Compositional Verification Research Articles

EP-1501: Field-by-field and composite plan pseudo-3D verification of IMRT techniques with radiochromic film

EP-1501: Field-by-field and composite plan pseudo-3D verification of IMRT techniques with radiochromic film

Formal architecture modeling of sequential non-recursive C programs

To manage the complexity of C programs, architecture models are used as high-level descriptions, allowing developers to understand, assess, and manage the C programs without having to understand the intricate complexity of the code implementations. However, for the architecture models to serve their purpose, they must be accurate representations of the C programs. In order to support creating accurate architecture models, the present paper presents a mapping from the domain of sequential non-recursive C programs to a domain of formal architecture models, each being a hierarchy of components with well-defined interfaces. The hierarchically organized components and their interfaces, which capture both data and function call dependencies, are shown to both enable high-level assessment and analysis of the C program and provide a foundation for organizing and expressing specifications for compositional verification.

Synthesizing and verifying controllers for multi-lane traffic maneuvers

Abstract The dynamic behavior of a car can be modeled as a hybrid system involving continuous state changes and discrete state transitions. We show that the control of safe (collision free) lane change maneuvers in multi-lane traffic on highways can be described by finite state machines extended with continuous variables coming from the environment. We use standard theory for controller synthesis to derive the dynamic behavior of a lane-change controller. Thereby, we contrast the setting of interleaving semantics and synchronous concurrent semantics. We also consider the possibility of exchanging knowledge between neighboring cars in order to come up with the right decisions. Finally, we address compositional verification using an assumption-guarantee paradigm.

Transactional execution of hierarchical reconfigurations in cyber-physical systems

Cyber-physical systems reconfigure the structure of their software architecture, e.g., to avoid hazardous situations and to optimize operational conditions like their energy consumption. These reconfigurations have to be safe so that the systems protect their users or environment against harmful conditions or events while changing their structure. As software architectures are typically built on components, reconfiguration actions need to take into account the component structure. This structure should support vertical composition to enable hierarchically encapsulated components. While many reconfiguration approaches for cyber-physical and embedded real-time systems allow the use of hierarchically embedded components, i.e., vertical composition, none of them offers a modeling and verification solution to take hierarchical composition, i.e., encapsulation, into account thus limiting reuse and compositional verification. In this paper, we present an extension to our existing modeling language, MechatronicUML, to enable safe hierarchical reconfigurations. The three extensions are (a) an adapted variant of the 2-phase-commit protocol to initiate reconfigurations that maintain component encapsulation, (b) the integration of feedback controllers during reconfiguration, and (c) a verification approach based on (timed) model checking for instances of our model. We illustrate our approach on a case study in the area of smart railway systems by showing two different use cases of our approach. We show that using our approach the systems can be easily designed to reconfigure safely.

Checklist of Rhodophyta of the White Sea (the Arctic Ocean)

Abstract Most data on the White Sea flora are scattered in Russian publications and are largely inaccessible to researchers. The aim of the present work is to compile a checklist as well as to provide verification of the species composition of the Rhodophyta of the White Sea. This checklist is based on an exhaustive bibliographic search. As a result of a careful revision, a total of 61 species of Rhodophyta has been revealed, and 17 species and one forma were excluded on the basis of being doubtful records or misidentifications. The distribution of four species in the White Sea was clarified. Nineteen species occur throughout the White Sea, six species are widespread except for Mezen Bay, whereas seven taxa are restricted to the northern regions of the White Sea. The analysis of the species composition permits the red algal flora of the White Sea to be interpreted as representing the depleted Barents Sea flora. An extensive bibliography and data on the presence of the specimens in the Komarov Botanical Institute of the Russian Academy of Sciences are given.

