A notorious serial killer used complex chess moves to encode hidden messages to police
The Zodiac Killer's most complex cipher remained unsolved for 51 years until a team of amateur codebreakers used a custom algorithm to reveal its taunting message in 2020.
Between 1968 and 1969, the Zodiac Killer terrorized Northern California and sent four coded messages to local newspapers. While the first cipher was solved within days, the 340-character 'Z340' resisted decryption for over half a century. In 2020, David Oranchak and his team discovered the killer used a homophonic substitution cipher combined with a diagonal 'knight's move' transposition.
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