BAN - A Logic of Authentication Essay Example | Topics and Well Written Essays - 2250 words

BAN - A Logic of Authentication - Essay Example As a result, Borrows, Abadi and Needham formulated a logic of belief and action, to address these errors. The logic allows people to formally describe the beliefs of trustworthy parties involved in these authentication protocols, thus uncovering subtleties, redundancies and flaws through an analysis of the protocols’ syntax and semantics. Borrows, Abadi and Needham take four published protocols into account, in order to show how they illustrate the appropriateness of this logical method of analysis. But how sound is the logic that they are proposing? How far can a vague and ambiguous logic take us? This paper aims to introduce the famous BAN (Borrows, Abadi and Needham) logic and it’s use on one of the published protocols (i.e. Kerberos), to discuss the logic’s success, its successors, and to review the critiques made on the logic. This paper is based on the article †A Logic of Authentication† published in 1989 by the authors Michael Burrows, Martin A badi and Roger Needham, University of Cambridge. The paper was nominated for publication in TOCS by the Program Committee for the ACM SIGOPS Symposium on Operating Systems Principles, December 1989. The three authors completed part of this work at Digital Equipment Corporation and part at the University of Cambridge. 2 Chapter 2 Introduction In this chapter a brief introduction to the basic principles of the BAN logic is discussed as well as a short section about security protocols. 2.1 An Introduction to Borrows, Abadi, Need- ham (BAN) Logic The BAN Logic is named after Borrows, Abadi and Needham. The logic is, as they stated, a logic of belief and action. It contains no logical inversions; therefore it cannot be used to prove that a protocol is flawed. But when proof, that a protocol is correct, cannot be obtained, that protocol deserves to be treated with suspicion [?]. In other words BAN logic does not aim to prove the security of a protocol; it can only catch certain kinds of s ubtle errors, help us to reason about the protocol, and help us identify and formalize our assumptions and analysis. Details of the BAN logic such as the idealization of protocol transactions, along with the various inference rules, will be discussed on the later sections. The authors of †A Logic of Authentication† introduce the BAN logic to protocol designers whom they believe are inappropriately copying available techniques; thus coming up with protocols containing many security flows. The authors explain the basic notation of the logic and five rules that are applied to analyze protocols. Afterwards, they move on to actually idealize different existing protocols to conclude that such a simple logic can capture subtle differences between protocols. If there is one thing that the authors forgot to mention, that would be the basic definitions of frequently used terms. So in this paper I will try my best to define those terms. 3 CHAPTER 2. INTRODUCTION 4 2.1.1 Security Pr otocols A security protocol usually uses cryptography to distribute messages, authenticate the communicating parties and protects data over an insecure network. It can be defined as a set of transactions or traces. Each transaction consists of a series of communication events, some of which are perhaps interleaved protocol runs. Every desirable