RE: [Cfrg] Re: [saag] Bad day at the hash function factory

[Alex Alten <alten at EscalonNetworks.com>]

At 03:03 PM 8/26/2004 -0700, Scott Fluhrer wrote:
> At 12:22 PM 8/26/2004, Hallam-Baker, Phillip wrote:
> > RC4 has related key weaknesses that make it a poor choice of
> > cipher. Shamir's attack was a cryptanalytic one.
>
> Actually, how WEP used it caused other significant weaknesses, even beyond 
> what we found:
> - Only 2^24 distinct keystreams.  This means that after (at best) 16 
> million packets, you're reusing keystreams, even if RC4 had no related key 
> weakness.
> - No real packet authentication.  With WEP, this mean that if he collects 
> an encrypted packet and guesses its contents, he can then spoof *any* 
> packet (possibly limited to packets of the same length).

I've always wanted a good, short hash for packet authentication.
MD5 or SHA-1 are overkill for packets of 1518 bytes or less, that
last only hundreds of milliseconds on a communications link.

Maybe this is why WEP doesn't have it.

- Alex


--

Alex Alten
alten at EscalonNetworks.com
(510)-353-1104


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