Would have to be with a very noticable warning. Other than that, it could use TOFU like Gemini.
@Hyolobrika
It almost works like that already.
When you open a page on a server with self-signed cert, it gives you a warning, if you accept it, it adds an exception for that cert — you can see the list in preferences under Privacy & Security → Certificates → View certificates → Servers
@Hyolobrika
It also keeps the fingerprints so if you get a different cert on a later visit, it will give you a warning again.
To simplify adding an exception on the first visit you might want to consider this: http://kb.mozillazine.org/Browser.xul.error_pages.expert_bad_cert
@Hyolobrika @Hyolobrika
Self-signed certs do not provide the capability to revoke them. Imagine that a malicious actor isn't just spoofing the site you trust with their own self-signed cert, but that the private key got compromised. With self-signed certs you have no way of telling users that the already trusted certificate is no longer valid, such a capability implies some sort of infrastructure and infrastructure implies hierarchy as someone has to operate it🤷
@Hyolobrika
It does — and it does have infrastructure for that, but as PGP has much smaller user base, keeping it up it isn't a problem.
Also, AFAIK while it is possible to revoke your certificate, you can't just update the entry in this DB if your key gets compromised in a straightforward way — as far as I recall, it involves jumping through lots of hoops.