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Harry @cipher-challenge.bsky.social · 18/09/2026

Ssh don't tell*, but cipherchallenge.org has soft-launched for a week of bug hunting before we go live with the 25th National Cipher Challenge! Registration opens 24/09, competition starts 08/10, but if you want a sneak peak ... *Actually, please tell everyone!

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Harry @cipher-challenge.bsky.social · 13/08/2026

Thinking of all our Cipher Challenge alumni getting their results today, and the teachers and family who support them. Congratulations to all of you on getting to this point and wishing you all the very best in the next stage of your adventure wherever it leads!

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Harry @cipher-challenge.bsky.social · 09/07/2026

Quick request for all the teachers out there who love the National Cipher Challenge. We will hold our 25th prizegiving at Bletchley Park in early 2027. Which of the following dates is best? 10th February (before half term) or 4th March (after half term).

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Harry @cipher-challenge.bsky.social · 15/02/2026

It's basically logarithms and lookup tables. Very elegant, but despite the fact that they were used extensively at NASA not really rocket science.

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Harry @cipher-challenge.bsky.social · 15/02/2026

At the other end of the scale I have one of the models that was used by the Apollo astronauts. Not quite as big!!! Might be fun to get a photo of the two of them together?

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Harry @cipher-challenge.bsky.social · 13/02/2026

We've a few tickets spare for the National Cipher Challenge event at Bletchley on 4th March. With speakers including Rob Eastaway. If you or your school took part in the competition in the Autumn, email us at cipher@soton.ac.uk with your details so we can see if we can fit you in.

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Harry @cipher-challenge.bsky.social · 04/02/2026

Is it because the National Cipher Challenge is over and the long wait to the next one has just begun?

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Harry @cipher-challenge.bsky.social · 27/01/2026

I know, and will contact her too, but the skill of a puzzle master lies in the taste and judgment in selecting them so I am hoping you both should have something to offer!

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Harry @cipher-challenge.bsky.social · 27/01/2026

Slow to pick up on this, but thank you for your lovely solution. Perhaps we could chat about next year's competition some time? It would be nice to have a guest puzzle setter at some point!

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Harry @cipher-challenge.bsky.social · 16/12/2025

Pick up the dollies and take a deep breath! You know you can do this!! Have you looked at the letters that go wrong? And have you inspected the grid in the Casefiles?

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Harry @cipher-challenge.bsky.social · 15/11/2025

At the moment the only order is by score and you can't conclude anything within the same score (=1st etc). For the very final overall leaderboard we will separate out the special few awarded prizes at the top.

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Harry @cipher-challenge.bsky.social · 11/11/2025

That would be great! Not sure we can do it at the moment, but will ask the developers!

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Harry @cipher-challenge.bsky.social · 06/11/2025

We are looking forward to the launch of the official competition challenges at cipherchallenge.org at 3pm this afternoon. If you want to find out why the three Charles (Babbage, Dickens and Wheatstone) need to talk to the US president, there is only one way to find out!

cipherchallenge.org

National Cipher Challenge

An annual codebreaking competition for UK schools and homeschooled students run by the School of Mathematical Sciences at the University of Southampton

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Harry @cipher-challenge.bsky.social · 23/10/2025

Just like last year we broke the records for Challenge 2 entries with nearly 8100 of you signed up to take part. Practice Challenge 3 starts at 3pm today, so if you haven't signed up yet head over to cipherchallenge.org to get involved

cipherchallenge.org

National Cipher Challenge

An annual codebreaking competition for UK schools and homeschooled students run by the School of Mathematical Sciences at the University of Southampton

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Harry @cipher-challenge.bsky.social · 18/10/2025

Excellent! Hope you all have fun!

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Harry @cipher-challenge.bsky.social · 16/10/2025

The clock is ticking down to the 3pm start of Practice Challenge 2 at cipherchallenge.org! We had over 7000 registered for the first round and there is still time to register for the competition. Hope to see you there!

cipherchallenge.org

National Cipher Challenge

An annual codebreaking competition for UK schools and homeschooled students run by the School of Mathematical Sciences at the University of Southampton

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Harry @cipher-challenge.bsky.social · 15/10/2025

We couldn't be happier with the response to the first cipher challenge this year. Over 7400 signed up already and we're still on the 1st practice challenge! Head over to www.cipherchallenge.org/ to to get your students signed up in time for the 2nd practice challenge tomorrow.

The best of times - Challenge 1 form cipherchallenge.org, featuring a playing card depicting Charles Dickens as the Jack of Clubs

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Harry @cipher-challenge.bsky.social · 08/10/2025

Over 5000 already registered at www.cipherchallenge.org ready for the practice challenges to start tomorrow at 3pm. If you are aged 11-18 and want to learn codebreaking and show the world what you can do then head over and sign up!

cipherchallenge.org

National Cipher Challenge

An annual codebreaking competition for UK schools and homeschooled students run by the School of Mathematical Sciences at the University of Southampton

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Harry @cipher-challenge.bsky.social · 30/09/2025

Love it! Would also love it if any musical cipher challenge aficionados out there feel like adding to our collection of themes!

