Tightly secure identity-based multisignatures
Naoto Yanai · 2017
ID-based multisignatures are digital signatures where each signer generates a partial signature with any identity as its own public key and combine them into a single signature as one of a group of signers. In this work, we discuss a tight security reduction of an ID-based multisignature scheme, which is an open problem in this work. Here, a tight reduction means that a reduction cost in a security proof is independent of a capability of an adversary. Our main idea is to utilize one-more DH assumption, which is an interactive assumption with an oracle to return a CDH instance. It can also support combination of signatures required for constructing multisignatures. Thus, our scheme is fairly practical.