A coded message sent by a brutal serial killer who was never caught was cracked over 51 years after it was sent.
The male suspect, known as Zodiac killer, killed at least five people and attempted to kill at least two more in northern California in 1968 and 1969. In the first three attacks, he targeted couples. The first two murder victims were high school students who were parked in a car on their first date. In attacks on the other two couples, he managed to kill the women, but the men survived. A San Francisco taxi driver was the last known victim.
During the murder spree, the Zodiac Killer sent a series of letters to the media taking credit for the murders. To prove the authenticity of the allegations, the letters included unseen details and evidence from the crime scenes.
In August 1969, following the murders of three of the five known victims, the Zodiac Killer sent three almost identical letters to three Bay Area newspapers. Each letter also included a third of a cryptogram of 408 symbols which, according to the suspect, would reveal his identity. The killer demanded that the newspapers publish the letters in full or he would kill again.
A week after sending the letters, a couple in Salinas, Calif., Deciphered the number. The Zodiac Killer, the plaintext revealed, said he was collecting slaves for the afterlife and would not disclose his identity as it would interfere with those plans.
In November 1969, after killing the other two known victims, the Zodiac Killer sent a letter to The Chronicle of San Francisco which included a new puzzle. The cryptogram was known as Z-340, or simply 340, because it contained 340 characters.
Since then, both amateur and professional cryptographers, including those working for the FBI, have worked to crack the encryption. It wasn’t until this week that an international team fixed the problem.
“The encryption hadn’t been solved for so long, it had a huge target on its back, and I felt like it was a challenge that had a chance to be solved,” Dave Oranchak, the one of the three men who deciphered the coded message, said by email. “It was an exciting project to work on, and it was on many people’s ‘best unresolved ciphers of all time’ lists.”
The full text of the cracked cipher reads as follows: