Clarify the description of the protocol

[dbosk]

In section 6, protocol functions should be explained more to
make the reader understand the CROUS. Besides, some functions using hash
functions or PRF should be explained. For generating t_e, is the same
hash function for cid used?

Protocol functions in Sec.6 are not easy to read. Authors should make
them more readable with a deep explanation.

[dbosk]

What do they mean by readable? Do they want all technical details there and not indirected (refs to building blocks). Or do they want more why in the description?

@sbuc what do you think?