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WEP troubleshooting and clarification

I have a Linksys dual band A+B, 5 GHz and 2.4 GHz wireless router, and a USB 2.4 GHz wireless adapter. If I disable the WEP encryption on the router then I can connect from the USB adapter to the router, however, if I enable the WEB and put a network key on any of the frequency (5 or 2.4 GHz), then I cannot connect. Why is that? (Is it because of the difference in frequency?) I already tried all combinations, setting WEP on 2.4 GHz frequency only or setting WEP on 5 GHz frequency only, or both, etc. None of the combination works. It seems like it will only connect if I disable the WEP.
Before I launch into a 'one size fits all answer' I'd like to clarify a few things for both yourself and other readers; the IEEE 802.11 standard defines 40bit WEP only - 40bit may be called 64bit WEP by some vendors but they are the same thing (64bit WEP it just 40bit WEP with 16 bits of padding.)

When the standard was first released, laws surrounding the export of certain encryption schemes prevented the export of anything more than 40bit WEP from the United States. As such, the IEEE decided to standardize on 40bit WEP to ensure that other countries could benefit from their work without having to worry out digital encryption export regulations.

However, when WEP was released (and the digital encryption laws relaxed somewhat) quite a few researchers found flaws in the WEP encryption algorithm and subsequently vendors implemented their own higher-bit encryption WEP algorithms. Some vendors implemented a 112 bit shared key WEP algorithm with 16 bits of padding and called it "128 bit WEP" whilst others implemented 128 bit shared key WEP algorithm with an additional 16 bits of padding and also called it "128 bit WEP." The lack of standardization in "128 bit WEP" has meant that very few vendors' "128 bit WEP" actually operates with any other vendor.

So, given that you're having problems configuring WEP there are two potential issues;

  1. You're using "128 bit WEP" on each device but the WEP isn't interoperable.
  2. You've mis-configured the WEP settings.

In the first case the solution is simple. Use 40 bit WEP. The inherent flaw in the WEP algorithm means that a 128 bit shared key WEP algorithm is only slightly harder to crack that 40 bit WEP and doesn't provide much protection from any determined hacker anyway ? however it still keeps out the 'war-driving script kiddies.'

In the second case you need to ensure that you have configured WEP on both the wireless router AND the wireless adapter. If the wireless adapter appears on your PC as a standard network connection (which I'm pretty sure it would) there should be a configuration utility that goes with it in which you can configure the security/WEP. You will also need to ensure that the wireless router is set to 'require WEP'.

Remember: WEP is a SHARED KEY security architecture. You need to use the SAME key at both ends to enable communication.

This was last published in June 2003

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