Sam Blake, an Australian mathematician, first learned of the Zodiac Killer’s unsolved ciphers — a series of encrypted messages — from a documentary in the 1990s. His interest marginally increased in 2007 after the release of David Fincher’s “Zodiac,” but it wasn’t until last year that it completely was cemented while watching code-breaking expert David Oranchak’s “Let’s Crack Zodiac” YouTube series.
The series was dedicated to solving the codes the Northern California serial killer sent in letters to newspapers in the late 1960s and early 1970s. One of the ciphers, called the 408 cipher, was solved in 1969 by a schoolteacher and his wife, but it did not reveal the killer’s identity; the additional three puzzles remained unsolved for over 51 years, despite advances in computer technology.
