BREAKING NEWS: The Zodiac’s “340 Cipher” has been solved


Written by Michael Butterfield / Posted: December 11, 2020 / 6:00 AM EST

Over the years, I have heard many rumors about some break in the case and proposed solutions to the Zodiac’s unsolved ciphers. Every amateur codebreaker is certain that their solution is correct but the evidence debunks their claims. The result is immediate skepticism whenever someone declares that they have unlocked the secrets of a Zodiac cipher. One learns not to get too excited about such claims in order to avoid the inevitable disappointment. 

Several years ago, I came to rely on David Oranchak for guidance when trying to understand the many complex issues surrounding the Zodiac’s ciphers. A computer programmer, David’s approach to the ciphers was refreshing and his analysis was informative. I often receive emails from people who claim to have solved the ciphers and I always refer them to David for his examination and conclusions. He always provides a fair assessment of proposed solutions and encourages people to bring new ideas to the discussion. His website has been a valuable resource for anyone seeking information about the ciphers.

For these and other reasons, I was not immediately skeptical when I received a message from David on the morning of Saturday, December 5th, which read: “I and two other programmers have a solution for the 340 cipher. No joke. I just sent off the solve to the FBI. I’m pretty sure it’s correct.” 

I believed that David would not make such claims if he could not back them up with clear evidence, so I was instantly intrigued by the thought that such evidence was obviously forthcoming, and I was not disappointed. I soon learned the incredible story behind the solution, a story about the pursuit of a seemingly random clue in a mundane search of data.  

The mystery was finally solved with the collaborative efforts of three individuals in different countries across the globe. From his home in Flanders, Belgium, computer programmer Jarl Van Eycke has worked online with David Oranchak in the United States, and Sam Blake in Melbourne, Australia.


David Oranchak, Sam Blake, and Jarl Van Eycke.

As members of Mike Morford’s forum at, the trio shared information, examined possible decryption methods, and searched for any clue which could crack the Zodiac’s three unsolved ciphers. Van Eycke created AZdecrypt, described by David as “a fast and powerful cipher solver,” and a modified version of this software helped Van Eycke and entrepreneur Louie Helm set a world record for deciphering of a bigram substitution of the shortest cipher length.

Studying the Zodiac’s 340 cipher, Sam identified and collected information about variations in the cipher text, which ultimately proved to be the key to cracking the cipher. “My main contribution here was actually enumerating many possible reading directions through the cipher, in total over 650,000,” Sam explained. “David and I both ran these through azdecrypt and zkdecrypto respectively. Interestingly, only azdecrypt was able to find the fragments of the complete solution. It was a needle in a haystack. Even finding the right haystack to search in was lucky.”

“Just one very partial solution, in a sea of 650,000 cipher variations I was running,” David added. That one partial solution was not completely correct but instead suggested information about the cipher’s construction. “By luck, we discovered that (Zodiac) split it into three pieces and rearranged the message in a predictable diagonal pattern in the first two pieces.” When the words ended at the right side of the text block the diagonal message would continue in the next line at the left side. The Zodiac made an obvious effort to thwart attempts to decipher the message by constructing the cipher in this way, and the resulting block of text may have been intended to encourage the false assumption that the 340 cipher was constructed with the same methods used to create the killer’s previous cipher, which was a simple message reading from left to right as normal text. By rearranging the message into three parts disguised as one block of text, the Zodiac may have believed that most people would never look beyond its appearance to discover the actual method used to hide the real message.

David explained, “Cracking it required undoing those arrangements then trying to discover his substitution key. That wasn’t enough because he made some mistakes in the second piece. Jarl discovered the mistakes and corrected them, which greatly cleared up the second piece.” After Jarl’s corrections were included and the proper adjustments were made, the decryption process quickly produced actual results. “We had a nugget of a solution on Thursday. I took Friday off and worked on it all day. My teammates Sam and Jarl also worked on it a lot. By (Saturday) morning, Jarl had worked out the remaining bit and it was finally complete enough to send off to the FBI. They responded almost immediately.” David said that he had received three telephone calls from the Bureau on Saturday morning. “When I talked to the FBI, they only needed to make one change to the solution.” David and his team had deciphered a section of six letters to read, “soo her.” “We couldn’t figure out the part that says, ‘soo her,’ [but] their cryptanalyst called me and she said she thinks it’s supposed to say, ‘sooner’” instead.

