Public storage for public keys

[Jason Stone]

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> > Yes, saved in a trusted location (ie, local file system).
> > A key in DNS is not trustworthy, since DNS is easily
> > compromised.
>
> Then the hard part - JH would have to play man-in-the-middle between A
> and B enough to convince A that the spoofed host key for B is okay...
> but how can JH do this without knowing the REAL private host key for
> system B?  What am I missing?

No, JH doesn't have to know B's private key - that's the point.  A doesn't
know B's public key ('cause this whole discussion is about how to give it
to him), so JH gets in the middle of A and B (check out dsniff, ettercap,
etc - this is real easy nowadays), and when A asks for B's public key, JH
hands his own public key to A.  Now A encrypts all his packets with JH's
key and sends them to JH.  JH then requests B's public key, decrypts all
of A's packets, re-encrypts them with B's public key, and passes them on
to B.  Neither A nor B realizes, because at a fundamental level, they
don't _really_ know each other if they haven't already exchanged keys and
cached them locally.

Man-in-the-middle attacks are no longer strictly theoretical, nor reserved
for hardcore hackers.  Easy and powerful tools are widely available to let
just anyone perform active attacks against a local net, even a switched
one, and shoddy key exchange is completely unacceptable.


You _could_ use DNSSEC to distribute the keys, and I'm interested in why
this ended up being rejected?


 -Jason

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