From: Jens Lechtenboerger <jens.lechtenboerger@fsfe.org>
To: info-gnus-english@gnu.org
Subject: Re: Trust and public keys
Date: Mon, 16 Nov 2015 22:15:33 +0100 [thread overview]
Message-ID: <87k2phprwq.fsf@informationelle-selbstbestimmung-im-internet.de> (raw)
In-Reply-To: <87io53j7ji.fsf@mat.ucm.es> (Uwe Brauer's message of "Sun, 15 Nov 2015 21:07:29 +0000")
On 2015-11-15, at 21:07, Uwe Brauer wrote:
> If I had to communicate something really secret say with Ed Snowden, I
> would use of course use gpg[1] and not smime, ,
> then I would try somehow to compare the fingerprints of the keys by some
> secure means (a secure chat).
>
> Now if you say that all the above scenarios are usually out of reach of
> «normal» attackers,
That came out wrong, then. Part of my problem would be to figure
out the “real” e-mail address of “Ed Snowden”. If you registered
the fresh e-mail address “ed.snowden@gmail.com” and uploaded a
matching key to usual keyservers, then I might fall for that. No
special attack skills required.
I don’t know too much about CAs that issue e-mail certificates for
free. However, based on your description of Comodo I guess that you
could also obtain an S/MIME certificate in the above case (for
ed.snowden@gmail.com after registering that address). So the
“trust” built into S/MIME seems worthless.
> When I apply for a certificate the private key is generated by the crypt
> module of my browser. Are you suggesting that this is also hacked? That
> indeed would be disastrous. Then indeed the intruder could obtain a copy
> of my private key and sell it to some sinister organisation.
For me as malicious CA (or intruder into a CA) there is no reason to
steal the private key as I could generate a certificate with
matching private key in your name for your e-mail address, which is
“trusted”. Then I could send signed e-mails in your name. That
alone might get you into trouble, but you might receive responses
that alert you about some ongoing attack. If I was a powerful
attacker, able to replace e-mails on the way, I could additionally
re-encrypt (modified) responses to your real certificate (or drop
messages entirely), and you would never know I was there.
If I cannot replace e-mails on the way, I can still send “trusted”
signed e-mails in your name and tell the recipients to switch to
different e-mail addresses with “trusted” certificates. Then,
again, I can re-encrypt responses to your real certificate and
e-mail address.
Best wishes
Jens
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next prev parent reply other threads:[~2015-11-16 21:15 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-08 16:15 S/MIME with OpenSSL? Jens Lechtenboerger
2015-11-10 16:42 ` Uwe Brauer
2015-11-10 21:41 ` Adam Sjøgren
2015-11-11 9:38 ` Uwe Brauer
2015-11-11 16:12 ` Adam Sjøgren
2015-11-12 9:31 ` Uwe Brauer
2015-11-12 15:31 ` Adam Sjøgren
2015-11-13 18:55 ` Uwe Brauer
2015-11-14 15:37 ` Trust and public keys (was: S/MIME with OpenSSL?) Jens Lechtenboerger
2015-11-15 21:07 ` Trust and public keys Uwe Brauer
2015-11-16 21:15 ` Jens Lechtenboerger [this message]
2015-11-18 15:04 ` Uwe Brauer
2015-11-19 17:05 ` Jens Lechtenboerger
2015-11-22 18:09 ` [smime and gpg] (was: Trust and public keys) Uwe Brauer
2015-11-16 11:32 ` Trust and public keys Uwe Brauer
2015-11-12 19:20 ` S/MIME with OpenSSL? Peter Münster
2015-11-13 18:21 ` Uwe Brauer
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