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.


The origins of modern cryptography date back approximately 3000 years. The procedures used to encrypt messages before 1900 were primitive compared to modern approaches, but they are easy to understand and provide a good basis to study the more complicated methods. In recent times, especially after the emergence of telecommunication equipment, more complex encryption methods have become necessary. Today, an exorbitant amount of information is transmitted via the internet. Millions of people use websites for their banking activities causing the transmission of sensible data via networks where the precise routing of data is not always known and data may be manipulated or stolen.

This website gives you the opportunity to learn about ciphers and to test them in an interactive way within your browser. Try to encrypt a message for yourself and send it to a friend. Learn about the weak spots of popular ciphers and how they can be decrypted without knowing the key.

Ciphers are popular for geocaching (www.geocaching.com, http://en.wikipedia.org/wiki/Geocaching) to provide hints for the "treasure hunt". The ROT13 cipher is mostly used for geocaching, but also other classic ciphers like substitution, rail fence, Enigma. Often a hint is provided which indicates the cipher that was used.