Discovering Unknown Non-Consecutive Double Byte Biases in RC4 Stream Cipher Algorithm

Sura Mahroos^*1, Rihab Hazim ², AbdulRahman Kareem Oliwe ³, Nadia Mohammed⁴, Yaqeen Saad ⁵, Ali Makki⁶, Ibrahiem El Emary⁷

^1,2,5,6University Of Anbar, College Of Computer Sciences and Information Technology,

Anbar, Ramadi, 31001, IRAQ

³ University Of Anbar, Center for Continuing Education,

Anbar, Ramadi, 31001, IRAQ

⁴ University Of Anbar, College Of Islamic Sciences,

Anbar, Ramadi, 31001, IRAQ

⁷ King Abdulaziz University, KAU, Jeddah, 22233, SAUDI ARABIA

Emails: surasms917@uoanbar.edu.iq ; rehz1991@uoanbar.edu.iq ; tim25112019@gmail.com; nadia.fahad@uoanbar.edu.iq; yaqeen.cs91@uoanbar.edu.iq; ali_makki@uoanbar.edu.iq; omary57@hotmail.com

Abstract

RC4 is one of the most widely used stream cipher algorithms. It is fast, easy and suitable for hardware and software. It is used in various applications, but it has a weakness in the distribution of generated key bytes. The first few bytes of Pseudo-Random Generation Algorithm (PRGA) key stream are biased or attached to some private key bytes and thus the analysis of key stream bytes makes it potential to attack RC4, and there is connection between the key stream bytes that make it weak and breakable by single- and double-byte biases attack. This work shows the analysis of RC4 key stream based on its non-consecutive double byte biases by using newly designed algorithm that calculates the bias in a standard time (seconds). The results are shown that the bias of RC4 keystream is proved and got the same results that were shown in the literature with less time and discover a set of new non-consecutive double byte biases in the positions (i) and (i+n). The analysis of 256 positions is required additional requirements such as supercomputer and the message passing interface environment that are not available in Iraq, therefore; the analysis is done for 32 positions.

Keywords: RC4; Key Scheduling Algorithm (KSA); PRGA; Double Byte Bias; Non-Consecutive Double Byte Bias.