Stateful public key encryption: How to remove gap assumptions and maintaining tight reductions
Peng Yang, Rui Zhang, Kanta Matsuura · 2008
Stateful public key encryption schemes are introduced recently with improved efficiency over traditional stateless schemes. However, previous proposals are either based on strong assumptions; or admitting very loose security reductions. In this paper, we improve these aspects by presenting a stateful public key encryption scheme with tight security reduction to the computational Diffie-Hellman assumption (cf. gap Diffie-Hellman in [5]), as well as a stateful identity based encryption scheme with tighter security reduction (than [12]) to the computational bilinear Diffie-Hellman problem. It is worth reminding that it is always desirable to have the proofs with tight reductions such that the actual schemes can be practically-meaningful.