Observing biases in the state: case studies with Trivium and Trivia-SC

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• 作者：Santanu Sarkar ; Subhamoy Maitra ; Anubhab Baksi
• 关键词：Cryptanalysis ; Cube tester ; Slide attack ; Stream cipher ; Trivium ; Trivia ; SC
• 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：351-375
• 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

One generic model of stream cipher considers updating the states and then combining the state bits to produce the key-stream. In case there are biases in the state bits, that may be reflected on the key-stream bits resulting certain weaknesses (distinguisher and/or key recovery) of the cipher. In this context, we study the state biases as well as key-stream biases with great details. We first experiment with cube testers and heuristically obtain several distinguishers for Trivium running more than 800 rounds (maximum 829) with cube sizes not exceeding 27. Further, we apply our techniques to analyze Trivia-SC (the stream cipher used in TriviA-ck AEAD scheme, selected in second round of CAESAR competition) and obtain distinguishers till 950 rounds with a cube size of 25 only. On Trivia-SC, our results refute certain claims made by the designers against both cube and slide attacks. Our detailed empirical analysis provides new results in reduced-round cryptanalysis of Trivium and Trivia-SC.