The Alan Turing Cryptography Competition, now in its 7th year, is an online competition run by the University of Manchester School of Mathematics, for school students up to year 11 or equivalent. Cryptographic puzzles are released every couple of weeks and teams of up to four compete to solve the puzzles, with prizes for the fastest and other randomly selected correct entries. Registrations are open now, and the competition starts on 28th January 2019.
For sixth form pupils, there is also MathsBombe – an online competition, with two mathematical puzzles released every fortnight. The puzzles are not directly related to the A-Level syllabus but will require students to use their problem-solving skills.
Alan Turing Cryptography Competition