Zodiac Killer cipher cracked after 51 years of evading sleuths | GeekComparison

Police sketches side by side on a WANTED poster.
Enlarge / Composite drawings of the Zodiac Killer.

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An encrypted message from a ruthless serial killer who was never caught has been cracked more than 51 years after it was sent.

The male suspect, known as the 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 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 male San Francisco cab driver was the last known victim.

During the killing spree, the Zodiac Killer sent the media a series of letters taking credit for the killings. To prove the authenticity of the claims, the letters contain undisclosed details and evidence from the crime scene.

In August 1969, after murdering three of the five known victims, the Zodiac Killer sent three nearly identical letters to three Bay Area newspapers. Each letter also contained a third of a 408-symbol cryptogram that the suspect said would reveal his identity. The killer demanded that the newspapers publish the letters in full or he would kill again.

A week after the letters were sent, a couple in Salinas, California, crunched the cipher. The Zodiac Killer, the cleartext revealed, said he was collecting slaves for the afterlife and would not reveal his identity as it would interfere with those plans.

In November 1969, after killing the remaining two known victims, the Zodiac Killer sent a letter to the San Francisco Chronicle containing a new puzzle. The cryptogram was known as the Z-340, or 340 for short, because it contained 340 characters. The full image of the cryptogram appears below:

Since then, both amateur and professional cryptographers, including those working for the FBI, have been working to crack the cipher. Only this week, an international team solved it.

“The cipher had been unsolved 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, one of three men who wrote the coded message cracked, said by email. “It was an exciting project to work on, and it was on many people’s lists of ‘top unsolved numbers of all time’.”

The full text of the cracked cipher reads:

I HOPE YOU HAVE FUN TRYING TO CATCH ME THAT I WAS NOT IN THE TV SHOW WHICH MAKES A POINT ABOUT ME. HAVE ENOUGH SLAVES TO WORK FOR ME WHERE EVERYONE HAS NOTHING WHEN THEY REACH PARADISE, SO THEY ARE FEAR OF DEATH.

The decoded message matches much of what is already known about the case. The mention of the TV show and the gas chambers refers to a call to a talk show on KGO-TV a month earlier in which someone claiming to be the Zodiac Killer said, “I need help. I am ill. I don’t want to go to the gas chamber.” In other communications, the killer used the same misspelling for the word “paradise.” And of course there were earlier references to collecting slaves for the afterlife.

The FBI in San Francisco has since confirmed that the team has solved the cryptogram correctly. In a statement Friday, the agency wrote:

The FBI is aware that a figure attributed to the Zodiac Killer has recently been solved by private citizens. The Zodiac Killer case remains an ongoing investigation for the San Francisco FBI Division and our local law enforcement partners. The Zodiac Killer terrorized multiple communities in Northern California and though decades have passed, we continue to seek justice for the victims of these brutal crimes. Due to the ongoing nature of the investigation and out of respect for the victims and their families, we will not be commenting further at this time.

Oranchak, a 46-year-old software developer in Virginia, said the 340 is what’s called a transposition number. Most numbers used by computers today rely on math to scramble messages. Conversion numbers, on the other hand, are largely relics of the past that use rules to rearrange the characters or groups of characters in the message.

Transposition ciphers rearrange messages in a wide variety of ways. A common way is to rearrange the columns of a post. The message in the 340 was probably rearranged by manipulating triangular sections cut out of messages written in rectangles. Oranchak and his colleagues developed an app that helped him and his colleagues unravel the puzzle.

In the video below, Oranchak gives a much more detailed explanation of the cipher and how he and his colleagues cracked it.

Let’s Crack Zodiac – Episode 5 – The 340 Has Been Fixed!

Oranchak said he has been working off and on solving the 340 since 2006. The other two men on the team are Sam Blake, an applied mathematician who lives in Australia, and Jarl Van Eycke, a warehouse manager in Belgium. Van Eycke is also the software developer behind the AZdecrypt, a code-breaking app that was inspired by his drive to crack the 340.

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