WLAN无线局域网安全性分析与研究
摘要
众所周知，无线局域网中的WEP加密机制并不能够为无线用户提供足够的
安全保护。因此，自无线局域网开始商业应用之时，安全问题就成为了限制其进
一步发展的主要制约因素。许多潜在的用户对于WLAN技术所带来的灵活性十
分感兴趣，但却由于不能够得到可靠的安全保护而对是否采用WLAN系统犹豫
不决。
为了使WLAN技术从这种被动局面中解脱出来，IEEE802 11的工作组致力
于制订新一代安全标准，以增强WLAN的数据加密和认证性能。
本文对IEEE802 11无线局域网安全机制进行研究。对IEEE802 11无线局域
网安全机制进行深入的分析。
首先本文介绍了无线局域网的几种标准，主要介绍了IEEE802 11标准的网
络拓扑结构。随后介绍了IEEE802 11标准的介质访问控制层和它的认证和加密
的安全机制，分析了IEEE802 11的有线等价协议WEP加密机制、RC4算法及其
数据完整性算法，指出了其在安全方面的漏洞、给出了改进的对策，最后对WPA
中的EAP认证、TKIP加密协议进行了分析，提出了WPA中潜在的问题。
The IEEE 80211 standard defines the Wired Equivalent Privacy, or WEP, encapsulation of 80211 data frames The goal of WEP is to provide data privacy to the level of a wired network
The 80211 design community generally concedes that the WEP encapsulation fails to meet its design goal, but widely attributes this failure to WEP's use of 40-bit RC4 as its encryption mechanism Even at this late date, it is still repeatedly suggested, asserted, and assumed that WEP could meet its design goal by migrating from 40-bit to 104- or 128-bit RC4 keys instead
This report seeks dispel this notion once and for all: it is infeasible to achieve privacy with the WEP encapsulation by simply increasing key size The submission reports easily implemented, practical attacks against WEP that succeed regardless of the key size or the cipher In particular, as currently defined, WEP's usage of encryption is a fundamentally unsound construction; the WEP encapsulation remains insecure whether its key length is 1 bit or 1000 or any other size whatsoever, and the same remains true when any other stream cipher replaces RC4 The weakness stems from WEP's usage of its initialization vector This vulnerability prevents the WEP encapsulation from providing a meaningful notion of privacy at any key size
WPA greatly increases the level of over-the-air data protection and access control on existing Wi-Fi networks It addresses all known weaknesses of Wired Equivalent Privacy (WEP), the original native security mechanism in the 80211 standard
Wi-Fi Protected Access fixes all known vulnerabilities in Wi-Fi network security and greatly enhances data protection and access control on existing and future Wi-Fi wireless LANs It provides an immediate, strong, standards-based, interoperable security solution that addresses all known flaws in the original WEP-based security
安全保护。因此，自无线局域网开始商业应用之时，安全问题就成为了限制其进
一步发展的主要制约因素。许多潜在的用户对于WLAN技术所带来的灵活性十
分感兴趣，但却由于不能够得到可靠的安全保护而对是否采用WLAN系统犹豫
不决。
为了使WLAN技术从这种被动局面中解脱出来，IEEE802 11的工作组致力
于制订新一代安全标准，以增强WLAN的数据加密和认证性能。
本文对IEEE802 11无线局域网安全机制进行研究。对IEEE802 11无线局域
网安全机制进行深入的分析。
首先本文介绍了无线局域网的几种标准，主要介绍了IEEE802 11标准的网
络拓扑结构。随后介绍了IEEE802 11标准的介质访问控制层和它的认证和加密
的安全机制，分析了IEEE802 11的有线等价协议WEP加密机制、RC4算法及其
数据完整性算法，指出了其在安全方面的漏洞、给出了改进的对策，最后对WPA
中的EAP认证、TKIP加密协议进行了分析，提出了WPA中潜在的问题。
The IEEE 80211 standard defines the Wired Equivalent Privacy, or WEP, encapsulation of 80211 data frames The goal of WEP is to provide data privacy to the level of a wired network
The 80211 design community generally concedes that the WEP encapsulation fails to meet its design goal, but widely attributes this failure to WEP's use of 40-bit RC4 as its encryption mechanism Even at this late date, it is still repeatedly suggested, asserted, and assumed that WEP could meet its design goal by migrating from 40-bit to 104- or 128-bit RC4 keys instead
This report seeks dispel this notion once and for all: it is infeasible to achieve privacy with the WEP encapsulation by simply increasing key size The submission reports easily implemented, practical attacks against WEP that succeed regardless of the key size or the cipher In particular, as currently defined, WEP's usage of encryption is a fundamentally unsound construction; the WEP encapsulation remains insecure whether its key length is 1 bit or 1000 or any other size whatsoever, and the same remains true when any other stream cipher replaces RC4 The weakness stems from WEP's usage of its initialization vector This vulnerability prevents the WEP encapsulation from providing a meaningful notion of privacy at any key size
