THF: Designing Low-Latency Tweakable Block Ciphers

We introduce the Three-Hash Framework (THF), a new instantiation of the LRW+ paradigm that employs three hash functions to process tweak inputs. We prove that THF achieves beyond-birthday-bound security under standard assumptions. By extending the general practical cryptanalysis framework to the multiple-tweak setting, we further demonstrate that THF offers balanced resistance to both singleand multiple-tweak attacks, thereby enabling the potential for lower latency compared to existing constructions. Building on this framework, we design Blink, a family of tweakable block ciphers optimized for ultra-low latency. Blink features logarithmic-depth Toeplitz-based hashing, which ensures efficient diffusion and scalability with varying tweak lengths. Our cryptanalysis shows that Blink achieves strong security with fewer rounds, while hardware evaluations confirm its superior latency performance. Notably, Blink maintains comparable latency even when the tweak length is doubled, underscoring the scalability advantage of THF.