Solution to the 340

Raw text of the solution, after reversing transposition

Presumed errors are in boldface:

I HOPE YOU ARE HAVING LOTS OF FAN IN TRYING TO

CATCH ME THAT WASN'T ME ON THE TV SHOW WHICH

BRINGO UP A POINT ABOUT ME I AM NOT AFRAID OF THE

GAS CHAMBER BECAASE IT WILL SEND ME TO PARADLCE

ALL THE SOOHER BECAUSE E NOW HAVE ENOUGH SLAVES

TO WORV FOR ME WHERE EVERYONE ELSE HAS NOTHING

WHEN THEY REACH PARADICE SO THEY ARE AFRAID OF

DEATH I AM NOT AFRAID BECAUSE I VNOW THAT MY NEW

LIFE IS LIFE WILL BE AN EASY ONE IN PARADICE DEATH

With errors corrected:

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 IS LIFE WILL BE AN EASY ONE IN PARADICE DEATH

Interpretations of the seemingly misplaced words "LIFE IS" and "DEATH"

Group "LIFE IS" with "DEATH"

Example 1:

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.

LIFE IS DEATH

Example 2:

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 IS LIFE

Example 3:

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 IS DEATH. LIFE WILL BE AN EASY ONE

IN PARADICE

Example 4:

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. LIFE IS DEATH. I AM NOT AFRAID

BECAUSE I KNOW THAT MY NEW LIFE WILL BE AN EASY

ONE IN PARADICE

Example 5:

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: DEATH IS LIFE

IN PARADICE.

Additional speculation: The original ciphertext starts with the letters "HER", so perhaps the intended message formed from these fragments is "HER LIFE IS DEATH".

Change "THAT" to "WHAT"

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 WHAT MY NEW

LIFE IS: LIFE WILL BE AN EASY ONE IN PARADICE DEATH

"MY DEATH IS NEW LIFE"

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

DEATH IS NEW LIFE. LIFE WILL BE AN EASY ONE

IN PARADICE

"WHERE DEATH IS LIFE" (suggested by Brandon Baskin)

I HOPE YOU ARE HAVING LOTS OF FUN IN TRYING TO

CATCH ME THAT WASNT 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 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 WHERE DEATH IS LIFE

"DEATH WILL BE AN EASY ONE" (suggested by @muzutus on YouTube)

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 IS LIFE IN PARADICE

DEATH WILL BE AN EASY ONE

Verifications of the solution

• FBI confirmations:
  • FBI statement on their twitter account
  • Article with excerpt from more detailed FBI statement
  • The full press release that was sent to me from the FBI press office:
    • 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.
• f.reichmann's argument based on unicity distance
  • • Full FBI press release was included in Michael Butterfield's article
• Nils Kopal's verification
• Unicity distance of the Zodiac-340 cipher by Joachim von zur Gathen

More info

• Solution video 1
• Solution video 2
• Image of the Z340 substitution key
• Compilation of news reports about the solution
• Sam's slides from his presentation, "The Quest to Solve the Zodiac 340 Cipher".
• Transposition matrices

Timeline of arriving at the solution

Times reported are in Eastern time in the USA

Saturday, January 3, 2015

• 05:56PM: Jarl's first post about availability of his new codebreaking software, AZdecrypt. (broken link)
  • Working link

Tuesday, July 28, 2015

• 01:02PM: Jarl posts his observations including period 19 bigram repeats (original version in Wayback) (Live version)

Wednesday, August 5, 2015

• 12:45AM: Daikon posts his observations including period 19 bigram repeats (original version in Wayback) Live version

Wednesday, January 16, 2019

• 09:12AM: Sam Blake's first contact with me, via comment on my 2018 ACA presentation video on Youtube.

Thursday, August 1, 2019

• 09:14PM: Sam Blake starts emailing me enumerations of Z340

Sunday, May 17th, 2020

• 07:03AM: Jarl posts a transposition of the 340 which is extremely close to the correct final result.
  • Transcription
  • Plaintext resulting from applying final Z340 key to his transposed ciphertext
  • Old broken link

Wednesday, December 2nd, 2020

• 04:14PM: Began running 655,088 ciphers, the cumulative collection of all cipher enumerations and decimations Sam Blake has sent me to date, through AZDecrypt v1.19 with default settings (except for loading jarlve's reddit 6-grams). Had run many of them before, but this time I wanted to be more careful about sorting the results based on the cipher lengths (some manipulations remove parts of the cipher, which sometimes leads to azdecrypt reporting higher scores compared to ones for ciphers of length 340).

