you can also take matasano's own practical crypto course http://cryptopals.com http://cryptopals.com. If you're taking a vacation, for example, it can be fun to

you can also take matasano's own practical crypto course http://cryptopals.com http://cryptopals.com. If you're taking a vacation, for example, it can be fun to do some of the exercises, write stuff on a notepad, go back to doing exercises and so forth. highly recommended and lighthearted.