How to cut out the CA middleman
SSL certificates work on trust: end users trust their browsers, and browsers trust “certificate authorities” (CAs) like Gandi. But the chain goes one step further: the CA trusts DNS. When you buy an SSL certificate for foo.com
from a CA like Gandi, Gandi verifies that you foo.com
by challenging you to modify the DNS for that domain. The ultimate trusted authority is not the CA; it is the Domain Name System.
There is therefore a much simpler alternative to SSL certificates, which cuts out the CA middleman: have the browser consult DNS directly. The browser already consults DNS for the server’s IP; we would additionally have the browser ask DNS for a public key for that domain. It would run like this:
- Company buys
foo.com
from the.com
registrar. - Company generates keypair.
- Company puts public key in
foo.com
DNS under aTXT
record (or some newPUBKEY
record). - Company puts private key on server.
- Company points
foo.com
’sA
record to the server’s IP. - User visits
foo.com
in browser. - Browser asks DNS for the
A
record andPUBKEY
record forfoo.com
. - Browser opens connection to the server, using server’s public key to establish shared secret.
- Browser and server communicate in a session.
Here, no Certificate Authorities are involved, but the user still has the same guarantees: it is talking in private to a server which is operated by the owner of foo.com
.
Tagged . All content copyright James Fisher 2017. This post is not associated with my employer.