Contributor analysis

Presented at REcon Brussels 2017, Jan. 27, 2017, 2 p.m. (30 minutes)

Contributor analysis is a simple cryptanalysis technique which allowsdetecting and attacking blatantly broken cryptographic algorithms and implementations. Although the technique is inspired by the techniques employed by algebraic approachesit aims at being much simpler to understand and reason with, making itpossible not only to automate the testing but also to even run testsusing pen and paper.In this talk we will introduce the participants to this technique,explain briefly the theoretic principles that make it work and how itrelates to algebraic cryptanalysis and then explain how to handlecontributor lists with different common operations. We will explain howthese lists can be used to mount an attack therefore proving why asuccesfully attacked cipher can be considered broken. Finally we willshow some simple examples of ciphers affected by these techniques.No mathematical nor cryptographical knowledge is needed to follow thistalk although some programming or computer architecture knowledge isrecommended.