Welcome to the 10th National Cipher Challenge

The competition will run from September 29th 2011 to January 4th 2012. Over the next few months you will be attempting to uncover the secrets of the Tempest Conspiracy. You will need to crack the enemy's devious codes and ciphers and in doing so you will uncover the history of a criminal agency which has played a major role in World history. As the adventure unfolds you will find that the enemy's cunning increases making it harder to break their messages.

Part A will consist of letters, notes etc. sent between the students as they try to unravel the conspiracy they have stumbled upon. You can expect these messages to be fairly lightly encrypted, at least at first, although in the latter stages of the competition, as they realise the danger they are in, their security will be tightened and you will find the part A ciphers harder to crack.

Part B consists of the notes of the mysterious T on ciphers he has discovered in historic texts. These will reveal the activities of the Tempest Conspiracy, and since the conspirators have been around so long and have so much to hide, these messages will often be much more securely encrypted than the part A challenges. (Though you may find that previous part B messages themselves contain clues to the decryption of the current one.)

If you get stuck on a Challenge don't give up, sometimes a good night's rest is all you need. Other times you need more practical help and you can turn to the website for clues. You might find them posted (by us) as comments, on the bulletin board, though we ask you not to post hints of your own without checking them with us first as this will spoil the Challenge for others. Anyone posting solutions or links to solutions here or on other websites will be barred from the site and disqualified from the competition. (Yes we do check, Google is our friend too!)

You will also find clues in the Challenges themselves. So the solution to any previous Challenge may give hints about how the current one is encrypted. It is also possible that part A messages can give clues for part B at each stage so it is worth deciphering the part A challenge even if your main interest is the part B competition.

The Challenges will be published at 3.15pm on a Thursday, according to the schedule below. You can submit your solution any time after the challenge has been published and before the deadline at one minute to midnight the day before the next Challenge is published. Solutions to each Challenge will be published after the deadline, so if you can't crack a particular Challenge don't give up. After you submit you can check for feedback on your solution by logging in at this page This won't work straight away as we delay the feedback as an incentive to get it right first time. So you will lose points if you rely on the feedback instead of correcting your own mistakes! If you have submitted a solution with amistake in it you can submit again and you don't have to wait for the feedback but do watch out for rule 20. We discourage multiple random guesses every way we can!

For each Challenge you will receive a score based on your speed and accuracy, and we will use these scores to compile an Honours Board for each Challenge part A and for each part B. These lists will be published so you can see how you are getting on. The part B Honours Lists will be compiled into the overall Championship Leader Board which will be used to determine the winners of the competition. Entries for each challenge, which may be from individuals or from teams, should be submitted using the submissions web-form. Be careful to follow the instructions on the form. Sorry, but failure to adhere to all the instructions could result in an entry being deemed invalid. The detailed rules are given below, so make sure you read them well.

PLEASE NOTE THE CHANGE OF DEADLINE FOR CHALLENGE 8 WHICH HAS BEEN MOVED FROM JANUARY 4th TO JANUARY 8th. (Amended 02/12/11, Harry)

There will be a number of main prizes to be shared by the top three teams on the overall Championship Leaderboard at the end of the competition. These prizes, which are awarded for performance in the part B challenges, will include the GCHQ prize of £1,000, the IBM Prize of £800 and the Trinity College Cambridge prize of £700. Our new sponsors this year, Netcraft, are offering a number of prizes to the top performers in Challenge 8B. These will be Targus Backpacks decorated with the Netcraft logo and are collectors items!

The major prizes will be awarded to the winners at the prizegiving ceremony at Bletchley Park on March 30th 2012. See the scoring section of the rules to understand how the winners will be determined. In addition there will be 8 prizes of £25 each awarded at random for each part A challenge to teams submitting correct solutions in each round. These are sponsored by the School of Mathematics at the University of Southampton.

1. The competition is only open to persons who are in full time school-level education in the United Kingdom*.
2. The competition is only open to persons aged 18 or under on 31 August 2011.
3. Entries may be received from individuals or from teams. The teams may be of any size, but we reserve the right to restrict the number of team members listed on the honours board. If you are in a big team you should make sure we have a team name as well.
4. Teams must nominate a captain who we may contact via email.
5. The schedule of messages to be deciphered is given here, the list of prizes is given below.
6. Each challenge consists of two parts, part A and part B. You may submit solutions to either or both parts of the current challenge on the entry form.
7. For each of the challenges 1 to 8 there will be a small cash prize (this replaces the previously advertised book prize) awarded to 8 teams/competitors chosen at random from those who submit a correct entry to part A.
8. For each of the challenges 1 to 8 for which you submit an entry for part B you will be awarded a score, based on the accuracy of your best submission for that challenge and the order in which we receive the submissions. The scores will be used to determine the winners of the main Prizes, who will be chosen from among those achieving the highest total scores.
9. A solution will only be deemed to be correct if, disregarding the punctuation [and spacing], the deciphered plaintext (only involving the Roman characters A to Z [UPPER or lower case is fine]) is letter perfect as compared to our master solution.
10. A submission will only be deemed to be valid if it is submitted on the entry form and all the instructions on the entry form are adhered to.
11. The Challenge Committee may publish clues on the competition web-site if it considers it appropriate to do so.
12. If a correct solution of a challenge is not received before the deadline given on the schedule the Challenge Committee will have the discretion to not award the prize or award some or all of it to the entrant or entrants whom it judges to represent the best solution or solutions.
13. The competition will be judged by the Prize Committee, whose decision will be final in all matters regarding the competition including the award of prizes.
14. In order to qualify for any of the prizes all entrants, whether solo or part of a team agree to their school names being used in publicity associated with the competition including publication on the competition web-site. We will publish team member names only with your permission. When registering you will be asked to list the team member names, or appropriate nicknames for them that you are happy for us to publish on the website and in publicity associated with the competition.
15. In submitting an entry solo entrants vouch that it is solely their own work and teams warrant that it is solely their own collective work.
16. Entrants who do not abide by the rules will be disqualified from the competition and will not qualify for any of the prizes.
17. In submitting an entry to the competition, all entrants, be they individuals or members of a team agree to be bound by all the rules of the competition.
18. Winners and their schools will be notified as soon as possible after the solution deadline for each message. We will inform you on the website in the News and Info section and by email using the email address you provide. Please ensure that our messages to you are not filtered by your spam filters by adding our email address This email address is being protected from spambots. You need JavaScript enabled to view it. to your address book.
19. The organisers reserve the right to change any aspect of the competition at short notice and to split prizes where it is deemed appropriate. Such changes will be announced on the competition web-site as soon as practical.
20. Rapid fire multiple submissions put an unreasonable load on the servers and make it difficult for others to submit. Anyone who makes an unreasonable number of submissions will be open to disqualification. In the first instance this will mean that anyone who submits more than 20 times in 10 minutes will be disqualified.
21. Anyone posting a solution in any public forum before the deadline for the given Challenge will be disqualified and barred from the forums. Please do not publish hints without checking with us first as this may spoil the competition for others.

* Home-schoolers also qualify as do those attending schools in the Channel Islands and the Isle of Man.