One of the Few Remaining Ciphers Has Been Solved - Zodiac's Z-340 Cipher

After remaining unsolved for 51 years, three amateur cryptanalysts have finally cracked the serial killer Zodiac's cipher.
Marcia Wendorf

Despite its beauty, or maybe because of it, the state of California has been a magnet for history's worst serial killers.

In 2018 the "Golden State Killer," Joseph DeAngelo, was finally caught thanks in part to the tireless efforts of author Michele McNamara whose book, I'll Be Gone in the Dark was published posthumously by her widower, comedian Patton Oswalt.

Still unknown is the identity of the serial killer who terrorized Northern California from December 1968 until October 1969, and is known as "Zodiac". What makes Zodiac so compelling are the cryptograms, or ciphers, he sent to newspapers.

The Zodiac killings

On December 20, 1968, in Benicia, California, 17-year-old David Feraday and 16-year-old Betty Jensen were on their first date. While they had intended to go to a Christmas concert at their high school, they instead went to a local restaurant, then on to a well-known lovers' lane, where Feraday parked his mother's car.


A short while later, Feraday was found next to the car, shot in the head, and Jensen was found 28 feet from the car and shot five times in the back.

Over six months later, on the holiday of July 4, 1969, in neighboring Vallejo, California, 19-year-old Michael Mageau and 22-year-old Darlene Ferrin drove Ferrin's car to Blue Rock Springs Park, which was only four miles (6.4 km) from where Faraday and Jensen had been killed.

A car appeared behind their parked vehicle, then the killer appeared at the passenger window and shot both Ferrin and Mageau multiple times. Starting back to his car, the killer heard Mageau moaning, and returned to put two more bullets into each of them.

At 12:40 a.m. on July 5, 1969, police at the Vallejo Police Department received a call from a phone booth with a man claiming responsibility for the attack. Incredibly, despite being shot in the face, neck, and chest, Mageau survived, and he described his attacker to police as a white male with short, light brown curly hair, 26 to 30 years of age, 195 to 200 pounds (88 to 91 kg) and 5-foot-8-inches (1.73 mt) in height.

On September 27, 1969, in Napa County, California 20-year-old Bryan Hartnell and 22-year-old Cecelia Shepard, were picnicking at Lake Berryessa when a strangely dressed man approached them.

The man was wearing a black executioner's hood with clip-on sunglasses covering the eye holes. His chest was covered with a bib that displayed a white 3" by 3" (7.6 cm × 7.6 cm) cross within a circle, and the man was carrying a gun.

The man handed lengths of plastic clothesline to Hartnell and Shepard, and had Shepard bind Hartnell's hands before the man bound her own hands. Instead of using the gun, the killer stabbed both young people multiple times, then he hiked back to where the couple had left their car. On one of the car's doors, he drew the following message:

Bryan Hartnell's car door
Bryan Hartnell's car door Source: Wikimedia Commons

The killer next called the Napa County Sheriff's office from a payphone, reporting the crime. When sheriff's deputies arrived a couple of minutes later, they were able to lift a palm print from the telephone, but unfortunately, it didn't match anyone in the fingerprint system. This meant that whoever the killer was, he didn't have a criminal record.

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Back at the crime scene, incredibly, both victims were clinging to life. Cecelia Shepard was able to give officers a detailed description of the attacker; however, by the time she arrived at the hospital, she had lapsed into a coma, and she died two days later. Hartnell survived his injuries, and he corroborated Shepard's description of the killer.

Two weeks later, on October 11, 1969, a San Francisco cab driver named Paul Stine picked up a fare who was going to the Presidio Heights neighborhood. As they arrived at the destination, the passenger shot Stine in the head with a 9mm handgun, stole Stine's wallet and car keys, and ripped off a piece of Stine's bloodstained shirt.

Three teenagers walking across the street witnessed the crime and called the police. When a patrol car passed a white man walking near the crime scene, officers didn't bother to stop him because somehow, the dispatch had become garbled, and the police thought they were looking for a black suspect.

The ciphers begin

On August 1, 1969, after the first two attacks but before the second two attacks, three letters arrived at the Vallejo Times Herald, the San Francisco Chronicle, and The San Francisco Examiner newspapers. The writer took credit for the murders, and included with each letter was one-third of a 408-symbol cryptogram which, the killer claimed, contained his real identity.

