Welcome to the seventh National Cipher Challenge.

The competition will run from September 25th 2008 to January 1st 2009. Over the next few months you will be joining George Scovell and the Duke of Wellington in their fight to eject Napoleon's army from Portugal and Spain.

It will be your job to help the British army in its efforts to decipher French messages intercepted by George Scovell's Army Guides and their brave allies the Spanish Guerilla fighters. As the war progresses and the French ciphers become hard hard to crack you will need all your wit and skill to break them, and your hardest Challenge will be to break the Great Paris Cipher.

Challenges will be set on this web-site in the Challenges section, and will come in two parts. Part A will consist of letters, notes and despatches from the British army. As they come from a military organisation in a state of war you can expect these messages to be formally (though perhaps surprisingly not heavily) encrypted. In the early stages of the campaign, before battle is joined in earnest these will be only lightly encrypted, although in the latter stages of the competition, as George Scovell takes a firm grip on the Army's communications, security will be tightened and you will find the part A ciphers harder to crack. Part B consists of intercepted messages between the elements of Napoleon's army. These might be orders from Paris, or from Napoleon's brother King Joseph in Madrid, or they may be intelligence reports between the four main forces in the field, the French Armies in Portugal, the North, the South and the Centre. As Wellington concentrates his forces for a major offensive the French ciphers will become increasingly hard to crack. As a result of the terrifying effectiveness of Scovell's field agents the French ciphers need to be, and are, much more securely encrypted than the British, though you may find that the British messages themselves contain clues to the decryption of the French texts.

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 web-site for clues. You might find them posted 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 will be barred from the site and disqualified from the competition. 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. Also the part A message might 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. 24 hours after you submit you can check for feedback on your solution by logging in at this page. If you have submitted a solution with a mistake in it you can then submit again (though watch out for rule 20 below). 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. Failure to adhere to all the instructions may result in the entry being deemed invalid. The detailed rules are given below.

Scoring

Each submission you make for Challenge part A or for part B is marked by computer in the following way. Your solution is stripped of spaces, punctuation and numerals, all characters are converted to upper case and the resulting string is compared with our master solution which has been treated in the same way. The comparison yields a "similarity score" out of 100. For the part A Challenge your position on the leader board is based entirely on the highest accuracy mark you get for your submissions to that round, so if you make a mistake you can dramatically improve your ranking by trying again. For the part B Challenges you will also be given a mark for the speed with which you submitted your most accurate solution (bearing in mind that we are taking the first of any identical submissions you make!)
In week one the part B mark for speed will be out of five, with a mark of 5 for a submission on 25th or 26th September , 4 for a submission on 27th and so on with a mark of 1 for submitting on September 30th or October 1st. Your overall mark in Challenge 1B will therefore look like (x%, y) with a maximum of (100%, 5), and we will compare these using the dictionary order so that a score of (100%, 5) beats everything, (70%, 5) is beaten by (71%, 1) and (70%,5) beats (70%, 4). Other part B challenges will be marked in a similar way, though the number of marks available for speed increases as the Challenge gets harder and we will distinguish them by smaller time periods, part day, hours or minutes rather than by the day. We will combine your marks in the part B challenges to produce the final rankings. The outcome is that being delayed by even several hours in the early stages will not affect your position in the final league table. This scoring system is not open to negotiation!
Note that we will disqualify anyone who crashes the server by hammering at the submit button like a woodpecker at a tree so go easy on it! Given our scoring scheme you don't need to do this, and you are more likely to get a response from the server if you don't wear it out.

Prizegiving

There will be a prizegiving ceremony at Bletchley Park Code and Cipher Museum on the afternoon of March 27th 2009. The top three prizewinners will be invited to attend for lunch to meet our sponsors, and there will be an afternoon of lectures, starring Marcus du Sautoy, author of the amazing book, "Music of the Primes", and a tour of the museum for around 100 selected participants, including the top ten teams. Tickets will be awarded to schools and competitors at the discretion of the Prize Committee.

Rules

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 2009.
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 book prize awarded to 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 IBM and Trinity College Championship 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 teh 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.