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Yes, SSL prevents MITM but my point was that a self-signed certificate does this just as well as an automated certificate from LetsEncrypt.
by zaptheimpaler 5y ago
Yes, SSL prevents MITM but my point was that a self-signed certificate does this just as well as an automated certificate from LetsEncrypt.
- xg15 5y agoIt doesn't though. The attacker could simply present their own self-signed certificate - and there'd be no reliable way to determine which certificate is the right one. You could mitigate this with some kind of (non-scary) trust-on-first-use UI. But even that doesn't help you if you're unlucky enough to encounter the attacker before the real site. (Which isn't even that unlikely if the attacker is e.g. an ISP proxying all connections by default) What LE gives you is a signed statement saying in effect: "we've seen that the owner of this cert can make changes to the domain which are visible from multiple different network locations - so they are very likely the real owner of the domain and not a MITM". That's valuable, even if it doesn't tell you anything about who that entity is. What I absolutely would wish for is some mechanism to include a cert hash in the URL. Then you could e.g. distribute QR codes with the cert hash embedded and circumvent the trust problem that way. Then, I agree, there would be no reason not to use self-signed certificates with that technique.
- zaptheimpaler 5y agoOh cool, that makes sense now. Thanks!