Revisiting (nested) Roos bias in RC4 key scheduling algorithm

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• 作者：Santanu Sarkar ; Ayineedi Venkateswarlu
• 关键词：Stream cipher ; Cryptanalysis ; RC4 ; Roos bias
• 刊名：Designs, Codes and Cryptography
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：82
• 期：1-2
• 页码：131-148
• 全文大小：
• 刊物类别：Mathematics and Statistics
• 刊物主题：Combinatorics; Coding and Information Theory; Data Structures, Cryptology and Information Theory; Data Encryption; Discrete Mathematics in Computer Science; Information and Communication, Circuits;
• 出版者：Springer US
• ISSN：1573-7586
• 卷排序：82

文摘

RC4 is one of the most popular stream cipher with wide industrial applications, it has received serious attention in cryptology literature in the last 2 decades. In 1995, Roos pointed out that the elements \(S_N[y]\) of the permutation \(S_N\) after the key scheduling algorithm for the first few values of y are biased to certain combinations of secret key bytes. These correlations were theoretically studied by Paul and Maitra (SAC, 2007). The formula for the correlation probabilities provided by them gives a wrong impression that the probabilities decrease as the value of y becomes larger, which is not true. In this paper, we point out some gaps in their analysis and present a detailed analysis of Roos bias. We provide a more accurate formula for the correlation probabilities. We further study nested Roos type biases and present comparison results. These types of biases are used to reconstruct key from the permutation \(S_N\) for better success probability.