Lancom AirLancer MC-54, Manual

Page: 38 / 47

Security within the Wireless LAN
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AirLancer
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38
EN
The access to an infrastructure network can be restricted to known MAC
addresses for certain Wireless LAN devices solely. To do so, Access Control
lists are available within the LANCOM base stations, in which the granted
MAC addresses can be deposited.
This method of access control is not available for ad-hoc networks.
7.3 Encryption of the data transfer (WEP)
A special role comes up to the encryption of data transfer for Wireless LANs.
For IEEE 802.11 radio transfer the supplementing encryption standard is WEP,
which means
W ired E quivalent P rivacy. The function of WEP is to ensure the
security level of cable-bound LANs also in Wireless LANs.
The WEP protocol encrypts the radio data with a typical key length of 40, 104
or 128 bit.
7.3.1 WEP functionality
WEP encrypts data frames on level 2 of the OSI model. Thus data frames of
higher protocols (in particular IP packets) are automatically protected by
WEP.
WEP uses the well-known RC4 algorithm of the american cryptography spe-
cialist RSA Data Security for encryption. Several variants with different key
lengths are available:
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WEP64
The nominal key length is 64 bit, with 40 bit (5 characters, each 8 bit)
freely selectable.
•
WEP128
The nominal key length is 128 bit, with 104 bit (13 characters, each 8 bit)
freely selectable.
•
WEP152
The nominal key length is 152 bit, with keys of 128 bit length, whereof
128 bit (16 characters, each 8 bit) are freely selectable. WEP152 is only
available for 54 Mbps devices.
The shorter effective key lengths result from the encryption method of the
RC4 algorithm. RC4 uses the remaining 24 bits in order to produce a unique
key for each encrypted block. These 24 bits are the so-called ’initialization
vector’.