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Re: Please kill preshared key.
Just for argument sake,
what if these pre-shared symmetric keys are from the DH keys that generated
off-line.
(no real exchnage but using the same process to get the key)
Although this is not DH key exchange's function,
it does achieve the same key quality...
It can be used as both authentication and encryption.
(the key is distributed through 'out-of-band' secured channel)
--- David
----- Original Message -----
From: "Henry Spencer" <henry@spsystems.net>
To: "david chen" <ietf_davidchen@hotmail.com>
Cc: <ipsec@lists.tislabs.com>
Sent: Saturday, December 08, 2001 11:39 PM
Subject: Re: Please kill preshared key.
> On Fri, 7 Dec 2001, david chen wrote:
> > > > What I infered is that
> > > > the pre-shared symmetric key can be used for both authentication and
> > > > encryption without key-exchange (KE) ...
> > > Your inference is incorrect. That is not how today's IPSec PSK works.
> >
> > Agree,..
> > However, do you agree my statement make sense?
>
> Only if the preshared key is fairly high quality, which it often isn't.
> Using a poor key only for gateway authentication exposes you to
> impersonation attacks, but those are typically much more difficult to
> mount than eavesdropping attacks, which are the dominant failure mode with
> a poor encryption key.
>
> Henry Spencer
> henry@spsystems.net
>
>
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