Polytopic Cryptanalysis

Standard differential cryptanalysis uses statistical dependencies between the difference of two plaintexts and the difference of the respective two ciphertexts to attack a cipher. Here we introduce polytopic cryptanalysis which considers interdependencies between larger sets of texts as they traverse through the cipher. We prove that the methodology of standard differential cryptanalysis can unambiguously be extended and transferred to the polytopic case including impossible differentials. We show that impossible polytopic transitions have generic advantages over impossible differentials. To demonstrate the practical relevance of the generalization, we present new low-data attacks on round-reduced DES and AES using impossible polytopic transitions that are able to compete with existing attacks, partially outperforming these

Security Analysis Techniques Using Differential Relationships For Block Ciphers

The uses of block cipher has become crucial in nowadays’ computing era as well as the information security. Information must be available only for authenticated and authorized users.However,flaws and weaknesses in the cryptosystem can breach the security of stored and transmitted information.A weak key in the key schedule is well-known issues which may affect several round keys have same bits in common.Besides,information leaked from the implementation also affects the security of block ciphers.Based on the flaws and leakage,the adversary is able to assess the differential relationships in block cipher using differential cryptanalysis technique. Firstly,the existing differential cryptanalysis techniques have been evaluated.Secondly,based on the gaps that have to be filled in the existing differential cryptanalysis techniques,new frameworks of differential cryptanalysis techniques have been proposed and designed by using Pearson correlation coefficient,Hamming-weight leakage assumption and reference point.The Pearson correlation coefficient is used to determine the repeated differential properties in the key schedules.Meanwhile, reference point and Hamming-weight leakage assumption are used to assess the security of the implementation of block ciphers against side-channel cube attack and differential fault analysis.Thirdly,all proposed frameworks have been assessed.The results show that the repeated differential properties are found for AES, PRESENT and Simeck key schedules.However,AES key schedule is definitely ideal to be adopted in the design for the future cryptographic algorithm.In addition,the newly designed frameworks for side-channel differential analysis techniques have been able to reduce the attack complexities for Simeck32/64,KATAN32 and KTANTAN32 compared to previous work.In conclusion,the proposed frameworks are effective in analyzing the security of block ciphers using differential cryptanalysis techniques

Multiple Differential Cryptanalysis: Theory and Practice (Corrected)

Differential cryptanalysis is a well-known statistical attack on block ciphers. We present here a generalisation of this attack called multiple differential cryptanalysis. We study the data complexity, the time complexity and the success probability of such an attack and we experimentally validate our formulas on a reduced version of PRESENT. Finally, we propose a multiple differential cryptanalysis on 18-round PRESENT for both 80-bit and 128-bit master keys