In 1969 the Zodiac Killer flooded San Francisco newspapers with homemade cryptograms, promising his name was hidden inside. Amateurs cracked the first in days — then the 340-character cipher swallowed every codebreaker alive for half a century, until three hobbyists on three continents finally broke it in December 2020. What it said was chilling, useless, and somehow more haunting than silence.
The documented record of the never-identified murderer who terrorized Northern California and sent taunting letters signed with a crossed-circle symbol. Four ciphers in all; he swore one held his name.
Software engineer David Oranchak opens his legendary series by interrogating the most famous 'solution' of all — Robert Graysmith's — and asking which claimed answers actually survive scrutiny.
The story of the 340 — why a cipher only 340 characters long defeated the NSA, the CIA, and generations of obsessives, and what made it so uniquely resistant to attack.
The breakthrough itself, narrated by one of the three men who did it. Oranchak, Sam Blake (Australia), and Jarl Van Eycke (Belgium) show how they sifted 650,000 possible reading directions to unlock a 51-year-old wall.
How the custom solver AZdecrypt, a transposition scheme read diagonally in triangular chunks, and sheer brute-force search finally forced the 340 to speak.
After 51 years the payoff was a sneering non-confession — 'I hope you are having lots of fun trying to catch me' — with no name, no clue, just more of the same attention-seeking venom.
Two ciphers remain: the 13-character 'My name is ___' and the 32-character map code. People claim solutions constantly. Oranchak weighs whether any of them could possibly be real.