Skip to main content

Rules, Regulations & Policies

Who can take part?

  1. The competition is open to anyone but only individuals in full time school level education in the UK qualify for prizes.
    1. 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 leader board.

Submitting your solutions

    1. Each challenge round consists of two parts, part A and part B each with its own entry form. Entries must be submitted on the correct form for each part of the challenge.
    2. Only designated Team Captains, or those with the Team Captain account login, can submit answers for a team.
    3. 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.
    4. A submission will only be deemed to be valid if it is submitted on the correct entry form and all the instructions on this site are adhered to.
    5. 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.
    6. In submitting an entry to the competition, all entrants, whether individuals or members of a team, agree to be bound by all the rules of the competition.
    7. Any “mistake” in the text might be deliberate, so  don’t try to correct any errors you think we have made. Always type in an exact decryption of the text, otherwise you risk losing points when it is compared to our solution.
    8. Don’t try to tell us what cipher we used, or to ask us a question, or to say how you solved the cipher in the entry form, we don’t read it and it will be marked as an error in the solution.
    9. Do not include any headers like Challenge 1A or the title in your solution as these will also be marked as an error.
    10. If you do make a mistake you can resubmit using the usual submission box on the Challenge page, but be careful not to abuse this (see 3 above on rapid fire submissions).
    11. Check for feedback in your account area under will sometimes be a bit delayed but will at least appear after the next Part B points deadline, which you can find listed on the current Challenge page under the Deadlines link.
    12. Please DO NOT abuse the feedback mechanism to try to engineer a solution. This is in breach of the spirit of the competition (and now also the letter of the rules) and will be taken into account by the Prize Committee in the award of prizes. Egregious breaches of this rule will result in disqualification.
    13. You may use spreadsheets and text editors to help you tackle the challenges and any software we provide on the Official BOSS Deciphering Tools page. You can also use any software that you write yourself. You should not use deciphering tools you find elsewhere on the web and doing so can result in disqualification.

Scoring the challenge

  1. For each of the challenges 1 to 10 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. For those of you who like this sort of thing (which is, perhaps unsurprisingly, quite a few of the Cipher Challenge aficionados) accuracy will be measured using the Damerau-Levenshtein metric. Time points will be based on a schedule published alongside the challenge. Accuracy is more important than speed, so we will use the lexicographic order on the pairs (accuracy, speed) to determine your position on the leaderboard.
  2. The scores for Challenges 4B, 5B, 6B, 7B, 8B, 9B and 10B  will be aggregated to determine the Championship Leaderboard for the part B competition.
  3. 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 is letter perfect as compared to our master solution. UPPER or lower case solutions will be treated the same.

Variations in the rules

  1. 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 is practical.
  2. The Challenge Committee may publish clues on the competition web-site if it considers it appropriate to do so.


  1. Anyone posting a solution or partial solution in any public forum before the deadline for the given Challenge will be spoiling the competition for others. Please do not publish hints without checking with us first! We reserve the right to disqualify anyone breaking this rule.
Report a problem