I think it's important to have a decent understanding of types of crypto (including salt/hashing) as well as where to apply what. IMHO it gets harder when it comes down to protocols used for communications, sync/async, etc.

Also, if you're ever interested in something.. find a protocol in a language, and try to refactor it, but first create a bunch of test cases, and make SURE to include unicode characters, etc in any strings you're testing, high byte characters are often missed as a use case, and it gets weird.

Getting multiple systems in multiple languages talking can sometimes be frustrating to say the least.