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Harry @cipher-challenge.bsky.social · 22/09/2025

The 24th National Cipher Challenge is now open for registrations and we have already had 1200 sign ups. The competition starts on October 9th, so there is time to register your teams and get them investigating codes and ciphers. Catch up on our news at www.cipherchallenge.org.

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Harry @cipher-challenge.bsky.social · 18/09/2025

Day 1 and we have reached our first 500 registrations at www.cipherchallenge.org already! Will we beat last year's record 9,000? That is up to you!

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Harry @cipher-challenge.bsky.social · 17/09/2025

Ready to register for the National Cipher Challenge? The site opens tomorrow. Did you know that as a teacher you can monitor the teams at your school? You will be able to read more about that at www.cipherchallenge.org/how-to-bulk-...

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Harry @cipher-challenge.bsky.social · 15/09/2025

Just a few days now until the 2025 National Cipher Challenge opens for registration! If you know someone aged 11-18 who might like codes and ciphers (or who might not yet know that they do!) then get them to take a look at www.cipherchallenge.org on Thursday.

cipherchallenge.org

Registration opens 18th September 2025. Competition starts 9th October 2025.

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Harry @cipher-challenge.bsky.social · 12/09/2025

Tom, this looks great! Congratulations!

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Harry @cipher-challenge.bsky.social · 12/09/2025

We are looking for additional content to add to our Community page. You can read last year's at 2024.cipherchallenge.org/boss-your-ci... If you took part and would like to feature on this year's site, then do get in touch either here or by email at cipher@soton.ac.uk. We would love to hear from you!

2024.cipherchallenge.org

Meet some of the Cipher Challenge community ... - National Cipher Challenge 2024

Your stories about taking part in the competition.

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Harry @cipher-challenge.bsky.social · 08/09/2025

Posters for this years www.cipherchallenge.org should be arriving in schools this week. If you want to help promote the competition, why not post a picture of the poster on your boards?

cipherchallenge.org

Registration opens 18th September 2025. Competition starts 9th October 2025.

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Harry @cipher-challenge.bsky.social · 02/09/2025

Yes! Should arrive in schools for around 8th Sept!

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Harry @cipher-challenge.bsky.social · 02/09/2025

Holding a Clubs/Societies/Enrichment Fair for your school or college? The National Cipher Challenge might be just what you need. Here is a poster you can use to promote it! The site will open for registration on Sept 18th and the competition starts Oct 9th. Challenges weekly throughout term!

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Harry @cipher-challenge.bsky.social · 26/08/2025

Thank you! We will soft launch around 18th Sept for registration, with all the usual resources available then. Competition starts with the usual practice rounds from 9th Oct.

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Harry @cipher-challenge.bsky.social · 26/08/2025

Yes it is! Posters are stacked ready to go out, and the website is being updated. We really hope you like it!

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Harry @cipher-challenge.bsky.social · 12/08/2025

Want something to read on these idle summer days? You could take a look at this short article by one of our cipher challenge competitors: mathsrant.com/2025/07/28/t... (Not that the Elves at CC HQ are idle. Far from it - too much to be done in prep for the new adventure. More soon!

mathsrant.com

The National Cipher Challenge – More Than Just Codebreaking

I’ve been meaning to write about how I got into codebreaking — so here’s the start of a small series on maths, ciphers, and curiosity. A lot of experiences have shaped the curious, questioning pers…

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Harry @cipher-challenge.bsky.social · 14/01/2025

It's true that you sometimes need to generalise a conjecture in order to prove it, but as a general principle I think "generalise then prove" (rather than "prove then generalise") is what Sir Humphrey might call "brave".

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Harry @cipher-challenge.bsky.social · 11/01/2025

Just a heads up that now the challenge is finished we are working on the leaderboards, prizes and invitations to the National Cipher Challenge event @bletchleypark. Please do keep an eye out for messages from us on the site, and log in regularly to see if we have left one for you in your account!

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Harry @cipher-challenge.bsky.social · 09/01/2025

Great! Will be very pleased to see you back!

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Harry @cipher-challenge.bsky.social · 09/01/2025

Sorry I didn't pick up on this before, it's a really important issue-also why time bands on the challenges are broad. Except the very last challenge any correct entry before 11pm on Friday gets maximum marks, so even if they don't meet til lunchtime Friday they still have every chance of success.

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Harry @cipher-challenge.bsky.social · 14/11/2024

PS, we are keen to hear about your experiences with the challenge, so do reply if you are happy to talk about it. And if you have any news that you would like us to share then reply or email us at cipher@soton.ac.uk to let us know.

