Verifiably encrypted cascade-instantiable blank signatures to secure progressive decision management

摘要

In this paper, we introduce the notion of verifiably encrypted cascade-instantiable blank signatures (CBS) in a multi-user setting. In CBS, there is a delegation chain that starts with an originator and is followed by a sequence of proxies. The originator creates and signs a template, which may comprise fixed fields and exchangeable fields. Thereafter, each proxy along the delegation chain is able to make an instantiation of the template from the choices passed down from her direct predecessor, before generating a signature for her instantiation. First, we present a non-interactive basic CBS construction that does not rely on any shared secret parameters among the users. In verifying an instantiation signature, all the preceding instantiation signatures leading back to the template signature are also verified concurrently. It is formally proved to be secure against collusion attacks by the originator and proxies. Second, we investigate verifiably encrypted CBS to provide fairness between the originator and proxies, where the security model is stricter than basic CBS in that the adversary may also collude with the arbitrator. Efficiency analysis shows that the proposed CBS schemes enjoy linear computation costs. Finally, we extend our scheme to CBS supporting designated instantiations, free instantiations, privately verifiable template signature, identity-based CBS, as well as CBS secure against proxy-key exposure.