Releasing the PSYCO

The Java PathFinder extension Psyco generates interfaces of Java components using a combination of dynamic symbolic execution and automata learning to explore different combinations of method invocations on a component. Such interfaces are useful in contract-based compositional verification of component-based systems. Psyco relies on testing for validating learned interfaces and currently cannot guarantee that a generated interface is correct. Instead, it simply returns the most recent learned interface once a user-defined time limit is exceeded. In this paper, we report on work that was performed during the 2016 Google Summer of Code. The aim of this work is to extend Psyco with symbolic search. During symbolic search, Psyco uses fully symbolic method summaries for exploring the state space of a component symbolically. We plan to eventually use symbolic search to compute a termination criterion for Psyco that guarantees the correctness of learned interfaces (e.g., by using symbolic search as a basis for symbolically model-checking a component against a learned interface)

Thread modularity at many levels: a pearl in compositional verification

A thread-modular proof for the correctness of a concurrent program is based on an inductive and interference-free annotation of each thread. It is well-known that the corresponding proof system is not complete (unless one adds auxiliary variables). We describe a hierarchy of proof systems where each level k corresponds to a generalized notion of thread modularity (level 1 corresponds to the original notion). Each level is strictly more expressive than the previous. Further, each level precisely captures programs that can be proved using uniform Ashcroft invariants with k universal quantifiers. We demonstrate the usefulness of the hierarchy by giving a compositional proof of the Mach shootdown algorithm for TLB consistency. We show a proof at level 2 that shows the algorithm is correct for an arbitrary number of CPUs. However, there is no proof for the algorithm at level 1 which does not involve auxiliary state.

A methodological approach for checking safety-critical systems software

The complexity of modern safety-critical systems together with the absence of appropriate software verification tools is one reason for the large number of errors in the design and implementation of these systems. A methodological approach named formal compositional verification approach that uses model checking techniques to verify safety-critical systems software is presented. This approach facilitates decomposition of complex safety-critical systems software into independently verified individual software components, and establishes a compositional method to verify these systems using state-of-the-art model checkers. Our objective in this paper is to facilitate the description of a safety-critical system software as a collection of verified software components, allowing the software verification of complex safety-critical systems. An application on a real-life software project in the field of mobile phone communication is discussed to demonstrate the applicability of the proposed approach.

Verification of Implementations of Cryptographic Hash Functions

Cryptographic hash functions have become the basis of modern network computing for identity authorization and secure computing; protocol consistency of cryptographic hash functions is one of the most important properties that affect the security and correctness of cryptographic implementations, and protocol consistency should be well proven before being applied in practice. Software verification has seen substantial application in safety-critical areas and has shown the ability to deliver better quality assurance for modern software; thus, applying software verification to a protocol consistency proof for cryptographic hash functions is a reasonable approach to prove their correctness. Verification of protocol consistency of cryptographic hash functions includes modeling of the cryptographic protocol and program analysis of the cryptographic implementation; these require a dedicated cryptographic implementation model that preserves the semantics of the code, efficient analysis of cryptographic operations on arrays and bits, and the ability to verify large-scale implementations. In this paper, we propose a fully automatic software verification framework, VeriHash, that brings software verification to protocol consistency proofs for cryptographic hash function implementations. It solves the above challenges by introducing a novel cryptographic model design for modeling the semantics of cryptographic hash function implementations, extended array theories for analysis of operations, and compositional verification for scalability. We evaluated our verification framework on two SHA-3 cryptographic hash function implementations: the winner of the NIST SHA-3 competition, Keccack; and an open-source hash program, RHash. We successfully verified the core parts of the two implementations and reproduced a bug in the published edition of RHash.

A methodological approach for checking safety-critical systems software

The complexity of modern safety-critical systems together with the absence of appropriate software verification tools is one reason for the large number of errors in the design and implementation of these systems. A methodological approach named formal compositional verification approach that uses model checking techniques to verify safety-critical systems software is presented. This approach facilitates decomposition of complex safety-critical systems software into independently verified individual software components, and establishes a compositional method to verify these systems using state-of-the-art model checkers. Our objective in this paper is to facilitate the description of a safety-critical system software as a collection of verified software components, allowing the software verification of complex safety-critical systems. An application on a real-life software project in the field of mobile phone communication is discussed to demonstrate the applicability of the proposed approach.

