A Survey of Symbolic Methods in Computational Analysis of Cryptographic Systems

Since the 1980s, two approaches have been developed for analyzing security protocols. One of the approaches relies on a computational model that considers issues of complexity and probability. This approach captures a strong notion of security, guaranteed against all probabilistic polynomial-time attacks. The other approach relies on a symbolic model of protocol executions in which cryptographic primitives are treated as black boxes. Since the seminal work of Dolev and Yao, it has been realized that this latter approach enables significantly simpler and often automated proofs. However, the guarantees that it offers have been quite unclear. For more than twenty years the two approaches have coexisted but evolved mostly independently. Recently, significant research efforts attempt to develop paradigms for cryptographic systems analysis that combines the best of both worlds. There are two broad directions that have been followed. {\em Computational soundness} aims to establish sufficient conditions under which results obtained using symbolic models imply security under computational models. The {\em direct approach} aims to apply the principles and the techniques developed in the context of symbolic models directly to computational ones. In this paper we survey existing results along both of these directions. Our goal is to provide a rather complete summary that could act as a quick reference for researchers who want to contribute to the field, want to make use of existing results, or just want to get a better picture of what results already exist

Real-or-Random Key Secrecy of the Otway-Rees Protocol via a Symbolic Security Proof

AbstractWe present the first cryptographically sound security proof of the well-known Otway-Rees protocol. More precisely, we show that the protocol is secure against arbitrary active attacks including concurrent protocol runs if it is implemented using provably secure cryptographic primitives. We prove secrecy of the exchanged keys with respect to the accepted cryptographic definition of real-or-random secrecy, i.e., indistinguishability of exchanged keys and random ones, given the view of a general cryptographic attacker. Although we achieve security under cryptographic definitions, our proof is performed in a deterministic setting corresponding to a slightly extended Dolev-Yao model; in particular, it does not have to deal with probabilistic aspects of cryptography and is hence in the scope of current proof tools. The reason is that we exploit a recently proposed ideal cryptographic library, which has a provably secure cryptographic implementation, as well as recent results on linking symbolic and cryptographic key secrecy. Besides establishing the cryptographic security of the Otway-Rees protocol, our result also exemplifies the potential of this cryptographic library and the recent secrecy preservation theorem for symbolic yet cryptographically sound proofs of security

Cryptographically Sound Security Proof for On-Demand Source Routing Protocol EndairA

We present the first cryptographically sound security proof of a routing protocol for mobile ad-hoc networks. More precisely, we show that the route discovery protocol does not output a non-existing path under arbitrary active attacks, where on a non-existing path there exists at least one pair of neighboring nodes without communication connection during the run of the route discovery protocol. The proof relies on the Dolev-Yao-style model of Backes, Pfitzmann and Waidner, which allows for mapping results obtained symbolically within this model to cryptographically sound proofs if certain assumptions are met

Nonce-based Kerberos is a Secure Delegated AKE Protocol

Kerberos is one of the most important cryptographic protocols, first because it is the basisc authentication protocol in Microsoft\u27s Active Directory and shipped with every major operating system, and second because it served as a model for all Single-Sign-On protocols (e.g. SAML, OpenID, MS Cardspace, OpenID Connect). Its security has been confirmed with several Dolev-Yao style proofs, and attacks on certain versions of the protocol have been described. However despite its importance, despite its longevity, and despite the wealth of Dolev-Yao-style security proofs, no reduction based security proof has been published until now. This has two reasons: (1) All widely accepted formal models either deal with two-party protocols, or group key agreement protocols (where all entities have the same role), but not with 3-party protocols where each party has a different role. (2) Kerberos uses timestamps and nonces, and formal security models for timestamps are not well understood up to now. As a step towards a full security proof of Kerberos, we target problem (1) here: We propose a variant of the Kerberos protocol, where nonces are used instead of timestamps. This requires one additional protocol message, but enables a proof in the standard Bellare-Rogaway (BR) model. The key setup and the roles of the different parties are identical to the original Kerberos protocol. For our proof, we only require that the authenticated encryption and the message authentication code (MAC) schemes are secure. Under these assumptions we show that the probability that a client or server process oracle accepts maliciously, and the advantage of an adversary trying to distinguish a real Kerberos session key from a random value, are both negligible. One main idea in the proof is to model the Kerberos server a a public oracle, so that we do not have to consider the security of the connection client--Kerberos. This idea is only applicable to the communication pattern adapted by Kerberos, and not to other 3-party patterns (e.g. EAP protocols)

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

Information Assurance Protocols for Body Sensors Using Physiological Data

Griffith Sciences, School of Information and Communication TechnologyFull Tex