It's one way to do that... but the present format and management of the domain name system isn't important. You can create a security certificate for any form

It's one way to do that... but the present format and management of the domain name system isn't important. You can create a security certificate for any form of text string and use it to validate the other end of the connection. The certificates are essentially a trusted authority saying cryptographically "we have verified this is really the person you think this name is" and that can be done for any identifier. Also, this system was set up before public key encryption became common, and there are plenty of other ways to accomplish the same function with PK crypto.