation. We note that the attack results in this paper are far from threatening the security of GIFT-COFB, SUNDAE-GIFT, HyENA, and GIFT-128.

Symbolic Control of Hybrid Systems from Signal Temporal Logic Specifications

In safety-critical systems, it is desirable to automatically synthesize controllers for complex tasks with guaranteed safety and correctness. Although much progress has been made through controller synthesis from temporal logic specifications, existing approaches generally require conservative assumptions and do not scale well with system dimensionality. We propose a scalable, provably complete algorithm that synthesizes continuous trajectories for hybrid systems to satisfy temporal logic specifications. Specifically, we harness highly efficient Boolean satisfiability (SAT) and Linear Programming (LP) solvers to find trajectories that satisfy non-convex Signal Temporal Logic (STL) specifications for a class of high dimensional hybrid systems. The proposed design algorithms are proven sound and complete, and are validated in simulation experiments.