Skip to main content

About the Challenge

Welcome to the National Cipher Challenge, a nationwide, online codebreaking competition, which will run again from October 4th 2018 to January 9th 2019.  If you have any questions please contact Harry at [email protected].

The competition is structured as a series of encrypted messages which tell a story. This year we rejoin our hero Jodie, who is recovering from her adventures in last year’s competition, The Lost Legion, by taking a quiet job cataloguing Victorian government secrets for the British Library. Unfortunately (or, just maybe, fortunately?) the dark world of espionage is lurking, ready to draw her back in, and she will need your help to survive and to solve the mystery of The Kompromat Files.

Who is the competition for?
The competition is aimed at school an sixth form students of mathematics and computer science, and is a great extension activity (or a fantastic maths club project) that can be tackled by them in teams or on their own.

How to register and join in
There is no charge to register or take part, and all you need to get involved is a reasonably modern web browser. We publish news about the competition at, and you can also keep up to date with competition news by following us on Twitter.

Entrants can take part alone or in teams of any size. To take part you will need to register for an account on the website, and we will ask you for a Code Name (which we will use to identify you on the forum, where you can discuss a whole range of things connected to the competition, and quite a few that are totally unrelated). You will then be asked to create or join a team which you will use to submit your entires. If you ask to join an existing team then we will email your request to the team captain and let you know the outcome. If your request is turned down, don’t worry, you can request to join another team, or set up your own.

If you want others to join your team let them know and they can submit a request through their team page which is linked under their user name at the top right of every page.  The names of everyone on a team will be on the certificate and we will publish the team name on the leaderboards so you can see how everyone is getting on.

When setting up the team we ask you to say whether or not you are eligible for a prize. The rules are below. If you are eligible we will ask you for some information about your school, including the name and email address of a teacher contact. We need this in case you win a prize, but please do ask them first. If you are home educated then state that in the School name box and give the name and email address of an adult we can contact if we need to. We will not publish your name or the contact information of your teacher without your (or their) permission, but of course if you win a prize we will want to tell the world about your success!


You can download lessons and notes on codebreaking from the resources page on the competition website. This is the competition library and, alongside the materials we have produced you will find links to books, online videos and help guides that contain everything you need to be a successful code-breaker. You can even build your own cipher machines, including the simple cipher wheel and the more complicated Pringle Can Enigma Machine.

The history of the competition

The National Cipher Challenge has been run by the Mathematics department at the University of Southampton since 2002. It regularly attracts entries from teams at over 700 UK schools and colleges. Long time competitor, Julian Bhardwaj, said of the Challenge

If I were to name one thing which has undoubtedly influenced my academic drive, interests and overall career to date, it would be the National Cipher Challenge. Since being introduced to cryptography and the challenge in Year 8, it has been my one passion and driving force in pursuing further education in maths.

Julian went on to study Discrete Mathematics and made it to the Grand Final of the UK National Cyber Security Championship in 2013, following in the footsteps of the 2008 National Cipher Challenge winner, Jonathan Millican, who was crowned winner of the UK National Cyber Security Championship the previous year. Naomi Andrew, who operates under a code name as one of the Elves on the site, took part from Year 8 until she was sadly too old to compete, but managed to stay involved as a student at Southampton. She is now studying for her PhD here and we like to think the Cipher Challenge had an important part to play in that journey:

It was fun seeing a different side of maths to what I was learning in class, and the elation of finally understanding a difficult cipher is a feeling that’s hard to beat. The challenge was my first taste of how much there is to maths, and more than 10 years later the subject continues to amaze and excite me!

Our competition has attracted support from a number of people over the years, who have encouraged us by giving up their time to launch the competition, to meet with competitors and to attend the annual prize giving at Bletchley Park. These include the media scientists Adam Hart-Davis and Simon Singh; Newsnight editor Mark Urban who has a passion for military history;  comedy writer James Cary who wrote Bluestone 42 and the Radio 4 comedy Hut 33, and the star of that show (and many others),  Robert Bathurst  whose aunt worked at Bletchley in the war. We have also had the pleasure of introducing the Cipher Challenge team from Saint Anne’s School in Southampton to the Duke of Edinburgh.

Two Foreign Secretaries, Boris Johnson and William Hague have supported the competition (though Boris was London Mayor at the time), and we are also grateful to our sponsors who give time as well as money to support the competition. It is not unknown for our winners to meet members of the secret world of GCHQ at the awards dinner despite their busy schedules.

Competition schedule

Registration will open online on 21st September and the first episode will be published at 3pm on Thursday October 4th. The first three episodes are designed as a warm up, and while we will publish leader boards, the marks for those challenges won’t count towards the final competition standings. There will be a break for half term from and the main competition starts with episode 4 on 1st November, with the remaining challenges published weekly until December 13th. NOTE: all times stated on the site refer to current UK time. The clocks change back from British Summer time to GMT at around 2am on Sunday October 28th and our competition clock resets with that.

ChallengePublication Date
15:00 on
Final submission deadline
23:59 on
Challenge 0This is an introduction to the
story and not a challenge
Not applicable
Practice Challenge 14/10/201810/10/2018
Practice Challenge 211/10/201817/10/2018
Practice Challenge 318/10/201831/10/2018
Competition Challenge 401/11/201807/11/2018
Competition Challenge 508/11/201814/11/2018
Competition Challenge 615/11/201821/11/2018
Competition Challenge 722/11/201828/11/2018
Competition Challenge 829/11/201805/12/2018
Competition Challenge 906/12/201812/12/2018
Competition Challenge 1013/12/201809/01/2019

As usual we apologise in advance if your school holidays clash with the schedule. It is impossible to set the schedule to avoid them all, but there is nothing to stop you doing the challenge during the break, you only need a web browser and your brain!

Rewards and Prizes

Points are awarded for speed and accuracy (with accuracy more important) but you do not have to rush to download the first challenges immediately as you have a day or two in which you can still get top marks. In later challenges speed will become important, and the full schedule of marks is published on the Challenge pages so you can see how quickly you will need to get started in each round.

The first three challenges should be thought of as a “warm-up” exercise and will not count in the final leader board rankings or for the award of main prizes, however it is still worth tackling them as they give excellent practice and they do develop the storyline. You will be able to download certificates recording your team’s performance at each stage.