Paper 2023/746

Homomorphic Signatures for Subset and Superset Mixed Predicates and Its Applications

Abstract

In homomorphic signatures for subset predicates (HSSB), each message (to be signed) is a set. Any signature on a set $M$ allows us to derive a signature on any subset $M'\subseteq M$. Its superset version, which should be called homomorphic signatures for superset predicates (HSSP), allows us to derive a signature on any superset $M'\supseteq M$. In this paper, we propose homomorphic signatures for subset and superset mixed predicates (HSSM) as a simple combination of HSSB and HSSP. In HSSM, any signature on a message of a set-pair $(M, W)$ allows us to derive a signature on any $(M', W')$ such that $M'\subseteq M$ and $W'\supseteq W$. We propose an original HSSM scheme which is unforgeable under the decisional linear assumption and completely context-hiding. We show that HSSM has various applications, which include disclosure-controllable HSSB, disclosure-controllable redactable signatures, (key-delegatable) superset/subset predicate signatures, and wildcarded identity-based signatures.