ZyXEL Communications 2602HWNLI-D7A User Manual

 

All contents copyright (c) 2007 ZyXEL Communications Corporation.   

101 

 

 

The 802.11 standard describes the communication that occurs in wireless LANs. 

The Wired Equivalent Privacy (WEP) algorithm is used to protect wireless communication from 

eavesdropping, because wireless transmissions are easier to intercept than transmissions over wired 

networks, and wireless is a shared medium, everything that is transmitted or received over a wireless 

network can be intercepted. 

WEP relies on a secret key that is shared between a mobile station (e.g. a laptop with a wireless Ethernet 

card) and an access point (i.e. a base station). The secret key is used to encrypt packets before they are 

transmitted, and an integrity check is used to ensure that packages are not modified during the transition. 

The standard does not discuss how the shared key is established. In practice, most installations use a 

single key that is shared between all mobile stations and access points APs. 

WEP employs the key encryption algorithm, Ron's Code 4 Pseudo Random Number Generator (RC4 

PRNG). The same key is used to encrypt and decrypt the data. 

 

 

WEP has defended against this attack. To avoid encrypting two cipher texts with the same key stream, an 

Initialisation Vector (IV) is used to augment the shared WEP key (secret key) and produce a different 

RC4 key for each packet, the IV is also included in the package. WEP key (secret key) are available in 

two types, 64-bits and 128-bits. Many times you will see them referenced as 40-bits and 104-bits instead. 

The reson for this misnomer is that the WEP key ( 40/104 bits ) is concatenated with the initialisation 

vector ( 24 bits ) resulting in a 64/128 bit total key size.