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The official Challenge 10 tips and hints thread

The Body in My Library Forums Harry’s Meeting Place The official Challenge 10 tips and hints thread

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    We will publish occasional, official hints for Challenge 10 here, so bookmark it and check regularly. Hope they help, but not too much! We might also publish your own hints, especially if we think are suitably devious and don’t give too much away, but we will try to keep pretty much to the pace below, so if you submit a hint that is significantly stronger than the ones we have already published then we are likely to hold it back and it might not appear. Still worth sending them in, as we like to read them!

    Following a successful introduction last year  there is a schedule for the planned hints and tips. Best not to rely on it if you can avoid it, but if you get stuck you will at least know when help will arrive!!

    Challenge 10A

    Publication at 9am on

    Challenge 10B

    A hint for 10A 15/12/2023
    Another hint for Challenge 10A 16/12/2023 A first hint for Challenge 10B
    A third hint for Challenge 10A 17/12/2023 A second hint for Challenge 10B
    A fourth hint for Challenge 10A 18/12/2023 A third hint for Challenge 10B
    A fifth hint for Challenge 10A 19/12/2023
    A sixth hint for Challenge 10A 20/12/2023
    A seventh hint for Challenge 10A 21/12/2023 A fourth hint for Challenge 10B
    An eighth and final hint for Challenge 10A 22/12/2023 A fifth hint for Challenge 10B
    26/12/2023 A Boxing Day hint for Challenge 10B
    27/12/2023 The seventh official hint for Challenge 10B
    28/12/2023 The eighth official hint for Challenge 10B
    29/12/2023 The ninth official hint for Challenge 10B
    30/12/2023 The tenth official hint for Challenge 10B
    31/12/2023 The last official hint of 2023!
    01/01/2024 The first official hint of 2024, Happy New Year!
    02/01/2024 The thirtheenth official hint for Challenge 10B
    03/01/2024 The fourteenth and final official hint for this year’s National Cipher Challenge!

    Good luck,



    Is the cipher somewhat simplified, and can one play it alone?


    Is it fair to ask what kind of ciphers we will get?

    [It is not unfair to ask, but we won’t be telling you! (At least not yet!) Have fun, Harry]


    Harry is the spelling of ‘not’ as ‘note’ a typo or the first unofficial hint?

    [Typo! Thanks for pointing it out. Harry]


    Harry the ‘<tr>’ became ‘,tr>’

    [Good catch, thank you! I think it is fixed now, but let me know if you spot anything else. Harry]


    A note on feedback

    We have switched off the automatic feedback mechanism for Challenge 10 so that you can try to solve it without our immediate help. We will switch it back on at some point, so if you are really stuck don’t give up hope! Even without it, we think that the programme of hints and tips we are providing here should allow everyone to break the cipher before the end of the competition.


    If a solution is totally correct will we still get a score and will the submission window close indicating that the solution is correct?

    [Yes, that is right. We won’t leave you hanging once you have cracked it, but we just won’t tell you what mistake you might have made if you have made an is an error. The score might also be a bit misleading in the absence of the feedback, and depending on the actual error, so if you get less than 100% I would check your answer very carefully. A very low or absent score might not necessarily indicate a major error. Good luck, Harry]


    I got a decrypted text that made perfect sense, but the system said it was wrong??
    Did I do something wrong or was it the system? I know the system being wrong is highly unlikely, but I’m not understanding why its wrong.


    [Keep trying, sounds like you might be on the right lines, though I haven’t checked and couldn’t give any feedback anyway! Good luck, Harry]


    Is the Part B cipher a [… cipher]?

    [Nice try, but do I look like the sort of Cipher_Master who would answer that? Ho Ho Ho, Merry Christmas, Harry]


    been trying for five hours and all we’ve got are headaches. :/

    Hope to get it in the future but wont get max points.

    next time!


    Couldn’t agree more.


    this is the hardest cipher so far im so stumped by part B this is insane i think ive worked out the type of cipher but i have zero clue on how to decode that cipher without the key 🙁 is there a small hint i could have maybe please?

    [There is, indeed there is a series of them and we will publish them on the schedule shown at the top of this thread! In the meantime try to enjoy your befuddlement! It will make the solve much sweeter. Best of luck, Harry]


    Can’t say I’m anywhere near cracking ANY of this, but thanks for pointing me in the direction of John Finnemore – Quite enjoyed listening to some of his radio shows this evening! Ooooooh… there’s not a little hint in the epg is there?


    Will solving part A help in any way with the decryption of part B?


    Not really, but it can help you eliminate a few ciphers.

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