MysteryTwister C3

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Getting involved in modern and classic Cryptanalysis

What is MTC3?


MysteryTwister C3 (MTC3) is an international cryptography competition. Its origin is a design study called "A Crypto Challenge by CrypTool (C3)" and the integration of parts of the renowned MysteryTwister site. A variety of tasks and riddles (challenges) are offered at four levels of difficulty. These challenges can be as easy as deciphering a Caesar cipher (Level I) and as hard as breaking a modern encryption algorithm such as AES (Level III). Level X challenges are a kind of "mysterious" (e.g. it could be that they are still unsolved for a long time). The various topics covered by the MTC3 challenges are intended to offer a survey of cryptology for everyone. The four levels of difficulty in MTC3 offer cryptographic challenges for a student just starting to learn about cryptography as well as for experts with many years of experience and plenty of resources at their disposal.

How does it work?


In the MTC3 challenges in the levels I to III the website automatically verifies if your solution is correct. The solution may be the entire plaintext, the key, or a secret codeword hidden within the determined plaintext. By breaking the cipher you will obtain this solution. If you think you have found the correct solution, you can login to this website and submit it. Be aware that the solutions are case-sensitive! If your answer is correct, you will automatically be added to the list of successful code breakers: Every successful candidate will appear on the "Overall Hall-of-Fame". The first four successful code breakers of each challenge will we immortalized in the "Challenges Hall-of-Fame" separately for each challenge.

Take note, however, that you only have a limited number of attempts at each challenge. Therefore, you should be certain  that your answer is correct before submitting a solution. Once you have used all of your attempts, you will not be able to submit additional answers for that particular challenge.

Challenges categorized as level X are not validated automatically. If you solve one of the level X challenges, you should contact the author of the challenge or the MTC3 team via email. If your solution is sound, you will be added to the Overall Hall-of-Fame. We will publish your results only with your explicit permission.

Discuss your approaches in the forum.


For every challenge there is a forum. There you can ask questions and submit hints -- but please do not provide the solution.

Additionally, authors sometimes add hints if too many users get set on the wrong track.

Are you ready to rock the Hall of Fame?

Submit your own Challenge!


In order to continuously enhance MysteryTwister C3 with new challenges we need your help. If you have an idea for an interesting challenge, don't hesistate to submit us your suggestion.

To do so you have to register (if you are already registered in order to solve challenges, this is sufficient). We then will check the suggestion and will publish it as an MTC3 challenge. Ideally, your submission contains

  • a challenge description (text document is sufficient, we take care of the formatting),
  • a secret text and the corresponding plaintext,
  • a solution (solution phrase) to be used for automatic feedback to the participating solvers, 
  • a suggestion for the level your challenges should be part of, 
  • a suggestion to the maximal number of tries, as well as
  • the name of the author of the challenge (optional).

Once logged in you will find an additional link in the "Challenges" menu with the possibility to send a zip file to us containing your challenge.

powered by the CrypTool project  CrypTool


   +++    [20:18 - 26.06.2017] george4096 solved the Level II challenge 'ORYX Stream Cipher — Part 4a'    +++    [19:43 - 26.06.2017] D3d4lu5 solved the Level I challenge 'Zodiac Cipher'    +++    [19:41 - 26.06.2017] D3d4lu5 solved the Level I challenge 'Post-Quantum Cryptography: Unbalanced Oil and Vinegar System — Part 1'    +++    [21:32 - 25.06.2017] kasia-tutej solved the Level II challenge 'Brute-Force-Attack on Triple-DES with Reduced Key Space'    +++    [10:46 - 25.06.2017] kynguyenngoc solved the Level II challenge 'Cracking SHA1-Hashed Passwords'    +++