A framework for formal analysis and simulative evaluation of security attacks in wireless sensor networks

AbstractWhen designing Wireless Sensor Networks it is important to analyze their security risks and provide adequate solutions for protecting them from malicious attacks. Unfortunately, perfect security cannot be achieved, for performance reasons. Therefore, designers have to devise security priorities, and select security mechanisms accordingly. However, in the early stages of the design process, the concrete effects of security attacks on the system may not be clearly identified. In this paper, we propose a framework that integrates formal verification and network simulation for enabling designers to evaluate the effects of attacks, identify possible security mechanisms, and evaluate their effectiveness, since design time. Formal methods are used to build the abstract model of the application, together with a set of attacks, and to state properties of general validity. The simulator measures the impact of the attacks in terms of common network parameters, like energy consumption or computational effort. Such information can be used to select adequate security mechanisms, then the initial abstract model can be refined to adopt them, and finally prove that former system properties are still verified. The framework relies on UPPAAL for formal modeling and verification and uses the Attack Simulation Framework on top of Castalia as a network simulator. As proof of concept, a case study is shown

Towards Applying Cryptographic Security Models to Real-World Systems

The cryptographic methodology of formal security analysis usually works in three steps: choosing a security model, describing a system and its intended security properties, and creating a formal proof of security. For basic cryptographic primitives and simple protocols this is a well understood process and is performed regularly. For more complex systems, as they are in use in real-world settings it is rarely applied, however. In practice, this often leads to missing or incomplete descriptions of the security properties and requirements of such systems, which in turn can lead to insecure implementations and consequent security breaches. One of the main reasons for the lack of application of formal models in practice is that they are particularly difficult to use and to adapt to new use cases. With this work, we therefore aim to investigate how cryptographic security models can be used to argue about the security of real-world systems. To this end, we perform case studies of three important types of real-world systems: data outsourcing, computer networks and electronic payment. First, we give a unified framework to express and analyze the security of data outsourcing schemes. Within this framework, we define three privacy objectives: \emph{data privacy}, \emph{query privacy}, and \emph{result privacy}. We show that data privacy and query privacy are independent concepts, while result privacy is consequential to them. We then extend our framework to allow the modeling of \emph{integrity} for the specific use case of file systems. To validate our model, we show that existing security notions can be expressed within our framework and we prove the security of CryFS---a cryptographic cloud file system. Second, we introduce a model, based on the Universal Composability (UC) framework, in which computer networks and their security properties can be described We extend it to incorporate time, which cannot be expressed in the basic UC framework, and give formal tools to facilitate its application. For validation, we use this model to argue about the security of architectures of multiple firewalls in the presence of an active adversary. We show that a parallel composition of firewalls exhibits strictly better security properties than other variants. Finally, we introduce a formal model for the security of electronic payment protocols within the UC framework. Using this model, we prove a set of necessary requirements for secure electronic payment. Based on these findings, we discuss the security of current payment protocols and find that most are insecure. We then give a simple payment protocol inspired by chipTAN and photoTAN and prove its security within our model. We conclude that cryptographic security models can indeed be used to describe the security of real-world systems. They are, however, difficult to apply and always need to be adapted to the specific use case

Soft Constraint Programming to Analysing Security Protocols

Security protocols stipulate how the remote principals of a computer network should interact in order to obtain specific security goals. The crucial goals of confidentiality and authentication may be achieved in various forms, each of different strength. Using soft (rather than crisp) constraints, we develop a uniform formal notion for the two goals. They are no longer formalised as mere yes/no properties as in the existing literature, but gain an extra parameter, the security level. For example, different messages can enjoy different levels of confidentiality, or a principal can achieve different levels of authentication with different principals. The goals are formalised within a general framework for protocol analysis that is amenable to mechanisation by model checking. Following the application of the framework to analysing the asymmetric Needham-Schroeder protocol, we have recently discovered a new attack on that protocol as a form of retaliation by principals who have been attacked previously. Having commented on that attack, we then demonstrate the framework on a bigger, largely deployed protocol consisting of three phases, Kerberos.Comment: 29 pages, To appear in Theory and Practice of Logic Programming (TPLP) Paper for Special Issue (Verification and Computational Logic

