Not a cryptocurrency course per se, but Dan Boneh's course on Cryptography[1] is an excellent introduction to most of the building blocks of cryptosystems, including the technology underlying most cryptocurrencies.

In terms of level, it is more than a little technical (programming exercises in both cryptography and cryptanalysis await you!), while still remaining far from rigorous (compared to, say, a graduate-level cryptography text).

[1]https://www.coursera.org/learn/crypto