  Non-Stop University CRYPTO is the International Olympiad in Cryptography that
was held for the eight time in 2021. Hundreds of university and school
students, professionals from 33 countries worked on mathematical problems in
cryptography during a week. The aim of the Olympiad is to attract attention to
curious and even open scientific problems of modern cryptography. In this
paper, problems and their solutions of the Olympiad'2021 are presented. We
consider 19 problems of varying difficulty and topics: ciphers, online
machines, passwords, binary strings, permutations, quantum circuits, historical
ciphers, elliptic curves, masking, implementation on a chip, etc. We discuss
several open problems on quantum error correction, finding special permutations
and s-Boolean sharing of a function, obtaining new bounds on the distance to
affine vectorial functions.
