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.
@cite_30: A methodology is presented for using a general-purpose state enumeration tool, Mur spl phi , to analyze cryptographic and security-related protocols. We illustrate the feasibility of the approach by analyzing the Needham-Schroeder (1978) protocol, finding a known bug in a few seconds of computation time, and analyzing variants of Kerberos and the faulty TMN protocol used in another comparative study. The efficiency of Mur spl phi also allows us to examine multiple terms of relatively short protocols, giving us the ability to detect replay attacks, or errors resulting from confusion between independent execution of a protocol by independent parties.
@cite_38: We present a logic for analyzing cryptographic protocols. This logic encompasses a unification of four of its predecessors in the BAN family of logics, namely those given by Li (1990); M. Abadi, M. Tuttle (1991); P.C. van Oorschot (1993); and BAN itself (M. , 1989). We also present a model-theoretic semantics with respect to which the logic is sound. The logic presented captures all of the desirable features of its predecessors and more; nonetheless, it accomplishes this with no more axioms or rules than the simplest of its predecessors. >
@cite_33: In the past few years a lot of attention has been paid to the use of special logics to analyse cryptographic protocols, foremost among these being the logic of Burrows, Abadi and Needham (the BAN logic). These logics have been successful in finding weaknesses in various examples. In this paper a limitation of the BAN logic is illustrated with two examples. These show that it is easy for the BAN logic to approve protocols that are in practice unsound.
@cite_22: Due to the rapid growth of the “Internet” and the “World Wide Web” security has become a very important concern in the design and implementation of software systems. Since security has become an important issue, the number of protocols in this domain has become very large. These protocols are very diverse in nature. If a software architect wants to deploy some of these protocols in a system, they have to be sure that the protocol has the right properties as dictated by the requirements of the system. In this article we present BRUTUS, a tool for verifying properties of security protocols. This tool can be viewed as a special-purpose model checker for security protocols. We also present reduction techniques that make the tool efficient. Experimental results are provided to demonstrate the efficiency of BRUTUS.
@cite_8: We present an improved logic for analysing authentication properties of cryptographic protocols, based on the SVO logic of Syverson and van Oorschot (1994). Such logics are useful in electronic commerce, among other areas. We have constructed this logic in order to simplify automation, and we describe an implementation using the Isabelle theorem-proving system, and a GUI tool based on this implementation. The tool is typically operated by opening a list of propositions intended to be true, and clicking one button. Since the rules form a clean framework, the logic is easily extensible. We also present in detail a proof of soundness, using Kripke possible-worlds semantics.
@cite_41: Part I. Tutorial: 1. Introduction to ML 2. The HOL logic 3. Introduction to proof with HOL 4. Goal-oriented proof: tactics and tacticals 5. Example: a simple parity checker 6. How to program a proof tool 7. Example: the binomial theorem Part II. The Meta-Language ML: 8. The history of ML 9. Introduction and examples 10. Syntax of ML 11. Semantics of ML 12. ML types 13. Primitive ML identifier bindings 14. General purpose and list processing functions 15. ML system functions Part III. The Hol Logic: 16. Syntax and semantics 17. Theories Part IV. The Hol System: 18. The HOL logic in ML Part V. Theorem-Proving With HOL: 19. Derived inference rules 20. Conversions 21. Goal-directed proof: tactics and tacticals Appendices.
@cite_9: 
@cite_29: Authentication protocols are the basis of security in many distributed systems, and it is therefore essential to ensure that these protocols function correctly. Unfortunately, their design has been extremely error prone. Most of the protocols found in the literature contain redundancies or security flaws. A simple logic has allowed us to describe the beliefs of trustworthy parties involved in authentication protocols and the evolution of these beliefs as a consequence of communication. We have been able to explain a variety of authentication protocols formally, to discover subtleties and errors in them, and to suggest improvements. In this paper we present the logic and then give the results of our analysis of four published protocols, chosen either because of their practical importance or because they serve to illustrate our method.
