The GCHQ Christmas Challenge 2023

December 14, 2023 4:28 AM

"Today the GCHQChristmasChallenge returns, pitting 11 to 18-year-olds [and bored adults!] against a series of tricky puzzles set by some of our finest minds."

Seven little puzzles designed to test skills such as codebreaking, maths and analysis. Direct link to the puzzles [PDF]
posted by Dysk (21 comments total)

I, naturally solved all the problems, I won't spoiler the answers here... ahem... Uh, curious thing though, I opened up social media site and there was an ad for "topazlabs" (whatever that is) some image something program/site/service and their image of choice was the same figure holding gifts as that in the quiz. Coincidence? Secret message? Or just another example of the porosity of imagery?
posted by From Bklyn at 4:45 AM on December 14, 2023

We're a bit into the season already, but it's never to late to jump in to the Advent of Code if you want to build your code-puzzling skills. Two puzzles released per day between Dec 1 and Dec 25.

The puzzles are not super challenging if you have a background in programming, but can have tricky bits. People I work with who are "pros" like to handicap themselves by using a new language or sticking to a certain coding style.
posted by bgribble at 5:37 AM on December 14, 2023 [1 favorite]

(So far, I've got five of the seven, I think, and haven't even looked at the final challenge at the bottom yet. Some of them are - to me - quite easy, some are quite hard, and the order doesn't reflect their relative difficulty. A couple may require some UK cultural knowledge. Please no spoilers in the thread, at least not without obfuscation!)
posted by Dysk at 5:39 AM on December 14, 2023

The good news is that after you solve all these puzzles they don't invite you to apply for a job at a fraction of what you're worth.
posted by Cardinal Fang at 5:40 AM on December 14, 2023 [1 favorite]

Oooo thanks. we might be able to knock some of these off - I know an handy 11 y.o. Looks to require a bit less UK/patriarchy local knowledge than, say, The King William College Quiz. Mental cogs . . . ENGAGE!
posted by BobTheScientist at 5:42 AM on December 14, 2023

What sorcery is this?!
posted by mittens at 6:21 AM on December 14, 2023

(Have the final answer, but kinda worked backwards at a couple of bits, so don't quite understand the logic of all of the puzzles... The answers should be posted on the first linked page tomorrow!)
posted by Dysk at 7:28 AM on December 14, 2023

Simon from Cracking The Cryptic solves it here (SLYT)
posted by jvbthegolfer at 8:01 AM on December 14, 2023 [4 favorites]

I think I have solved it.

The one that requires the most UK knowledge is probably clue 3. I think clue 4 is tricky unless you like maths puzzles. You can use quite a bit of guess work for clue 2, clue 5 and clue 7. Of the remaining two I think clue 1 is substantially easier than clue 6.
posted by plonkee at 8:25 AM on December 14, 2023

This was fun! I solved #1, #2, and #4 outright. On #3, I figured out the overall linking word, and which words go in which groups, but am still not exactly sure of the linking word for one of the groups.

For #5, I was able to figure out the first pair and last pair and took an educated guess as to the rest, though I don't know what the pattern is.

All the above plus a lucky guess for #6 was enough to help me solve the final puzzle.

I'm still not sure how to solve either #6 or #7, though I know the first three letters of #7 from solving the final puzzle, and I can guess what the fourth might be.
posted by timestep at 8:29 AM on December 14, 2023

Ah, I am watching the solutions video now, and I actually had one of the groupings wrong, though I had the correct linking word and the word I'd misplaced actually does fit with it. Tricky!
posted by timestep at 8:36 AM on December 14, 2023

Ah, the cute state surveillance apparatus and its adorable propaganda. Tis the season to be sure.
posted by rdc at 8:45 AM on December 14, 2023 [2 favorites]

I got the final result, but I still don't have a full solution for 5 or anything at all for 3.
posted by eruonna at 10:03 AM on December 14, 2023

This right here is the perfect definition of hell.
posted by tafetta, darling! at 10:06 AM on December 14, 2023

I have part of #3 from solving the final result, but I'm out of my depth on that one. One of the harder bits was matching up the puzzles to their icons at the bottom. Fun!
posted by figurant at 10:12 AM on December 14, 2023

eruonna: I got the final result, but I still don't have a full solution for 5 or anything at all for 3.

Pretty much the same for me, eruonna! I was able to get one of the three words for 3 but most of the cultural references are too UK-specific for this American. (Even the answer to 3 is very British!)

I did figure out the solution to TH, RD, ND, ?? before Cracking the Cryptic did so at least I get to feel smug about that. :)
posted by capricorn at 10:55 AM on December 14, 2023 [1 favorite]

Me too, capricorn! I actually found watching that video almost as delightful as solving the puzzle. It was fun to see how his thought processes compared to mine. Highly recommended for those who solve the whole thing (or who just can't help themselves from taking a peek).
posted by timestep at 10:59 AM on December 14, 2023

I've printed this out and left it on my daughter's desk. I'll let her finish it first and then she can watch me try to work out the solutions.
posted by any portmanteau in a storm at 11:31 AM on December 14, 2023

My 11 y.o. Effective abandoned me, preferring to work with their Cousin (which, fair enough). So I had to struggle through on my own. EIGHT HOURS later, I've just solved the Final Challenge - yay me. I'm still missing 1/3 of Q3 (not British enough) and 3/4 of Q5 (not clever enough). Alan Turing would defo not have given me room in his hut.
posted by BobTheScientist at 1:40 PM on December 14, 2023

That youtube video of solving it was really impressive: I thought for sure he'd have to write something down at some point, but no. I only solved 1,4,6 and 7 by the time I watched it, and I didn't see some very obvious things about them.
posted by netowl at 4:27 PM on December 14, 2023

#1 went very quickly.
#2 took a bit of thought.
#3 I didn't get - eventually reverse-engineered it after solving the final challenge
#4 I got with a lot of writing down numerals
#5 I got the first and last and extrapolated - didn't know why the other two were what they were until watching the vid
#6 I reverse-engineered the word from the final challenge, then reverse-engineered why
#7 I was able to suss out starting with gq'l

All in all, super fun! Thanks for sharing.
posted by skullhead at 2:38 PM on December 15, 2023 [1 favorite]