Dear Charles,

Still stuck? As I said before this is based on the idea of the ADFGVX cipher, but instead of starting with a 6x6 grid it starts with a 3x3x3 grid in which the 26 letters of the alphabet and the underscore, representing a space, are entered in some order. This encodes those twenty seven characters as triples AAA, AAB, AAC, ABA, ABB, ABC, ACA ACB, ... and so on.

Harry

PS. The rest of the clues will be published at 3.15 on the 27th, 28th, 29th and 30th Dec. all the best, Harry

Dear Charles,

if you are having difficulty cracking the last section you should probably take note of the underscore - I didn't think anything of it at first, especially given all the formatting, but it does stand out as unusual. For some reason this cipher uses 27 characters. The formatting is actually a red herring apart from that and is best removed, though it is correct in that it does encode the original word shapes, so it is worth keeping it around somewhere as a sanity check!

Harry

Next clue at 3.15 Christmas Eve

UPDATE

The first hint for challenge 8B will be published here at 3.15 Friday 21st Dec.

So once more we reach the final round (actually that doesn't quite make sense, but I hope you see it from my perspective) with over 270 schools still in the challenge!

We have had 1784 teams attempt at least part of the competition this year with 723 schools involved. There are still 129 teams in joint first place vying for one of the major prizes this year and it all comes down to the last Challenge! Good luck to all of you. Do be extra careful to check your submission! Accuracy is still king. On the other hand speed is important too and I know a number of you have been practicing and preparing for this moment. We have developed a custom cipher for Challenge 8B that we hope will slow you down a bit! You will have four two weeks to crack it and we will not give out any information about when (or even whether) it has been done until the final deadline on January 4th, so please don't ask.

We will publish hints here on the news page as messages to Charles so if you are stuck check back here for updates.

We never cease to be amazed by the skill and enthusiasm of our participants, it has been a real pleasure watching from on high as you tackled the competition this year. Sorry I couldn't spend so much time in the forum with you all, but I was following and enjoying your conversations.

It would be good to meet some of you and the Prizegiving at Bletchley on April 12th would be a good opportunity. There will be talks, poems and a tour of the Park and we have a small number of free tickets to award.

If you would like to be considered for some then you can register online at https://www.cipher.maths.soton.ac.uk/index.php?option=com_cipher&controller=tickets.

Hope to see you there, 

Harry

OHOHOY <-- Harry's best (encrypted) Santa impersonation

The penultimate winners of the part A prizes - just in time for Christmas - are:

Sherlock Watson from The Godolphin School
Tim Woo, Tom Poskitt, Jem Corcoran, Jamie Bamber, Christopher Stone from The Perse Upper School
Ian Wilson, Natasha Wilson from Reading School
Jchang Aminshall from Perse school
Lucy, Anusha, Lea, Johanna from Durham High School for Girls
Joe Lewis, Tom Lewis, Jack Anderson, Illya Nuzbrokh, Thomas Kendell, Jeffrey Chan from Wycliffe College
Will W from Malmesbury
Hokay from South Wilts Grammar School

Congratulations to you, and a Merry Christmas to EVERYONE taking part this year!

Harry