An improved attack on clock-controlled shift registers based on hardware implementation

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• 作者：Lei Li (1)
  XiangHui Liu (1)
  Zheng Wang (1)
  FengHua Li (2)
  
• 关键词：stop/go clocking ; A5/1 ; state space convergence ; SMITH ; special ; purpose hardware
• 刊名：SCIENCE CHINA Information Sciences
• 出版年：2013
• 出版时间：November 2013
• 年：2013
• 卷：56
• 期：11
• 页码：1-10
• 全文大小：
• 作者单位：Lei Li (1)
  XiangHui Liu (1)
  Zheng Wang (1)
  FengHua Li (2)
  
  1. Department of Applied Mathematics, Zhengzhou Information Science and Technology Institute, Zhengzhou, 450002, China
  2. Institute of Information Engineering, Chinese Academy of Sciences, Beijing, 100195, China
  
• ISSN：1869-1919

文摘

We cryptanalyze a type of stream generator with three linear-feedback shift registers that are mutually clocked in a stop/go manner and have the property of sequences of state space convergence. By guessing the clock-controlled sequence and employing a backtracking search, we propose an algorithm attack on the type of stream generator based on hardware implementation. In particular, the time complexity of the algorithm attacking the encryption algorithm A5/1 is 243.869 clock periods. With our hardware architecture, we investigate the implementation of the algorithm on field programmable gate array and application-specific integrated circuit for an attack on A5/1. As a result, we can retrieve the initial states of A5/1’s registers in 2 s on average without pre-computation if we have 64 known key-stream bits.