Re: radius+ wireless

[Tomas Wolf <tomas () skip cz>]

Hello,

 Assuming from your e-mail that you are using 802.11b w/ WEP enabled. 
Long story short - it is possible to crack using off-the-shelf 
(non-expensive) equipment.
 I'm making assessment of my network with such equipment (notebook, 
PCMCIA wireless card, and Linux) and tried how hard it is to crack into 
a WLAN. It is fairly easy - if your network is busy enough (try to 
google for AirSnort).

 Now here is the reason: WEP uses RC4 stream encryption engine to 
encrypt data. In order for this to be "secure" the key it uses for 
encryption shouldn't be used more times than once. Problem is that the 
key is made out of two parts - one of which is static (base key or 
password of 104 bits) and the other one is dynamically perpended to the 
key... But the length of this dynamic key is 24 bits - which means that 
after 2^24 packet is sent we experience key re-usage = prone to 
cryptographic attacks. Also .11b lacks the static key management 
protocol, therefore it is static and doesn't change until it is changed 
manually (unless complimentary protocols are implemented by the 
manufacturer).

 If you use Radius, I would suggest to switch to .11g protocol, where 
WPA can be utilized. Beware of WPA for SOHO users, that is prone to 
attacks as well - but with the combination with Radius the gates are 
stronger.

 I believe that if you go:
http://www.wi-fi.org/
You might get a better picture of standing standards... And if you 
google for WEP you should find plenty to read as well...

Thank you and have a nice day...

Tomas Wolf

Gaspar de Elías wrote:
> hello
> I'm an isp, and i'm providing internet to my customers via wireless,
> authenticating with a radius server on freeBSD. My question is the
> folowing: Can somebody sniff the wireless conections, crack WEP
> alghoritm, and cheat his mac and ip addresses in order to steal
> information from one of my customers?
> A friend told me that doing this is incredibly easy, so i'm investigating. 
> What should i implement to make my wireless lan more secure?