Abstract

For several years, Ad hoc networks is a major field of research. In such networks, extreme cases occur, such as advanced attacks due to the wireless aspect of the communications between nodes and the fact that the network is self-organized. Moreover, mobility in such networks is an important inconvenient as it leads to unstable networks.

Many studies deals with routing techniques in such environments. The main works done in this case are the design of efficient routing protocols to solve problems such as non-bidirectional links or highly-mobile nodes and to manage security aspects.

With the emergence of security needs in wireless networks and more specifically in ad hoc networks (for military's applications or consumers ones, for instance with multi-players games or tele conferences), several secured protocols at the application layer have been proposed, mainly to build secure groups. In order to provide group communication privacy, we need to have a common secret key. However, efficiently managing group keys in mobile networks, such as ad hoc networks, is difficult as every time the group changes (a node joins or leaves the group), the group key needs to be modified. Moreover, due to the wireless and the self-organized aspects of such networks, the notion of centralized trusted third party has to be reconsidered. In such cases, designing a secured group management protocol is not so easy. Thus, we undertake the design of a secure group management protocol.

In the first chapter, we introduce briefly the notion of ad hoc networks and examples of such protocols, the existing security issues and solutions at the routing layer. The next chapter introduces the notion of group management in ad hoc networks. In this chapter, we present the core aspect of our S-TGDH¹ protocol (our extension of the existing TGDH protocol) with the group management core algorithms (such as join and leave algorithms). Then, in chapter 3, we present our reputation solution which can be seen as a reinforcement of S-TGDH to support internal malicious nodes (more precisely, to secure the join algorithm and to detect malicious nodes inside the group). The last chapter ( and ) studies the formal proofs of the security properties.

keywords: ad hoc networks, group management, reputation, authentication, cryptography

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