COMPARATIVE ANALYSIS OF NON-CONTACT ULTRASONIC METHODS FOR DEFECT ESTIMATION OF COMPOSITES IN REMOTE AREAS

There are various ultrasonic systems, developed for the effective testing and estimation of defect parameters in composite materials. Non-contact ultrasonic testing has already achieved significance over traditional contact methods that require coupling of media and are not well suited for the transmission of surface acoustic waves (SAW), which can cover a large area of structure under investigation. This paper compares approaches of air-coupled transmission/reception, laser ultrasonic, and electromagnetic acoustic transducer (EMAT), for testing and verification of composites and defect estimation in remote areas. It reviews the various practical applications. The study found the hybrid solution, consisting of the laser system as a transmitter and the air-coupled method as a detector, is the best among all.

Modeling and verification of Web services composition based on model transformation

SummaryWith the rapid development of Cloud computing, social computing, and Web of Things, an increasing number of requirements of complexity and reliability for modeling Web services composition have emerged too. As more reliable methods are needed to model and verify current complex Web services composition, this paper proposes a method to model and verify Web services composition based on model transformation. First, a modeling and verifying framework based on model transformation is established. Then, Communicating Sequential Process (CSP) is defined according to the features of Web services composition and the corresponding model checking tool Failure Divergence Refinement (FDR) is introduced. The transformation approaches between Business Process Execution Language (BPEL) and CSP are later defined in detail. Lastly, the effect of this method is evaluated by modeling and verifying the Web services composition of a Online Shopping System. The results of the experiments show that this method can greatly increase the reliability of Web services composition. Copyright © 2016 John Wiley & Sons, Ltd.

A sufficient condition to polynomially compute a minimum separating DFA

The computation of a minimal separating automaton (MSA) for regular languages has been studied from many different points of view, from synthesis of automata or Grammatical Inference to the minimization of incompletely specified machines or Compositional Verification. In the general case, the problem is NP-complete, but this drawback does not prevent the problem from having a real application in the above-mentioned fields. In this paper, we propose a sufficient condition that guarantees that the computation of the MSA can be carried out with polynomial time complexity.

Learning Weighted Assumptions for Compositional Verification of Markov Decision Processes

Probabilistic models are widely deployed in various systems. To ensure their correctness, verification techniques have been developed to analyze probabilistic systems. We propose the first sound and complete learning-based compositional verification technique for probabilistic safety properties on concurrent systems where each component is an Markov decision process. Different from previous works, weighted assumptions are introduced to attain completeness of our framework. Since weighted assumptions can be implicitly represented by multiterminal binary decision diagrams (MTBDDs), we give an >i<L>/i<*-based learning algorithm for MTBDDs to infer weighted assumptions. Experimental results suggest promising outlooks for our compositional technique.

Toward compositional verification of interruptible OS kernels and device drivers

An operating system (OS) kernel forms the lowest level of any system software stack. The correctness of the OS kernel is the basis for the correctness of the entire system. Recent efforts have demonstrated the feasibility of building formally verified general-purpose kernels, but it is unclear how to extend their work to verify the functional correctness of device drivers, due to the non-local effects of interrupts. In this paper, we present a novel compositional framework for building certified interruptible OS kernels with device drivers. We provide a general device model that can be instantiated with various hardware devices, and a realistic formal model of interrupts, which can be used to reason about interruptible code. We have realized this framework in the Coq proof assistant. To demonstrate the effectiveness of our new approach, we have successfully extended an existing verified non-interruptible kernel with our framework and turned it into an interruptible kernel with verified device drivers. To the best of our knowledge, this is the first verified interruptible operating system with device drivers.

