There is the free "Cryptography 1" course on Coursera ( https://www.coursera.org/course/crypto https://www.coursera.org/course/crypto ). I'm taking it right no

There is the free "Cryptography 1" course on Coursera ( https://www.coursera.org/course/crypto https://www.coursera.org/course/crypto ). I'm taking it right now. There's a lot of maths and theory, and it's quite a difficult course, but it's been a great way to learn the foundations of cryptography.