Same here. I also took the course from Coursera a few years ago and I really enjoyed it. The conclusion? It’s hard to get it right so don’t do crypto yourself! Quite cynical, but it kinda killed my interest in pursuing it further.

Yes, the Coursera title was "Cryptography I", so I was expecting another part, but ten years after, I still do not see any. A great course anyway.

There's a running joke among cryptographers that Dan will release Crypto II next semester =)

Yes that is a lesson I took from it, I'm not sure if it was this class or another one that showed how crypto on a computer could be defeated by monitoring its power consumption while checking a password. Even though the code knew to wait a set amount of time whether or not the password was correct, it wasn't drawing any power after the first incorrect digit allowing attackers to workout the correct digits one at a time.