2,738 research outputs found
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
Symmetric block ciphers with a block length of 32 bit
Subject of the thesis at hand is the analysis of symmetric block ciphers with a block length of 32 bit. It is meant to give a comprising overview over the topic of 32 bit block ciphers. The topic is divided in the examination of three questions. It contains a list of state of the art block ciphers with a block length of 32 bit. The block ciphers are being described, focussing on the encryption function. An SPN-based cipher with 32 bit block length is being proposed by rescaling the AES cipher.
The 32 bit block length results in certain security issues. These so called risk factors are analysed and mitigating measures are proposed. The result of the thesis is, that 32 bit block ciphers can be implemented in a secure manner. The use of 32 bit ciphers should be limited to specific use-cases and with a profound risk analysis, to determine the protection class of the data to be encrypted
General Classification of the Authenticated Encryption Schemes for the CAESAR Competition
An Authenticated encryption scheme is a scheme which provides privacy and integrity by using a secret key. In 2013, CAESAR (the ``Competition for Authenticated Encryption: Security, Applicability, and Robustness\u27\u27) was co-founded by NIST and Dan Bernstein with the aim of finding authenticated encryption schemes
that offer advantages over AES-GCM and are suitable for widespread adoption.
The first round started with 57 candidates in March 2014; and nine of these
first-round candidates where broken and withdrawn from the competition. The
remaining 48 candidates went through an intense process of review, analysis
and comparison. While the cryptographic community benefits greatly from the
manifold different submission designs, their sheer number
implies a challenging amount of study. This paper provides
an easy-to-grasp overview over functional aspects, security parameters, and
robustness offerings by the CAESAR candidates, clustered by their underlying
designs (block-cipher-, stream-cipher-, permutation-/sponge-,
compression-function-based, dedicated). After intensive review and analysis of all 48 candidates by the community, the CAESAR committee selected only 30 candidates for the second round. The announcement for the third round candidates was made on 15th August 2016 and 15 candidates were chosen for the third round
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