CrypTool 1 (CT1) is an open-source Windows program for cryptography and cryptanalysis. It’s the most wide-spreaded e-learning software of its kind.
Land der Ideen - Statements
"The non-numerate students found the pictorial descriptions of how the various processes work invaluable. They speak of CrypTool helping to remove their fear of the subject. A few have even reluctantly admitted that CrypTool brought the subject to life and made it fun."