Study On Data Transmission Securely Of WLAN Based On Chaotic Techniques

Wireless LAN (Wireless Local Area Network, WLAN) as an extension of traditional wired networks greatly facilitates people's communication. Wireless communication is one of the important technologies and it has been widely applied everywhere. Otherwise, the security problems are becoming more and more prominent. Because of that WLAN adopts public electromagnetic wave (2.4GHz) as its carrier; and the wireless transceiver is commonly used omni-directional antenna. With several devices, some one can receive wireless LAN signal easily. And then they are able to listen, steal or tamper the useful information so that legitimate users may suffer losses. Therefore, wireless LAN security has become our focus.For problems of the existing WEP, TKIP, AES and the WAPI wireless LAN data encryption algorithm, a series of algorithms and related solutions have been analyzed. By learning chaotic encryption, depth-study on WLAN data transmission and reading a large number of references about Secure of WLAN, some new research points have been proposed in this paper. Firstly, considering characteristics of the frame for WLAN, a new policy is proposed to encrypt the data frames. The improved Logistic mapping can carry information in the WLAN data frame through the change of single parameterμand x0, which can lead to morphological changes of chaotic attracts, in order to achieve the purpose of confidentiality. Secondly, about RC4 algorithm, an improved policy is raised. The Logistic chaotic sequence is employed in PRGA algorithm to enhance the pseudo-random key and network security.This total is divided into six chapters, the specific contents as follows: The first chapter is an introduction section. In this part, wireless local area network has been introduced. This chapter provides an overview of the characteristics of the WLAN. To a variety of loopholes in the network, researchers have put forward many different types of security encryption. The research development for several key contents, important research objectives and applications has been summarized. At last, the main research work and the chapter structure of this thesis has been specified.In the chapterⅡ, we describe the structure of the Wireless LAN and OSI seven- layer structure, whose similarities and differences have been compared and analyzed. We also introduce the protocol system of IEEE 802.11 as well as a minimal system of WLAN. By analyzing the properties of the BBS network, we have got the point of software for the simulation in order to prepare for the next work.In the chapterⅢ, the basic concepts of cryptography are summarized, at the same time, the public key cryptography, hash function, and elliptic cryptography are all introduced, including the encryption algorithm of WLAN and the traditional encryption algorithm of the data. The corresponding theories provided research theoretical foundation for the following chapters.In the chapterⅣ, we describe the chaotic encryption algorithm in the application of WLAN. Based on the analysis, we chose a new chaotic encryption systems-logistic chaotic system, which is more suitable for the data frame of WLAN than any other. A new policy based on the WLAN transmission of data security was proposed.The improved Logistic mapping can carry information in the WLAN data frame through the change of single parameter u, which can lead to morphological changes of chaotic attracts. The receiver decision device is used to restore the original signals at the receiving end. As the data frame of WLAN is a digital signal composed by 0 and 1, the logistic chaotic mapping is an ideal module while selecting chaotic encryption model. Because the logistic mapping's expression is easy to operate and calculate, and it is set by single parameter and applies to binary encryption; moreover, the chaotic digital communication has an excellent capacity of resisting disturbance and is simple to implement and easily combined with traditional cryptology to improve the secure performance. A security policy of WLAN data transmission based on the Logistic chaotic modulation whose security performance is better than some of the existing security mechanisms, and compared with the original network, its throughput and time delay increased by 9.09% and 17.3% respectively, and the packet loss rate basically remains the same as the original network. The results show that the Logistic chaotic modulation policy can effectively protect the WLAN network security, and also can provide a high communication quality. In a word, this policy is very suitable for encrypting the WLAN data frame.In the Chapter V, considering the deficiencies of the WEP RC4 algorithm, a policy of logistic mapping was presented, which is based on RC4 algorithm. The policy that logistic chaotic modulation is introduced to enhance the pseudorandom key in the second part of RC4-PRGA can make it more difficult for unauthorized users to decipher the data. It can be seen from the results of simulation, the average load of the network and the number of packets retransmission are reduced by 1%, 5.3% than that of original RC4 algorithm, while the negative impact of MAC delay is only increased by 7.2%.In the last chapter, finally, a conclusion for the entire has been made. And the issues that needed to be investigated and solved in the future research on Wireless LAN data security have been pointed.