HASH FUNCTION SECURITY, ACTA UNIVERSITATIS OULUENSIS C Technica 433
|Kustantaja:||Oulun yliopisto|| |
|Sijainti:||Print Tietotalo|| |
|Tekijät:||HALUNEN KIMMO|| |
In recent years, the amount of electronic communication has grown enormously. This has posedsome new problems in information security. In particular, the methods in cryptography have beenunder much scrutiny. There are several basic primitives that modern cryptographic protocolsutilise. One of these is hash functions, which are used to compute short hash values from messagesof any length. In this thesis, we study the security of hash functions from two different viewpoints. First ofall, we analyse the security of the Very Smooth Hash against preimage attacks. We develop animproved method for finding preimages of Very Smooth Hash, compare this method with existingmethods and demonstrate its efficiency with practical results. Furthermore, we generalise thismethod to the discrete logarithm variants of the Very Smooth Hash. Secondly, we describe the methods for finding multicollisions in traditional iterated hashfunctions and give some extensions and improvements to these. We also outline a method forfinding multicollisions for generalised iterated hash functions and discuss the implications of thesefindings. In addition, we generalise these multicollision finding methods to some graph-basedhash functions.