GCHQ Is Using This Puzzle To Recruit Aspiring Spies — Try It Out

GCHQ's distinctive 'doughnut' headquarters in Cheltenham, England. Ministry of Defence

GCHQ put a puzzle on the radio to entice recruits — and you can try it here.

The listening agency is pushing hard to recruit a more diverse staff, especially women.

LONDON — GCHQ, the British government's listening agency, has broadcast a puzzle in an effort to encourage potential spies — particularly young girls — to pursue a career in the highly-classified organisation.

The challenge was supplied to BBC Radio 4's "Today" programme, which broadcasts a puzzle every morning as part of its regular "Puzzle for Today" slot.

Monday's puzzle was submitted by the National Cyber Security Centre (NCSC), a recently-created GCHQ sub-division dedicated to protecting critical UK infrastructure from cyber attack.

The NCSC is specifically trying to pique the interest of secondary school girls and submitted its puzzle as part of a campaign aimed at girls aged 12 to 13.

Here's the text of the puzzle:

Thirteen rotters stole my answer and they ROTated it by 4 and then ROTated it by 10 and all I have left is Uccr ziqy hc ozz QmpsfTwfgh Uwfzg! - can you help me get my answer back?

How it works

Although NCSC is a brand-new agency focused on the internet, this puzzle is actually thousands of years old.

It's an example of a "Caesar cipher", in which every letter of a message is shifted (or rotated, as per the pun above) through the alphabet by a fixed number of letters.

"Thirteen rotters" is a reference to the common "ROT13" cipher, which shifts letters exactly halfway along the alphabet (a=n, n=a), and is a hint that the puzzle is dealing with a regular, 26-letter alphabet.

To follow the cues above, you have to take each letter of the alphabet ten spaces back (so the first letter, U, becomes K), and then another four spaces (So K becomes G).

Apply this to every letter in the puzzle, and you get:

Good luck to all CyberFirst Girls!

It's a slightly cheesy payoff that plugs their "CyberFirst" campaign, but still: if you had the wherewithal to work that out by yourself, you may have a shot at being a spy one day.