November 1, Tuesday 12:15, Room 506, Jacobs Building

Title: Versatile algorithms for searching guess-and-determine and meet-in-the-middle attacks on byte-oriented symmetric primitives

Lecturer: Pierre-Alain Fouque

Lecturer homepage : http://www.di.ens.fr/~fouque/

Affiliation : Ecole Normale Superieure

 
The AES encryption scheme is actually the target of many new attacks. Two important classes of attacks are meet-in-the-middle attacks and guess-and-determine attacks. Such attacks are very simple and efficient (since a small number of plaintext/ciphertext are required) and it is possible to automatically look for these attacks.

In this talk I will present some versatile and powerful algorithms for searching guess-and-determine and meet-in-the-middle attacks on byte-oriented symmetric primitives. These algorithms exploit the algebraically simple byte-oriented structure of the AES. To demonstrate the strengh of these tool, I will show that they allow to automatically discover new attacks on round-reduced AES with very low data complexity, and to find improved attacks on the AES-based MACs Alpha-MAC and Pelican-MAC, and also on the AES-based stream cipher LEX.

This is a joint work with Charles Bouillaguet and Patrick Derbez.