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Developer(s)Bernhard Esslinger
Initial release1998; 26 years ago (1998)
Stable release
CT 1.4.42 (December 2021)

CT 2.1 (release 2022.1) (December 2022)
JCT 1.0.3 (February 2021)

Operating systemCT1 and CT2: Microsoft Windows,
JCT: Win, Linux and macOS
TypeCryptography, Encryption, Privacy, E-Learning
LicenseApache Licence 2.0

CrypTool is an open-source project[1] that is a free e-learning software for illustrating cryptographic and cryptanalytic concepts. According to "Hakin9",[2] CrypTool is worldwide the most widespread e-learning software in the field of cryptology.[3][4]

CrypTool implements more than 400 algorithms.[5]

Development, history and roadmap[edit]

The development of CrypTool started in 1998. Originally developed by German companies and universities, it is an open-source project since 2001. More than sixty people worldwide contribute regularly to the project. Contributions as software plugins came from universities or schools in the following towns: Belgrad, Berlin, Bochum, Brisbane, Darmstadt, Dubai, Duisburg-Essen, Eindhoven, Hagenberg, Jena, Kassel, Klagenfurt, Koblenz, London, Madrid, Mannheim, San Jose, Siegen, Utrecht, Warsaw.[6]

Currently 4 versions of CrypTool are maintained and developed: The CrypTool 1 (CT1) software is available in 6 languages (English, German, Polish, Spanish, Serbian, and French). CrypTool 2 (CT2) is available in 3 languages (English, German, Russian). All others, JCrypTool (JCT) and CrypTool-Online (CTO), are available only in English and German.[7]

The goal of the CrypTool project is to make users aware of how cryptography can help against network security threats and to explain the underlying concepts of cryptology.[8]

CrypTool 1 (CT1) is written in C++ and designed for the Microsoft Windows operating system. A port of CT1 to Linux with Qt4 was started, but there is no progress anymore.[9]

In 2007, development began on two additional projects, both based on a pure-plugin architecture, to serve as successors to the original CrypTool program. Both successors regularly publish new stable versions:

  • CrypTool 2[10][11] (built with C#/.NET/WPF) (abbreviated CT2)
uses the concept of visual programming to clarify cryptographic processes. Currently, CT2 contains more than 150 crypto functions.

Brute-force attack on a reduced version of AES in CrypTool 2

  • JCrypTool 1.0[12][13] (built with Java/Eclipse/RCP/SWT) (abbreviated JCT)
runs on Windows, macOS, and Linux, and offers both a document-centric and a function-centric perspective. Currently, JCT contains more than 100 crypto functions. One of its focal points are modern digital signatures (like Merkle trees and SPHINCS).


CrypTool has received several international awards as an educational program, such as the TeleTrusT Special Award 2004, EISA 2004, IT Security Award NRW 2004, and Selected Landmark in the Land of Ideas 2008 award.[14]


CrypTool is used in schools, universities,[15] companies and agencies for education and awareness training.[16][17][18][19]

Worldwide, the CrypTool packages are downloaded more than 10,000 times per month from the CrypTool website. Just over 50% of the downloads are for the English version.

CrypTool-Online (abbreviated CTO)[edit]

The CrypTool project also includes the website CrypTool-Online,[20] launched in 2009. This website allows users to try cryptographic methods directly within a browser on a PC or on a smartphone (using JavaScript), without the need to download and install software. This site aims to present the topic in an easy and attractive way for new users and young people.[21] Advanced tasks still require the offline versions of CrypTool.

MysteryTwister (MTC3)[edit]

In 2010, the international cipher contest MTC3 started as part of the CrypTool project.[22] The contest currently offers more than 200 challenges derived from old and modern ciphers and designed by more than 30 different authors from different countries. All challenges are presented in PDF templates in English and German. The challenges are clustered in four levels of difficulty, which range from simple riddles solvable with paper-and-pencil to mathematical challenges from modern cryptanalysis for researchers and experts. Additionally, a moderated forum, user statistics, and a hall-of-fame are available. Currently, more than 10,000 registered users are engaged in solving these challenges.

Merger with CrypTools[edit]

In early 2020, the CrypTool project decided to merge[23] with a similar project of the same name, CrypTools, founded in 2017 in Australia by Luka Lafaye de Micheaux, Arthur Guiot, and Lucas Gruwez.[24] CrypTool, much older and known, thus completely "absorbs" the project under its name.

Old logo, still used in CrypTool portal

The first impact of this merger is the rebranding of the project. A new logo, a new website, and the new CTO version are announced. Currently, it's still in development. Another change was the targeted audience. Previously, CrypTool focused on (university) students, and CrypTools on developers and young people. It was therefore necessary to broaden the audience.