The solution was also examined by Dan Olson, Cryptanalyst Forensic Examiner for the FBI’s Racketeering Records Analysis Unit in Washington, D.C. Oranchak said, “They are running the solution up the chain now. Dan says it looks solid. I was happy to hear Dan Olson tell me personally that he thinks it’s solid.”


During his appearance in the 2009 History Channel series MysteryQuest, Dan Olson shared his theory that the text block of the Z340 may have been intended to be separated into two parts in order to be deciphered. The cipher was actually separated into three parts and the message was found in the first two parts.

The FBI experts were so confident that the solution was valid that the bureau would essentially close the file on the 340 cipher. “FBI is amending their original report to include our solution as the actual solution,” David reported, “Then they’ll submit it back to the San Francisco Police Department (the original requestor of assistance with the cipher in 1969).”

The solution revealed a message which seemed consistent with the Zodiac’s persona and character as displayed in his previous communications, including the deciphered text of the 408 symbol cipher. In that message, the killer wrote that he was killing people in order to collect slaves to serve him during his afterlife in “paradice.” The Zodiac also included the same misspelling in text using the words “paradice” and “slaves” to form a cross. In the solution to the 340, the writer returned to this theme and declared that he was not afraid of death.


David noted that, unlike other proposed solutions, this new solution revealed a clear and discernible message. “(We) didn’t have to do too many steps, and yet a coherent message pops out.”

The writer apparently referred to the Bay Area television talk show, The Jim Dunbar Show, and an episode featuring famous attorney Melvin Belli.  On October 22, 1969, someone called the Oakland police station and claimed to the Zodiac. The caller demanded that Belli, or Boston attorney F. Lee Bailey, appear on the show with host Jim Dunbar.


TV host Jim Dunbar and attorney Melvin Belli talk with the Zodiac impostor “Sam.”

During the broadcast, a man called several times but kept hanging up in an effort to prevent police from tracing the calls to his location. The caller agreed to be referred to as “Sam,” and he complained that headaches had driven him to murderous impulses. “Sam” expressed his fears of being “hurt,” and Belli promised to help the caller avoid “the gas chamber.” After the broadcast, a recording of the caller’s voice was played for the three people who had spoken to the Zodiac. Surviving victim Bryan Hartnell and police dispatchers David Slaight and Nancy Slover all concluded that “Sam” was not the Zodiac. Police reports, FBI files and other accounts indicated that “Sam” later called Melvin Belli’s home several times and that police were finally able to trace those calls to a patient in a mental institution. Investigators concluded that the man was not the Zodiac, but the incident became an often misunderstood chapter of the story and some people continued to believe that “Sam” was actually the killer.

The writer of the cipher text stated, “That wasn’t me on the the TV show.” The incident with Sam occurred on October 22, 1969, and the cipher was sent two and a half weeks later in November. On December 20, 1969, the Zodiac sent a letter to Belli’s home in an envelope which also contained a piece of a victim’s bloodstained shirt to confirm the writer’s identity as the real killer. The tone and text of the letter’s message seemed somewhat insincere, and the message could be interpreted as mockery of Sam’s imposter version of the “Zodiac” character. [To learn more, read the ZodiacKillerFacts article MELVIN & SAM: The Strange Saga of a Zodiac Impostor or listen to the audio version of the article ZODIAC: A TO Z – Ep# 10 – Melvin & Sam: The Strange Saga of a Zodiac Impostor.]

David said that, at first, he did not expect much to come from the possible decipher method, but everything changed when a message materialized before his eyes. “When ‘that wasn’t me on the TV show’ popped out during the solve, I jumped out of my chair and said, ‘Holy ****!’ since that show happened like a few weeks before the cipher was received. That’s when I knew it was on the right track.”

After more than fifty years, the mystery of the 340 cipher had finally been solved, thanks to the extraordinary efforts of three men working together from different parts of the world. “It’s exciting. We were really lucky to come across this solution,” David said. “It was only a handful of words to start with. Could have very easily ignored them and moved on. But ‘gas chamber’ really stood out.”

When David explained to me how the cipher was solved, I was reminded of his previous statements in interviews for my podcast series about possible decryption methods and different theories about the construction of the ciphers. I said to him, “This really bolsters so many things you said in your interviews.” David replied, “Yeah, the statistics in the cipher text really did turn out to reflect the way it was constructed.”

