Knowledge Flow Analysis for Security Protocols

Knowledge flow analysis offers a simple and flexible way to find flaws in security protocols. A protocol is described by a collection of rules constraining the propagation of knowledge amongst principals. Because this characterization corresponds closely to informal descriptions of protocols, it allows a succinct and natural formalization; because it abstracts away message ordering, and handles communications between principals and applications of cryptographic primitives uniformly, it is readily represented in a standard logic. A generic framework in the Alloy modelling language is presented, and instantiated for two standard protocols, and a new key management scheme.Comment: 20 page

Design and analysis of group key exchange protocols

A group key exchange (GKE) protocol allows a set of parties to agree upon a common secret session key over a public network. In this thesis, we focus on designing efficient GKE protocols using public key techniques and appropriately revising security models for GKE protocols. For the purpose of modelling and analysing the security of GKE protocols we apply the widely accepted computational complexity approach. The contributions of the thesis to the area of GKE protocols are manifold. We propose the first GKE protocol that requires only one round of communication and is proven secure in the standard model. Our protocol is generically constructed from a key encapsulation mechanism (KEM). We also suggest an efficient KEM from the literature, which satisfies the underlying security notion, to instantiate the generic protocol. We then concentrate on enhancing the security of one-round GKE protocols. A new model of security for forward secure GKE protocols is introduced and a generic one-round GKE protocol with forward security is then presented. The security of this protocol is also proven in the standard model. We also propose an efficient forward secure encryption scheme that can be used to instantiate the generic GKE protocol. Our next contributions are to the security models of GKE protocols. We observe that the analysis of GKE protocols has not been as extensive as that of two-party key exchange protocols. Particularly, the security attribute of key compromise impersonation (KCI) resilience has so far been ignored for GKE protocols. We model the security of GKE protocols addressing KCI attacks by both outsider and insider adversaries. We then show that a few existing protocols are not secure against KCI attacks. A new proof of security for an existing GKE protocol is given under the revised model assuming random oracles. Subsequently, we treat the security of GKE protocols in the universal composability (UC) framework. We present a new UC ideal functionality for GKE protocols capturing the security attribute of contributiveness. An existing protocol with minor revisions is then shown to realize our functionality in the random oracle model. Finally, we explore the possibility of constructing GKE protocols in the attribute-based setting. We introduce the concept of attribute-based group key exchange (AB-GKE). A security model for AB-GKE and a one-round AB-GKE protocol satisfying our security notion are presented. The protocol is generically constructed from a new cryptographic primitive called encapsulation policy attribute-based KEM (EP-AB-KEM), which we introduce in this thesis. We also present a new EP-AB-KEM with a proof of security assuming generic groups and random oracles. The EP-AB-KEM can be used to instantiate our generic AB-GKE protocol

An IDE for the Design, Verification and Implementation of Security Protocols

Security protocols are critical components for the construction of secure and dependable distributed applications, but their implementation is challenging and error prone. Therefore, tools for formal modelling and analysis of security protocols can be potentially very useful to support software engineers. However, despite such tools having been available for a long time, their adoption outside the research community has been very limited. In fact, most practitioners find such applications too complex and hardly usable for their daily work. In this paper, we present an Integrated Development Environment for the design, verification and implementation of security protocols, aimed at lowering the adoption barrier of formal methods tools for security. In the spirit of Model Driven Development, the environment supports the user in the specification of the model using the simple and intuitive language AnB (and its extension AnBx). Moreover, it provides a push-button solution for the formal verification of the abstract and concrete models, and for the automatic generation of Java implementation. This Eclipse-based IDE leverages on existing languages and tools for the modelling and verification of security protocols, such as the AnBx Compiler and Code Generator, the model checker OFMC and the cryptographic protocol verifier ProVerif

Privacy compliance verification in cryptographic protocols

To provide privacy protection, cryptographic primitives are frequently applied to communication protocols in an open environment (e.g. the Internet). We call these protocols privacy enhancing protocols (PEPs) which constitute a class of cryptographic protocols. Proof of the security properties, in terms of the privacy compliance, of PEPs is desirable before they can be deployed. However, the traditional provable security approach, though well-established for proving the security of cryptographic primitives, is not applicable to PEPs. We apply the formal language of Coloured Petri Nets (CPNs) to construct an executable specification of a representative PEP, namely the Private Information Escrow Bound to Multiple Conditions Protocol (PIEMCP). Formal semantics of the CPN specification allow us to reason about various privacy properties of PIEMCP using state space analysis techniques. This investigation provides insights into the modelling and analysis of PEPs in general, and demonstrates the benefit of applying a CPN-based formal approach to the privacy compliance verification of PEPs

Performance and cryptographic evaluation of security protocols in distributed networks using applied pi calculus and Markov Chain

