| Cryptographic hash functions are a vital part of our current computer systems. They are a core component of digital signatures, message authentication codes, file checksums, and many other protocols and security schemes. Recent attacks against well-established hash functions have led NIST to start an international competition to develop a new hashing standard to be named SHA-3.;In this thesis, we provide cryptanalysis of some of the SHA-3 candidates. We do this using a new cryptanalytical technique introduced a few months ago called cube attacks. In addition to summarizing the technique, we build on it by providing a framework for estimating its potential effectiveness for cases too computationally expensive to test. We then show that cube attacks can not only be applied to keyed cryptosystems but also to hash functions by way of a partial preimage attack. We successfully apply this attack to reduced-round variants of the ESSENCE and Keccak SHA-3 candidates and provide a detailed analysis of how and why the cube attacks succeeded. We also discuss the limits of theoretically extending these attacks to higher rounds. Finally, we provide some preliminary results of applying cube attacks to other SHA-3 candidates. |
