Improving the Message Expansion of the Tangle Hash Function

摘要

Tangle is an iterative one-way hash function based on the Merkle-Damgard scheme strengthened by a message dependent round function. It was submitted to the NIST SHA-3 competition, being accepted for first round evaluation. We propose an alternative message expansion scheme for Tangle in order to thwart the collision attacks found during such evaluation. Based on the fact that differences at the beginning of the expanded message contribute to better avalanche, the improved message expansion scheme presents much better properties than the original version while maintaining very good performance characteristics.