GCHQ released a puzzle, dubbed Xmas Puzzle, on 9th December in the form of a Christmas Card that went viral online soon after its release. Nearly 600,000 people shot a “Go” for the challenge since early December, but only 30,000 had made it reach the final stage. David MacBryan, 41, from Edinburgh, Wim Hulpia, 40, from Lovendegem in Belgium and US-born Kelley Kirklin, 54, came closest to the fiendish puzzle game.
Source: https://thehackernews.com/2016/02/gchq-crypto-puzzle.html