Fred Piper

Key storage in secure networks

Abstract In this paper the key storage problem associated with the provision of secure communications between every pair of users in a large network is described, and a possible method of alleviating the problem is discussed. This method, based on the use of finite incidence structures with special properties called key distribution patterns, is shown to generalize earlier work in the area. The more general formulation of the storage saving scheme contained here enables use to made of the extensive body of knowledge already existing on the theory of block designs. From this theory we are able to extract a number of new families of examples of potentially useful key distribution systems.

The stop-and-go generator

Under the correct assumptions cascading of primitive shift registers leads to interesting results. But from Gollmann’s work it is clear that general results on cascaded arbitrary shift registers cannot be expected.

A general zero-knowledge scheme

There is a great similarity between the Fiat-Shamir zero-knowledge scheme [8], the Chaum-Evertse-van de Graaf [4], the Beth [1] and the Guillou-Quisquater [12] schemes. The Feige-Fiat-Shamir [7] and the Desmedt [6] proofs of knowledge also look alike. This suggests that a generalization is overdue. We present a general zero-knowledge proof which encompasses all these schemes.

A General Zero-Knowledge Scheme

There is a great similarity between the zero-knowledge proof of quadratic residuocity presented by Goldwasser-Micali-Rackoff and the graph isomorphism proof presented by Goldreich-Micali-Wigderson. There is also a resemblance between the zero-knowledge proofs of Fiat-Shamir, Chaum-Evertse-van de Graaf, Beth and Guillou-Quisquater. A similar observation holds for zero-knowledge proofs based on encryption: the 3-colourability proofs and the Hamiltonian-circuit proofs of Blum and Goldreich-Micali-Wigderson, and the Brassard-Chaum-Crepeau proof for SAT. Feige, Fiat and Shamir introduced the concept of zero-knowledge proofs of knowledge. In this paper we present a general zero-knowledge scheme which unifies all these Arthur-Merlin proofs.

The cost of reducing key-storage requirements in secure networks

In large secure networks where each node needs to have the capability to communicate securely with every other node, the key storage requirement can become a significant problem. Various authors have suggested methods for using combinatorial and algebraic techniques to ease this storage problem. However, the use of such schemes can result in an unacceptable reduction of security. Therefore in this paper we list some formal requirements for a key distribution scheme and show that one of the proposed schemes fails to satisfy them.

The status of National PKIs - A European overview

A series of European Union initiatives and frameworks have been issued during the last years, for the provision of electronic services to individuals, businesses and government organizations. Most of these efforts imply the use of digital certificates for a wide variety of national and transnational transactions. This paper presents the concept of National PKI through a systemic view, compares and contrasts the main inhibitors and enablers, discusses popular use cases, and also examines the European landscape together with open issues.

Perfect binary arrays and difference sets

Abstract A perfect binary array is an r -dimensional array with elements ± 1 such that all out-of-phase periodic autocorrelation coefficients are zero. Such an array is equivalent to a Menon difference set in an abelian group. We give recursive constructions for four infinite families of two-dimensional perfect binary arrays, using only elementary methods. Brief outlines of the proofs were previously given by three of the authors. Although perfect binary arrays of the same sizes as two of the families were constructed earlier by Davis, the sizes of the other two families are new.

Ten Years of Information Security Masters Programmes

Royal Holloway launched its MSc programme in Information Security in 1992. In the subsequent ten years this programme has grown steadily in popularity, with just over 250 students registered in the current 2002-2003 session. In this paper we reflect on the apparent success of the first ten years of the programme and comment on a number of issues that we feel have wider relevance to information security education programmes in general. We also discuss some challenges facing such programmes in the future and how we propose to address them.

Linear recursion properties of uncorrelated binary sequences

Abstract A proof is provided that a finite sequence which is balanced and uncorrelated cannot satisfy the linear recursion property expected of a randomly generated finite binary sequence. A corollary of this applies the result to PN-sequences (which additionally have optimal run statistics). The proof is obtained by establishing a tight upper bound on the linear complexity of uncorrelated sequences which are based on Hadamard difference sets.

Recent Developments in Cryptography

This talk is in two halves. In the first we give an introductory overview of the ‘classical’ encryption techniques and look at their relative merits. This is an abridged form of[Mit2]. Then, in the second half, we look at some recent developments; notably the arrival of public key cryptography. The aim is to illustrate various applications of public key systems and to motivate the lectures of I.F. Blake and Y. Desmedt.