What do gift tags, candy canes and several layers of hardened code have in common?
They are all elements of an annual brainteaser for UK school children set by the nation's spy agency.
Ensuring sharp minds do not fall idle as the winter break approaches, GCHQ has released its code-breaking challenge, aimed at 11 to 18-year-olds.
More than 1,000 secondary schools signed up for the 2023 event, which this year features some of the trickiest puzzles yet.
This is the third edition of the challenge, which is designed around a Christmas card sent by Anne Keast-Butler, the director of the Cheltenham-based intelligence agency.
Challenges enclosed in the card are designed to test skills such as codebreaking, maths and analysis and each is designed to be harder than the last.
Let's ease ourselves in with one of the (apparently) less demanding questions.
This challenge asks youngsters to place the nine gift tags in three groups of three. Each group is defined by a single word linking the tags. Together, those three answers are linked by another word that can follow 'Christmas'.
For the more numerically minded, the next brainteaser may be more appealing...
If MIxMI=MAA, and TI+TI=RA, and if DO-SO+TI-MI=RE, then what does RExRE give you, it asks.
You are looking for a collection of letters that, again, form a word that can follow 'Christmas'.
These are just a taste of the seven questions the challenge poses to secondary school pupils and sixth formers. A maths-based bonus puzzle has also been included - and is billed as the toughest task included to date.
Children are encouraged to approach the challenge with teammates, drawing on individual skills to uncover the code, but the public can also informally try their hand.
Colin, a chief puzzler at the spy agency, explained: "Like the work at GCHQ, solving the puzzles on the card requires a mix of minds, and we want to show young people that thinking differently is a gift."
Historical nod
This year's Christmas challenge presents a more historical theme than the previous, featuring Bletchley Park - the wartime home of the spy agency - on the card.
It's where, more than 80 years ago, a group of scientists broke the German Enigma code.
The photo was taken in 1940, and was discovered in the personal family album of codebreaker Joan Wingfield, who worked on Italian naval codes.
Bletchley Park was also host of this year's AI Safety Summit in the UK.
"GCHQ's history at Bletchley Park is represented in this year's Christmas card as a reminder of the role this historic place has played in our wartime efforts but also as home to this year's AI Safety Summit," agency director Ms Keast-Butler said.
"Puzzles have been at the heart of GCHQ from the start. These skills represent our historic roots in cryptography and encryption and continue to be important to our modern-day mission to keep the country safe," she added.
