Between December 1968 and October 1969 five people were murdered in the San Francisco Bay Area by an unknown serial killer known as the Zodiac Killer. It is probably the most famous unsolved murder case in US history. The Zodiac Killer Ciphers were messages he sent to newspapers to taunt them. Some have been solved, can you solve the others?
Brief overview of the Zodiac murders
The Zodiac Murders refer to a series of unsolved killings attributed to somebody the press named the ‘Zodiac Killer’, a mysterious figure responsible for at least five murders between 1968 and 1969 in Northern California. The Zodiac Killer is one of the most infamous serial killers in American history, mainly because of his cryptic letters, ciphers, and taunting messages to the media and police, which have fuelled decades of speculation and investigation.
The First Murders
The first known victims of the Zodiac Killer were high school students Betty Lou Jensen (16) and David Faraday (17), who were shot and killed on December 20, 1968, on a remote road near Vallejo, California. The pair had been on a date when they were ambushed by an unknown assailant. While this was the beginning, it wasn’t until the following year that the Zodiac began to leave cryptic messages, marking the start of his more infamous crimes.
On July 4, 1969, the Zodiac struck again, murdering Darlene Ferrin (22) and Michael Mageau (19) in a secluded area near Blue Rock Springs Park, also in Vallejo. The killer approached their car, fired multiple shots, and then walked away. In this case, Michael survived and was able to provide a description of the shooter, but the killer’s identity remained unknown.
The Zodiac’s Taunts
Shortly after these killings, the Zodiac began to communicate directly with local newspapers, sending letters to journalists and police. His letters included detailed accounts of the murders, and he often claimed responsibility for other, unconfirmed killings. The Zodiac’s most chilling form of communication involved encrypted messages that he sent along with his letters. Some of these ciphers were cracked by amateur codebreakers, but others remain unsolved to this day.
In one of his letters, the Zodiac boldly declared his love for killing, saying he was collecting “slaves for his afterlife.” His disturbing behavior, combined with the bizarre nature of the letters, intensified public fear and intrigue surrounding the case.
Further Confirmed Murders
On September 27, 1969, the Zodiac murdered Bryan Hartnell and Cecelia Ann Shepard near Lake Berryessa, close to Napa, California. Hartnell survived the attack and was able to provide a sketch of the Zodiac. The killer approached the couple, dressed in an executioner’s hood with a cross-circle symbol on it, and tied them up before stabbing them multiple times. Afterward, he drew the same symbol on Hartnell’s car door, further solidifying his eerie persona.
The final confirmed murder took place on October 11, 1969, when the Zodiac killed Paul Stine, a taxi driver in San Francisco. This was the last known victim, and the case remained cold thereafter, despite numerous sightings, theories, and claims that the Zodiac continued his killing spree.
Map of the victims of the Zodiac Killer. From top to bottom:
Bryan Hartnell and Cecelia Ann Shepard
Darlene Ferrin and Michael Mageau
Betty Lou Jensen and David Faraday
Paul Stine
The Zodiac Killer ciphers
From 1969 to 1974 Zodiac mailed 17 misspelt letters to law enforcement and media outlets. Many of them were signed with crosshairs 
. Four of these mailings had cryptograms enclosed and these are what we’re interested in here.
Two of them have been solved: one in 1969 and one in 2020. The other two remain unsolved.
SOLVED: The 408-Symbol Cipher (Z408)
The first major Zodiac Killer cipher was the 408-symbol cipher (known as Z408), sent in a letter on July 31, 1969 to the San Francisco Chronicle, San Francisco Examiner and Vallejo Times. The killer claimed it would reveal his identity. It didn’t.
Section sent to the Vallejo Times-Herald
Section sent to the San Francisco Examiner
Section sent to the San Francisco Chronicle
The cipher was solved on 8th August 1969 by a schoolteacher Donald Gene Harden and his wife Bettye June Harden (née Tischer) of Salinas, California who were able to break it using a standard cipher key. Donald Harden and Betty used homophonic substitution to identify the solution, after spending about 4 days on the cipher:
I LIKE KILLING PEOPLE BECAUSE IT IS SO MUCH FUN IT IS MORE FUN THAN KILLING WILD GAME IN THE FORREST BECAUSE MAN IS THE MOST DANGEROUE ANAMAL OF ALL TO KILL SOMETHING GIVES ME THE MOST THRILLING EXPERENCE IT IS EVEN BETTER THAN GETTING YOUR ROCKS OFF WITH A GIRL THE BEST PART OF IT IS THAT WHEN I DIE I WILL BE REBORN IN PARADISE AND ALL THE I HAVE KILLED WILL BECOME MY SLAVES I WILL NOT GIVE YOU MY NAME BECAUSE YOU WILL TRY TO SLOW DOWN OR STOP MY COLLECTING OF SLAVS FOR MY AFTER LIFE. EBEORIETEMETHHPITI
Section of the Harden Solution
Section of the Harden Solution II
Section of the Harden Solution III
The solution is a homophonic simple substitution cipher. In a basic simple substitution cipher, each ciphertext letter corresponds to a plaintext letter. However, in a homophonic substitution cipher, more than one ciphertext letter could correspond to a plaintext letter.
