WEP is a protocol for securing wireless LANs. WEP stands for “Wired Equivalent Privacy” which means it should provide the level of protection a wired LAN has. WEP therefore uses the RC4 stream to encrypt data which is transmitted over the air, using usually a single secret key (called the root key or WEP key) of a length of 40 or 104 bit.
A history of WEP and RC4
WEP was previously known to be insecure. In 2001 Scott Fluhrer, Itsik Mantin, and Adi Shamir published an analysis of the RC4 stream cipher. Some time later, it was shown that this attack can be applied to WEP and the secret key can be recovered from about 4,000,000 to 6,000,000 captured data packets. In 2004 a hacker named KoReK improved the attack: the complexity of recovering a 104 bit secret key was reduced to 500,000 to 2,000,000 captured packets.
In 2005, Andreas Klein presented another analysis of the RC4 stream cipher. Klein showed that there are more correlations between the RC4 keystream and the key than the ones found by Fluhrer, Mantin, and Shamir which can additionally be used to break WEP in WEP like usage modes.
