Question:

Consider that you have to configure a small WLAN of 8 computers using Wired Equivalent Privacy (WEP) and that you have to best make use of its available security features.

(a) How many keys will WEP hold and what is the key index range?

(b) Which key length could you adopt for the WEP passphrase? Provide a sample passphrase that you would have used for the configuration.

(c) The CRC field remains unencrypted during transmission. Show how an attacker can take advantage of this weakness in WEP.

(d) The Initialisation Vector (IV) used in WEP is known to be too short.

i. Describe what is meant by the term Initialisation Vector.
ii. What is the total number of IVs possible?
iii. Show how the short IV in WEP leads to security problems.

(e) List any two tools that an attacker can use to crack WEP.

(f) Show how an attacker perform a double encryption attack on this newly configured network.

(g) Briefly explain the best practices you would adopt to configure WEP in order to make best use of it.