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RE: Safety of pre-shared keys? (Re: Reliable delete notifies)
Arne:
> If one can snoop the network but not inject new packets, then
> he cannot
> break authenticity but can break confidentiality.
Unless of course the packets are encrypted. My previous statement doesn't
apply unless you try...
If the channel is somehow magically protected against spoofing, but not
against snooping then an unauthenticated Diffie-Hellman is sufficient to
generate a secure encryption key.
My whole point here was that if you already have an authenticated channel
then setting up encryption is trivial. Therefore, the confidentiality
requirement is equally or less difficult to satisfy than the authentication
requirement.
Chris:
> There are many ways to verify that the correct key has been
> transferred - an
> attacker would have to defeat them all. Confidentiality is muh more
> fragile.
Only if you assume that multiple weak authentications can add up to a strong
authentication.
Andrew
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Beauty with out truth is insubstantial.
Truth without beauty is unbearable.
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