ISSN: 1813-0410

Author : Ali Mohammed Al, Hussein

Frequency Postulate's Theoretical Calculation for the Sequences Produced by Modified Geffe Generator

Sharifi; Hussein Ali Mohammed Al

journal of kerbala university, Volume 10, Issue 0, Pages 199-208

The Randomness is one of the basic criterions to measure stream cipher efficiency. The stream cipher generator depends basically on Linear FeedBack Shift Register (LFSR) which is considered as one of the basic units of Stream Cipher Systems (SCS).
The basic idea of this paper is attacking and analysis of cryptosystems. So any developing in some kinds of stream cipher generators without taking in considers the basic criteria of efficiency may give no security to the generator, so this paper consists of two parts
First, the design part, this paper introduces developing of Geffe generator by increasing the LFSR's from (three) to (five) with new combining nonlinear function which has good statistical properties. The new generator called Modified Geffe generator.
Second, the attacking part, the frequency postulate of randomness criteria is calculated theoretically, this mean the generated sequence product by the new generator can estimated and this mean clear weakness in the suggested generator.