An Improved Signcryption with Proxy Re-encryption and its Application

Signcryption with proxy re-encryption was proposed recent by Chandrasekar. However, his scheme did not provide public verifiability, which is a desirable property in applications such as certified e-mail protocol. In this paper we firstly improve a id-based signcryption with proxy re-encryption scheme, which provides public verifiable property in a way that any third party can verify the validity, then based on this scheme we propose a modified signcryption with proxy re-encryption so that it can be used as a cryptographic primitive of certified e-mail protocol, finally we present a certified e-mail protocol in id-based setting with semi-trusted third party which reduce the trust extent of third party, and improve the efficiency and practice.