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GCHQ Has Included A Brainteaser In Its Christmas Cards

No spoilers, because we can't solve it either. Update: GCHQ has now released the answers.

Originally posted on
Updated on

GCHQ's Christmas cards this year include a cryptic twist in the form of this puzzle.


The cards were sent out to a select few people, but you can download a printable version of the puzzle here (once everyone else stops trying to – the site currently appears to be down).

Its website explains:

In this type of grid-shading puzzle, each square is either black or white. Some of the black squares have already been filled in for you.

Each row or column is labelled with a string of numbers. The numbers indicate the length of all consecutive runs of black squares, and are displayed in the order that the runs appear in that line.

For example, a label "2 1 6" indicates sets of two, one and six black squares, each of which will have at least one white square separating them.

Some are taking the brainteaser more seriously than others.

Solved it. Classy move of GCHQ to play tribute to @Snowden with their xmas puzzle.

But so many people tried to download the puzzle that the website appears to have been down for most of the morning.

have GCHQ crashed their own website under the traffic to their Xmas puzzle? the cutting edge of online security there


UPDATE: GCHQ has now published the answers to the puzzle.


It said that more than half a million people attempted the brainteaser.

The grid shading stage created a QR code which led to puzzles on a page of the GCHQ website testing participants "analytical prowess and knowledge of phonetics, semaphore, French, snooker, The Lord of the Rings" and more.

No-one found all of the answers, but three people came close and will be awarded with a GCHQ paperweight and an Alan Turing biography for their efforts.

Kelly Oakes is science editor for BuzzFeed and is based in London.

Contact Kelly Oakes at

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