On May 15, 2020, in the midst of the COVID-19 pandemic, CrypTool announces the creation of tools to test Decentralized contact tracing protocols.[25] A new page is added to CTO with technical description of the algorithms involved in DP-3T and Exposure Notification.[26] In addition to this, CrypTool also announced the implementation of a page dedicated to raising awareness of the cryptographic means related to privacy in these protocols, called the Corona Tracing Animation. The newer page stands out for its new design and its accessibility to ordinary users.[25]

See also[edit]


  1. ^ Esslinger, Bernhard (22 September 2016). "CrypTool: An Open-Source E-Learning Project for Cryptography and Cryptanalysis" (PDF). Gesellschaft fuer Informatik, Crypto Day at SAP. This presentation delivers an overview. University of Siegen. Archived from the original (PDF) on 8 January 2017. Retrieved 26 September 2018.
  2. ^ Litwinczuk, Arkadius (January 2011). "CrypTool-Projekt – Der beste Weg, Kryptographie zu lernen und anzuwenden" (PDF). IT Security Magazine. January 2011: 30–37.
  3. ^ McDermott, John (20 April 2016). "An Introduction: Using CrypTool to Show How Ciphers Work". Learning Tree International. Archived from the original on 5 September 2017. Retrieved 26 September 2018.
  4. ^ Balasubramanian, Kannan (2018). Algorithmic Strategies for Solving Complex Problems in Cryptography. Mepco Schlenk Engineering College. pp. 186–194. ISBN 978-1522529156. Retrieved 26 September 2018.
  5. ^ Algorithms: Functions in different CrypTool versions Within a table all cryptographic functions implemented are listed. This list can be adjusted using categories, search phrases and by specifying the CT versions.
  6. ^ Esslinger, Bernhard (23 April 2013). "CrypTool: Modern open-source e-learning programs for cryptography and cryptanalysis" (PDF). Forum for Research and Innovation in Security and Communications. Retrieved 26 September 2018.
  7. ^ "CrypTool 1: Downloads". CrypTool 1. Retrieved 26 September 2018.
  8. ^ "CrypTool for Awareness". CrypTool Portal. Retrieved 26 September 2018.
  9. ^ CrypTooLinux project Archived 17 October 2016 at the Wayback Machine Porting CT1 to Linux.
  10. ^ CrypTool 2: Developer site of the CT2 project Besides release and beta versions, each day a so called "Nightly Build" is produced for download.
  11. ^ CrypTool 2: Facebook Site of the CT2 project
  12. ^ JCrypTool 1.0: GitHub project of JCT Beta versions are updated each weekend as so called "Weekly Builds" for download.
  13. ^ JCrypTool 1.0: Site of the JCT project
  14. ^ "Awards for CrypTool". CrypTool Portal. Retrieved 26 September 2018.
  15. ^ Adamovic, Sasa; Sarac, Marko; Veinovic, Mladen; Milosavljevic, Milan; Jevremovic, Aleksandar (2014). "An Interactive and Collaborative Approach to Teaching Cryptology". Educational Technology & Society. 17 (1): 197–205. JSTOR jeductechsoci.17.1.197.
  16. ^ "Winter School in Information Security. Overview presentation, Finse 1222, April 21-26, 2013". Forum for Research and Innovation in Security and Communications. 6 February 2013. Retrieved 26 September 2018.
  17. ^ Eckert, Claudia; Clausius, Thorsten; Esslinger, Bernd; Schneider, Jorg; Koy, Henrik. "CrypTool, 2003-08-07" (PDF). Technische Universitaet Darmstadt. Technische Universitaet Darmstadt. Retrieved 26 September 2018.[permanent dead link]
  18. ^ Kopal, Nils. "Solving Classical Ciphers with CrypTool 2" (PDF). Linköping University Electronic Press. Linköping University Electronic Press. Retrieved 26 September 2018.
  19. ^ Ronald, Kenneth. "Crypto Casino". Retrieved 14 January 2024.
  20. ^ "About CrypTool-Online (CTO)". CrypTool-Online. Retrieved 26 September 2018.
  21. ^ "The CrypTool project – The best way, to learn and apply cryptography" – Article in Hackin9 by Arkadius Litwinczuk, March 2011, page 10-14 (PDF 6.1 MB)
  22. ^ "Welcome to the MTC3 – International Cipher Contest". MysteryTwister. Retrieved 22 January 2022.
  23. ^ "Arthur Guiot - Merging CrypTool & CrypTools". arguiot.com. Archived from the original on 6 June 2020. Retrieved 17 May 2020.
  24. ^ CrypTools project (2017), An introduction to CrypTools.
  25. ^ a b Guiot, Arthur (15 May 2020). "How to explain the role of cryptography during COVID-19?". Medium. Retrieved 17 May 2020.
  26. ^ "Corona Tracing - CrypTool Portal". www.cryptool.org. Retrieved 17 May 2020.

External links[edit]