Analysis of the design methods of word oriented linear feedback shift registers

Based on analysis of the structure characteristics and implementation methods of some representative word oriented linear feedback shift registers (LFSRs) in several modern software oriented stream ciphers, this paper firstly classifies the word oriented LFSRs into two classes: the machine instruction type and the arithmetic type. The similarities and differences between each type are illustrated by concrete examples. Then we give a detailed analysis about the word oriented LFSRs in each category from design structure, cryptographic properties and implementation issue aspects. Finally, some basic design criteria for modern word oriented LFSRs and suitable for software implementation are summarized. Biorgraphy: ZENG Guang(1980–), male, Ph. D. candidate, research direction: cryptography and their application, stream cipher.