Spy agency director Robert Hannigan gives away a cryptographic grid-shading brainteaser as a stocking stuffer this festive seasonFour calling birds,three french hens, two turtle doves and a cryptographic grid-shading brainteaser.
It may not possess the same ring to it, or but eavesdropping agency GCHQ has nevertheless stuck an infuriatingly complex puzzle in its official Christmas card this year,inviting participants to crack the complex code and reply with their answers.
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Source: theguardian.com