Tools to practice cryptanalysis and cryptography techniques

Question

I am looking for tools (preferably free) to practice various cryptoanalysis and cryptography techniques. Something along the lines of following two online tools but with more techniques.

http://www.cryptool-online.org/index.php?option=com_content&view=article&id=55&Itemid=53&lang=en

http://www.simonsingh.net/The_Black_Chamber/letterfrequencies.html

Any suggestions would be very welcome.

Thanks, Ambi.

Answer 1

The Matasano Crypto Challenges are an excellent learning resource for cryptography.

We've built a collection of 48 exercises that demonstrate attacks on real-world crypto.

This is a different way to learn about crypto than taking a class or reading a book. We give you problems to solve. They're derived from weaknesses in real-world systems and modern cryptographic constructions. We give you enough info to learn about the underlying crypto concepts yourself. When you're finished, you'll not only have learned a good deal about how cryptosystems are built, but you'll also understand how they're attacked.

The first couple of sets may seem a bit too easy for someone acquainted with cryptography, but the challenges quickly get more tricky and advanced.