Un articolo di Popular Mechanics: racconta la storia dei tre crittografi dilettanti che sono riusciti a decifrare il cosiddetto 340 Cipher, uno dei messaggi lasciato al San Francisco Chronicle dal serial killer noto come Zodiac.

The envelope arrived at the San Francisco Chronicle in November 1969 without a return address, its directive to the recipient, in handwriting distinctively slanted and words unevenly spaced, to “please rush to editor.” The Chronicle newsroom had seen the scrawl before, on previous letters sent from the Zodiac, a self-monikered serial killer who threatened to go on a “kill rampage” if the paper didn’t publish his writing on its front page. By the time of the November letter, the Zodiac had already attacked seven people, murdering five. His most recent murder—of a San Francisco cab driver, by gunshot—had occurred just four weeks before this new envelope arrived. The Zodiac had mailed the Chronicle a piece of the victim’s bloodied shirt as evidence of the crime.

The Zodiac’s letters were replete with grisly imagery. He signed his “name” with a crosshairs symbol. He shared haunting details of his attacks. He promised to blow up buses of schoolchildren and unleash a “death machine” on San Francisco. But in addition to these overt threats, he included baffling ciphers for investigators to crack, troubling grids of symbols and letters that presumably masked a secret about his identity, intentions, or victims (to this day, the killer has never been found). The Zodiac’s first cipher, included in the July 31 letter, had been solved within a week by an amateur husband-and-wife team—but it had only revealed more of the killer’s raving. The second, now known as “the 340” due to the number of characters in it, would prove a much more difficult challenge.

[…]

Dave Oranchak has always been a puzzle geek. When he’s not running ultramarathons near his home in Roanoke, Virginia, the 47-year-old computer programmer spends most of his time working out practical solutions to problems, whether in his coding work or his passion for Shinro, a Japanese derivation of Sudoku. Around 2006, Oranchak became intrigued by the 340’s apparent resistance to a solution, a key had eluded the best efforts of professionals and experts. Tempted by the chance to unlock a slate of notorious cold cases, he started nosing around online discussion boards about the Zodiac. Before he knew it, he was down the rabbit hole, immersed in the Zodiac’s story and gaining a reputation as one of the reigning experts on the killer’s ciphers.

[…]

The community of amateur Zodiac hunters can be sensationalistic. “There’s a lot of chatter and nonsense and arguing about suspects,” Oranchak says. But one member of the forums struck him as level-headed and critical: Jarl Van Eycke, a reclusive warehouse worker living in Belgium who had gained respect in the cryptology community after developing his own decryption software program. “Jarl was technically minded, and [he was] approaching the [Zodiac] problem rationally,” Oranchak says.