Thursday, December 3rd, 2020

• 12:04PM: Reported an interesting result to Sam from one of his older vertical 3-split decimations
  • Transcription: z340_vertical_3split_decimations_9_9_1_19_2.txt
    • Plaintext resulting from applying the final Z340 key to his transposed ciphertext
  • AZdecrypt generated this candidate plaintext:
    • EHOPE YOU ARE HE SING IST TORRA ENN
    • TRYING TO CATCH METH AFTAINT MT ON THE
    • TS SHOT WHICH BRINGS UP ALS IN TABS IT
    • ME NAME OF AR HEED OR THE GAS CHAMBER
    • BECA ATE IT WILD VENT ME ROLER A DICE
    • AI I THE VS SHEN BECAUSE TOO WHA SEEN
    • TIGHT DESERTS WORS ROS ME THERE
    • EVERYONEED HE HAS NOTHING THEN THEY HE
    • ACH PARADICT IS THEY ALREARE AND NORDER
    • THER AMEO EARRE AND BECAUITE IS YOT TV
    • HAT MR NEWE ITLE NEVER IND BAEYN NEIA
    • AT A HOE CDR PET
  • A few interesting legible phrases stood out right away:
    • HOPE YOU ARE
    • TRYING TO CATCH ME
    • SHOT WHICH BRINGS UP
    • OR THE GAS CHAMBER
    • HE HAS NOTHING THEN THEY
  • Phrases were more noticeable due to the auto-whitespace feature Jarl added for v1.19.
• 03:25PM: Determined the transposition (decimation) steps that were performed for that cipher among Sam's batch.
• 07:50PM: Sam provides details on the 9,9,1,19,2 enumeration, which is actually split into 4 vertical groups of size 9, 9, 1, and 1. A decimation of 19,2 is applied to each group.
• 09:36PM: I reported to Sam my solution to the first 9 lines, obtained by isolating those 9 lines, feeding them into AZdecrypt, but locking in cribs for some of the interesting phrases discovered earlier.
  • The plaintext read: I HOPE YOU ARE HAVING LOTS OF FUN IN TRYING TO CATCH ME THAT WASNT ME ON THE TV SHOW WHICH BRING OR PA POINT ABOUT ME I UM NOT A FRA IF OF THE GAS CHAMBER BECUASE IT WILL SEND ME TO PAY UNLCE ALL THE
  • The first section contains every symbol used in the entire cipher, so applying the key to the entire cipher text gave this plaintext: I HOPE YOU ARE HAVING LOTS OF FUN IN TRYING TO CATCH ME THAT WASNT ME ON THE TV SHOW WHICH BRING OR PA POINT ABOUT ME I UM NOT AFRAID OF THE GAS CHAMBER BECUASE IT WILL SEND ME TO PAY UNLCE ALL THE SOO HEN BE CURSEE OOW HAVE ENSUGH SLAVER TO WOR V FOV ME WHERE ESERYONE EL HEH US NOTHING WHEN THEY REACH PAY UNICE SO TREY ALREU FAA I FI OF NET TH IF AM NO EA FREA IF BNC ARISE IV YO WT SHAT MR NEW EIW LENESE FLIL BAAYNNE I UADAHO I CFR PET
  • Appearance of phrase "THAT WASNT ME ON THE TV SHOW" locked this in as a solid lead towards a real solution. Second 9 lines yielded from the same key have a relatively high score (compared to random plaintext or gibberish) but is somewhat garbled. Also noticed the word DEATH appearing at the very end of the last line of the entire cipher, using same key as the one discovered for the first 9 lines. Asked Sam for help to figure out the remaining 11 lines.
• 10:04PM: Notified Jarl to also ask for his help.

