Screenshots of CrypTool 1 (CT1). A free Windows program for cryptography and cryptanalysis.

A number of different text analysis procedures are available in CrypTool. These will bring out the weaknesses of simple encryption algorithms, while some of the algorithms can be broken automatically.

Text analysis

CrypTool reveals the inner working of digital signatures and hybrid encryption (RSA-AES und ECC-AES) with interactive data flow diagrams.

Data flow diagrams

The capabilities of CrypTool are actively supported through the comprehensive help facilities.

Help

CrypTool offers the possibility of getting to know and test modern encryption algorithms. Brute-force analysis is also available for modern symmetric algorithms.

Brute-force

You can examine variants of the RSA algorithm (different key lengths, different alphabets, different block sizes) using the dialog box "The RSA Cryptosystem".

From UID/PW (user id/password) and one-time password. By (unilateral) challenge-response (symmetric + asymmetric). To asymmetric mutual authentication. The user interactively can control what an attacker can do (take over a computer, connect or disconnect interconnections, eavesdrop). Learning objective is, that only the mutual asymmetric authentication is secure against man-in-the-middle-attacks.

Demonstration of ways to authenticate within the net

If the implementation is not correct (as has happened in reality), then the attacker can calculate the session key very efficiently.

Demonstration of a side-channel attack against a typical hybrid encryption protocol

Three attacks against the RSA method based on lattice reduction. They all have special pre-conditions. One of the factors of N is partly known ("Factoring with a Hint"). Parts of the cleartext of a captured encrypted message is known and e is small ("Attack on Stereotyped Messages"). If d is chosen too small compared to N, then you can factorize N ("Attack on small Secret Exponents").

RSA attack

Implementation of MACs (combination of hashes and symmetric encryption to authenticate messages). Hashes are already used in CrypTool within the concepts of PKCS#5 and digital signatures. Three applications based on the Chinese Remainder Theorem. Solution of a system of linear modular equations applied to the planets of our solar system. Illustrating how you can do calculations with remainders instead of the original numbers. Illustrating the shared secret method (this is analogous to needing any three out of 5 key owners to open a vault).

Chinese Remainder Theorem

Illustrating algorithms (Caesar, Vigenère, Nihilist und DES) using the animation software ANIMAL (Java application which allows to specify and model the single steps of algorithms or the components of data structures with as much detail as desired, and run these steps forwards, backwards, or automatically). Animations can be created with the Animal system using a GUI, a script language or a Java API.

ANIMAL system

3D visualization of big sets of random numbers with the rendering engine from OpenQVis.

OpenQVis

Implementation and analysis of ADFGVX as an example for cascading cipher.

ADFGVX

Efficient analysis of the monoalphabetic substitution cipher.

Analysis of monoalphabetic substitution

NumberShark is a game for pupils which trains them to calculate factors.

NumberShark

Flash animations for AES and Enigma

Educational software describing and visualizing elementary number therory.

Number therory

An ECC demo shows how points on an elliptic curve can be added and multiplied in discrete and real fields (written as a Java application).

CrypTool 1 Screenshots