| Summary: | This thesis focuses on the cryptanalysis of symmetric-key cryptography, one of the most important branches of modern cryptography. The research spans two aspects of cryptanalysis. Studying cryptanalysis provides better evaluation on the security of symmetric-key primitives. At first, we develop a new tool of boomerang attack and apply it to the analysis of the block cipher AES and the tweakable block cipher Deoxys-BC. We then introduce the technique of structure to key materials for the first time, with the help of which the currently best related key
attack on full-round AES-256 can be improved. Lastly, we improve the meet-in-the-middle preimage attacks on AES hashing modes. Aside from providing security evaluation, cryptanalysis can also be used intentionally to create weakness in a cipher, so-called backdoor. We propose the MALICIOUS framework, a new method to build tweakable block ciphers that have backdoors hidden, based on differential cryptanalysis. A concrete instantiation of this framework named LowMC-M is then proposed.
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