The 802.11 standard for wireless networks includes a Wired Equivalent Privacy (WEP) protocol, used to protect link-layer communications from eavesdropping and other attacks. We have discovered several serious security flaws in the protocol, stemming from misapplication of cryptographic primitives. The flaws lead to a number of practical attacks that demonstrate that WEP fails to achieve its security goals. In this paper, we discuss in detail each of the flaws, the underlying security principle violations, and the ensuing attacks. 1.

draft-ietf-krb-wg-kerberos-clarifications-00.txt

In a security system that allows people to choose their own passwords, those people tend to choose passwords that can be easily guessed. This weakness exists in practically all widely used systems. Instead of forcing users to choose well-chosen secrets, which are likely to be di cult to remember, we propose solutions that maintain both user convenience and a high level of security at the same time. The basic idea is to ensure that data available to the attacker is sufficiently unpredictable to prevent an off-line verification of whether a guess is successful or not. We examine common forms of guessing attacks, develop examples of cryptographic protocols that are immune to such attacks, and suggest a systematic way to examine protocols to detect vulnerabilities to such attacks.

In this paper we give a survey of the state of the art in the application of formal methods to the analysis of cryptographic protocols. We attempt to outline some of the major threads of research in this area, and also to document some emerging trends.

This paper presents a methodology to facilitate the design and analysis of secure cryptographic protocols. This work is based on a novel notion of a fail-stop protocol, which automatically halts in response to any active attack. This paper suggests types of protocols that are fail-stop, outlines some proof techniques for them, and uses examples to illustrate how the notion of a failstop protocol can make protocol design easier and can provide a more solid basis for some proposed protocol analysis methods.

The Internet Engineering Task Force (IETF) is in the process of adopting standards for IP-layer encryption and authentication (IPSEC). We describe a number of attacks against various versions of these protocols, including confidentiality failures and authentication failures. The implications of these attacks are troubling for the utility of this entire effort. 1 Introduction The Internet Engineering Task Force (IETF) is in the process of adopting standards for IP-layer encryption and authentication (IPSEC) [Atk95c, Atk95a, Atk95b, MS95, MKS95a]. While these protocols should provide a marked increase in Internet security, they themselves have had a checkered history. It is very much worth recounting the design history, not just to avoid the "oral history" problem in the IPSEC working group, but also because we as a profession learn more from knowing what doesn't work. As a wise sage 1 once said, "Learn from the mistakes of others; you'll never live long enough to make them all yours...

The history of the application of formal methods to cryptographic protocol analysis spans over 20 years and recently has been showing signs of new maturity and consolidation. Not only have a number of specialized tools been developed, and generalpurpose ones been adapted, but people have begun applying these tools to realistic protocols, in many cases supplying feedback to designers that can be used to improve the protocol’s security. In this paper, we will describe some of the ongoing work in this area, as well as describe some of the new challenges and the ways in which they are being met.

The history of the application of formal methods to cryptographic protocol analysis spans nearly twenty years, and recently has been showing signs of new maturity and consolidation. A number of specialized tools have been developed, and others have effectively demonstrated that existing general-purpose tools can also be applied to these problems with good results. However, with this better understanding of the field comes new problems that strain against the limits of the existing tools. In this paper we will outline some of these new problem areas, and describe what new research needs to be done to to meet the challenges posed.

A general method is described for formally specifying and reasoning about distributed systems with any desired degree of immediacy for revoking authentication. To effect revocation, ‘authenticating entities’ impose freshness constraints on credentials or authenticated statements made by trusted intermediaries. If fresh statements are not presented, then the authentication is questionable. Freshness constraints are derived from initial policy assumptions and authentic statements made by trusted intermediaries. By adjusting freshness constraints, the delay for certain revocation can be arbitrarily bounded. We illustrate how the inclusion of freshness policies within certificates enables the design of a secure and highly available revocation service. We illustrate the application of the method and new techniques in an example. 1.

In this paper we present a formal language for specifying and reasoning about cryptographic protocol requirements. We give sets of requirements for key distribution protocols and for key agreement protocols in that language. We look at a key agreement protocol due to Aziz and Diffie that might meet those requirements and show how to specify it in the language of the NRL Protocol Analyzer. We also show how to map our formal requirements to the language of the NRL Protocol Analyzer and use the Analyzer to show that the protocol meets those requirements. In other words, we use the Analyzer to assess the validity of the formulae that make up the requirements in models of the protocol. Our analysis reveals an implicit assumption about implementations of the protocol and reveals subtleties in the kinds of requirements one might specify for similar protocols. Introduction The past few years have seen a proliferation of formal techniques for the specification and analysis of cryptographic pro...