CrypTool-Online (CTO) runs in a browser and provides a huge variety of encryption methods and analysis tools including many illustrated examples.
Land der Ideen - Statements
"CrypTool 2 is a great app. All of my students use it every semester. Students have really enjoyed doing the projects that use CrypTool. They really like seeing how encryption works. CrypTool makes learning cryptography fun. I highly recommend it to undergraduate and graduate students. I wish there were more room in my books to write more about CrypTool."
Dr. Randall Boyle, Professor at Longwood University (Virginia)