An Efficient Identity-Based Certified E-mail Protocol

Signcryption is to perform encryption and signature in a single logical step, and is more efficient than the sign-then-encryption scheme. However, most of the proposed signcryption approaches cannot be used directly by certified e-mail protocol. In this paper, we first develop an id-based signcryption method, which allows a trusted third party to compute a cipher text of a message together with other parties. Then based on the signcryption scheme we propose a new id-based certified e-mail protocol. The fairness, efficiency, and effectiveness of our protocol have been proved.