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Security in the wireless LAN
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AirLancer
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EN
8.3 Encryption of the data transfer (WEP)
The encryption of the transferred data plays a special part in the wireless
LANs. The supplementary encryption standard WEP is available for IEEE
802.11 radio transfer. WEP means
W ired E quivalent P rivacy. The aim of WEP
is to guarantee the degree of security of cable-based LANs in wireless LANs.
8.3.1 How WEP works
WEP encrypts frames on level 2 of the OSI model. WEP automatically protects
any data of higher protocols (especially IP packets).
WEP uses the established RC4 encryption algorithm of the American
cryptography specialist RSA Data Security, Inc. Two versions with different
key lengths are used:
WEP64
The nominal key length is 64 bits, of which 40 bits (5 characters of 8 bits
each) are user-defined.
WEP128
The nominal key length is 128 bits, of which 104 bits (13 characters of 8
bits each) are user-defined.
The shorter effective key lengths are related to the encryption method of the
RC4 algorithm. RC4 uses the remaining 24 bits to generate a unique key for
every block that needs to be encrypted. These 24 bits form the so-called
“initialization vector”.
Encryption requires computing resources on the part of the wireless LAN
device and has an impact on the transmission rate. With
AirLancer the
speed loss may reach up to 15% independent of the key length used.
8.3.2 Notes for the correct use of keys
By following some important rules regarding the use of keys, you can improve
the security of the encryption process considerably.
Keep your keys as secret as possible.
Never write a key down. Popular, but completely unsuitable storage
options include: note-books, wallets, and text files in your computer. Do
not pass on your key unnecessarily.
Choose a random key.
Use randomly chosen letter and number sequences. Keys that consist of
actual words are not secure.