臺灣博碩士論文加值系統

當無線區域網路的應用愈來愈普遍，為我們帶來更多的便利的同時，資訊安全的課題也愈來愈重要。因為無線電波在空氣中傳遞隨時有被監聽的可能性，更增加了無線區域資訊被截取的威脅，在802.11標準中雖然提出了有線等效加密演算法(WEP)，希望提供足夠的安全性來防止資料的流失，但有線等效加密演算法所採取的架構已經被証明是不夠安全的，駭客可以在短短的幾個小時或幾天之內就輕易的破解密碼，本文主要就是在討論在801.11的無線區域網路中，當系統管理者採用了有線等效加密演算法之後，仍可能會面臨的各項可能攻擊，導致資料的不完整或被竊取。
最後再就目前所發展的各項資訊安全技術中，系統管理者在建置一個無線區域網路時，可以採用的各種方法以提高資訊安全提出建議，例如新的Fast Packet Keying或目前在802.1X標準中所提出的EAP標準作一介紹，希望對系統管理者在面對資訊安全的威脅時能有所助益。

Wireless Local Area Network(WLAN) provides convenience and mobility but it also poses security challenges. The IEEE 802.11 standard defines the Wired Equivalent Privacy(WEP), which is an encapsulation of 802.11 data frames. The goal of WEP is to provide data security to the level of a wired network. But the WEP encapsulation fails to meet its design goal hacker maybe take the shared key in several hours or in few day to break the encryption because the weakness in WEP algorithms. The weakness stems from the usage of the initialization vector in WEP. This vulnerability prevents the WEP encapsulation from providing a useful measure for data security at any key size.
In this thesis we discuss the issues of data security in WEP and then we suggest some useful methods to enhance the security in WLAN.

中文摘要…………………………………………………………………..i
英文摘要…………………………………………………………………..ii
誌謝..………………………………………………………………………iii
目錄………………………………………………………………………..iv
圖表目錄…………………………………………………………………..vi
第一章 簡介……………………………………………………………….1
第二章IEEE 802.11通信協定標準簡介………………………………….4
2.1 802.11的實體層…………………………………………………..5
2.2 IEEE 802.11的基本通信協定……………………………………5
2.3 802.11的存取服務………………………………………………..6
2.4 802.11的網路基本架構…………………………………………..6
2.5 IEEE 802.11的服務模式…………………………………………8
2.6 IEEE 802.11的訊框格式………………………………………..12
2.6 IEEE 802.11的認証與保密……………………………………..15
第三章 有線等效保密演算法…………………………………………...18
3.1 WEP 演算法特色……………………………………………….18
3.2 WEP 運作原理………………………………………………….19
第四章WEP加密演算法可能面對的威脅………………………………31
4.1 IV重複使用的問題……………………………………………...31
4.2 已知明文的破解………………………………………………..32
4.3 封包的篡改……………………………………………………..33
4.4 位址的變造……………………………………………………..34
4.5 鑰匙選擇的問題………………………………………………..34
4.6 鑰匙保管的問題………………………………………………..35
4.7 WEP設計上的缺失……………………………………………..35
第五章 初使向量的漏洞………………………………………………...36
5.1 {n+3 , 255 ,X}模型…………………………………………...…37
5.2 {X , 257-X+n , (IV[2] + + )=n+2}模型……………..41
5.3 {X , 256-X , (IV[2] + + )=1}模型…………………..44
5.4 提高破解鑰匙的可能性………………………………………..46
第六章 結論……………………………………………………………...50
參考文獻………………………………………………………………….55
附錄A WEP KEY搜尋程式……………………………………………..57

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