Stream ciphers pdf

Translate PDF. This paper describes a fast software stream cipher called Fish based on the shrinking principle applied to the lagged Fibonacci generator Fish - Fibonacci shrinking. It is designed to make full use of the 32 bit word length of popular processors.

It is based on linear shift registers with linear feedback. The output bits of one shift register decide which of the output bits of the other shift registers are used and which are discarded. The design is well suited for hardware implementation.

In software shift registers are not very efficient because each machine instruction operates on a single bit only. The remaining bits in the registers of the processor are unused. In this paper we suggest an algorithm called Fish. We apply the shrinking principle to a stream cipher based on the lagged Fibonacci generator [KnuS1] Fish - F ibonacci shrinking. We use the full 32 bit wordlength of popular pro- cessors in order to achieve a high data rate.

We consider two pseudo random generators A and S. A produces a sequence a0, a l ,. S produces a sequence so, s l ,. In the original shrinking generator only elements genererated by A are accepted or discarded, in our generalization the results of S are treated the same. Another difference of our scheme is that the accepted elements are not yet the final result, another stage of processing is needed.

Reference - P. Ekdahl, T. Cryptography: Theory and Practice. Stream Cipher. Mantin, I. Weakness in the key scheduling algorithm of RC4. Galanis, P. Kitsos, G. Kostopoulos, O. Batina, J. It covers the mathematics of stream ciphers and its history, and also discusses many modern examples and their robustness against attacks.

Part I covers linear feedback shift registers, non-linear combinations of LFSRs, algebraic attacks and irregular clocked shift registers. Part II studies some special ciphers including the security of mobile phones, RC4 and related ciphers, the eStream project and the blum-blum-shub generator and related ciphers.

Stream Ciphers requires basic knowledge of algebra and linear algebra, combinatorics and probability theory and programming. Appendices in Part III help the reader with the more complicated subjects and provides the mathematical background needed.

It covers, for example, complexity, number theory, finite fields, statistics, combinatorics. Stream Ciphers concludes with exercises and solutions and is directed towards advanced undergraduate and graduate students in mathematics and computer science. Get BOOK. Stream Ciphers. Unlike block ciphers, stream ciphers work on single bits or single words and need to.

Stream Ciphers and Number Theory. Authors: Thomas W.