Schneier Block Cipher Self-Study - https://www.schneier.com/paper-self-study.html
I'm thinking of working through this. If anyone else is interested we could set up some kind of mailing list (I will be making slow progress, I imagine, and am not the kind of person who solves problems in a group, so for me the list would likely be more about finding relevant papers and the like, or sharing ratings about which are harder, but each to his own...)