1 A Framework for Iterative Hash Functions — HAIFA ∗

For years hash functions were built from compression functions using the Merkle-Damg̊ard construction. Recently, several flaws in this construction were identified, allowing for pre-image attacks and second preimage attacks on such hash functions even when the underlying compression functions are secure. In this paper we propose the HAsh Iterative FrAmework (HAIFA). Our framework can fix many of the found flaws while supporting several additional properties such as randomized hashing and variable hash size. HAIFA allows for an online computation of the hash function in one pass with a fixed amount of memory independent of the number of blocks in the message.