Design of New Algorithms to Analyze RC4 Cipher Based on Its Biases

Abstract

RC4 is an effective stream cipher and it is more popular. It is fast, simple and suitable for software and hardware. It is used in many applications, it was analyzed by different researchers and several weaknesses were detected, these weaknesses in the distribution of key stream bytes, the first few key stream bytes of PRNG are biased or related to some secret key bytes and thus the analysis of key stream bytes makes it possible to attack RC4, and there is a correlation between the key stream bytes that make it weak and breakable by single and double byte bias attack. Analyzing these bytes makes them probable for attacking RC4. This chapter shows the analysis of RC4 key stream based on its single and double byte biases by using new designed algorithms that calculate the bias in a standard time (few seconds for single bias and few minutes for double bias). Also, shows the single byte bias attack on RC4 by using the newly designed algorithm. The results showed that the bias of RC4 keystream proved and got the same results that shown previously with less time and could retrieve the first 32 bytes of the plain text by using the proposed algorithm of single byte bias attack with a probability of 100%. The analysis of 256 positions required additional requirements such as supercomputer and message passing interface (MPI) environment that not available in Iraq, therefore; the analysis is done for 32 positions to reduce the search space