Why CAs or public keysigning?
Wed Jun 18 19:27:02 2003
** Kyle Hasselbacher (Mittwoch, 18. Juni 2003 18:44)
> If I don't know my intended recipient personally, I can't see that my
> communication would be important enough to worry about this attack.
> If I DO know the recipient personally, this is easy to defend against
> (send an initial message confirming the identity; ask something like
> "how did we meet?").
> Also, it's hard to imagine this attack being deliberate. I could
> imagine someone making a fake ID for the purpose of getting a trusted
> signature on a key, but that's not the situation we're talking about
> (different person who REALLY DOES have the same name), or is it?
This is all true, also Peter's objections against third party trust.
But let's face the praxis:
1. What do I use keys for?
I use them for signing a message. This verifies that it was really I who
wrote the message and the message was not changed after I sent it.
I use them to encrypt messages. This verifies the 2 points in the first
chapter plus hides the contents from third party's eyes.
2. Who do I send signed messages to?
I send them to mailinglists, persons I don't know personally, any
persons if I want to make sure named points in chapter 1.1.
For this a CA verification is enough because I sent those messages to
mail addresses rather than real persons (although behind every mail
address there sleeps a human being - almost).
If the recipient is in doubt he can always mail back for my fingerprint.
Or, as many users do, I put my ascii armored public key on my website
where one can also find personal information about me (including
3. Who do I send encrypted messages to?
I send them to persons I either stayed in touch to for some time or
persons I know in RL. In both cases there is already an established
communication history which makes it easy to exchange fingerprints
and/or public keys within signed messages or via phone or in RL.
I don't see any reason why I should send an encrypted message to any
other person. At least I did not find any reason through my years of
using the private/public key system (first pgp, then gnupg).
IMHO this discussion may be academical interesting but has only little
relevance to real life.
Public GnuPG key available at http://www.wolf-b.de/misc