National Geographic - Code Breakers Murder, War and Treason (2007)

Experts in code writing and breaking tell tales of heroic risks and cat-and-mouse secrecy, where science meets deadly adventure and everyone from queens to soldiers to everyday citizens can pay the price. Around the world, without realizing it, millions of people daily use secret codes. There is a constant struggle between those who want to keep information secret and those who want to reveal it. This struggle has been going on for centuries. The codes are cracked, changing the course of history forever. Queen Mary Stuart of Scots lost her head when her coded messages about the conspiracy were intercepted and deciphered. An intercepted telegram sent by Arthur Zimmerman caused America to enter World War I. The killer, nicknamed the Zodiac, continued to terrorize the streets of San Francisco and killed again and again … Because no one could decipher his coded messages. This is a story about the ciphers that have changed the world and the constant quest to make them unsolvable.

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