Prof. Dan Boneh's Cryptography I is really good.

Compared to many other MOOCs, it provides solid foundations while being easy to follow.

https://www.coursera.org/learn/crypto

Computer Networks is definitely the best MOOC I ever took. I hope they bring it back.

Computer Networks looks great it's a shame they pulled it down.

Take a look at https://lagunita.stanford.edu/courses/Engineering/Networking.... Haven't taken either, but Stanford typically puts out pretty good MOOCs.

Lectures are great. Material is at a solid undergrad level (should be suitable for someone with 1-2yrs of CS background). No programming assignments, so I would go look at Phil Levis's website to find the "regular" course website and do the programming assignments from there.

I LOVED discrete optimisation