Differential cryptanalysis is among the oldest and most popular cryptanalysis techniques against block ciphers and other symmetric primitives. Despite many years of study and the existence today of many improvements, applying these attacks in the most optimal way is a non-trivial task. In this talk, I will first present our recent work that fully breaks the SPEEDY-7-192 block cipher by means of differential cryptanalysis. In a second part, I will introduce a new type of attack, called the differential meet-in-the-middle attack, that can be seen as a combination of a MITM together with a differential attack.
The first part of the talk is based on a joint work with Nicolas David, Rachelle Heim Boissier and María Naya-Plasencia and was recently accepted to EUROCRYPT 2023. The second part is a joint work with Nicolas David, Patrick Derbez, Gregor Leander and María Naya-Plasencia.