| With the rapid development of social economy and the sharp rise of wireless networks, the demands of wireless communications which provides information services keep increasing. As the wireless frequency resources becoming precious, short-range wireless communications technology has broad market prospects, and WLAN becomes people's hot topic of discussion. However, there are security problems both in the Wi-Fi and the IEEE802.11 WLAN. But there are many WLAN encryption protocol holes in the encryption aspesct, and leaves a lot of space to be attacked for the aggressor. Consequently, the security problems become urgent problem to be solved for their developments.This paper takes the most common dictionary attack as the example firstly, analyses the aggressor how to crack the secret key of security agreement and how to use this technique to carry the attack on the network. So the method that does not change the hardware environment to prevent dictionary attacks is to be the meaningful practical application study for strengthening the security of WLAN.This paper then introduces the general WLAN security technologies, and elicits security protocols WPA of WLAN. We compare WPA with its predecessor WEP, illustrate the application technologies and work principle of this two security agreements respectively. Analyze the dictionary attack technology formation from attacker's point , explain how to crack the key using the dictionary attack, and illustrate the general process of crack by an experiment. The results of experiments show that dictionary attack cracks the encryption protocol successfully.At the end, this paper has established a plan to improve the prevention of a dictionary attack by the dictionary attack experiment. The main idea of plan is how to strengthen authentication to prevent a dictionary attack. Propose four information exchanges process based on the one-way hash function, using the debarkation time consumption to ensure the attacker can not have enough capacity to carry on online dictionary attacks. In addition, this paper use a variable to add off-line dictionary attack time consuming for makeing up the deficiencies. This plan have been verified.And the results show that the improved plan in the same experimental conditions can effectively prevent dictionary attacks.So this plan can be achieved completely without any hardware changes. It reduces the development costs effectively and improves economic efficiency. |
