The differential cryptanalysis and design of natural stream ciphers

Abstract

This paper introduces the differential cryptanalysis of additive stream ciphers, and develops its theoretical basis. The relationships between differential and other types of stream cipher analysis are presented. The conservation laws of patterns and of mutual information are derived. The cryptographic significance of pattern distribution of keystream sequences is shown. The cryptographic transformation densities are introduced, and their relations with other cryptographic factors are summarized. This work is illustrated by reference to the design and security of additive natural stream ciphers, which are nonlinear filtered sequences driven by a counter rather than by a shift register.