National Cipher Challenge: registration opens
Southampton University's competition. A story unfolds over eight to ten rounds, each with a message to break, and the ciphers are the ones on this site: Caesar, transposition, Playfair, Vigenere. The early rounds are practice, with a certificate for finishing one.
cipherchallenge.orgNational Cipher Challenge: the competition starts
Rounds are released through the autumn. The archived challenges can be worked from last year at their own pace instead, which is the gentler way in.
cipherchallenge.orgBebras, some time in November
A forty five minute challenge of logic and pattern puzzles, run in more than ninety countries each November. No coding and no jargon. There are categories for six to eight and eight to ten, which makes it the one competition on this page a beginner can actually enter.
bebras.orgComputer Science Education Week and the Hour of Code
Schools run a one hour computing activity. Everything here works for that with no account and no setup: a cipher page, a printed booklet, or the terminal. Sources disagree on the exact week this year, so confirm before planning.
hourofcode.comThe GCHQ Christmas Challenge, some time in December
Seven puzzles plus a bonus that needs all seven answers, released each December and notoriously hard. Solutions are published afterwards, and previous years stay up. Our own Christmas Challenge is the same shape and rather more finishable.
gchq.gov.ukpicoCTF, some time in March
Carnegie Mellon's capture the flag, run over about ten days in March. Cryptography is one category among several. The better part for most people is picoGym, where past challenges stay open all year.
picoctf.orgIf you only do one
Bebras in November. It runs through schools, takes forty five minutes, costs nothing, and starts younger than anything else here. Ask a teacher whether the school is entering; most have never heard of it.
After that, the National Cipher Challenge in October, and the Hour of Code in December if you want an excuse to bring this into a classroom.
Things you can do on any day
A warning about dates
Every date here was taken from the organiser's own site, but competitions move, and some announce late. Check the link before planning anything around it. If something on this page has gone stale, it is worth telling us: schoolofcypher@gmail.com