W.G. Chambers

Bio: W.G. Chambers is an academic researcher from King's College London. The author has contributed to research in topics: Alternating step generator & Shift register. The author has an hindex of 1, co-authored 1 publications receiving 143 citations.

Clock-controlled shift registers: a review

Abstract: Key-stream generators are discussed in which shift registers are clocked in a quasi-random manner under the control of other shift registers. They are a promising practical alternative to those using nonlinear combining functions on the outputs from regularly stepped shift registers and are now almost as well understood. Some World War II ciphers using stuttered rotors are briefly described as natural predecessors, including one cryptanalyzed on the Colossus machines. The algebraic theory is discussed, from which it is shown how large periods and linear equivalences can readily be obtained. The work of a number of authors on cascades is reviewed; these are linear hierarchies in which each register except the first is clock controlled by its predecessor. Other schemes are considered. Results on statistical properties and autocorrelation functions are quoted. >

Handbook of Applied Cryptography

Abstract: From the Publisher: A valuable reference for the novice as well as for the expert who needs a wider scope of coverage within the area of cryptography, this book provides easy and rapid access of information and includes more than 200 algorithms and protocols; more than 200 tables and figures; more than 1,000 numbered definitions, facts, examples, notes, and remarks; and over 1,250 significant references, including brief comments on each paper.

The shrinking generator

Abstract: We present a new construction of a pseudorandom generator based on a simple combination of two LFSRs. The construction has attractive properties as simplicity (conceptual and implementation-wise), scalability (hardware and security), proven minimal security conditions (exponential period, exponential linear complexity, good statistical properties), and resistance to known attacks. The construction is suitable for practical implementation of efficient stream cipher cryptosystems.

Fundamentals of Computer Security

Abstract: From the Publisher: The book studies modern concepts of Computer Security. It is selfcontained in the sense that it introduces the basic mathematical background necessary to follow computer security concepts. Next we examine modern developments in Cryptography starting from private-key and public-key encryption, going through hashing, digital signatures, authentication, secret sharing, group-oriented cryptography, pseudorandomness, key establishment protocols, zero-knowledge protocols, identification and finishing with an introduction to modern e-business systems based on digital cash. Intrusion detection and access control provide examples of security systems implemented as a part of operating system. Database and network security is also discussed.

More on average case vs approximation complexity

Abstract: We consider the problem to determine the maximal number of satisfiable equations in a linear system chosen at random. We make several plausible conjectures about the average case hardness of this problem for some natural distributions on the instances, and relate them to several interesting questions in the theory of approximation algorithms and in cryptography. Namely we show that our conjectures imply the following facts: (1) Feige's hypothesis about the hardness of refuting a random 3CNF is true, which in turn implies inapproximability within a constant for several combinatorial problems, for which no NP-hardness of approximation is known. (2) It is hard to approximate the nearest codeword within factor n/sup 1 - /spl epsi//. (3) It is hard to estimate the rigidity of a matrix. More exactly, it is hard to distinguish between matrices of low rigidity and random ones. (4) There exists a secure public-key (probabilistic) cryptosystem, based on the intractability of decoding of random binary codes. Our conjectures are strong in that they assume cryptographic hardness: no polynomial algorithm can solve the problem on any non-negligible fraction of inputs. Nevertheless, to the best of our knowledge no efficient algorithms are currently known that refute any of our hardness conjectures.

Theory and applications of q-ary interleaved sequences

Abstract: A new class of q-ary sequences, called interleaved sequence, is introduced Their periods, shift equivalence, linear spans, and autocorrelation functions are derived The interleaved sequences include a large number of popular sequences, such as multiplexed sequences, clock-controlled sequences, Kasami (1966) sequences, GMW sequences, geometric sequences, and No (1989) sequences A special class of the interleaved sequences is constructed by mapping GF(q/sup m/) sequences into GF(q) sequences in terms of different bases of GF(q/sup m/) over GF(q) As an application of the theory of interleaved sequences, some new families of binary pseudo-random sequences are constructed, which have large linear spans, optimal periodic cross/autocorrelation functions, balance, and the rapidly "hopped" properties A complete comparison of the new family of sequences with the Gold sequence family, the Kasami (small and large set) sequence families, the Bent-function sequence family, and the No sequence family is discussed This shows that the new sequence families have important advantages for use in spread-spectrum multiple-access communication systems >