On the side he invented a precursor to the Vigenere cipher, a code so strong it took three centuries to crack.

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The Government Code and Cipher School in Bletchley, where Alan Turing did pioneering work on early computers, is a popular site of pilgrimage.

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In Mary's case, Elizabeth's master code breaker Thomas Phelippes cracked the cipher and exposed her crime.

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But what we have instead is a game that hands you a key and tells you to go find a lock, or gives you a cipher and tells you to go find a code.

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