Abstract
Mobile devices have become very important for our daily needs. The user authentication protocols with the key agreement are required to deal with the security issues that arise from the use of mobile devices through Internet applications. However, existing user authentication protocols are only suitable if the client and the server use a similar cryptographic approach. Therefore, it is important to develop an authentication protocol for mobile environments with heterogeneous cryptographic approaches. In this paper, an efficient user authentication and key agreement protocol is proposed for a heterogeneous client-server mobile environment. The security of the proposed scheme is formally proved under the q-strong Diffie-Hellman problem (q-SDH), the q-bilinear Diffe-Hellman inversion problem (q-BDHI), and the modified bilinear Diffie-Hellman inversion problem (mBDHI), respectively. Our scheme has reasonable processing costs and communication costs on the client and server sides. Moreover, our scheme is suitable for applications that use different cryptographic approaches. In particular, the proposed protocol can work when the client applies the identity-based cryptosystem and the server applies the certificateless cryptosystem.