Construction of Threshold Public-Key Encryptions through Tag-Based Encryptions
In this paper, we propose a notion of threshold tag-based encryption schemes that simplifies the notion of threshold identity-based encryption schemes, and we show a conversion from any stag-CCA-secure threshold tag-based encryption schemes to CCA-secure threshold public-key encryption schemes. Moreover, we give two concrete constructions of stag-CCA-secure threshold tag-based encryption schemes, under the decisional bilinear Diffie-Hellman assumption and the decisional linear assumption, respectively. Thus, we obtain two concrete constructions of threshold public-key encryption schemes, both of which are non-interactive, robust and can be proved secure without random oracle model. Our threshold public-key encryption schemes are conceptually more simple and shown to be more efficient than those of Boneh, Boyen and Halevi.