User's Manual

Appendix
BreezeNET PRO.11 Series 8-30 User’s Guide
8.5.7.1 Preventing Access to Network Resources
This is done by the use of an Authentication mechanism where a station
needs to prove knowledge of the current key. This is very similar to Wired
LAN privacy, in the sense that an intruder needs to enter the premises (by
using a physical key) in order to connect his workstation to the wired LAN.
8.5.7.2 Eavesdropping
Eavesdropping is prevented by using the WEP algorithm which is a Pseudo
Random Number Generator initialized by a shared secret key. This PRNG
outputs a key sequence of pseudo-random bits equal in length to the largest
possible packet which is combined with the outgoing/incoming packet
producing the packet transmitted in the air.
The WEP is a simple algorithm based on RSA’s RC4 which has the
following properties:
• Reasonably strong:
Brute-force attack to this algorithm is difficult because every frame is
sent with an Initialization Vector which restarts the PRNG for each
frame.
• Self Synchronizing:
The algorithm re-synchronizes for each message. This is necessary in
order to work in a connection-less environment, where packets may get
lost (as any LAN).
8.5.8. Power Saving
Wireless LANs are typically related to mobile applications. In this type of
application, battery power is a scare resource. This is the reason why the
802.11 standard directly addresses the issue of Power Saving and defines an
entire mechanism which enables stations to go into sleep mode for long
periods of time without losing information.
The main idea behind the Power Saving Mechanism is that the AP
maintains a continually updated record of the stations currently working in
Power Saving mode, and buffers the packets addressed to these stations
until either the stations specifically request the packets by sending a polling
request, or until they change their operation mode.
As part of its Beacon Frames, the AP also periodically transmits information
about which Power Saving Stations have frames buffered at the AP, so these