An engineer and hobbyist codebreaker believes he has deciphered the Zodiac Killer’s last two scrambled messages, one of which appears to reveal his identity.
In the late 1960s, early 1970s, a serial killer going by the alias “Zodiac” murdered at least five people in California. During his spree, the killer sent defiant messages to the press written through a cipher, where letters are replaced with different letters or numbers (or in the case of the Zodiac killer, a series of symbols).
The first letters were sent to three Bay Area newspapers, each containing a different part of the cipher. Newspapers printed the ciphers (or cryptograms) as Zodiac threatened to kill again if his instructions were not followed.
The cipher, which was simpler than later efforts, was solved a week later by hand, on August 8, 1969, by Donald Gene and Bettye June Harden. This Lily:
“I LOVE KILLING PEOPLE BECAUSE IT’S SO FUN IT’S MORE FUN THAN KILLING WILD GAME IN THE FOREST BECAUSE MAN IS THE MOST DANGEROUS ANIMAL OF ALL TO KILL. A GIRL THE BEST PART IS THAT WHEN I DIE I WILL BE BORN IN HEAVEN AND ALL I HAVE KILLED WILL BE MY SLAVES I WILL NOT GIVE YOU MY NAME BECAUSE YOU WILL TRY TO SLOW DOWN OR STOP MY SLAVES COLLECTING FOR MY AFTERLIFE EBEORIETEMETHHPITI”.
Based on that, it’s pretty incredible that he could come up with a number complicated enough to fool the FBI for years, but couldn’t put in the effort to quickly check its spelling, or maybe ask to a friend of: “listen, try not to read too much into the content, but can you quickly check that my grammar is correct”.
However, other messages took until the end of 2020 to be decrypted, having been worked on for years by codebreakers.
Today, Fayçal Ziraoui claims to have decrypted the last two messages in just two weeks, thanks to the use of the encryption key discovered in December. (For the rest of the article to make sense, you might want to take a look at this key for yourself).
The main problem with final posts is the length. The Z13 message is only 13 characters long, making it much harder to figure out what the encryption might be. It’s especially frustrating, given that according to the post before it, it reveals the Zodiac Killer’s name.
Let’s start with the number Z32, as Ziraoui did. This particular 32-character number claimed to reveal the location of a bomb the killer had planted and was accompanied by a map showing the cities of Berkley and Oakland in California, USA.
This new solution proposes that the encryption does not have its own key, and uses a key revealed in previous messages. Ziraoui suggests that the key he used was the Z340 key, decrypted last December.
He maintains that this key was not solved at the time, which means the killer did not need to create a new code. When used against the Z32, he claims it also draws sequences that look almost like words, including strings that look like scrambled versions of north (“nort” in the cipher), east, and west, which would make sense given that the encryption supposedly reveals a location. In addition to that, he thinks you can also see the string “IDOBLA”, which is close to “diablo”, matching with California’s Mount Diablo. Diablo has been highlighted on the Zodiac Killer map.
He also thinks the code revealed coordinates relative to magnetic north (the killer had written Mag. N on the map), which gives a rough idea of what kind of numbers you’re looking for. On top of that, he guessed the kind of accuracy with which someone in the 1970s would be able to determine the location. With 3 digits after the decimal point, you can mark a location with an accuracy of approximately 100 meters (328 feet). With four you can reduce that to around 10 meters (32.8 feet), which is about the accuracy of modern GPS.
Using this, he guessed that the code would eventually reveal two numbers, indicating longitude and latitude, each with two numbers, followed by 3-4 numbers depending on how accurate the Zodiac Slayer was trying to be. He also guessed that the first two digits of the latitude had to be around 44 – to put it near Mount Diablo – and the longitude around 60 for the same reason.
Using the Z340 cipher, then applying a single letter to the digital switch (A=2, B=2, C=3, etc.), he found coordinates he thinks are in Lake Tahoe, which he deems interesting considering this murder victim. Donna Lass disappeared from there a few months later and assumes he was sending a message that he would commit murder there.
Using the remaining letters (see the video above for a full explanation), he found the scrambled words “find”, “work” and “day“. It matters, he thinks, because Labor Day was the date Donna Lass disappeared.
If (and it is an if) this is a correct translation of the Zodiac Killer’s message, it could mean that he used the same key again for his Z13 short cipher. That would be much more helpful in finding out who he is, since the message above said he would reveal his name.
Again, Ziraoui applied Z340 encryption to the short string. For symbols that look like zodiac signs, he translated them into numbers based on where they appear in the calendar. The remaining letters were translated to digits using the same A=1 translation above, leaving a string of 13 digits:
Since the numbers were mostly repeats of 1, 4 and 5, he was struck by the fact that it looked a lot like the Trifid alphabetanother classic cipher invented in 1902. For this, however, the total number of digits would have to be divisible by three (unless it had an unnecessary extra character).
Ziraoui’s next step was to find the difference between each number (the difference between 4 and 8 is 4, the difference between 8 and 5 is 3, etc.) until he ended up with a code at 12 digits, which he could translate into four letters using the trifid alphabet:
434 333 113 411
The reason this matters is that one of the prime suspects in the case was Lawrence “Kane” Kaye, who served in the Navy during World War II before moving to California, where he began receiving a number of criminal convictions.
Kane was in the area when the Zodiac Killer was active and was 45 when the killer was most active. Following brain damage in 1965, he would have has lost the ability to control gratification. Additionally, he was identified as someone who bothered victim Darlene Ferrin at a restaurant, by Darlene’s sister. Kathleen Johns fled from someone who may have been the Zodiac Killer and also identified Kane as her potential captor, while a retired police officer also claimed that Kane’s name had been baked into the killer’s code.
While it’s easy to say “case closed”, the reaction to Ziraou’s solution has been mixed. Cryptography specialist at the National Institute for Research in Digital Sciences and Technologies Emmanuel Thomé told the New York Times that his methods were right and that the police should investigate seriously, while others think he made arbitrary choices and that the code is too short to crack.
Ziraoui sent his solution to the FBI for further investigation. The FBI recently confirmed that the Z340 cipher has been crackedso it might not be long before we know for sure.
THIS WEEK IN IFLSCIENCE
Get our biggest science stories delivered to your inbox every week!