Key Management Problems
WEP uses a symmetric key encryption mechanism, meaning that the same shared secret (key) is used for both encryption and decryption. The key must be shared between the sender and receiver. One of the problems with the 802.11 protocol is that it does not address the issue of key management: How is the key distributed among users? This may not seem like a problem if you are using WEP in an environment with three laptops, but what happens if you try to deploy WEP across a campus of 5,000?
Each user must know the key and keep it a secret. What happens if one person leaves the company or has a laptop stolen? A new key must be given to every single user and re-entered in her client configuration. Also, if an attacker compromises the key from one session, the same key can be used to decrypt any other session, because everybody is using the same key.