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RE: Safety of pre-shared keys? (Re: Reliable delete notifies)
> The authenticity requirement is always equally or more difficult to satisfy
> than the confidentiality requirement so the point is moot.
I don't agree. One must have a write access to some data in order to break
its authenticity. In order to break it's confidentiality read access is
sufficient. Read access is usually much easier to gain than write access.
Examples:
If one can snoop the network but not inject new packets, then he cannot
break authenticity but can break confidentiality.
If one can read swap file or /dev/kmem or backup tape then one can break
the confidentiality of running system. On the other hand one needs a write
access to running system to break the authenticity.
The whole point of the Diffie-Hellman key exchange is to create
confidential communication channel using authentic communication channel.
Arne Ansper
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