Fail-Stop Signatures for Multiple-Signers: Definitions, Constructions, and Their Extensions

Abstract

Fail-stop signatures (FSS) provide the security for a signer against a computationally unbounded adversary by enabling the signer to provide a proof of forgery. Conventional FSS schemes are for a single-signer setting, but in the real world, there is a case where a countersignature of multiple signers (e.g., a signature between a bank, a user, and a consumer) is required. In this work, we propose a framework of FSS capturing a multi-signer setting and call the primitive fail-stop multisignatures (FSMS). We propose a generic construction of FSMS via the bundling homomorphisms proposed by Pfitzmann and then propose a provably secure instantiation of the FSMS scheme from the factoring assumption. Our proposed schemes can be also extended to fail-stop aggregate signatures (FSAS).