In November, 2019, David and I were discussing the Zodiac’s 340 cipher for the podcast ZODIAC: A TO Z – Ep. #8 – 340: The Mystery. Approximately 15 minutes into the show, David essentially predicted how the Z340 was actually constructed when he described possible encryption techniques. “Route transpositions are things like, read the message from left to right and then right to left and then left to right, kind of like a snake pattern, back and forth, a zigzag pattern. That’s an example of a route transposition. Or like, a diagonal, reading off the message diagonally. So in those situations, you’d end up with a plain text that doesn’t look like it makes any sense. And then the last step there would be to encrypt it using the same kind of substitution used in the first cipher. So the symbols are assigned to each of the letters.”

For years, I stated my belief that the Zodiac may have been somewhat disappointed that his first cipher was solved so quickly and, therefore, he may have intended that the next cipher was more difficult to solve. Some people had speculated that amateur codebreakers Donald and Betty Harden were able to solve the original 408 cipher so quickly because the Zodiac was little more than an amateur who possessed only a basic understanding of cryptography. I asked David if this new cipher solution cast doubt on those theories about the Zodiac’s knowledge of cryptography. “Yes, either he knew codes, or had a good intuition about how to make them.” David also agreed with my theory. “He definitely reacted to the Hardens solution and made it much harder.”

David thanked Mike Morford, owner of, and stated that “the site played a crucial role” in the events leading up to the solution. “It gave us a forum to collaborate. Me and the other nerds used it extensively… This could have only happened with the two other guys I worked with. Sam (Blake) sent me the 650,000 variations. One of them turned out to be extremely close to the right answer. And Jarl built the codebreaking software, and also helped fix up the solution. No way I could have done any of this without them.” Jarl Van Eycke said, “It is unbelievable how everything came together so perfectly between the three of us. And I am so happy to be a part of it.”

David was concerned that media coverage about the solution could be confusing. “It may be hard to convey to the general public because it does require additional steps— diagonal reading, splitting into three seconds, fixing the mistakes, and rearranging letters in the last two lines.” He has produced a new episode of his YouTube video series “Let’s Crack Zodiac with more details about the new solution and the methods used to decipher the message.

While the new solution did not provide any apparent clues to the killer’s identity, the deciphered message revealed another glimpse into the mind of the Zodiac. Whether or not he actually believed that his dead victims would serve as his slaves in his afterlife, the repeated theme was somehow important to the killer. In 1969, the Zodiac claimed that he was killing victims to become his slaves, and, more than half a century later, he remains significant because those victims were sacrificed to achieve his infamy. As his story continues to unfold in the pages of the history books, we are still haunted by the ghost of the Zodiac.


FBI Statement: The FBI has a team of cryptanalysis experts that decipher coded messages, symbols, and records from criminals known as the Cryptanalysis and Racketeering Records Unit. CRRU regularly works with the cryptologic research community to solve ciphers. On December 5, 2020, the FBI received the solution to a cipher popularly known as Z340 from a cryptologic researcher and independently verified the decryption. Cipher Z340 is one of four ciphers attributed to the Zodiac Killer. This cipher was first submitted to the FBI Laboratory on November 13, 1969, but not successfully decrypted. Over the past 51 years CRRU has reviewed numerous proposed solutions from the public–none of which had merit. The cipher was recently solved by a team of three private citizens. The Zodiac Killer case remains an ongoing investigation for the FBI San Francisco division and our local law enforcement partners. The Zodiac Killer terrorized multiple communities across Northern California and even though decades have gone by, 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 providing further comment at this time.

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Michael Butterfield is a writer who has conducted extensive research on the Zodiac case since the 1990s. As a recognized leading expert on the unsolved crimes, he has served as a media source and consultant for news articles, television documentaries, the History channel series The Hunt for the Zodiac Killer, and director David Fincher’s major motion picture Zodiac. Michael Butterfield appears in the Zodiac documentary Case Reopened, the History Channel series MysteryQuest, the E! Canada series The Shocking Truth, the Reelz channel documentary The Real Story of Zodiac, the HLN series Very Scary People, the documentary produced for Japanese television Darkside Mystery, and the podcast series Monster: The Zodiac Killer. He is also the producer of the podcast series Zodiac: A to Z and he is a contributing author for True Crime: Case Files, True Crime Magazine, and the two volume collection of essays titled A History of Evil in Pop Culture. Michael Butterfield is also a co-host with author/host Alan R. Warren for The House of Mystery on NBC News radio.


