Verifying security protocols by knowledge analysis

This paper describes a new interactive method to analyse knowledge of participants involved in security protocols and further to verify the correctness of the protocols. The method can detect attacks and flaws involving interleaving sessions besides normal attacks. The implementation of the method in a generic theorem proving environment, namely Isabelle, makes the verification of protocols mechanical and efficient; it can verify a medium-sized security protocol in less than ten seconds. As an example, the paper finds the flaw in the Needham-Schroeder public key authentication protocol and proves the secure properties and guarantees of the protocol with Lowe's fix to show the effectiveness of this method

Formal Verification of Security Protocol Implementations: A Survey

Automated formal verification of security protocols has been mostly focused on analyzing high-level abstract models which, however, are significantly different from real protocol implementations written in programming languages. Recently, some researchers have started investigating techniques that bring automated formal proofs closer to real implementations. This paper surveys these attempts, focusing on approaches that target the application code that implements protocol logic, rather than the libraries that implement cryptography. According to these approaches, libraries are assumed to correctly implement some models. The aim is to derive formal proofs that, under this assumption, give assurance about the application code that implements the protocol logic. The two main approaches of model extraction and code generation are presented, along with the main techniques adopted for each approac

Term-based composition of security protocols

In the context of security protocol parallel composition, where messages belonging to different protocols can intersect each other, we introduce a new paradigm: term-based composition (i.e. the composition of message components also known as terms). First, we create a protocol specification model by extending the original strand spaces. Then, we provide a term composition algorithm based on which new terms can be constructed. To ensure that security properties are maintained, we introduce the concept of term connections to express the existing connections between terms and encryption contexts. We illustrate the proposed composition process by using two existing protocols.Comment: 2008 IEEE International Conference on Automation, Quality and Testing, Robotics, Cluj-Napoca, Romania, May 2008, pp. 233-238, ISBN 978-1-4244-2576-

Reasoning about recognizability in security protocols

Although verifying a message has long been recognized as an important concept, which has been used explicitly or implicitly in security protocol analysis, there is no consensus on its exact meaning. Such a lack of formal treatment of the concept makes it extremely difficult to evaluate the vulnerability of security protocols. This dissertation offers a precise answer to the question: What is meant by saying that a message can be "verified''? The core technical innovation is a third notion of knowledge in security protocols -- recognizability. It can be considered as intermediate between deduction and static equivalence, two classical knowledge notions in security protocols. We believe that the notion of recognizability sheds important lights on the study of security protocols. More specifically, this thesis makes four contributions. First, we develop a knowledge model to capture an agent's cognitive ability to understand messages. Thanks to a clear distinction between de re/dicto interpretations of a message, the knowledge model unifies both computational and symbolic views of cryptography gracefully. Second, we propose a new notion of knowledge in security protocols -- recognizability -- to fully capture one's ability or inability to cope with potentially ambiguous messages. A terminating procedure is given to decide recognizability under the standard Dolev-Yao model. Third, we establish a faithful view of the attacker based on recognizability. This yields new insights into protocol compilations and protocol implementations. Specifically, we identify two types of attacks that can be thawed through adjusting the protocol implementation; and show that an ideal implementation that corresponds to the intended protocol semantics does not always exist. Overall, the obtained attacker's view provides a path to more secure protocol designs and implementations. Fourth, we use recognizability to provide a new perspective on type-flaw attacks. Unlike most previous approaches that have focused on heuristic schemes to detect or prevent type-flaw attacks, our approach exposes the enabling factors of such attacks. Similarly, we apply the notion of recognizability to analyze off-line guessing attacks. Without enumerating rules to determine whether a guess can be "verified'', we derive a new definition based on recognizability to fully capture the attacker's guessing capabilities. This definition offers a general framework to reason about guessing attacks in a symbolic setting, independent of specific intruder models. We show how the framework can be used to analyze both passive and active guessing attacks

Proof Theory, Transformations, and Logic Programming for Debugging Security Protocols

We define a sequent calculus to formally specify, simulate, debug and verify security protocols. In our sequents we distinguish between the current knowledge of principals and the current global state of the session. Hereby, we can describe the operational semantics of principals and of an intruder in a simple and modular way. Furthermore, using proof theoretic tools like the analysis of permutability of rules, we are able to find efficient proof strategies that we prove complete for special classes of security protocols including Needham-Schroeder. Based on the results of this preliminary analysis, we have implemented a Prolog meta-interpreter which allows for rapid prototyping and for checking safety properties of security protocols, and we have applied it for finding error traces and proving correctness of practical examples

A two‐step authentication framework for Mobile ad hoc networks

The lack of fixed infrastructure in ad hoc networks causes nodes to rely more heavily on peer nodes for communication. Nevertheless, establishing trust in such a distributed environment is very difficult, since it is not straightforward for a node to determine if its peer nodes can be trusted. An additional concern in such an environment is with whether a peer node is merely relaying a message or if it is the originator of the message. In this paper, we propose an authentication approach for protecting nodes in mobile ad hoc networks. The security requirements for protecting data link and network layers are identified and the design criteria for creating secure ad hoc networks using several authentication protocols are analyzed. Protocols based on zero knowledge and challenge response techniques are presented and their performance is evaluated through analysis and simulation

Verifying privacy by little interaction and no process equivalence

While machine-assisted verification of classical security goals such as confidentiality and authentication is well-established, it is less mature for recent ones. Electronic voting protocols claim properties such as voter privacy. The most common modelling involves indistinguishability, and is specified via trace equivalence in cryptographic extensions of process calculi. However, it has shown restrictions. We describe a novel model, based on unlinkability between two pieces of information. Specifying it as an extension to the Inductive Method allows us to establish voter privacy without the need for approximation or session bounding. The two models and their latest specifications are contrasted