Secure Medium Access Control Protocol In Wireless Ad Hoc Networks

Wireless Ad Hoc Network (WANET) has widely practical applications, especially suitable for tactical communication, emergency communication, wireless home network, and so on. WANET does not need infrastructure support and networks quickly and have strongly adaptive capacity, which broadens the application fields of wireless communications and has a broad development prospects. Medium Access Control (MAC) layer is critical to the performance of wireless network which makes MAC technology have become the research hotspot. However, the inherent characteristics of wireless network and the open wireless channel environment makes MAC layer be faced with lots of security attacks, such as eavesdropping, tamper, masquerading, replay attack, man-in-the-middle attack, misbehavior attack and so on. Therefore, these attacks must be considered when design the MAC protocol. At the same time, under premise of the security of WANET, we should make each node can fairly use wireless channel and make the system run efficiently and steadily. Hence, the research on secure MAC protocol for WANET is of great significance.First, this paper has designed a security MAC protocol by means of the asymmetric cryptography and authentication mechanism, which solves the security attacks such as eavesdropping, tamper, masquerading, replay attack, man-in-the-middle attack and provides the first security barrier for MAC layer. This paper designed a secure MAC protocol for WANET (SMC-WANET) which considered the inherent features of WANET, for instant, the lacking of control center, the limit of storage capacity, computing capacity and bandwidth. Besides, we take the advantage of Self-certified public key system (SCPK) and Elliptic Curves Cryptography (ECC). SMC-WANET protocol consists of four major phases:the setup phase, the user registration phase, negotiation phase and data transmission phase. The setup phase mainly completes the function that Certificate Authority (CA) generates system parameter and publishes them. In the user registration phase, users registers with CA and generate their public/private key pairs. The negotiation phase is to achieve the authentication between two communicating parties and the session key agreement. The data transmission phase mainly achieves data confidentiality. We analyze the security and performance of SMC-WANET protocol and the results indicates that the protocol shows good performance in terms of security, storage overhead, communication overhead and calculation overhead, and resists common attacks. Meanwhile, the SMC-WANET is analyzed for these security measures using Burrows-Abadi-Needham logic method. It is shown that the protocol is right and secure.In multi-rate Ad Hoc networks, nodes often utilize auto rate adaptation algorithm to select transmission rate based on channel to improve network performance, such as the IEEE 802.11 Multi-Rate Distributed Coordination Function (DCF) protocol. However, the DCF protocol exists the performance anomaly problem in multi-rate network, which makes some malicious seize this vulnerability to conduct the misbehavior, namely, when the channel conditions are relatively good, malicious nodes will intentionally choose low bit rate to degrade the performance of high data nodes, which leads to the unfairness occupy of channel resources. To relieve the affect of misbehavior attack, we can solve the phenomenon of the performance anomaly in multi-rate networks. In this case, different rate nodes can be guaranteed fair time to occupy wireless channel, and the performance of system can be improved. Even if malicious nodes conduct the misbehavior attack, system performance will not sharply decrease. Hence, this paper proposed a modified multi-rate DCF mechanism based on contention window differentiation. The Markov model is established for the modified multi-rate DCF mechanism to analyze performance and verify the simulation results. The simulation results show that the modified multi-rate DCF mechanism effectively alleviates the problem that nodes use channel unfairly, reduces collisions and improves the aggregated throughput. Meanwhile, it also effectively alleviate the phenomenon where malicious nodes occupy the channel for a long time to make system performance degrade.