An Experiment in Ping-Pong Protocol Verification by Nondeterministic Pushdown Automata

An experiment is described that confirms the security of a well-studied class of cryptographic protocols (Dolev-Yao intruder model) can be verified by two-way nondeterministic pushdown automata (2NPDA). A nondeterministic pushdown program checks whether the intersection of a regular language (the protocol to verify) and a given Dyck language containing all canceling words is empty. If it is not, an intruder can reveal secret messages sent between trusted users. The verification is guaranteed to terminate in cubic time at most on a 2NPDA-simulator. The interpretive approach used in this experiment simplifies the verification, by separating the nondeterministic pushdown logic and program control, and makes it more predictable. We describe the interpretive approach and the known transformational solutions, and show they share interesting features. Also noteworthy is how abstract results from automata theory can solve practical problems by programming language means.Comment: In Proceedings MARS/VPT 2018, arXiv:1803.0866

Visual Model-Driven Design, Verification and Implementation of Security Protocols

A novel visual model-driven approach to security protocol design, verification, and implementation is presented in this paper. User-friendly graphical models are combined with rigorous formal methods to enable protocol verification and sound automatic code generation. Domain-specific abstractions keep the graphical models simple, yet powerful enough to represent complex, realistic protocols such as SSH. The main contribution is to bring together aspects that were only partially available or not available at all in previous proposal

Towards Realistic Threat Modeling: Attack Commodification, Irrelevant Vulnerabilities, and Unrealistic Assumptions

Current threat models typically consider all possible ways an attacker can penetrate a system and assign probabilities to each path according to some metric (e.g. time-to-compromise). In this paper we discuss how this view hinders the realness of both technical (e.g. attack graphs) and strategic (e.g. game theory) approaches of current threat modeling, and propose to steer away by looking more carefully at attack characteristics and attacker environment. We use a toy threat model for ICS attacks to show how a realistic view of attack instances can emerge from a simple analysis of attack phases and attacker limitations.Comment: Proceedings of the 2017 Workshop on Automated Decision Making for Active Cyber Defens

e-Health for Rural Areas in Developing Countries: Lessons from the Sebokeng Experience

We report the experience gained in an e-Health project in the Gauteng province, in South Africa. A Proof-of-Concept of the project has been already installed in 3 clinics in the Sebokeng township. The project is now going to be applied to 300 clinics in the whole province. This extension of the Proof-of-Concept can however give rise to security aws because of the inclusion of rural areas with unreliable Internet connection. We address this problem and propose a safe solution

Sound Computational Interpretation of Formal Encryption with Composed Keys

The formal and computational views of cryptography have been related by the seminal work of Abadi and Rogaway. In their work, a formal treatment of encryption that uses atomic keys is justified in the computational world. However, many proposed formal approaches allow the use of composed keys, where any arbitrary expression can be used as encryption key. We consider an extension of the formal model presented by Abadi and Rogaway, in which it is allowed to use composed keys in formal encryption. We then provide a computational interpretation for expressions that allow us to establish the computational soundness of formal encryption with composed keys

Automated Cryptographic Analysis of the Pedersen Commitment Scheme

Aiming for strong security assurance, recently there has been an increasing interest in formal verification of cryptographic constructions. This paper presents a mechanised formal verification of the popular Pedersen commitment protocol, proving its security properties of correctness, perfect hiding, and computational binding. To formally verify the protocol, we extended the theory of EasyCrypt, a framework which allows for reasoning in the computational model, to support the discrete logarithm and an abstraction of commitment protocols. Commitments are building blocks of many cryptographic constructions, for example, verifiable secret sharing, zero-knowledge proofs, and e-voting. Our work paves the way for the verification of those more complex constructions.Comment: 12 pages, conference MMM-ACNS 201

Execution Models for Choreographies and Cryptoprotocols

A choreography describes a transaction in which several principals interact. Since choreographies frequently describe business processes affecting substantial assets, we need a security infrastructure in order to implement them safely. As part of a line of work devoted to generating cryptoprotocols from choreographies, we focus here on the execution models suited to the two levels. We give a strand-style semantics for choreographies, and propose a special execution model in which choreography-level messages are faithfully delivered exactly once. We adapt this model to handle multiparty protocols in which some participants may be compromised. At level of cryptoprotocols, we use the standard Dolev-Yao execution model, with one alteration. Since many implementations use a "nonce cache" to discard multiply delivered messages, we provide a semantics for at-most-once delivery