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
"In Warsaw University of Technology we have been using CrypTool for five years. It is especially useful for students who need soft, but comprehensive introduction into IT security. As far, as I know there are no other applications in this field with so many didactic features."