If you’re curious how the real world cryptography works and how it is being broken, join us in solving the Matasano Crypto Challenge exercises the next Tuesday. The last time we went up to Set 1, ex. 3 – we’ll recap the previous exercises if necessary, so feel free to join even if you missed the first meetup.

All you need is a basic familiarity with at least one programming language, 9th grade math knowledge and a laptop.
More info: http://cryptopals.com/
https://blog.pinboard.in/2013/04/the_matasano_crypto_challenges/