Problems, solutions and experience of the first international student's Olympiad in cryptography

A detailed overview of the problems, solutions and experience of the first international student’s Olympiad in cryptography, NSUCRYPTO’2014, is given. We start with rules of participation and description of rounds. All 15 problems of the Olympiad and their solutions are considered in detail. There are discussed solutions of the mathematical problems related to cipher constructing such as studying of differential characteristics of S-boxes, S-box masking, determining of relations between cyclic rotation and additions modulo 2 and 2n, constructing of special linear subspaces in F2 ; problems about the number of solutions of the equation F (x)+F (x+a) = b over the finite field F2n and APN functions. Some unsolved problems in symmetric cryptography are also considered.