Cryptanalysis of Some Block Ciphers

Abdul Ghani Haji Naim

Research output: ThesisDoctoral Thesis

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This thesis concerns the cryptanalysis of block ciphers and we look at two important examples: the Data Encryption Standard DES and the cipher RC5 proposed by Rivest. Although these ciphers may have been superseded by recent advances, there are lessons to be learnt in the art of cryptanalysis by studying them. The first half of our thesis focuses on the reduced variant of DES i.e. the 8-round version. We discussed the implementation of DES and various cryptanalytic attacks on 8-round DES such as, differential cryptanalysis, linear cryptanalysis, Differential-Linear cryptanalysis and also the use of multiple linear approximations in Differential-Linear cryptanalysis. By performing these cryptanalytic attacks on a PC, we were able to gain insight into the processes/steps involved in performing cryptanalysis and we were able to gauge the feasibility of the attacks with respect to the computing power of a normal PC. We discovered a different implementation when we used multiple linear approximations in Differential-Linear cryptanalysis of 8-round DES which gives experimental result comparable to previously known result based on similar attack. The second half of our thesis focuses on a comparative study of cryptanalytic attacks on both DES and RC5 block ciphers mainly concentrating
on the use of distinguishers to determine the strength or weakness of the block cipher based on known statistics.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Mitchell, Chris, Supervisor
Award date1 Mar 2016
Publication statusUnpublished - 2016


  • Cryptanalysis
  • Block ciphers

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