The killer demanded that each paper print his letter on its front page or else he would "cruse [sic] around all weekend killing lone people in the night then move on to kill again, until I end up with a dozen people over the weekend." It is not known if the misspelling of the word "cruise" was deliberate or unintentional.

All three papers eventually published the killer's letter, along with a message from Vallejo's police chief who requested that the letter writer send a second letter containing more facts to prove his identity. On August 7, 1969, a letter was received by The San Francisco Examiner which began: "Dear Editor This is the Zodiac speaking." This was the first time that the killer had referred to himself as the "Zodiac".

August 7, 1969 letter from
August 7, 1969 letter from "Zodiac" Source: Wikimedia Commons

The next day, on August 8, 1969, a husband and wife living in Salinas, California cracked the cryptogram included in the August 1st letter. It stated:

"I like killing people because it is so much fun it is more fun than killing wild game in the forrest [sic] because man is the most dangeroue [sic] anamal [sic] of all to kill something gives me the most thrilling experence [sic] it is even better than getting your rocks off with a girl the best part of it is thae [sic] when I die I will be reborn in paradice [sic] and the I have killed will become my slaves I will not give you my name because you will try to sloi [sic] down or atop [sic] my collectiog [sic] of slaves for my afterlife ebeorietemethhpiti."

Harden worksheet
Harden worksheet Source: Donald and Betty Harden/Wikimedia Commons

In the cryptogram, Zodiac might have been referring to the short story, "The Most Dangerous Game" by Richard Connell which was first published on January 19, 1924. The story is about a hunter whose prey is human beings.

On October 14, 1969, the San Francisco Chronicle received another letter from Zodiac that contained a piece of Paul Stine's bloody shirt. In the letter, Zodiac threatened to shoot schoolchildren on a school bus. That horrific plot was used in Clint Eastwood's 1971 blockbuster film, Dirty Harry.

Zodiac composite sketch
Zodiac composite sketch Source: SFPD/Wikimedia Commons

Police artists worked with the teenagers who had witnessed Paul Stine's murder to produce a composite sketch of the killer. On October 20, 1969, in a call to the Oakland Police Department, someone demanded that either F. Lee Bailey or Melvin Belli, two famous lawyers at the time, appear on a talk show to which he would call in. Someone called the program several times, agreeing to meet up with Belli, but never showed up to the meeting.

Zodiac's bomb schematic
Zodiac's bomb schematic with the circle and cross symbol Source: Wikimedia Commons

In a June 26, 1970 letter to the Chronicle, Zodiac sent a map of the San Francisco Bay area on which he had drawn his trademark symbol of a cross within a circle on top of Mount Diablo. He had also placed a zero, three, six, and nine around the edge of the circle along with instructions that the zero "be set to Mag. N." Included with the map was a 32-symbol cipher which, Zodiac said, would lead authorities to a bomb he had hidden.

When the authorities were unable to solve the cipher, Zodiac sent an additional note saying, "P.S. The Mt. Diablo code concerns Radians + # inches along the radians." In 1981, Zodiac researcher Gareth Penn superimposed radian measurements onto Zodiac's map and found that the map pointed to the locations of two of Zodiac's attacks.

After a three year hiatus during which no communications were received from Zodiac, on January 29, 1974, he sent a final letter to the Chronicle claiming to have killed 37 people.

Solving the Z-340 cipher

Z-340 cipher
Z-340 cipher Source: Wikimedia Commons

On November 8, 1969, Zodiac had mailed a 340-character cipher which became known as the "Z-340 Cipher". For over 51 years, it remained one of the few unsolved ciphers in the world, with both amateur and professional cryptographers taking a crack at it, and cryptanalysts at the FBI working on it. On December 12, 2020, it was announced that three men — a Virginia software developer named David Oranchak, a Belgian computer programmer named Jarl Van Eycke, and an Australian mathematician named Sam Blake had solved it.

AZD program
AZD program Source: David Oranchak/YouTube

The Z-340 Cipher contains 63 unique symbols, and using a suggestion from Van Eycke, Oranchak split the cipher into three sections, with the first two sections containing nine lines, and the last section containing two lines. Oranchak next used a computer program written by Van Eycke called AZ Decrypt to examine 650,000 different permutations of the cipher text.

Three sections of the Z-340 Cipher
Three sections of the Z-340 Cipher Source: David Oranchak/YouTube

The men latched onto a transposition scheme whereby you start at the upper left-hand corner, move down one letter and over two letters to the right, and continue this scheme until you reach the right edge of the cipher. You then begin the same scheme again starting with the second letter from the left in the top row.

