This is a typeset version of Alan Turings Second World War research paper textit{The Applications of Probability to Cryptography}. A companion paper textit{Paper on Statistics of Repetitions} is also available in typeset form from arXiv at arXiv:1505.04715. The original papers give a text along with figures and tables. They provide a fascinating insight into the preparation of the manuscripts, as well as the style of writing at a time when typographical errors were corrected by hand, and mathematical expression handwritten into spaces left in the text. Working with the papers in their original format provides some challenges, so they have been typeset for easier reading and access.
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