Paper 2024/163

On Tweakable Correlation Robust Hashing against Key Leakages

Abstract

We continue the study of blockcipher-based (tweakable) correlation robust hash functions, which are central building blocks of circuit garbling and oblivious-transfer extension schemes. Motivated by Roy (CRYPTO 2022), we first enhance the multi-user tweakable correlation robust notion of Guo et al. (CRYPTO 2020) with a {\it key leaking oracle} that tells the adversary whether a certain user key satisfies the adversarially-chosen predicate. We then investigate the state-of-the-art hash construction of Guo et al. with respect to our new security definition, providing security proof as well as matching attacks. As an application, we exhibit an OT extension protocol with non-trivial multi-user security.

Note: We have noted some errors in the previous version that hinder understanding and verifying the proof. We have corrected them. On the other hand, they don't affect the proven bounds. Meanwhile, we have generalized the multi-user definition to the setting where the u user keys are drawn from different sets, in order to support a further application (that was not mentioned in this paper).