How The Zodiac Killer’s Cipher Z340 Was Finally Solved

An internationally group of cryptographers released a whitepaper in April 2024 that described the difficult task of cracking the Z340 encryption used by the Zodiac Killer. The new whitepaper provides the most thorough explanation of the process, even though it was initially described in a 2020 YouTube video. The process required a significant amount of effort, crowdsourcing, and computer programming.

The Zodiac Killer’s cipher was mostly cracked by three men: David Oranchak, Sam Blake, and Jarl Van Eycke. However, their article makes it apparent that several other people throughout the years made substantial contributions that were necessary for this to happen.

This is the story of the Z340 Zodiac Killer cipher, its deciphering process, and its meaning.

What Did The Zodiac Killer Do and Who Was He?

An unnamed serial murderer operating in Northern California in the late 1960s and maybe early 1970s was known as “The Zodiac Killer.” In addition to a string of horrific killings, the Zodiac is notorious for teasing law enforcement and the general public with coded messages, phone calls, and ciphers.

Between 1968 and 1969, the Zodiac Killer allegedly killed five people, killing one male taxi driver and numerous young couples. David Faraday, Betty Lou Jensen, Darlene Ferrin, Bryan Hartnell (survivor), Cecelia Shepard, Michael Mageau (survivor), and Paul Stine were among his known victims.

Written letters detailing the killings were provided to local media by the Zodiac Killer, who also insisted they be published. Though some of these Zodiac ciphers are said to have been cracked in recent years, some of these letters featured intricate cryptograms that were left unresolved for almost fifty years.

The identity of the Zodiac Killer is still unknown after several investigations leading to no lead. Many investigators have claimed to have cracked the Zodiac case over the years; the most well-known suspects are Gary Francis Poste and Arthur Leigh Allen, but none of them have been shown to be the Zodiac beyond a reasonable doubt.

For decades, the case has captivated both the general public and detectives, leading to a number of books, films, and hypotheses on the identity of the the criminal.

How Cryptographers Cracked The Z340 Cipher Used by the Zodiac Killer

The Z340 letter, the second cipher used by the Zodiac Killer, was delivered to The San Francisco Chronicle on November 8, 1969, and it was incredibly challenging to decipher. In fact, it was so challenging that no one was able to solve it for 51 years.

On December 5, 2020, that day arrived when Australian mathematician Sam Blake, Belgian cipher specialist Jarl Van Eycke, and U.S.-based software developer David Oranchak deciphered the riddle of the Zodiac Killer’s encryption and had their work verified by the FBI. The three men revealed their long procedure in a whitepaper they released earlier this year, demonstrating the amount of work required to interpret the letter.

They discovered that Z340’s cipher alphabet was made up of 63 distinct symbols, making the system even more complex because a single alphabet letter may be represented by more than one symbol. The letter had several misspellings and transpositions, which added to the complexity of the codebreaking.

The authors claim that the “hundreds, if not thousands” of alleged answers put out by others over the years would not have been possible if not for software developed by Van Eycke and named AZdecrypt, which at last assisted in revealing the solution.

They added, “Many people raced to decipher it shortly after Zodiac mailed [Z340], and some claimed their decryptions were correct.” However, none had the official support of law enforcement, thus these initiatives persisted for many years.

The paper also detailed the number of efforts throughout the years to decipher the code. The NSA, the Navy, and the FBI all failed to accomplish it. Over the years, the American Cryptogram Association has also attempted to decrypt it, but to no success.

The three cryptographers stated that “many amateur codebreakers joined the efforts to solve the cipher due to the popularity of the case and noteworthy nature of Z340.” “A lot of purported fixes were created that ‘went viral’ and attracted a lot of media attention.”

The code was ultimately cracked thanks to a recent modification to Van Eycke’s AZdecrypt software.

Because Z340 and another cipher, Z408, lack word divisions, any program that attempted to decrypt them did as well. Because words frequently blended together and the cipher was complicated, it was difficult to determine whether the letters themselves were accurate. The end result was often a disorganized mess.

But now, thanks to a variety of facts, AZdecrypt could add white spaces automatically to split words where they probably belonged.

The authors said that “this made partial solutions much more comprehensible.”

We now finally know what Z340 says, over 50 years after the Zodiac Killer sent it.

The Z340 Cipher’s Decoded Text Used by the Zodiac Killer

The Z340 cipher starts, “I hope you are having a lot of fun trying to catch me.” “THAT WASN’T ME ON THE TV SHOW” — a reference to a recent live call that was allegedly made on an early morning in San Francisco, presumably from the Zodiac. The cipher goes on:

“WHICH BRINGS UP A POINT ABOUT ME

I AM NOT AFRAID OF THE GAS CHAMBER

BECAUSE IT WILL SEND ME TO PARADICE ALL THE SOONER

BECAUSE I NOW HAVE ENOUGH SLAVES TO WORK FOR ME

WHERE EVERYONE ELSE HAS NOTHING WHEN THEY REACH PARADICE

SO THEY ARE AFRAID OF DEATH

I AM NOT AFRAID BECAUSE I KNOW THAT MY NEW LIFE IS

LIFE WILL BE AN EASY ONE IN PARADICE DEATH”

Even if not all of the riddles surrounding the Zodiac Killer are resolved by this translated message, it is nevertheless an impressive achievement. The world was made aware of the contents of the letter by Oranchak, Blake, and Van Eycke, but the cryptographers also stated that their work would not have been possible without the efforts of those who came before them.

“We finally stood on the shoulders of many others’ great cryptanalytic contributions”, they stated, adding that “the solution of this cipher was the result of a large, multi-decade group effort.”

Maybe more investigators may build on these efforts in the future to provide further insight into the Zodiac Killer’s story.

Thank you for reading!

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