Contributions to security in wireless ad-hoc networks

There are many cases where people do not want or cannot deploy an infrastructure-based network, e.g. using PDAs to distribution documents in a conference, network for battlefield soldiers, etc. Wireless ad-hoc networks are needed in these cases. With wireless ad-hoc networks, users can get connected with each other, anytime, anywhere. Along with this convenience, users should also be aware that wireless ad-hoc networks, without the support from infrastructure, are weak against adversaries' attacks. The security problems that were previously dealt with in traditional networks, now have to be addressed again. This thesis aims to provide a secure communication channel for wireless ad-hoc networks users. This can be achieved by providing two fundamental cryptographic schemes: Encryption/Decryption and Digital Signature. By encrypting the content of communication, users can assure that even the communication is eavesdropped by adversaries, they can not obtain any information. The challenge is how do you setup the required encryption/decryption keys for each user efficiently, where there is no support from infrastructure. We provide a solution in this thesis. On the other hand, digital signatures provide a way for users to authenticate others within the network. When a suspicious user wants to join the network group, decision can be made if he can not provide a valid signature. These schemes provided in this thesis, give wireless ad-hoc network users a secure communication environment.