Wired Equivalent Privacy (WEP) algorithm (part of the 802.11)

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Security of the WEP algorithm

This is some information about our analysis of the Wired Equivalent Privacy (WEP) algorithm, which is part of the 802.11 standard. This work was performed jointly by Nikita Borisov, Ian Goldberg, and David Wagner. If you have any questions, please contact us at wep@isaac.cs.berkeley.edu.

Executive Summary
We have discovered a number of flaws in the WEP algorithm, which seriously undermine the security claims of the system. In particular, we found the following types of attacks:

Passive attacks to decrypt traffic based on statistical analysis.
Active attack to inject new traffic from unauthorized mobile stations, based on known plaintext.
Active attacks to decrypt traffic, based on tricking the access point.
Dictionary-building attack that, after analysis of about a day's worth of traffic, allows real-time automated decryption of all traffic.
Our analysis suggests that all of these attacks are practical to mount using only inexpensive off-the-shelf equipment. We recommend that anyone using an 802.11 wireless network not rely on WEP for security, and employ other security measures to protect their wireless network.

Note that our attacks apply to both 40-bit and the so-called 128-bit versions of WEP equally well. They also apply to networks that use 802.11b standard (802.11b is an extension to 802.11 to support higher data rates; it leaves the WEP algorithm unchanged).

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Conclusions
Wired Equivalent Privacy (WEP) isn't. The protocol's problems are a result of misunderstanding of some cryptographic primitives and therefore combining them in insecure ways. These attacks point to the importance of inviting public review from people with expertise in cryptographic protocol design; had this been done, the problems stated here would have surely been avoided.



источник: http://www.isaac.cs.berkeley.edu/isaac/wep-faq.html