A Provably Secure ID-Based Mediated Signcryption Scheme

It has been a critical issue to find efficient methods for fast revocation of a user´s identity in identity (ID)-based cryptosystems. Unfortunately, none of the previous ID- based cryptography can find a practical way. Motivated by Boneh et al. ´s idea of mediated RSA, in this paper, we propose the concept of ID-based mediated signcryption and give a concrete scheme, which yields a complete solution to the fast revocation of a user´s identity in ID-based signcryption schemes. To address the security issues, we formulate security model and define strong security notions for ID- based mediated signcryption schemes. We also prove that our scheme satisfies these security requirements in the random oracle model.