@cite_21: In recent years, a method for analyzing security protocols using the process algebra CSP (C.A.R. Hoare, 1985) and its model checker FDR (A.W Roscoe, 1994) has been developed. This technique has proved successful, and has been used to discover a number of attacks upon protocols. However the technique has required producing a CSP description of the protocol by hand; this has proved tedious and error prone. We describe Casper, a program that automatically produces the CSP description from a more abstract description, thus greatly simplifying the modelling and analysis process.
@cite_1: The NRL Protocol Analyzer is a prototype special-purpose verification tool, written in Prolog, that has been developed for the analysis of cryptographic protocols that are used to authenticate principals and services and distribute keys in a network. In this paper we give an overview of how the Analyzer works and describe its achievements so far. We also show how our use of the Prolog language benefited us in the design and implementation of the Analyzer.
@cite_6: 
@cite_24: The pioneering and well-known work of M. Burrows, M. Abadi and R. Needham (1989), (the BAN logic) which dominates the area of security protocol analysis is shown to take an approach which is not fully formal and which consequently permits approval of dangerous protocols. Measures to make the BAN logic formal are then proposed. The formalisation is found to be desirable not only for its potential in providing rigorous analysis of security protocols, but also for its readiness for supporting a computer-aided fashion of analysis. >
@cite_34: A mechanism is presented for reasoning about belief as a systematic way to understand the working of cryptographic protocols. The mechanism captures more features of such protocols than that given by M. (1989) to which the proposals are a substantial extension. The notion of possession incorporated in the approach assumes that principles can include in messages data they do not believe in, but merely possess. This also enables conclusions such as 'Q possesses the shared key', as in an example to be derived. The approach places a strong emphasis on the separation between the content and the meaning of messages. This can increase consistency in the analysis and, more importantly, introduce the ability to reason at more than one level. The final position in a given run will depend on the level of mutual trust of the specified principles participating in that run. >
@cite_12: We propose a new efficient automatic verification technique, Athena, for security protocol analysis. It uses a new efficient representation - our extension to the Strand Space Model, and utilizes techniques from both model checking and theorem proving approaches. Athena is fully automatic and is able to prove the correctness of many security protocols with arbitrary number of concurrent runs. The run time for a typical protocol from the literature, like the Needham-Schroeder protocol, is often a fraction of a second. Athena exploits several different techniques that enable it to analyze infinite sets of protocol runs and achieve such efficiency. Our extended Strand Space Model is a natural and efficient representation for the problem domain. The security properties are specified in a simple logic which permits both efficient proof search algorithms and has enough expressive power to specify interesting properties. The automatic proof search procedure borrows some efficient techniques from both model checking and theorem proving. We believe that it is the right combination of the new compact representation and all the techniques that actually makes Athena successful in fast and automatic verification of security protocols.
@cite_17: This paper describes the Convince toolset for detecting common errors in cryptographic protocols, protocols of the sort used in electronic commerce. We describe using Convince to analyze confidentiality, authentication, and key distribution in a recently developed protocol proposed for incorporation into a network bill-payment system, a public-key version of the Kerberos authentication protocol. Convince incorporates a "belief logic" formalism into a theorem-proving environment that automatically proves whether a protocol can meet its goals. Convince allows an analyst to model a protocol using a tool originally designed for Computer-Aided Software Engineering (CASE).
The first formalisms designed for reasoning about cryptographic protocols are belief logics such as BAN logic @cite_29 , used by the Convince tool @cite_17 with the HOL theorem prover @cite_41 , and its generalizations (GNY @cite_34 , AT @cite_9 , and SVO logic @cite_38 which the C3PO tool @cite_8 employs with the Isabelle theorem prover @cite_6 ). Belief logics are difficult to use since the logical form of a protocol does not correspond to the protocol itself in an obvious way. Almost indistinguishable formulations of the same problem lead to different results. It is also hard to know if a formulation is over constrained or if any important assumptions are missing. BAN logic and its derivatives cannot deal with security flaws resulting from interleaving of protocol steps @cite_33 and cannot express any properties of protocols other than authentication @cite_24 . To overcome these limitations, the knowledge flow formalism has, like other approaches @cite_21 @cite_30 @cite_22 @cite_12 @cite_1 , a concrete operational model of protocol execution. Our model also includes a description of how the honest participants in the protocol behave and a description of how an adversary can interfere with the execution of the protocol.