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GCHQ spooks' code-breaking puzzle solved

'Rather disappointing', says prof - both puzzle and prize

The GCHQ-set code-breaking puzzle was solved over the weekend.

The signals intelligence agency last week set a puzzle at canyoucrackit.co.uk in its attempt to unearth potential recruits beyond its traditional graduate programme. Late last week it emerged that the successful completion page for the puzzle was available by a simple Google search.

Many people have since cracked the code properly including Dr Gareth Owen, a computer scientist and senior lecturer at the University of Greenwich in England. Owen has posted a full video explanation of how to solve the three-part puzzle here.

Would-be code-breakers were presented with a 16x10 grid of paired hexadecimal numbers. The first stage involves recognising executable code as well as unpicking some steganography.

Stage two involves developing a virtual machine to execute code.

The final stage involves constructing a file with 'gchqcyberwinAAAABBBBCCCC' where A, B, C are the codes from earlier in the challenge. This code, when run, generates a web address which has the keyword (the web address is wrong if you put the wrong a,b,c in).

"The last stage contains a deliberate security hole, which GCHQ emailed me to say was deliberate to make solving the problem easier - but it turns out I took a short cut instead and bypassed this bit," Owen explained.

Reaching the successful completion page was a "rather disappointing end to quite a lot of work," as he puts it.

GCHQ is offering would/be applicants who crack the code a starting salary of just £25k, very low for a skilled job, as the Daily Telegraph notes.

As one Reg reader put it in an email to Vulture Central: "Why are we paying world-class cyber security experts what we pay passport-stampers at the border-control-agency?" ®

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