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Harry @cipher-challenge.bsky.social · 14/11/2024

We are well underway with the competition at www.cipherchallenge.org, though it is not too late to get involved if you fancy it. You'll be joining over 8500 other participants & there are still 6 challenges to break over the next few weeks. The next one goes live at 3pm today. Hope to see you there.

cipherchallenge.org

National Cipher Challenge

An annual codebreaking competition for UK schools and homeschooled students run by the School of Mathematical Sciences at the University of Southampton

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Harry @cipher-challenge.bsky.social · 07/11/2024

Over 8,000 signed up ready to take part in the competition at cipherchallenge.org this year! The first competition challenge runs until next Wednesday, so it is not too late to join in. Hope to see you there!

cipherchallenge.org

National Cipher Challenge

An annual codebreaking competition for UK schools and homeschooled students run by the School of Mathematical Sciences at the University of Southampton

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Harry @cipher-challenge.bsky.social · 26/10/2024

"In the past, I have made no secret of my disdain for Chef Gusteau's famous motto, "anyone can cook". But I realize only now do I truly understand what he meant. Not everyone can become a great artist, but a great artist can come from anywhere." Anton Ego, Ratatouille

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Harry @cipher-challenge.bsky.social · 26/10/2024

"How do I explain that!" is a pretty good definition of the substance of mathematics!

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Harry @cipher-challenge.bsky.social · 26/10/2024

Not sure I agree that angles don't appear in modern geometry.

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Harry @cipher-challenge.bsky.social · 24/10/2024

Excellent point about the factors. I like the thought experiment: if we met and talked to aliens about the geometry of circles would we be more surprised if they used degrees or radians?

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Harry @cipher-challenge.bsky.social · 24/10/2024

We have over 8,000 subscribers for the first time ever.They are all beavering away at cipherchallenge.org and putting a LOT of pressure on the marking system. If you get errors submitting, then it may be worth waiting. It won't affect your marks and will give the chips a chance to cool down!

cipherchallenge.org

National Cipher Challenge

An annual codebreaking competition for UK schools and homeschooled students run by the School of Mathematical Sciences at the University of Southampton

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Harry @cipher-challenge.bsky.social · 24/10/2024

The main argument is surely that radians are natural. Whereas degrees are just an arbitrary measurement.

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Harry @cipher-challenge.bsky.social · 23/10/2024

Tantalisingly close to 8,000 users registered at www.cipherchallenge.org with just over 24 hours to go til we publish the final practice challenge. Competition challenges start on November 7th, so if you want to join the fun head over to cipherchallenge.org and sign up! Teams or individuals welcome.

cipherchallenge.org

National Cipher Challenge

An annual codebreaking competition for UK schools and homeschooled students run by the School of Mathematical Sciences at the University of Southampton

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Harry @cipher-challenge.bsky.social · 22/10/2024

No, they are just used to build the leader boards for those rounds. Only scores from rounds 4-10 are used to compute the overall leaderboard at the end of the competition. Do email if you have any other questions - cipher@soton.ac.uk

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Harry @cipher-challenge.bsky.social · 21/10/2024

Half way through Challenge 2 in this year's National Cipher Challenge and we already have over 7,800 participants. Will we break 8000? It's possible, the first 3 challenges are for practice and we usually get a bunch more signing up at the 4th round. Head over to www.cipherchallenge.org to see why!

cipherchallenge.org

National Cipher Challenge

An annual codebreaking competition for UK schools and homeschooled students run by the School of Mathematical Sciences at the University of Southampton

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Harry @cipher-challenge.bsky.social · 20/10/2024

I am not sure I should ask this while you are still dealing with that, but is there a list we could all weigh in on? Have to say, it would be all pros on my part, but would be very interested to see some cons to work out if I am missing something.

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Harry @cipher-challenge.bsky.social · 17/10/2024

Challenge 2 is live and we look forward to seeing what you make of it. These are still practice rounds, so we're trying to make them accessible to complete newbies. If you have more experience then avoid using the support we put in place at cipherchallenge.org and see how fast you can break it.

cipherchallenge.org

National Cipher Challenge

An annual codebreaking competition for UK schools and homeschooled students run by the School of Mathematical Sciences at the University of Southampton

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Harry @cipher-challenge.bsky.social · 17/10/2024

Challenge 1 is now complete and the leaderboard will be published at 11am this morning. If you can't wait to see how you did then log in at www.cipherchallenge.org and download your certificates for part A and part B to find out. And don't forget, Challenge 2 goes live at 3pm this afternoon

cipherchallenge.org

National Cipher Challenge

An annual codebreaking competition for UK schools and homeschooled students run by the School of Mathematical Sciences at the University of Southampton

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