An efficient user authentication and key exchange protocol for mobile client–server environment

Abstract

Considering the low-power computing capability of mobile devices, the security scheme design is a nontrivial challenge. The identity (ID)-based public-key system with bilinear pairings defined on elliptic curves offers a flexible approach to achieve simplifying the certificate management. In the past, many user authentication schemes with bilinear pairings have been proposed. In 2009, Goriparthi et al. also proposed a new user authentication scheme for mobile client–server environment. However, these schemes do not provide mutual authentication and key exchange between the client and the server that are necessary for mobile wireless networks. In this paper, we present a new user authentication and key exchange protocol using bilinear pairings for mobile client–server environment. As compared with the recently proposed pairing-based user authentication schemes, our protocol provides both mutual authentication and key exchange. Performance analysis is made to show that our presented protocol is well suited for mobile client–server environment. Security analysis is given to demonstrate that our proposed protocol is provably secure against previous attacks.

Introduction

Nowadays, handheld devices (i.e., cellular phones and PDAs) are popularly and widely used by people and many mobile applications, such as wireless internet services, mobile access services and mobile e-commerce. Considering the low-power computing capability of mobile devices, the security scheme design based on traditional public-key systems [1], [2], [3] is a nontrivial challenge, because most cryptographic algorithms require many expensive computations. If the traditional public-key based cryptographic schemes are designed for mobile users with handheld devices, the computational cost on the user side is a critical issue in practical implementation because of their low-power computing capability [4], [5], [6], [7], [8], [9].

In 1984, Shamir [10] proposed an identity (ID)-based public-key cryptosystem. As compared with the traditional certificate-based public-key systems, the ID-based public-key system may simplify the certificate management. However, the system has a disadvantage that the user’s private key must be generated by the Key Generator Center (KGC). Because the security of Shamir’s system is based on the integer factorization problem, Shamir’s system is not easy to be realized in practice. Fortunately, Boneh and Franklin [11] proposed a practical ID-based encryption scheme from the Weil pairing defined on elliptic curves in 2001. The security of their scheme is based on the discrete logarithm problem. In this case, the user’s private key can be generated by several sub-centers using a threshold scheme. Afterwards, the ID-based cryptographic schemes based on bilinear pairings have received much attention from cryptographic researchers. There are many ID-based cryptographic schemes based on bilinear pairings have been proposed such as authenticated key agreement protocols [12], [13], [14], [15], [16], [17], [18] and signature schemes [19], [20], [21], [22], [23], [24].

Recently, many pairing-based remote user authentication schemes with smart cards were proposed in [25], [26], [27], [28], [29]. In which, two schemes [25], [26] have security flaws and the proposed scheme in [27] required more computation. The point is that these schemes [25], [26], [27], [28], [29] do not provide mutual authentication and key exchange between the client and the server. In wireless client–server networks, mobile devices adopt wireless mediums to communicate with the server. If a user authentication scheme does not provide mutual authentication and key exchange properties, an intruder is easy to intercept communications over the wireless networks. Thus, mutual authentication and key exchange properties are necessary for a user authentication scheme in mobile environment. This inspires us to propose a secure user authentication and key exchange protocol for mobile client–server environment.

In this paper, we propose a new user authentication and key exchange protocol with bilinear pairings. The client side is a low-power computing device and the server is regarded as a powerful one. We shift the computational burden to the powerful server and reduce the computational cost required by the client side. Based on the computational Diffie–Hellman (CDH) assumption [11] and in the random oracle model [30], we show that the proposed protocol is secure against impersonation attack and ID attack, as well as offers key agreement, mutual authentication, implicit key confirmation and partial forward secrecy. Performance analysis and experimental data are given to demonstrate that our protocol is well suited for mobile client–server environment with low-power computing devices.

The remainder of this paper is organized as follows. In Section 2, we present the related works. The preliminaries of bilinear pairings and related mathematical assumptions are given in Section 3. In Section 4, we propose our user authentication and key exchange protocol. Security analysis of our proposed protocol is presented in Section 5. In Section 6, we demonstrate performance analysis. Conclusions are given in Section 7.