Re: Trust and public keys

[Uwe Brauer]

   > On 2015-11-15, at 21:07, Uwe Brauer wrote:

   > 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.

Correct but this applies to smime and gpg.


   > 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.

For class 1 certificate yes, for class 2 not, there you have to show up
(and to pay.)

   > 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.

But in all of these scenarios you need to hack the email account. It is
not sufficent just to use a linux smptmail server and manipulate the
form field. You also have to intercept the reply.

I don't see much of a difference between

    -  the pgp scenario: to place a falsified  pgp key on a server 

    -  the smime scenario:  to crack a smime certificate by breaching a
       CA (which is more difficult that placing a falsified pgp key).


Best

Uwe

Again the question was is smime easier to use.