Slovak University of Technology, Bratislava

Faculty of Electrical Engineering and Information Technology

Degree Course: INFORMATICS

Author: Bc. Michal TURZO

Diploma thesis: Cryptanalysis of the Miniversions IDEA Algorithm

Supervisor: Mgr. Július ŠIŠKA

2002, May

The aim of this thesis was to verify known attack on the IDEA algorithm with stress upon the differential and linear cryptanalysis. Further, we concentrated us on an influence of parameters of algorithm (so called miniversions) on its resistance against these attacks.

A base for reaching the aim of this thesis was to become familiar with the IDEA cipher algorithm and to implement it. Maximum scalability and modularity were basic request for implementation. Because this, no emphasis was laid on a throughput (speed) of crypting and decrypting.

From known attacks, attacks by differential cryptanalysis on 8 and 16 bit versions of the algorithm were implemented.

As a reference attack also a Brute force attack was implemented.

In the process of learning IDEA, it was necessary to perform some direct calculations because of proving the implementation. These calculations were related to transition matrixes of 8-bit miniversion of IDEA cipher and verification of found differentials for differential cryptanalysis.