I took his Introduction to Cryptography class when he was a visiting professor at Columbia. Absolute master of an old-school chalkboard lecturer. They don't make them like that any more.
Hugely engaging, the margins of my notebook had many of his quips… there was an archive online somewhere.
e.g., x minus x is zero, even for Euler, so therefore…
Found on Archive, https://web.archive.org/web/20210509160248/http://www.eecs.h...
I know him from Harvard and came here to say pretty much the same thing. RIP.