A brief history of cryptography. It's got some errors in it (de Vigenère actually didn't like the de Vigenère cipher, and Lyon Playfair didn't like the Playfair cipher, as only two examples), and it's also limited to only symmetric algorithms, so it's not quite enough to get you through the exam. But it's quick to read, and uses the history to point out some very basic and important concepts in crypto. The cryptanalysis parts can also be fun.
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