Differential attacks using alternative operations and block cipher design

Cycle 30th Oral Defence of the Phd Thesis
6 marzo 2018
March 6, 2018

Venue: Seminar Room "-1" -  Department of Mathematics - Via Sommarive 14 - Povo - Trento
Hour: 12.30

  • Roberto Civino - PhD in Mathematics

Abstract:
Block ciphers and their security are the main subjects of this seminar.
In the first part it is described the impact of differential cryptanalysis, a powerful statistical attack against block ciphers, when operations different from the one used to perform the key addition are considered on the message space. It is proven that when an alternative difference operation is carefully designed, a cipher that is proved secure against classical differential cryptanalysis can instead be attacked using this alternative difference.
In the second part it is presented a new design approach of round functions for block ciphers. The proposed round functions can give to the cipher a potentially better level of resistance against statistical attacks. It is also shown that the corresponding ciphers can be proven secure against a well-known algebraic attack, based on the action of the permutation group generated by the round functions of the cipher.

Supervisor: Massimiliano Sala