Few years ago I read 'Between Silk and Cyanide': Britain's Wartime Spies and Saboteurs', the autobiography of Leo Marks who worked in the British Special Operations Executive. He designed cryptography for agents behind enemy lines (thus the title: you could print one time pads on silk, and silk was harder to discover during pat-downs than paper).

Lots of interesting stories in there, including when he suspected that Germans had captured all of their Dutch spies and were transmitting fake messages: real agents made mistakes when encoding due to stress, the Germans' fake encodings were all perfect.

How German, LOL.