International Conference on Historical Cryptology

Workshop

Breaking Homophonic Substitution Ciphers with CrypTool 2

CrypTool 2 (CT2) is an open-source e-learning tool consisting of several classical as well as of modern cryptographic algorithms (ciphers). The main goal of the CrypTool 2 team is to integrate every established cryptographic algorithm. Besides implementing the ciphers, the team also aims at integrating the state-of-the art of cryptanalytic algorithms, allowing to (automatically) break classical ciphers. CT2 implements a powerful graphical "programming language" allowing the user to combine arbitrary algorithms and analysis methods.

In the last year’s workshop, we focused on working with breaking classical ciphers in CT2 in general. In this year’s workshop, the participants will learn how to work with CT2 to break homophonic ciphers. They will learn (or repeat) the basic handling of the graphical programming language.

The workshop will consist of the following parts:

1. Basic classical encryption techniques

Topics here are:

What is a cipher?
What is a homophonic substitution cipher?

2. Basic handling of CT2

Learn (or repeat) what the main components of CT2 are
Learn how to create own graphical programs in CT2

3. Cryptanalysis of substitution ciphers

Breaking simple monoalphabetic substitution ciphers
Breaking polyalphabetic substitution ciphers (e.g. Vigenère cipher)
Main part: breaking homophonic substitution ciphers (e.g. the Zodiac Cipher)

4. A look into the future

Here we give an introduction on what we are working:

Break real-world homophonic substitution ciphers (like from the DECODE database)
Break real-world nomenclatures

Please bring your own PC with CrypTool 2 installed, see https://www.cryptool.org/modules/mod_ctdownloads/assets/curversion.php for download.

Organizer: Nils Kopal

Last update 2019-06-01