Apparently HTTPS is just plain HTTP over plain SSL:

<https://www.feistyduck.com/library/openssl-cookbook/online/ch-testing-with-openssl.html>

<https://en.wikipedia.org/wiki/HTTPS#Technical>

SSL is becoming so ubiquitous, and yet is so tricky to implement, that
it might be nice to have easy procedures to make SSL connections in
addition to ordinary unencrypted TCP connections. So the connection is
just an encrypted pipe, and you supply the application-layer protocol
that runs above it. The simplest implementation would be just to run
OpenSSL as a subprocess. This is an easy way to e.g. turn a pure-Scheme
HTTP client into a HTTPS client, leaving most of the security and
certificate considerations to others.

I don't have any particular crypto expertise; if someone here does, I'll
gladly defer to them.