Kryptografie v nedůvěryhodném prostředí

Bc. Dušan Klinec

Master's thesis

White-box attack resistant cryptography

Abstract:

Táto diplomová práca je zameraná na štúdium problémov z hladiska bezpečnosti, spôsobené vykonávaním kryptografických algoritmov v nedôveryhodnom prostredí. Zaoberá sa najmä štúdiom transformácií algoritmov, ktoré do určitej miery odolávajú útokom typu extrakcia kľúča a invertovanie. Konkrétne sa zameriava na transformácie AES-u a na útoky na tieto transformácie. Popisuje konštrukciu a implementáciu takýchto transformácií. V diplomovej práci sa zistilo, že známy útok funguje aj na transformáciu AES-u využívajúcu duálne šifry [Karroumi], o ktorej sa predpokladalo, že tomuto útoku odolá. Boli navrhnuté zlepšenia, ktoré by mohli zvyšovať rezistivitu na známe útoky.

Abstract:

This thesis is focused on a study of security issues related to an execution of cryptographic algorithms in an untrusted environment. It mainly studies whitebox cryptography methods of transforming algorithms in such a way they resist attacks like key-extraction and inverting in some extent. Particularly it examines whitebox transformations of AES cipher and attacks on these transformations. Transformations construction and implementation is described. In the thesis was discovered the known attack works also on AES transformation using dual ciphers by Karroumi that was supposed to resist the attack. The new improvements for increasing a resistance of transformations to known attacks were proposed.

Keywords

whitebox attack resistant cryptography, AES, dual ciphers, whitebox cipher implementation

Language used: English

Date on which the thesis was submitted / produced: 27. 5. 2013

Thesis defence

• Date of defence: 24. 6. 2013
• Supervisor: RNDr. Petr Švenda, Ph.D.
• Reader: Mgr. Marek Sýs, Ph.D.

Masaryk University

Faculty of Informatics

Master programme / field:
Informatics / Information Technology Security