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Mysteries at the Museum: Zodiac Killer


The Travel Channel featured a new episode of the series Mysteries at the Museum devoted to the Zodiac case. An episode synopsis posted at the Travel Channel website read: “Don Wildman searches for the identity of one of America’s most notorious serial killers. He meets with a retired inspector who worked on the case, learns code breaking from an expert cryptographer and reveals a new theory on who may be responsible.”


Don Wildman and cipher expert David Oranchak.

Host Don Wildman presented a basic overview of the Zodiac story and visited the four crime scenes. He also consulted with cipher expert David Oranchak. Wildman and Oranchak examined the Zodiac’s first coded message and the still-unsolved 340 cipher while discussing some of the killer’s methods as a cryptographer. 


During his tour of the Zodiac crime scenes, Wildman was accompanied by theorist Mark Hewitt, who also shared his theory that the Zodiac was Ted Kaczynski, the infamous “Unabomber” responsible for several bombings and three murders.


Zodiac theorist Mark Hewitt and host Don Wildman at the Lake Berryessa crime scene.

The episode promised a “new theory” regarding the Zodiac’s identity but Ted Kaczynski became a Zodiac suspect immediately after his arrest in 1996. Theorists Douglas Oswell and Michael Rusconi published a book about the possible “Zodiac/Unabomber connection” titled Dr. Zodiac, and others had promoted this theory over the years. The episode also included a brief recap of the theory that the Zodiac was Arthur Leigh Allen, the so-called “prime suspect” named in the books by Robert Graysmith and the 2007 film Zodiac.


Convicted child molester Arthur Leigh Allen and Ted Kaczynski aka “The Unabomber.”

Retired San Francisco police Inspector Vincent Repetto joined Wildman at the scene of the Zodiac’s last known murder, the intersection of Washington and Cherry Streets in the Presidio Heights neighborhood of San Francisco. Repetto expressed his doubts that the Zodiac would be captured and said he believed the killer was most likely dead, but he also shared optimism that the case could be solved if new evidence was discovered or DNA identified the killer. 


Retired SFPD Inspector Vincent Repetto at the scene of the Zodiac’s last known murder.

In the final segment of the episode, Wildman met with Gary Harmor, a DNA analyst at the Serological Research Institute who worked as a consultant on the Zodiac case. Wildman asked about the chances of finding sufficient DNA on old envelopes and stamps, and Harmor explained that new methods increased the odds of retrieving DNA from older materials. Harmor used an old envelope to demonstrate the methods used in the process. When asked about the reliability of this forensic process, Harmor replied, “It’s extremely dependable. The only thing that would hold up getting a type from the piece of evidence is not having enough good quality, reasonably good quality DNA to do the testing.”


Gary Harmor demonstrates a method used to obtain DNA from old stamps and envelopes.

The narrator stated, “The actual Zodiac evidence was collected in a state lab in May 2018 who then sent the DNA to a genealogical lab in Florida.” Previous news reports, comments from law enforcement sources, and internet rumors indicated that investigators were still waiting to hear if the lab could retrieve usable DNA evidence, but the narrator’s statement created the impression that usable DNA had already been obtained and had been sent to a lab in Florida to be used in forensic genealogy research to identify the Zodiac. The narration may have been a simple mistake as misinformation continues to create confusion about the status of the investigation. If the narrator was correct, then attempts to identify the Zodiac using forensic genealogy may be proceeding.

Mysteries at the Museum also featured an unusual representation of the costume worn by the Zodiac during the attack at Lake Berryessa. Unlike previous recreations, the actor portraying the Zodiac appeared to be wearing a large, narrowed black bag with a white crossed-circle over the chest. This version of the costume apparently had no eye-holes, meaning the Zodiac would not be able to see during the attack.


The Zodiac killer as depicted by Mysteries at the Museum.

The Travel Channel will rebroadcast the episode Mysteries at the Museum: Zodiac Killer on Sunday, October 7, 2018, and on Wednesday, October 10, 2018. Check local listings for channels and show times, and CLICK HERE TO WATCH PROMOS FOR THIS EPISODE.