A formal specification and verification framework for timed security protocols

Nowadays, protocols often use time to provide better security. For instance, critical credentials are often associated with expiry dates in system designs. However, using time correctly in protocol design is challenging, due to the lack of time related formal specification and verification techniques. Thus, we propose a comprehensive analysis framework to formally specify as well as automatically verify timed security protocols. A parameterized method is introduced in our framework to handle timing parameters whose values cannot be decided in the protocol design stage. In this work, we first propose timed applied π-calculus as a formal language for specifying timed security protocols. It supports modeling of continuous time as well as application of cryptographic functions. Then, we define its formal semantics based on timed logic rules, which facilitates efficient verification against various authentication and secrecy properties. Given a parameterized security protocol, our method either produces a constraint on the timing parameters which guarantees the security property satisfied by the protocol, or reports an attack that works for any parameter value. The correctness of our verification algorithm has been formally proved. We evaluate our framework with multiple timed and untimed security protocols and successfully find a previously unknown timing attack in Kerberos V

Formal Analysis of E-Cash Protocols

International audienceElectronic cash (e-cash) aims at achieving client privacy at payment, similar to real cash. Several security protocols have been proposed to ensure privacy in e-cash, as well as the necessary unforgery properties. In this paper, we propose a formal framework to define, analyze, and verify security properties of e-cash systems. To this end, we model e-cash systems in the applied π-calculus, and we define two client privacy properties and three properties to prevent forgery. Finally, we apply our definitions to an e-cash protocol from the literature proposed by Chaum et al., which has two variants and a real implementation based on it. Using ProVerif, we demonstrate that our framework is suitable for an automated analysis of this protocol

User-friendly Formal Methods for Security-aware Applications and Protocols

Formal support in the design and implementation of security-aware applications increases the assurance in the final artifact. Formal methods techniques work by setting a model that unambiguously defines attacker capabilities, protocol parties behavior, and expected security properties. Rigorous reasoning can be done on the model about the interaction of the external attacker with the protocol parties, assessing whether the security properties hold or not. Unfortunately, formal verification requires a high level of expertise to be used properly and, in complex systems, the model analysis requires an amount of resources (memory and time) that are not available with current technologies. The aim of this thesis is to propose new interfaces and methodologies that facilitate the usage of formal verification techniques applied to security-aware protocols and distributed applications. In particular, this thesis presents: (i) Spi2JavaGUI, a framework for the model-driven development of security protocols, that combines (for the first time in literature) an intuitive user interface, automated formal verification and code generation; (ii) a new methodology that enables the model-driven development and the automated formal analysis of distributed applications, which requires less resources and formal verification knowledge to complete the verification process, when compared to previous approaches; (iii) the formal verification of handover procedures defined by the Long Term Evolution (LTE) standard for mobile communication networks, including the results and all the translation rules from specification documents to formal models, that facilitates the application of formal verification to other parts of the standard in the future

Precise Analysis of Purpose Limitation in Data Flow Diagrams

Data Flow Diagrams (DFDs) are primarily used for modelling functional properties of a system. In recent work, it was shown that DFDs can be used to also model non-functional properties, such as security and privacy properties, if they are annotated with appropriate security- and privacy-related information. An important privacy principle one may wish to model in this way is purpose limitation. But previous work on privacy-aware DFDs (PA-DFDs) considers purpose limitation only superficially, without explaining how the purpose of DFD activators and flows ought to be specified, checked or inferred. In this paper, we define a rigorous formal framework for (1) annotating DFDs with purpose labels and privacy signatures, (2) checking the consistency of labels and signatures, and (3) inferring labels from signatures. We implement our theoretical framework in a proof-of concept tool consisting of a domain-specific language (DSL) for specifying privacy signatures and algorithms for checking and inferring purpose labels from such signatures. Finally, we evaluate our framework and tool through a case study based on a DFD from the privacy literature