Establishment of a Feasible Cyber Organization Structure to Enhance the Capabilities of Cyberspace Operations in the ROK`s Defense Forces

The paper discusses ways of establishing a feasible cyber organization for enhancing cyber response capabilities in defense of the ROK. To prepare for the rise of cyberspace as a war-combat domain, together with the realization that cyberspace is indispensable in fulfilling operational requirements, it is essential to search for and establish a new, suitable organization for cyberspace operations. To achieve this, the author suggests a design of an organization based on the so-called “three-party authority,” the ROK’s way of managing cyberspace, the difference in each echelon’s accountability for the fulfillment of the operational requirements-mission accomplishment for its commander as well as the characteristics of cyberspace. The article also presents validation and verification of the suggested composition of the cyber organization suitable for defense of the ROK to identify its pros and cons.

The growth and tensile deformation behavior of the silver solid solution phase with zinc

The growth of homogeneous silver solid solution phase with zinc are conducted at two different compositions. X-ray diffraction (XRD) and Scanning electron microscope/Energy dispersive X-ray spectroscopy (SEM/EDX) are carried out for phase identification and chemical composition verification. The mechanical properties of silver solid solution phase with zinc are evaluated by tensile test. The engineering and true stress vs. strain curves are presented and analyzed, with those of pure silver in comparison. According to the experimental results, silver solid solution phase with zinc at both compositions show tempered yield strength, high tensile strength and large uniform strain compared to those of pure silver. Fractography further confirmed the superior ductility of silver solid solution phase with zinc at both compositions. Our preliminary but encouraging results may pave the way for the silver based alloys to be applied in industries such as electronic packaging and structure engineering.

Pi-calculus based Bayesian Trust Web Service Composition

To enhance the reliability of trust Web service composition, Pi-calculus based formal verification of trust Web service composition is proposed. Bayesian trust Web service composition is firstly defined abstractly; then Pi-calculus is used to describe its composition structure and internal interaction, the mapping relation between trust entity and Pi-calculus is provided. The automatic reasoner MWB is adopted to manipulate and analyze the composition system, which is aimed at finding and correcting the faults before the implementation.

Distributed information flow verification for secure service composition in smart sensor network

Accelerate processor, efficient software and pervasive connections provide sensor nodes with more powerful computation and storage ability, which can offer various services to user. Based on these atomic services, different sensor nodes can cooperate and compose with each other to complete more complicated tasks for user. However, because of the regional characteristic of sensor nodes, merging data with different sensitivities become a primary requirement to the composite services, and information flow security should be intensively considered during service composition. In order to mitigate the great cost caused by the complexity of modeling and the heavy load of single-node verification to the energy-limited sensor node, in this paper, we propose a new distributed verification framework to enforce information flow security on composite services of smart sensor network. We analyze the information flows in composite services and specify security constraints for each service participant. Then we propose an algorithm over the distributed verification framework involving each sensor node to participate in the composite service verification based on the security constraints. The experimental results indicate that our approach can reduce the cost of verification and provide a better load balance.

Towards Unified Business Process Modeling and Verification for Role-based Resource-oriented Service Composition

With the prevalence of ubiquitous computing, big data, and Internet of things in cloud computing environment, it’s important to consider both of collaboration, heterogeneity, isolation of multi-tenant applications and information security and privacy in service composition. Current methods need to be readdressed to cope with cross-organizational, multi-roles participated and knowledge-intensive service composition in an integrated way. Based on the modeling and verification theories of hierarchical colored petri-net, a resource-oriented collaborative workflow model, its resource control model and the joint modeling and verification method are proposed which present a unified solution bridging the gap between traditional structure-oriented workflow execution model and resource-oriented workflow domain model taking into account the underlying roles, tasks, resources and their association and coordination in design-time and runtime as well. In our approach, a business process is divided into three layers: the backbone top-level process, the task fulfillment sub-process and the task execution sub-process in order to reduce the complexity of model verification. In addition this paper gives in-depth discussions on the fine control of implicit parallel and multi-threaded process executions. Finally, the case studies show that the proposed methods are not only applicable to modeling and verification of traditional task-oriented workflows, but also suited for knowledge or data-intensive workflows which involve