TY - THES

T1 - Cryptanalysis of Some Block Ciphers

AU - Haji Naim, Abdul Ghani

PY - 2016

Y1 - 2016

N2 - 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 Although these ciphers may have been superseded by recent advances, there are lessons to be learnt in the art of cryptanalysis by studying them.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 concentratingon the use of distinguishers to determine the strength or weakness of the block cipher based on known statistics.

AB - 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 Although these ciphers may have been superseded by recent advances, there are lessons to be learnt in the art of cryptanalysis by studying them.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 concentratingon the use of distinguishers to determine the strength or weakness of the block cipher based on known statistics.

KW - Cryptanalysis

KW - Block ciphers

M3 - Doctoral Thesis

ER -