Design Principles for Iterated Hash Functions

This paper deals with the security of iterated hash functions against generic attacks, such as, e.g., Joux’ multicollision attacks from Crypto 04 [6]. The core idea is to increase the size of the internal state of an n-bit hash function to w > n bit. Variations of this core idea allow the use of a compression function with n output bits, even if the compression function itself is based on a block cipher. In a formal model, it is shown that these modifications quantifiably improve the security of iterated hash functions against generic attacks.