Re: Hardware potential to duplicate existing host keys... RSA DS

RW <rwmaillists@googlemail.com> writes:
> Dag-Erling Sm=C3=B8rgrav <des@des.no> writes:
> > [host keys] are used for authentication only.  This is crypto 101.
> It also generates a shared secret for key exchange, which is pretty
> much what I said.

No.  It is used to *sign* the key exhange, in order to authenticate the
server.  It is not used to *generate* the key.  You need to read up on
Diffie Hellman and the SSH transport layer (RFC 4253).  The only way to
intercept the key is a man-in-the-middle attack (negotiate a KEX with
the client, sign it with the stolen host key, and negotiate a KEX with
the server, pretending to be the client)

> > Having a copy of the host key allows you to do one thing and one thing
> > only: impersonate the server.  It does not allow you to eavesdrop on
> > an already-established connection.
> It enables you to eavesdrop on new connections, and  eavesdroppers
> are often in a position to force reconnection on old ones.

No.

DES
--=20
Dag-Erling Sm=C3=B8rgrav - des@des.no
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