Attack analysis of cryptographic protocols using strand spaces

Security protocols make use of cryptographic techniques to achieve goals such as confidentiality, authentication and integrity. However, the fact that strong cryptographic algorithms exist does not guarantee the security of a communications system. In fact, it is recognised that the engineering of security protocols is a challenging task, since protocols that appear secure can contain subtle flaws that attackers can exploit. A number of techniques exist for the analysis of security protocol specifications. Individually they are not capable of detecting every possible flaw or attack against a protocol. However, when combined, these techniques all complement each other, allowing a protocol engineer to obtain a more accurate overview of the security of a protocol that is being designed. This is the rationale for multi-dimensional security protocol engineering, a concept introduced by previous projects of ours over several years. We propose an attack construction approach to security protocol analysis within a multi-dimensional context. This analysis method complements the existing inference construction analysis tools developed earlier in the group. We give a brief overview of the concepts associated with the project, including a summary of existing security protocol analysis techniques, and a description of the strand space model, which is the intended formalism for the analysis

Attack Analysis of Cryptographic Protocols Using Strand Spaces

Network security protocols make use of cryptographic techniques to achieve goals such as confidentiality, authentication, integrity and non-repudiation. However, the fact that strong cryptographic algorithms exist does not guarantee the security of a communications system. In fact, it is recognised that the engineering of security protocols is a very challenging task, since protocols that appear secure can contain subtle flaws and vulnerabilities that attackers can exploit. A number of techniques exist for the analysis of security protocol specifications. Each of the techniques currently available is not capable of detecting every possible flaw or attack against a protocol when used in isolation. However, when combined, these techniques all complement each other and allow a protocol engineer to obtain a more accurate overview of the security of a protocol that is being designed. This fact, amongst others, is the rationale for multi-dimensional security protocol engineering, a concept introduced by previous projects in the DNA group. We propose an attack construction approach to security protocol analysis within a multi-dimensional context. This analysis method complements the method used in the existing inference construction analysis tools developed earlier in the group. This paper gives a brief overview of the concepts associated with our project, including a summary of existing security protocol analysis techniques, and a description of the strand space model, which is the intended formalism for the analysis

Fair Exchange in Strand Spaces

Many cryptographic protocols are intended to coordinate state changes among principals. Exchange protocols coordinate delivery of new values to the participants, e.g. additions to the set of values they possess. An exchange protocol is fair if it ensures that delivery of new values is balanced: If one participant obtains a new possession via the protocol, then all other participants will, too. Fair exchange requires progress assumptions, unlike some other protocol properties. The strand space model is a framework for design and verification of cryptographic protocols. A strand is a local behavior of a single principal in a single session of a protocol. A bundle is a partially ordered global execution built from protocol strands and adversary activities. The strand space model needs two additions for fair exchange protocols. First, we regard the state as a multiset of facts, and we allow strands to cause changes in this state via multiset rewriting. Second, progress assumptions stipulate that some channels are resilient-and guaranteed to deliver messages-and some principals are assumed not to stop at certain critical steps. This method leads to proofs of correctness that cleanly separate protocol properties, such as authentication and confidentiality, from invariants governing state evolution. G. Wang's recent fair exchange protocol illustrates the approach

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

Automatic analysis of distance bounding protocols

Distance bounding protocols are used by nodes in wireless networks to calculate upper bounds on their distances to other nodes. However, dishonest nodes in the network can turn the calculations both illegitimate and inaccurate when they participate in protocol executions. It is important to analyze protocols for the possibility of such violations. Past efforts to analyze distance bounding protocols have only been manual. However, automated approaches are important since they are quite likely to find flaws that manual approaches cannot, as witnessed in literature for analysis pertaining to key establishment protocols. In this paper, we use the constraint solver tool to automatically analyze distance bounding protocols. We first formulate a new trace property called Secure Distance Bounding (SDB) that protocol executions must satisfy. We then classify the scenarios in which these protocols can operate considering the (dis)honesty of nodes and location of the attacker in the network. Finally, we extend the constraint solver so that it can be used to test protocols for violations of SDB in these scenarios and illustrate our technique on some published protocols.Comment: 22 pages, Appeared in Foundations of Computer Security, (Affiliated workshop of LICS 2009, Los Angeles, CA)

Heuristic Methods for Security Protocols

Model checking is an automatic verification technique to verify hardware and software systems. However it suffers from state-space explosion problem. In this paper we address this problem in the context of cryptographic protocols by proposing a security property-dependent heuristic. The heuristic weights the state space by exploiting the security formulae; the weights may then be used to explore the state space when searching for attacks