I see publication of source code as another security signal. Even though nobody will look at it, the mere fact that they publish it demonstrates their confidence that there are no back doors. If someone finds one it would be devastating to them, especially as a new company trying to establish a track record. By putting themselves at risk for this, they demonstrate that no such risk exists.

Source code publication is better understood as a case of security signalling than a method to improve the security of the product.

You say that SSH protects against MITM attacks. Well, it does, but that's like comparing apples and oranges. SSH is being used by admins/geeks that understand what it means when SSH tells them that the key of the remote site has changed. This may *help* to notice a MITM attack, but it doesn't protect against it. Further, the user usually knows the server to which he is connecting and may know if the existence of a new key is ok or not.

With email crypto this is different. I simply don't know if a user just changed his certificate or key (for whatever reason) or if I'm seeing a fake one. Personally, I simply want to be able to renew my key as often as I like and don't want to go through the pain of telling my peers that I've got a new key.

With Ciphire they could probably add a warning if the client sees a new certificate for a particular email address. AFAIK the client already checks the old certificates, ie it walks back the chain of old certificates to verify if it leads to a previously known/used certificate. But a certificate mismatch warning like the on used in SSH would probably scare a normal user to death. ... Most (normal) users are simply clicking 'Ok' if they are seeing a 'new SSL certificate' warning for their mail server because they don't understand what it means.

Petnames and logos ... well, I'm not sure if this is really going to be a solution. In the case of email crypto, what should I do if I found out that the certificate/key changed? The user may just renewed his key ... Fingerprint checks are annoying and the Web of Trust doesn't really work. I've several dotzens signatures on my PGP key, but does it help me to avoid fingerprint checks? No, it doesn't.