Re: Need some education: Man-in-the-Middle Attacks



The fact that SSH tells you the fingerprint has changes. If the user
is "dumb" enough to pass by it, and don't care, then he deserves to be
"Hijacked".

On 8/31/06, Christ, Bryan <bryan.christ@xxxxxx> wrote:
But if Eve is later challenged to prove her identity (that she must now
maintain the illusion of being Alice), what prevents Eve from passing
the challenge on to the real Alice, getting valid results, and then
passing them back to Bob?

On Thu, 2006-08-31 at 10:01 +0400, Eygene Ryabinkin wrote:
> Bryan,
> > I was looking at the diagram on the URL listed below and contemplating
> > how host fingerprinting prevents MITM attacks.
> >
> > http://www.vandyke.com/solutions/ssh_overview/ssh_overview_threats.html
> >
> > So my question is this... Given the illustration in the URL above, what
> > prevents Eve from *first* contacting Alice to obtain a fingerprint which
> > then gets passed to Bob on the first connection attempt?
>
> She can obtain it, but the fingerprint is closely related to the
> Alice's private key that Eve can not obtain easily. So there is
> no reason for Eve to pass Alice's fingerprint to Bob, because later
> she will not be able to prove to Bob that she has the corresponding
> private key and it will break the connection between Bob and Eve.




Relevant Pages

  • Re: Need some education: Man-in-the-Middle Attacks
    ... not have the private key, and therefore cannot decrypt, Alice does. ... Therefore Eve could send the information to Alice, get a valid response, ... and then Eve passes that response back to Bob. ... If Bob is cautious, however, he will have gotten the fingerprint from Alice beforehand, using the telephone, PGP/GPG or some other means, and he would notice that the fingerprint of Eve's key doesn't match the fingerprint that Alice told him to expect. ...
    (SSH)
  • Re: Need some education: Man-in-the-Middle Attacks
    ... But if Eve is later challenged to prove her identity (that she must now ... maintain the illusion of being Alice), ... then gets passed to Bob on the first connection attempt? ... but the fingerprint is closely related to the ...
    (SSH)
  • Re: =?ISO-8859-1?Q?Betr=FCgerische_Relativit=E4tstheorie=3A_?= =?ISO-8859-1?Q?Blauer
    ... Das Signal kommt aus der Vergangenheit. ... Man stelle Bob auf den Berg und Eve ins Tal und lasse Bob aus SEINER Sicht zu Zeitpunkt t_0 einen Stift fallen. ...
    (de.sci.physik)
  • =?iso-8859-1?q?Re:_Betr=FCgerische_Relativit=E4tstheorie:_Blauer_Himmel_widerlegt_Einstein?=
    ... Das Signal kommt aus der Vergangenheit. ... Man stelle Bob auf den Berg und Eve ins Tal und lasse Bob aus SEINER ... Sicht zu Zeitpunkt t_0 einen Stift fallen. ...
    (de.sci.physik)
  • Re: KA=>OWF
    ... >>Specifically, if Eve can ... since Alice and Bob together do compute ... must also be tractable functions g1 and g2 such that: ... assumed the key-agreement protocol *must* end with agreement on ...
    (sci.crypt)