Cycle 27th ORAL DEFENCE OF THE PHD THESIS (final exam) Monday, April 20, 2015 at 10.30 a.m. (Aula Seminari di Matematica) Marco Calderini (Dottorando Università di Trento) On Boolean functions, symmetric cryptography and algebraic coding theory In the first part of this talk we will see some "linear" trapdoors on a block cipher. In particular we are interested in any block cipher which has invertible S-boxes and that acts as a permutation on the message space, once the key is chosen. The message space is a vector space and it could be endowed with alternative operations for which the structure of vector space is preserved. We will present conditions on the S-box able to prevent trapdoors based on these hidden sums and some properties of the translation groups related to these. In the second part we will take into account the index coding with side information problem. We will extend some results on the error correction index codes to the case when the side information in the cache users are coded. Supervisor: Massimiliano Sala 38123 Povo (TN), Italy - Via Sommarive, 14 Tel. +39 0461 281625, Fax +39 0461 281624 e-mail: phd.math@unitn.it