Showing papers by "Chris J. Mitchell published in 1995"

A Proposed Architecture for Trusted Third Party Services

Abstract: In this paper we propose a novel solution to the problem of providing trusted third party services, such as the management of cryptographic keys for end-to-end encryption, in a way that meets legal requirements for warranted interception. Also included is a discussion of what might be a reasonable set of requirements for international provision of such services, as well as some analysis of the cryptographic properties of the architecture and how it might operate in practice.

Aperiodic and semi-periodic perfect maps

Abstract: Paterson (see ibid., vol.40, p.743, 1993) has shown that the trivial necessary conditions are sufficient for the existence of a (binary) perfect map. These periodic structures can be transformed very simply into corresponding aperiodic and semi-periodic perfect maps. However, aperiodic and semi-periodic perfect maps can exist for parameter sets for which the corresponding periodic perfect maps cannot. In this paper it is shown, by construction, that (binary) aperiodic and semi-periodic perfect maps exist for all possible parameter sets. >

Key distribution without individual trusted authentification servers

Abstract: Some recent research on key distribution systems has focussed on analysing trust in authentication servers, and constructing key distribution protocols which operate using a number of authentication servers, which have the property that a minority of them may be untrustworthy. This paper proposes two key distribution protocols with multiple authentication servers using a cross checksum scheme. Both protocol are based on the use of symmetric encryption for verifying the origin and integrity of messages. In these protocols it is not necessary for clients to trust an individual authentication server. A minority of malicious and colluding servers cannot compromise security and can be detected. The first 'parallel' protocol can prevent a minority of servers disrupting the service. The second 'cascade' protocol has to work with other security mechanisms in order to prevent a server breaking the procedure by refusing to cooperate. As compared with other proposed protocols with similar properties these two protocols require less exchanged messages.

A Storage Complexity Based Analogue of Maurer Key Establishment Using Public Channels

Abstract: We describe a key agreement system based on the assumption that there exists a public broadcast channel transmitting data at such a rate that an eavesdropper cannot economically store all the data sent over a certain time period. The two legitimate parties select bits randomly from this channel, and use as key bits those which they have selected in common. The work is inspired by recent work of Maurer, [3].

Minimal Weight k-SR Representations

Abstract: An algorithm for a minimal weight string replacement representation for the standard square and multiply exponentiation method is discussed, with a presentation of the design and proof of the algorithm. The performance of this new method is analysed and compared with previously proposed methods. The techniques presented in this paper have applications in speeding up the implementation of public-key cryptographic algorithms such as RSA [3].

Distributing Trust Amongst Multiple Authentication Servers

Abstract: Some recent research on key distribution systems has focussed on analysing trust in authentication servers, and constructing key distribution protocols which operate using a number of authentication servers, a minority of them may be untrusted. This paper proposes a key distribution protocol with multiple authentication servers using a cross checksum scheme. In the protocol, multiple untrusted servers generate candidate session keys for two clients. The clients use the cross checksum scheme for the verification of these candidate keys. It is not necessary for the clients to trust an individual server. A minority of corrupted and colluding servers cannot compromise security, and their inappropriate behaviour can be detected. Comparing our protocol to similar proposals, we will consider the number of messages exchanged, the length of messages, and the method of key generation.

Mathematics of dependable systems

Abstract: AW Andrews and RJ Cole: Simulated data experiment to test a software reliability growth model based on exercise frequencies JP Bowen, H Jifeng, RWS Hale and JMJ Herbert: Towards verified systems: the SAFEMOS project SK Das: Formalizing safety in decision support systems R de Lemos, A Saeed and T Anderson: Formal techniques for requirements analysis for safety-critical systems D Gollmann: Proving authentication protocols - what do authentication protocols prove? M Ingleby: A Galois theory of local reasoning in control systems with compositionality Z Liu and M Joseph: A formal framework for fault-tolerant programs Z Liu, J Nordahl and EV Sorensen: Composition and refinement of probabilistic real-time systems J May et al Fault prediction for software development processes P Mukerjee and BA Wichmann: single transferable vote: a case study of the use of VDM-SL DL Parnas: Mathematics of computation for (software and other) engineers FJ Pavey and LA Winsborrow: Formal demonstration of equivalence of source code and PROM contents: an industrial example CP Pfleeger: Uses and misuses of formal methods in computer security C Pulley and GV Coroy: Logical methods in the formal verification of safety-critical software H Zhu, PAV Hall and JHR May: Understanding software test adequacy - an axiomatic and measurement theory approach