Transposition scheme
Transposition scheme Source: David Oranchak/YouTube

With a final tweak, the plaintext of the first section of the cipher finally appeared; however, the second and third sections stubbornly remained unreadable. Then, the three men noticed that some words within the second section were spelled backwards, and that there was a coding error, possibly made by Zodiac, in that section. Fixing that error, and rearranging the words "LIFEIS" which appear in the upper right-hand corner, resulted in a solution.

One of the Few Remaining Ciphers Has Been Solved - Zodiac's Z-340 Cipher
"LIFEIS" Source: David Oranchak/YouTube

On December 5, 2020, Oranchak, Van Eycke and Blake submitted their findings to the FBI's Cryptoanalysis and Racketeering Records Unit who, on December 12, 2020, confirmed the solution. The Z-340 Cipher states:

"I hope you are having lots of fun in trying to catch me
That wasn't me on the TV show 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 will be an easy one in paradice death."

The current state of Zodiac

On December 12, 2020, the FBI tweeted the following statement:

In 1986, the cartoonist for the San Francisco Chronicle, Robert Graysmith, released a book about the killings entitled, Zodiac. In 2007, director David Fincher turned Graysmith's book into a movie of the same name starring Jake Gyllenhaal, Mark Ruffalo, and Robert Downey Jr. This film has become a true crime classic due to its pervasive feeling of dread and almost unbearable tension.

In May 2018, the Vallejo Police Department announced that they were trying to collect Zodiac's DNA from the backs of stamps he used to send his letters. If he's still alive, Zodiac must now be in his 70s or 80s. The question remains of how someone intelligent enough to have constructed these ciphers misspelled as many words as Zodiac did in his letters. Or, were the misspellings deliberate?

Since in most cases, Zodiac's female victims fared far worse than his male victims, did Zodiac's hatred of women come to an end sometime in the early 1970s? Did Zodiac finally find love, marry, have children, and perhaps grandchildren?

Zodiac's grandchildren would now be of an age similar to that of his victims when they were killed. 

Unsolved ciphers waiting to be solved

If the solution of the Z-340 Cipher has given you a taste for cryptanalysis, there are still many ciphers out there still waiting to be solved. Here are just a few of the more famous of them:

1. Voynich Manuscript – 15th Century, Italy

Page from the Voynich Manuscript
Page from the Voynich Manuscript Source: Wikimedia Commons

Purchased by book dealer Wilfrid Voynich in 1912, the 240-page Voynich Manuscript contains six sections which contain herbal, astronomical, biological, cosmological, and pharmaceutical illustrations, along with 170,000 undecipherable symbols.

A statistical analysis of the frequency of those symbols has revealed that their arrangement is similar to that of a natural language, and the manuscript is far too elaborate to be a hoax. The renowned American cryptanalyst William Friedman took a crack at solving the Voynich Manuscript during the 1940s but was unsuccessful. Today, the Voynich Manuscript resides at the Yale University library.

2. Linear A – Ancient Crete, 18th Century BCE

Linear A
Linear A Source: Arthur Evans/Wikimedia Commons

Linear A is a writing system that was used by the ancient Minoans who lived on the island of Crete from 1800 to 1450 BCE. Examples of the script were discovered by the British archaeologist Sir Arthur Evans, and other examples of Linear A have been found in Greece, Turkey, and Israel.

So far, 1,427 specimens of Linear have been found which contain up to 7,396 unique symbols. Linear A was succeeded by the "daughter" scripts, Linear B and Cyrpo-Minoan Syllabary, none of which have been deciphered.

3. Kryptos – 1990, CIA Headquarters, U.S.

Kryptos Sculpture
Kryptos Sculpture Source: Jim Sanborn/Wikimedia Commons

In 1990, the artist Jim Sanborn created a cryptographic sculpture called Kryptos which was placed on the grounds of the U.S. Central Intelligence Agency (CIA). The code is comprised of four sections, three of which have been solved, however, the fourth section remains unsolved.

The first two sections are encrypted with Vigenère polyalphabetic substitution ciphers, while the third is an elaborate transposition cipher, just like Z-340. These first three ciphers supposedly contain the clue to solving the fourth section. Kryptos makes an appearance in Dan Brown's popular novel, The Lost Symbol.

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