> and then the same mechanism that checks SSL certificates then also checks if the host's key actually matches what the rest of the system (the configured CAs)

> and then the same mechanism that checks SSL certificates then also checks if the host's key actually matches what the rest of the system (the configured CAs) is saying it should be. That's not what mjg59 is suggesting, to establish a trust chain to system shipped CAs. In fact that wouldn't be so easy anways because SSH certificates aren't X.509 compatible at all but use their completely homegrown specification. They explicitly say "please do not do this" about this idea. mjg59 suggests to make the TOFU approach on the client trust certificates if a certificate is provided. That's a way narrower suggestion: > OpenSSH has no way to do TOFU for CAs, just the keys themselves. This means there's no way to do a git clone ssh://git@github.com/whatever and get a prompt asking you to trust Github's CA. Instead, you need to add a @cert-authority github.com (key) line to your known_hosts file by hand, and since approximately nobody's going to do that there's only marginal benefit in going to the effort to implement this infrastructure. The most important thing we can do to improve the security of the SSH ecosystem is to make it easier to use certificates, and that means improving the behaviour of the clients.