Readers of this blog solve Zodiac Killer message after 51 years
This is the crypto sensation of the decade: the Zodiac Killer’s second message, unsolved for 51 years, has been deciphered by readers of this blog.
Yes, there is something German on this blog again. The following article is based on a press release that I sent out yesterday and that I don’t want to translate as well. If you are looking for English-language information, you can find it at Nick Pelling, for example. A link to a machine translation of this article (using Deepl) is given above.
And yes, one of the most important unsolved mysteries in cryptography history has been solved! Thanks to the many readers who brought this to my attention.
Who was the Zodiac Killer?
The Zodiac Killer killed at least five people in the San Francisco area in 1968 and 1969. Two other victims were seriously injured. Despite intensive manhunts, the police were never able to identify the perpetrator.
I have written and lectured about this case many times (among others in my book Nicht zu knacken). To illustrate, I created and photographed a couple of Lego models. The following picture shows the Zodiac Killer’s crime at Lake Berryessa on September 27, 1969, killing a man and seriously injuring a woman:
What acts did the Zodiac Killer commit?
One can safely attribute four acts to the Zodiac Killer:
- Dec. 20, 1968: The Zodiac kills 16-year-old Betty Lou Jensen and her 17-year-old boyfriend, David Faraday, in Vallejo, north of San Francisco.
- July 4, 1969: The Zodiac kills 22-year-old waitress Darlene Ferrin in a Benicia parking lot. Her 19-year-old companion Michael Mageau survives seriously injured.
- September 27, 1969: In a park on Lake Berryessa, a black-costumed man kills 22-year-old Cecelia Shepard and seriously injures her 20-year-old boyfriend, Bryan Hartnell.
- October 11, 1969: Taxi driver Paul Stine is shot dead in his cab by the Zodiac Killer.
Whether the Zodiac Killer committed other acts is unclear. There are several unsolved murders and attempted murders where at least it cannot be ruled out that the Zodiac Killer had something to do with them.
What is Z340?
The Zodiac killer sent numerous anonymous letters to the regional press, boasting of his deeds and taunting the police. Four of his letters contained coded messages. The following chart (from my book Not to be Cracked) shows when the murders occurred and when the letters were sent:
The first encrypted Zodiac message (408 letters, referred to in the picture as “Zodiac-408”) was solved within days by a teacher couple. The plain text reads:
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 THAE WHEN I DIE I WILL BE REBORN IN PARADICE AND THEI HAVE KILLED WILL BECOME MY SLAVES I WILL NOT GIVE YOU MY NAME BECAUSE YOU WILL TRY TO SLOI DOWN OR ATOP MY COLLECTIOG OF SLAVES FOR MY AFTERLIFE EBEORIETEMETHHPITI
Unfortunately, this decryption success did not bring the police any further.
The third and fourth encrypted messages (13 and 32 letters, respectively) are quite short and therefore unlikely to be solvable. Thus, for decades, hope rested on the killer’s third encrypted message, known as Z340 or Zodiak-340 after the number of letters it contains.
For 50 decades, countless code breakers all over the world cut their teeth on Z340. On my list of the 50 most important unsolved ciphers, this cryptogram is number 2.
How was Z340 solved?
On December 11, 2020, sensational news spread: Z340, the second message of the Zodiac killer, has been cracked. A team of three computer experts was able to report this success. The following video of the three code breakers explains how the encryption works:
The FBI examined the solution and confirmed that it made sense.
It turned out that the Zodiac killer had used two encryption methods in succession. First, he replaced each letter of the plaintext with a symbol. For the common letters, especially the E, he did not always use the same symbol, but chose one of several. This is called a homophonic cipher. The advantage for the user is that a codebreaker cannot easily deduce the meaning of a symbol from its frequency. Even the first Zodiac message was encrypted in this way.
The second method used by the Zodiac killer is rearranging the letters in the text (transposition cipher). He divided the message into three parts and rearranged each part so that the correct order could be read using the Rösselsprung method (two forward, one across).
By combining a homophonic encryption method with a transposition method, the resulting message was extremely difficult to solve.
What is the plain text?
The three successful code breakers determined the following plaintext:
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
Unfortunately, these lines do not contain any information that directly suggests the identity of the Zodiac killer.
Who has solved Z340?
Three computer experts who worked together are responsible for its success:
- David Oranchak: The software developer from Roanoke in the US state of Virginia is a reader of this blog. He has been considered the world’s leading expert on the Zodiac killer ciphers for years. I interviewed him in 2014.
- Jarl Van Eycke: The Belgian software developer is also a reader of this blog. Jarl has made a name for himself in recent names with some spectacular deciphering successes. Among other things, he and Louie Helm cracked two difficult digraph challenges I created for this blog, setting new world records.
- Sam Blake: The Australian mathematician has not been active in the crypto scene before.
The Z340 solution was teamwork. Jarl Van Eycke is one of the world’s leading specialists in homophonic encryption. However, his program AZDecrypt did not provide a solution to Z340. It was not until Sam Blake tried hundreds of thousands of letter rearrangements (transpositions) with software he developed and examined each one with AZDecrypt that the breakthrough came. David Oranchak, who coordinated the work as a Zodiac killer expert, recognized meaningful words in the results. This finally allowed the correct transposition method to be determined.
Does this solve all the crypto mysteries surrounding the Zodiac Killer?
No. Two of the encrypted Zodiac messages are still unsolved, namely Z13 …
… and Z32:
There were also several Zodiac freeloaders sending similar encrypted messages.
Apart from that, several other unsolved encrypted messages are known to be related to an unsolved criminal case.
How can I also crack unsolved encryption?
Encrypted texts that are still unsolved are presented on this blog in large numbers. Since a few days there is also a book by me (written with Elonka Dunin), which presents the most important methods for solving: Codebreaking: A Practical Guide. Unfortunately it is only available in English.
Solution methods for the two methods used by the Zodiac Killer (homophonic cipher and transposition cipher) are also described in detail in this book. The four encrypted Zodiac Killer messages are also discussed. However, Z340 is still classified as unsolved …
Further reading: The Top 50 unsolved encrypted messages: 9. The Rubin cryptogram