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For SSL certificates we have a web-of-trust principle. If we are allowed to make alterations to the certificate format, are there viable ways to automatically or semi-automatically authenticate the certificate information is really about the owner without a CA? It's not an option to distribute keys in advance.

So far I came up with one-time passwords after an handshake making sure that it's for the purpose to send this OTP. Which will have to be sent back through a medium that allows verification, such as texting from a known cellphone number.

Are there any other methods?

Edit: This question was not specific and had terminology mixed around, which resulted in a good practice to counter this. If you are interested in my original question it's been reformulated here: Authentication methods without trusting 3rd parties unless explicitly indicated

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CA != Web of Trust. A web of trust is what PGP uses and is decentralized. –  ewanm89 Apr 20 '12 at 14:02
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If using a side channel, verify the certificate/key fingerprints using it on first connect, pin them for later use (this is what one is supposed to do for SSH, but people often don't check the host fingerprint). –  ewanm89 Apr 20 '12 at 14:04
    
Ah, the PGP web of trust looks nice, didn't know about this. It would allow for a structure to build reputation and show I have X people that say this cert is legit. One issue I predict though. Doesn't this make it public knowledge you are likely to be related to or at least have met the owner of the cert you endorsed, giving somewhat of a privacy leak here? –  Beanow Apr 20 '12 at 14:19
    
Yes, there are issues with web of trust, CA is not better there, it says I've gone and paid money to them. Also there are variations of how to calculate how much trust in a web of trust model, if it's a best friend who I trust completely who has signed it, should I trust it more? Ultimately web of trust is more like an endorsement from a friend. –  ewanm89 Apr 20 '12 at 14:26
    
Yeah I see, though a certificate that says Comodo signed this reveals less about me as a person then a certificate that is signed by my 20 best friends with PGP. Imagine one of them is in the US and they consider them a terrorist for god knows what law this time, I would be directly associated to them. While this would not easily occur with one CA. Both socially and statistically because a CA would mean one relationship per certificate while web-of-trust would mean many relationships. –  Beanow Apr 20 '12 at 14:57
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up vote 2 down vote accepted

This is a bit muddled. SSL certificates do not use web-of-trust; they use certificate authorities (CAs). Basically, the CAs vouch that the public key for www.example.com is such-and-such. The web-of-trust model is used by PGP, and is intended as an alternative to CAs. So, if you want certificates without CAs, you could look at how the web-of-trust model works -- but beware, it's not clear that it works very well in practice.

It sounds like you want to somehow do without CAs. OK. So what properties do you want your certificates to vouch for? Basically, think of a certificate as a signed statement: "I promise that the public key for www.example.com is 0xD6EF...1E2, signed, Verisign". When relying parties receive this kind of certificate, that statement tells them what they can rely upon. In your new world, what do you want recipients to be able to rely upon? And, if you don't want to have a Verisign present, who is going to verify that those promises are in fact true?

In short, I suggest you think about what you are trying to achieve and what security guarantees you are looking for -- then we can talk about how to achieve them without CAs. Try to write down what you want recipients to be able to rely upon (ignoring the crypto), and who will be responsible for verifying those things are true, and then we can look at the technology.

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Yes I had my concept of web-of-trust wrong. (Thought that CA's signing CA's signing CA's signing your cert was meant with web of trust, but this is a PKI rather) –  Beanow Apr 22 '12 at 0:49
    
The concept of CA and the implications of signing are clear to me. And have indeed been writing down what you suggested. Which has taken shape quite well, just trying to find more optional authentication features so my question was poorly formulated and not concrete. –  Beanow Apr 22 '12 at 0:54
    
I'm unsure if I should edit it as it would take your answers completely out of context or leave it here and create a new question. Just this time better :P –  Beanow Apr 22 '12 at 0:55
    
I will leave it as is, give you the accepted answer and put up a new question. Since I do think it's a good practice to go through the steps you suggested to get a clear concept of the requirements. –  Beanow Apr 22 '12 at 1:12
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