WPA greatly increases the level of over-the-air data protection and access control on existing Wi-Fi networks It addresses all known weaknesses of Wired Equivalent Privacy (WEP), the original native security mechanism in the 80211 standard
Wi-Fi Protected Access fixes all known vulnerabilities in Wi-Fi network security and greatly enhances data protection and access control on existing and future Wi-Fi wireless LANs It provides an immediate, strong, standards-based, interoperable security solution that addresses all known flaws in the original WEP-based security
引文
[1] LAN MAN Standards Committee of the IEEE Computer Society, "Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications" ANSI/IEEE std 802 11,1999 edition
[2] Eric Ouellet,Robert Padjen,Arthur Pfund,Ron Fuller "Building a Cisco Wireless LAN" Syngress Publishing,Inc 2001
[3] Jim Geier Wireless LANs:Implenenting Interoperable Networks Macmillan Technical Publishing, Inc 2002
[4] William AArbaugh, Narendar Shankar, YC Justin Wan "Your 802 11 Wireless Network has No Clothes" http://wwwcsumdedu/-waa/wirelesspdf
[5] Scott Fluhrer, Itsik Mantin and Adi Shamir, "Weaknesses in the Key Scheduling Algorithm of RC4" http://onlinesecurityfocuscom/data/library/rc4_ksaprocpdf
[6] Borisov, Nikita Goldberg, Ian Wagner, David "Security of the WEP algorithm" http://wwwisaaccsberkeleyedu/issac/wep-faqhtml
[7] Using the Fluhrer, Mantin, and Shamir Attack to Break Wired Equivalent Privacy (WEP): http://wwwcsriceedu/-astubble/wep/wep attackpdf
[8] A security analysis of WEP from Berkeley http://wwwisaaccsberkeleyedu/isaac/wep-faqbtal
[9] Michael Sutton, "Hacking the Invisible Network", iALERT white paper, iDEFENSE Labs http://wwwastalavistanet/data/Wirelesspdf
[10] Adam Stubblefield, John loannidis, and Aviel Rubin, "Using the Fluhrer, Mantin,Shamir Attack to Break WEB" http://wwwcsriceedu/-astubble/wep/wep_attackpdf
[11] Tim Newsham, "Applying known techniques to WEP keys", http://wwwlavanet/-newsham/wlan/WEP password crackerppt
[12] V Moen, H Raddum, and K J Hole, "Weaknesses in the Temperai Key Hash of WPA," http://wwwii,uibno/-moen/wireless/
[13] Wireless (in)security @ SMAU 02 http://wwwsikurezzaorg/bh smau02/wirelesspdf
[14] WAP White Paper,http://wwwwapforumorg/what/WAP_white_pagespdf
[15] Wireless Network Security, http://csrcnistgov/publications/drafts/draft-sp800-48 pdf
[16] Wireless LAN Security in Depth, http://downloadssecurityfocuscom/library/safwl_wppdf
[2] Eric Ouellet,Robert Padjen,Arthur Pfund,Ron Fuller "Building a Cisco Wireless LAN" Syngress Publishing,Inc 2001
[3] Jim Geier Wireless LANs:Implenenting Interoperable Networks Macmillan Technical Publishing, Inc 2002
[4] William AArbaugh, Narendar Shankar, YC Justin Wan "Your 802 11 Wireless Network has No Clothes" http://wwwcsumdedu/-waa/wirelesspdf
[5] Scott Fluhrer, Itsik Mantin and Adi Shamir, "Weaknesses in the Key Scheduling Algorithm of RC4" http://onlinesecurityfocuscom/data/library/rc4_ksaprocpdf
[6] Borisov, Nikita Goldberg, Ian Wagner, David "Security of the WEP algorithm" http://wwwisaaccsberkeleyedu/issac/wep-faqhtml
[7] Using the Fluhrer, Mantin, and Shamir Attack to Break Wired Equivalent Privacy (WEP): http://wwwcsriceedu/-astubble/wep/wep attackpdf
[8] A security analysis of WEP from Berkeley http://wwwisaaccsberkeleyedu/isaac/wep-faqbtal
[9] Michael Sutton, "Hacking the Invisible Network", iALERT white paper, iDEFENSE Labs http://wwwastalavistanet/data/Wirelesspdf
[10] Adam Stubblefield, John loannidis, and Aviel Rubin, "Using the Fluhrer, Mantin,Shamir Attack to Break WEB" http://wwwcsriceedu/-astubble/wep/wep_attackpdf
[11] Tim Newsham, "Applying known techniques to WEP keys", http://wwwlavanet/-newsham/wlan/WEP password crackerppt
[12] V Moen, H Raddum, and K J Hole, "Weaknesses in the Temperai Key Hash of WPA," http://wwwii,uibno/-moen/wireless/
[13] Wireless (in)security @ SMAU 02 http://wwwsikurezzaorg/bh smau02/wirelesspdf
[14] WAP White Paper,http://wwwwapforumorg/what/WAP_white_pagespdf
[15] Wireless Network Security, http://csrcnistgov/publications/drafts/draft-sp800-48 pdf
[16] Wireless LAN Security in Depth, http://downloadssecurityfocuscom/library/safwl_wppdf