Knowing the difference between a an ephemeral keying scheme and a basic RSA key exchange does not make you prepared to implement either.
The Tor developers thought they knew enough to implement DH. Roger Dingledine has publications going back before 2000 and did his doctorate under Rivest. But they forgot to check DH parameters for 0-mod-p (a mistake lots of people manage to make) and so fielded an anonymity network that provided very little anonymity for several years.
Cryptography isn't rocket science. It's more like pyrotechnics. There aren't that many things to remember (though there are more of them than most people think; look how the browsers screwed up RSA a few years ago). It's just that the things you need to remember aren't obvious, and when you get them wrong, you blow your f'ing hands off.