Design and analysis of hash functions

Koçak, Onur
Hash functions are cryptographic tools that are used in various applications like digital signature, message integrity checking, password storage and random number generation. These cryptographic primitives were, first, constructed using modular arithmetical operations which were popular at that time because of public key cryptography. Later, in 1989, Merkle and Damgard independently proposed an iterative construction method. This method was easy to implement and had a security proof. MD-4 was the first hash function to be designed using Merkle-Damgard construction. MD-5 and SHA algorithms followed MD-4. The improvements in the construction methods accordingly resulted in improvements and variations of cryptanalytic methods. The series of attacks of Wang et al. on MD and SHA families threaten the security of these hash functions. Moreover, as the standard hashing algorithm SHA-2 has a similar structure with the mentioned hash functions, its security became questionable. Therefore, NIST announced a publicly available contest to select the new algorithm as the new hash standard SHA-3. The design and analysis of hash functions became the most interesting topic of cryptography. A considerable number of algorithms had been designed for the competition. These algorithms were tested against possible attacks and proposed to NIST. After this step, a worldwide interest started to check the security of the algorithms which will continue untill 4th quarter of 2011 to contribute to the selection process. This thesis presents two important aspects of hash functions: design and analysis. The design of hash functions are investigated under two subtopics which are compression functions and the construction methods. Compression functions are the core of the hashing algorithms and most of the effort is on the compression function when designing an algorithm. Moreover, for Merkle-Damgard hash functions, the security of the algorithm depends on the security of the compression function. Construction method is also an important design parameter which defines the strength of the algorithm. Construction method and compression function should be consistent with each other. On the other hand, when designing a hash function analysis is as important as choosing designing parameters. Using known attacks, possible weaknesses in the algorithm can be revealed and algorithm can be strengthened. Also, the security of a hash function can be examined using cryptanalytic methods. The analysis part of the thesis is consisting of various generic attacks that are selected to apply most of the hash functions. This part includes the attacks that NIST is expecting from new standard algorithm to resist.


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Öztop, Neşe; Doğanaksoy, Ali; Department of Cryptography (2009)
Cryptanalytic methods are very important tools in terms of evaluating the security of block ciphers in a more accurate and reliable way. Differential and linear attacks have been the most effective cryptanalysis methods since the early 1990s. However, as the technology developed and more secure ciphers are designed, these fundamental methods started to be not so efficient. In order to analyze the ciphers, new methods should be introduced. One approach is inventing new techniques that are different from the ...
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Sönmez Turan, Meltem; Doğanaksoy, Ali; Department of Cryptography (2008)
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Sulak, Fatih; Doğanaksoy, Ali; Department of Cryptography (2011)
One of the most basic properties expected from block ciphers and hash functions is passing statistical randomness testing, as they are supposed to behave like random mappings. Previously, testing of AES candidate block ciphers was done by using the statistical tests defined in the NIST Test Suite. As some of the tests in this suite require long sequences, data sets are formed by concatenating the outputs of the algorithms obtained from various input types. However, the nature of block cipher and hash functi...
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The ring signature scheme has a wide range of usage areas in public-key cryptography. One is leaking information within a group without exposing the signer's identity. The majority of the ring signature techniques in use, on the other hand, rely on classical crypto-systems such as RSA and ECDH, which are known to be vulnerable to Shor's algorithm on a large-scale quantum computer. In this thesis, we propose efficient quantum-resistant ring signature schemes based on GeMSS and Gui signature algorithms. Gui w...
Citation Formats
O. Koçak, “Design and analysis of hash functions,” M.S. - Master of Science, Middle East Technical University, 2009.