The development of cryptographic protocols goes through two stages, namely, security verification and performance analysis. The verification of the protocol’s security properties could be analytically achieved using threat modelling, or formally using formal methods and model checkers. The performance analysis could be mathematical or simulation-based. However, mathematical modelling is complicated and does not reflect the actual deployment environment of the protocol in the current state of the art. Simulation software provides scalability and can simulate complicated scenarios, however, there are times when it is not possible to use simulations due to a lack of support for new technologies or simulation scenarios. Therefore, this paper proposes a formal method and analytical model for evaluating the performance of security protocols using applied pi-calculus and Markov Chain processes. It interprets algebraic processes and associates cryptographic operatives with quantitative measures to estimate and evaluate cryptographic costs. With this approach, the protocols are presented as processes using applied pi-calculus, and their security properties are an approximate abstraction of protocol equivalence based on the verification from ProVerif and evaluated using analytical and simulation models for quantitative measures. The interpretation of the quantities is associated with process transitions, rates, and measures as a cost of using cryptographic primitives. This method supports users’ input in analysing the protocol’s activities and performance. As a proof of concept, we deploy this approach to assess the performance of security protocols designed to protect large-scale, 5G-based Device-to-Device communications. We also conducted a performance evaluation of the protocols based on analytical and network simulator results to compare the effectiveness of the proposed approach

Practical applications of performance modelling of security protocols using PEPA

PhD ThesisTrade-off between security and performance has become an intriguing area in recent years in both the security and performance communities. As the security aspects of security protocol research is fully- edged, this thesis is therefore devoted to conducting a performance study of these protocols. The long term objective is to translate formal de nitions of security protocols to formal performance models automatically, then analysing by relevant techniques. In this thesis, we take a preliminary step by studying five typical security protocols, and exploring the methodology of construction and analysis of their models by using the Markovian process algebra PEPA. Through these case studies, an initial framework of performance analysis of security protocol is established. Firstly, a key distribution centre is investigated. The basic model su ers from the commonly encountered state space explosion problem, and so we apply some efficient solution techniques, which include model reduction techniques and ordinary di fferential equation based fluid flow analysis. Finally, we evaluate a utility function for this secure key exchange model. Then, we explore two non-repudiation protocols. Mean value analysis has been applied here for a class of PEPA models, and it is compared with an ODE approximation. After that, an optimistic nonrepudiation protocol with off-line third trust party is studied. The PEPA model has been formulated using a concept of multi-threaded servers with functional rates. The nal case study is a cross-realm Kerberos protocol. A simplified technique of aggregation with an ODE approximation is performed to do efficient cient analysis. All these modelling and analysis methods are illustrated through numerical examples

Security analysis of standard authentication and key agreement protocols utilising timestamps

We propose a generic modelling technique that can be used to extend existing frameworks for theoretical security analysis in order to capture the use of timestamps. We apply this technique to two of the most popular models adopted in literature (Bellare-Rogaway and Canetti-Krawczyk). We analyse previous results obtained using these models in light of the proposed extensions, and demonstrate their application to a new class of protocols. In the timed CK model we concentrate on modular design and analysis of protocols, and propose a more efficient timed authenticator relying on timestamps. The structure of this new authenticator implies that an authentication mechanism standardised in ISO-9798 is secure. Finally, we use our timed extension to the BR model to establish the security of an efficient ISO protocol for key transport and unilateral entity authentication

Verification and validation of security protocol implementations

Security protocols are important and widely used because they enable secure communication to take place over insecure networks. Over the years numerous formal methods have been developed to assist protocol designers by analysing models of these protocols to determine their security properties. Beyond the design stage however, developers rarely employ formal methods when implementing security protocols. This may result in implementation flaws often leading to security breaches. This dissertation contributes to the study of security protocol analysis by advancing the emerging field of implementation analysis. Two tools are presented which together translate between Java and the LySa process calculus. Elyjah translates Java implementations into formal models in LySa. In contrast, Hajyle generates Java implementations from LySa models. These tools and the accompanying LySa verification tool perform rapid static analysis and have been integrated into the Eclipse Development Environment. The speed of the static analysis allows these tools to be used at compile-time without disrupting a developer’s workflow. This allows us to position this work in the domain of practical software tools supporting working developers. As many of these developers may be unfamiliar with modelling security protocols a suite of tools for the LySa process calculus is also provided. These tools are designed to make LySa models easier to understand and manipulate. Additional tools are provided for performance modelling of security protocols. These allow both the designer and the implementor to predict and analyse the overall time taken for a protocol run to complete. Elyjah was among the very first tools to provide a method of translating between implementation and formal model, and the first to use either Java for the implementation language or LySa for the modelling language. To the best of our knowledge, the combination of Elyjah and Hajyle represents the first and so far only system which provides translation from both code to model and back again

An approach for the automatic verification of blockchain protocols: the Tweetchain case study

This paper proposes a model-driven approach for the security modelling and analysis of blockchain based protocols. The modelling is built upon the definition of a UML profile, which is able to capture transaction-oriented information. The analysis is based on existing formal analysis tools. In particular, the paper considers the Tweetchain protocol, a recent proposal that leverages online social networks, i.e., Twitter, for extending blockchain to domains with small-value transactions, such as IoT. A specialized textual notation is added to the UML profile to capture features of this protocol. Furthermore, a model transformation is defined to generate a Tamarin model, from the UML models, via an intermediate well-known notation, i.e., the Alice &Bob notation. Finally, Tamarin Prover is used to verify the model of the protocol against some security properties. This work extends a previous one, where the Tamarin formal models were generated by hand. A comparison on the analysis results, both under the functional and non-functional aspects, is reported here too