Introduction - ZyXEL Communications P-660R-T1 Support Notes

P-660 series Support Notes

Introduction

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 mediu m,
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 po int (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 ins tallations 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 defensed 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 packets, 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 reason
for this misnomer is that the WEP key (40/104 bits ) is concatenated with the
initialisation vector ( 24 bits ) resulting in a 64/128 bits total key size.
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