Well, it would be, except the pipeline seems to be clogged. I'm waiting weeks and months to get a response. Which is frustrating because the early problems are already really interesting, and I want more!
This is a good choice. One of the challenges had me stuck for months because I hadn't realised that you really need fine-grained control over bitshifting that e.g. Ruby doesn't appear to give you. Taking twenty minutes to re-write my solution to that challenge in C sorted it out straight away.
Yeah, that ain't it! I'd warn you that it gets much tougher in later challenges. The beginning of set three resulted in many, many pages of ones and zeros in my notebook. All good fun though!
http://www.matasano.com/articles/crypto-challenges/
Myself, I'm trying them in ANSI C