Predicate Aggregate Signatures and Applications

Motivated by applications in anonymous reputation systems and blockchain governance, we initiate the study of predicate aggregate signatures (PAS), which is a new primitive that enables users to sign multiple messages, and these individual signatures can be aggregated by a combiner, preserving the anonymity of the signers. The resulting PAS discloses only a brief description of signers for each message and provides assurance that both the signers and their description satisfy the specified public predicate. We formally define PAS and give a construction framework to yield a logarithmic size signature, and further reduce the verification time also to logarithmic. We also give several instantiations for several concrete predicates that may be of independent interest. To showcase its power, we also demonstrate its applications to multiple settings including multi-signatures, aggregate signatures, threshold signatures, (threshold) ring signatures, attribute-based signatures, etc, and advance the state of the art in all of them.