Gary,
Thank you for that thorough response. Although I am technically literate
enough, going through the white paper would have been a time consuming task.
My questions have been thoroughly answered by your response.
Thanks again,
MP
"gary" <(E-Mail Removed)> wrote in message
news:1Yo1c.26260$(E-Mail Removed) m...
> The actual definition of WEP is in the 802.11 standard, which is available
> for free download from the IEEE web site. It will answer all of your
> questions, if you are comfortable reading standards (it's not a how-to
with
> examples).
>
> It's really pretty simple. The AP has a list of up to 4 keys. Each client
> has a list of up to 4 keys. The trick is that, if all lists are identical
in
> content AND order, then it doesn't matter which keys are selected for
> transmit at any endpoint. Each WEP-encrypted frame contains an index
number
> with a value from 0-3 that designates which key was used to encrypt the
> payload. If the receiver has the same last as the sender (in the same
> order), then the index allows it to find the same key for decryption.
>
> It's that simple. If the lists are different, or differently ordered, then
> decryption will only work if the sender happens to encrypt with a key that
> is in the same position on the receiver's list. Using identical lists, all
> endpoints are free to choose arbitrary different transmit keys.
>
> How the system breaks if encryption isn't working depends on the
> authentication method you choose, and to some extent on how the vendor
> implemented the AP firmware and the client driver. WEP has two forms of
> authenticaton: open system, and shared key authentication (only used with
> WEP). With shared key authentication, the AP sends out a random text
string
> as a challenge, and the client must encrypt it and return it to the AP. If
> the AP understands the decrypted frame, then authentication completes.
With
> open system, this step is skipped. Any client that knows the SSID can
> associate successfully under open system even if it does not use WEP,
> because encryption is not used for association except during the challenge
> step.
>
> So, with open system but broken WEP, your driver might tell you that your
> client connected to the network - but will not get a DHCP address. With
> shared key authentication, the driver will probably not indicate a
> successful network connection if WEP is not working.
>
> I recommend against using shared key authentication. It provides no
> additional security over open system (if WEP is enabled, the client still
> must have the key to do anything, whether it is associated or not). Using
> shared key authentication provides any eavesdropper a freebee for
> key-cracking - one frame from the AP with a couple of hundred bytes of
> plaintext, followed by a frame from the client with the same text
encrypted,
> plus the IV and key index use for the encryption. This is a big help.
>
> The only real authentication is provided by WPA using an authentication
> server (and the client also gets to authenticate the AP, making
> man-in-the-middle attacks much harder).
>
> "MP" <(E-Mail Removed)> wrote in message
> news:W1n1c.566$(E-Mail Removed)...
> > I've been trying to find some documentation on this topic but have been
> > unsuccessful. I would like to know what happens if the client is set up
> > with the 4 WEP keys but the wrong key is selected as the Transmit key.
> >
> > Say WEP key #2 needs to be set as the Client Transmit key but I have
> > selected key #4. What happens? How is communication affected? Will the
> > client still be able to register and authenticate? Will it only be able
to
> > register and not authenticate? Will the client try the other keys to
> > transmit until the Access Point accepts it?
> >
> > Any information (especially stuff that is documented) would really be
> > appreciated.
> >
> > Regards,
> > MP
> >
> >
> >
>
>
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