A hierarchical key management scheme for secure group communications in mobile ad hoc networks

Abstract

A mobile ad hoc network (MANET) is a kind of wireless communication infrastructure that does not have base stations or routers. Each node acts as a router and is responsible for dynamically discovering other nodes it can directly communicate with. However, when a message without encryption is sent out through a general tunnel, it may be maliciously attacked. In this paper, we propose a hierarchical key management scheme (HKMS) for secure group communications in MANETs. For the sake of security, we encrypt a packet twice. Due to the frequent changes of the topology of a MANET, we also discuss group maintenance in this paper. Finally, we conducted the security and performance analysis to compare the proposed scheme with Tseng et al.’s [Tseng, Y.-M., Yang, C.-C., Liao, D.-R., 2007. A secure group communication protocol for ad hoc wireless networks. In: Advances in Wireless Ad Hoc and Sensor Networks and Mobile Computing. Book Series Signal and Communication Technology. Springer] and Steiner et al.’s [Steiner, M., Tsudik, G., Waidner, M., 1998. CLIQUES: a new approach to group key agreement. In: Proceedings of the 18th IEEE International Conference on Distributed Computing System. Amsterdam, Netherlands, pp. 380–387] schemes.

Introduction

A mobile ad hoc network (MANET) (Macker and Corson, 1998, Marwaha et al., 2002) is a kind of wireless communication infrastructure that does not have base stations or routers. Its investment cost is less, and each mobile node acts as a router on the Internet. A MANET can be deployed rapidly, and it can be used in remote places and battlefields, etc.

In a MANET, a group can hasten message delivery and prevent bandwidth waste effectively. But if a message is sent out through a general tunnel without encryption, it may suffer malicious attacks (Mirkovic et al., 2002, Mishra et al., 2004, Patwardhan et al., 2005, Russell, 2001, Schmoyer et al., 2004). Because of these attacks, Internet security may be seriously affected. So in our scheme, a packet to be delivered will be encrypted, and only the receiver can decrypt the packet.

Key management schemes usually focus on improving security and reducing the memory storage of keys, as presented in MANETs (Chang and Chung, 2003, Jablon, 1996, Rafaeli and Hutchison, 2003). Two of the most common schemes for group structures are clustering (Tseng et al., 2007) and hierarchical trees (Amir et al., 2004, Chiang and Huang, 2003, Liu and Zhou, 2002, Steiner et al., 1996, Wong et al., 2000, Yang and Zheng, 2001). The advantage of clustering is that rekeying can be done quickly. The total cost of rekeying will increase greatly when members join or leave a larger group. Most group structures adopt a hierarchical tree. The main goal of a hierarchical tree is to decrease the cost of rekeying and to make management easy when changes in the group membership occur. The disadvantage of a hierarchical tree is that the maintenance cost increases when group membership increases.

Due to frequent changes of the network topology in a MANET, group maintenance of infrastructure wireless networks is not suitable. Therefore, we can use a common encryption key in a dynamic environment by following two rules. The first rule is forward secrecy. In this rule, when a new user joins a group, it cannot decrypt past encrypted messages. The second rule is backward secrecy. In this rule, when a group member leaves a group, it cannot decrypt future encrypted messages. If the two rules are followed, there will be better security for group key updating or protection. Managing keys efficiently within a group and reducing the amount of rekeying are the main goals we want to achieve. In this paper, we propose a hierarchical key management scheme (HKMS) for secure group communications in MANETs. A secure group can manage members efficiently and reduce the amount of rekeying.

The rest of the paper is organized as follows. In Section 2, we introduce the related work. The proposed scheme is presented in Section 3. In Section 4, we discuss the security analysis and time complexity analysis. In Section 5, we present the performance evaluation. Finally, conclusions are given in Section 6.