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?

MysteryTwister (MTC3) is an international Crypto Cipher Contest offering a broad variety of challenges, a moderated forum, and an ongoing hall-of-fame.

CrypTool Book

New Chapter 12: Lightweight Introduction to Lattices, June 2020

This 90-page chapter covers the basic theory behind lattices in a lightweight fashion. The theory is accompanied with lots of practical examples, SageMath code, and cryptographic challenges. The input data of the challenges is bundled in text files in chal_i_helper.zip.

New Chapter 13: CUDA Tutorial – Cryptanalysis of Classical Ciphers Using Modern GPUs and CUDA, April 2021

This 90-page chapter covers a practical introduction how to write CUDA programs on Linux and Windows. It explains what are the concepts, how to overcome problems (threads, shared memory, debugging) and how to deal with trade-offs. The theory is accompanied with practical examples, and two complete stand-alone GPU tools for automatically decrypting ciphertexts (ciphertext-only attack) are implemented. These tools target ciphertexts encrypted by monoalphabetic substitution (MAS) or by single-columnar transposition ciphers.

Current Book version: 12th edition, May 2018

In this free, 500+ pages book delivered with the CrypTool applications you will find predominantly mathematically oriented information on learning, using and experimenting cryptographic procedures. The 12th edition is a major update of the book.

  • The first chapter explains the principles of symmetric and asymmetric encryption, and describes shortly the current decryption records of modern symmetric algorithms. It introduces definitions for their resistibility, and shortly explains the importance of cryptology.
  • Because of didactic reasons, the second chapter gives an exhaustive overview about paper and pencil encryption methods.
  • Chapter three is dedicated to the fascinating topic of prime numbers.
  • In chapter 4, modular arithmetic and elementary number theory are introduced, and applied in many examples including the RSA procedure.
  • By reading chapter 5 you will gain an insight into the mathematical ideas and concepts behind modern cryptography.
  • Chapter 6 gives an overview about the status of attacks against modern hash algorithms and is then shortly devoted to digital signatures, which are an essential component of e-business applications.
  • Chapter 7 describes elliptic curves: Compared to RSA, they provide a very efficient alternative for the hardware based generation of digital signatures.
  • Chapter 8 introduces Boolean algebra, which is the foundation for most modern, symmetric encryption algorithms as these operate on bit streams and bit groups. Principal construction methods are described and implemented in SageMath.
  • Chapter 9 describes homomorphic crypto functions which got special attention in the course of cloud computing.
  • Chapter 10 provides a broad picture and comparison about the currently best algorithms for (a) computing discrete logarithms in various groups, for (b) the status of the factorization problem, and for (c) elliptic curves. This survey was put together as a reaction to a provocative talk at the Black Hat Conference 2013 which caused some uncertainty by incorrectly extrapolating progress at finite fields of small characteristics to the fields used in real world.
  • Chapter 11 discusses the threats for existing cryptographic methods and introduces alternative research approaches (post-quantum crypto) to achieve long-term security of cryptographic schemes.

Additionally the appendix contains a list of movies and novels where cryptography plays a role. The appendix also offers a quick overview about the cryptographic functions delivered by the different CrypTool variants.

For many algorithms there are small and executable code samples in Python and SageMath, or they are further explained with one of the CrypTool variants. You can download the SageMath scripts here.

General News

See all posts
CrypTool 2 Release 2021.1 published

In May 2021, we published the release "2021.1", which is the first one this year and a major functional update. The...

Read more ... 05/12/21
JCrypTool version 1.0 released

Version 1.0 of JCrypTool was released today, November 30th, 2020. It is intended for beginners and experts in cryptog...

Read more ... 11/30/20
CrypTool website completely renewed

In the course of 2020, the CrypTool portal was comprehensively renewed once again. The website at www.cryptool.o...

Read more ... 10/30/20