What is CrypTool 1?

CrypTool 1 (CT1) is an open-source Windows program for cryptography and cryptanalysis. It’s the most widespread e-learning software of its kind.

What is CrypTool 2?

CrypTool 2 (CT2) is an open-source program offering an innovative visual programming GUI to experiment with cryptographic procedures and to animate their workflow.

What is JCrypTool?

JCrypTool (JCT) is an open-source e-learning platform, allowing to experiment comprehensively with cryptography on Linux, macOS, and Windows.

What is CrypTool-Online?

CrypTool-Online (CTO) runs in a browser and provides a variety of encryption and cryptanalysis methods including illustrated examples and tools like password generator and password meter.

What is MysteryTwister C3?

MysteryTwister C3 (MTC3) is an international Crypto Cipher Contest offering a broad variety of challenges, a moderated forum, and an ongoing hall-of-fame.
Could you spare a few minutes? Please participate in this short UX survey about CT2 and CrypTool-Online. Your feedback will help us to improve the usability of our software for you.

About CrypTool 2

CrypTool 2 (CT2) is a modern e-learning program for Windows, which visualizes cryptography and cryptanalysis. It includes not only the encryption and cryptanalysis of ciphers, but also their basics and the whole spectrum of modern cryptography.

Modern Plug'n'play Interface / Visual Programming


CT contains over 200 ready-to-use templates with workflows. You can also easily combine and execute cryptographic functions to create workflows in CT2 by yourself (visual programming). With this approach, complex processes can be easily visualized and thus better understood.
By using vector graphics, the current view can be freely scaled.

Visualization of Algorithms

Visualization of Algorithms

The same component that is used in the workflow can also be used to visualize the internal process of the implemented algorithm. This makes it easier for the user to understand the details of a cryptographic process and not lose sight of the big picture – i.e. the real scenario in which the process is used.

Extensive Functions for Cryptanalysis

Frequency Test

CrypTool 2 (CT2) offers a wide range of tools that can be used to analyze and break both classic and modern encryption. For example, you can evaluate frequency distributions, determine the key lengths of polyalphabetic ciphers such as Vigenère, carry out a ciphertext-only attack against an Enigma encryption or a modern padding Oracle attack, or use differential cryptanalysis against block ciphers.

Integrated Online Help

Integrated Online-Help

From the beginning it was a main goal of all CrypTool versions to provide extensive documentation for the many functions. Whenever a user presses F1 on the keyboard, the relevant information of the currently selected function is displayed. In addition to information on how to use a function, the online help also includes theoretical background knowledge and references to according documents available on the Internet.


CrypTool has always been and will always be an open-source project. So, also CT2 is released under an open source license ( Apache Open Source License 2.0 ).

Anyone interested is free to contribute additional functions to CrypTool. CT2 is based on the latest .NET Framework (currently .NET 4.7.2) and implements a pure plug-in architecture that makes it particularly easy to support the development team and get started with programming new functions. As a beginner, you can fully concentrate on the functional aspects, i.e. the implementation of your new function, and only have to implement a few simple interfaces used by the core system.

To get access to the source code and the developer wiki, please have a look at the documentation.

In Wikipedia you will find a description of the whole open source project CrypTool.