Efficient Generic Construction of Forward-Secure Identity-Based Signature

We propose an efficient generic construction of forward-secure identity-based signature (FSIBS) that ensures unforgeability of past signatures in spite of the exposure of the current signing key. Our construction, supported by formal security analysis, brings about concrete FSIBS schemes which are more efficient than existing schemes in the literature. Especially, one of our instantiations of FSIBS based on discrete-log primitive turns out to be the most efficient among existing ones. As a secondary contribution, we refine the definition of security of FSIBS in such a way that users in the system can freely specify time periods over which their signing keys evolve.