Donald and Betty Harden looked for common patterns, and added letters that might fit into the ciphertext. For example, there were a high number of double symbols (double letters) found in the ciphertext. In frequency analysis, the letter “L” is doubled most frequently in English. Because the message came from a serial killer, they figured that the double letter “L” must be preceded by the letter “I” as in the word “KILL”. In cryptography terms, the word “KILL” served as the “crib,” a word that could be plugged into other parts of the message to determine other phrases. While the message had a few misspellings, the meaning of the message was clear.
SOLVED: The 340-Symbol Cipher (Z340)
On November 8, the Zodiac mailed a card with a 340-character cryptogram to the San Francisco Chronicle. The card read:
This is the Zodiac speaking
I though you would need a good laugh before you hear the bad news. You won’t get the news for a while yet. and i can’t do a thing with it!
PS could you print this new cipher on your frunt page? I get awfully lonely when I am ignored, so lonely I could do my Thing!!!!!!
⌖
Des July Aug Sept Oct = 7
Z340 Cipher, 08 NOV 1969
It remained unsolved for 51 years.
Z340’s cipher alphabet consists of 63 different symbols several representing the same English letter. That complexity, along with misspellings and transpositions in the actual message, made breaking the code more complicated.
Which symbols corresponded to which letters.
On 05 December 2020 a team of cryptographers from the University of California, Berkeley, in partnership with other experts and crowdsourced volunteers finally cracked the cipher. The cryptology group included American software engineer David Oranchak, Australian mathematician Sam Blake and Belgian programmer Jarl Van Eycke. Van Eycke had written a piece of software called AZdecrypt that ran through 650,000 different solutions until it came up with the best possible encryption key.
The solution was a somewhat nonsensical message, and it did not reveal the Zodiac Killer’s identity:
I HOPE YOU ARE HAVING LOTS OF FAN IN TRYING TOCATCH ME THAT WASN’T ME ON THE TV SHOW WHICHBRINGO UP A POINT ABOUT ME I AM NOT AFRAID OF THEGAS CHAMBER BECAASE IT WILL SEND ME TO PARADLCEALL THE SOOHER BECAUSE E NOW HAVE ENOUGH SLAVESTO WORV FOR ME WHERE EVERYONE ELSE HAS NOTHINGWHEN THEY REACH PARADICE SO THEY ARE AFRAID OFDEATH I AM NOT AFRAID BECAUSE I VNOW THAT MY NEWLIFE IS LIFE WILL BE AN EASY ONE IN PARADICE DEATH
UNSOLVED: The 13-Symbol Cipher (Z13)
This cipher, also known as Z13, was a short, 13-character cipher sent by the Zodiac in a letter to the San Francisco Chronicle dated 20th April 1970. It was much shorter and more cryptic than the others.
The Z13 cipher in full
This cipher has never been definitively solved, despite many attempts by cryptanalysts and hobbyists. Some believe it might have been a trick to taunt authorities further, given its brevity and lack of clarity.
UNSOLVED: The 32-Symbol Cipher (Z32)
The Zodiac also sent a 32-character cipher (Z32) on 26th July 1970, which was in a simpler, more straightforward format than his earlier ciphers.
Z32 cipher in full
This cipher has never been definitively solved either. While some amateur cryptanalysts have made attempts to crack it, its solution still remains a mystery.
True Identity
The Zodiac’s true identity remains one of the greatest mysteries in criminal history. Despite massive media attention and an intense investigation by law enforcement, the Zodiac Killer was never caught. Numerous suspects have been proposed over the years, but none have been definitively linked to the crimes. The most credible suspect was Arthur Leigh Allen, who died in 1992. He denied being the Zodiac.
The San Francisco Police Department reopened the Zodiac case in 2007. The case also remains open in the California Department of Justice, Federal Bureau of Investigation, the city of Vallejo, as well as in Napa and Solano counties.
