CrypTool 1 (CT1) is a free Windows program for cryptography and cryptanalysis.
It is part of the CrypTool Project.
CT1 is available in 6 languages and still one of our most popular software variants.
In future, only bugfix and maintenance versions of CrypTool 1 will be released. New features will be included in the successor versions CrypTool 2 and CrypTool-Online, which will be actively developed further.