Friday, December 4rd, 2020

• 08:04AM: Ran several other decimations from Sam to try to isolate other schemes that might lead to a solve for the remaining 11 lines.
• 09:29AM: Completed a search of over 400,000 AZdecrypt results and determined that the phrase GAS CHAMBER appears in no other result.
• 10:10AM: Ran some more decimations from Sam. Didn't notice anything substantial in the results.
• 11:19AM: First response from Jarl, "It looks genuine!"
• 02:17PM: I report reversed words in the last 2 lines to Sam and Jarl
• 02:23PM: Jarl independently reports reversed words in the last 2 lines.
• 02:31PM: I interpreted the garbled 2nd section to read like this:
  • BECAUSE ? SLAVES TO WORK FOR ME WHERE EVERYONE ELSE HAS NOTHING WHEN THEY REACH PARADICE SO THEY ARE AFRAID OF LETTING ?? BECAUSE I (VOW?)...
• 02:40PM: Refined 2nd section:
  • BECAUSE ??? HAVE ENOUGH SLAVES TO WORK FOR ME WHERE EVERYONE ELSE HAS NOTHING WHEN THEY REACH PARADICE SO THEY ARE AFRAID OF LETTING ?? BECAUSE I (VOW?)...
• 02:58PM: Jarl reports his refined solution:
  • I HOPE YOU ARE HAVING LOTS OF FUN IN TRYING
  • TO CATCH ME THAT WASNT 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
  • SOO HEN BECAUSE EOOW HAVE ENOUGH SLAVES TO
  • WORK FOR ME WHERE EVERYONE ELSE HAS NOTHING
  • WHEN THEY REACH PARADICE SO THEY ALRE UFA AID
  • I OF DET TH IF AM NO EA FREA ID BN CA AISE IV
  • YO WT SHAT MR NEW
  • EFIL WILL EB NA EASY E
  • NONI ECIDARAP DEATH
• 03:18PM: I report my finding about the errors on line 15 (the 6th line of the 2nd section). Several errors are happening on the same line, suggestive of a systematic mistake.
• 03:23PM: Jarl reports his interpretation of the plaintext:
  • SO THEY'RE ALL AFRAID OF DEATH I AM NOT AFRAID BECAUSE IT ...
• 04:19PM: I'm considering sending our partial solve to the FBI so they can help us work out the rest of it
• 05:47PM: Decided against reporting the solve early, to give our team more time to work it out. Developed a visualization of the errors on line 15 (6th line of the 2nd section).

Saturday, December 5th, 2020

• 01:26AM: Jarl reports progress on the plaintext, resulting from a possible "skip" in the 2nd part. Jarl's latest plaintext:
  • I HOPE YOU ARE HAVING LOTS OF FUN IN TRYING
  • TO CATCH ME THAT WASNT 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)
  • (SOO HEN) BECAUSE I NOW HAVE ENOUGH SLAVES TO
  • WORK FOR ME WHERE EVERYONE ELSE HAS NOTHING
  • WHEN THEY REACH PARADICE SO (THEYRE ALL) AFRAID
  • OF DEATH I AM NOT AFRAID BECAUSE IT
  • (YO WT SHAT MR NEW)
  • EFIL WILL EB NA EASY ENO
  • NI ECIDARAP DEATH
• 02:16AM: Jarl reports more detail on the skip in the 15th row, and the skip seems isolated to that row. But still some garble happening after that is fixed.
• 02:41AM: Jarl reports discovery that skipping cleartext "LIFEIS" in upper right section of the 2nd block fixes the remaining garbles. Plaintext now only has a few errors remaining.
• 02:50AM: Jarl reports full plaintext:
  • I HOPE YOU ARE HAVING LOTS OF FUN IN TRYING
  • TO CATCH ME THAT WASNT 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)
  • (SOO HER) 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 IS
  • EFIL WILL EB NA EASY ENO
  • NI ECIDARAP DEATH
• 03:44AM: Jarl reports details on steps that were required to fix the 2nd section:
  • Right-offset the RATENYRNOSRVSH fragment by 1 becoming HRATENYRNOSRVS. I think he skipped the H by mistake (during homophonic step) and then realized his error going into the 7th row and added the H back in at the end of the 6th row.
  • Skip the positions of the "LIFEIS" fragment during untransposition.
  • Now after transposition it will result in:
  • (SOO HER) BECUASE E NOW HAVE ENOUGH SLAVES TO
  • WORV FOR ME WHERE EVERYONE ELSE HUS NOTHING
  • WHEN THEY REACH PARUDICE SO THEY ARE UFRAID OF
  • DEATH I AM NOT AFRAID BECAASE I VNOW THAT MY NEW
  • Fixing a few errors:
  • (SOO HER) 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
  • Since the "LIFEIS" fragment was skipped it can be added in somewhere else, and I think it has to be at the end:
  • (SOO HER) 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 IS)
• 07:56AM: I completed a PDF report of our solution and submitted it to my contacts at the FBI crypto lab.
• 08:02AM: First response from FBI crypto lab, unofficial confirmation
• 08:48AM: Second response, unofficial confirmation
• 08:49AM: Third response, further confirmation, phone call

Not sure about further timing on this day, but during the day the FBI took action on the solution, notifying others in the agency as well as working on a report of the solution to submit back to SFPD, the original requestor. Submission also planned to SF FBI.

Sunday, December 6th, 2020

CRRU submitted the solution to FBI San Francisco in the evening. Waiting for contact with FBI National Press Office to coordinate release of this news.

Monday, December 7th, 2020

Talked to FBI National Press Office in the afternoon to discuss release plan. Allowing for all victim notifications to take place prior to releasing the news.

Thursday, December 10th 2020

Talked to FBI National Press Office in the afternoon and was informed that final notifications will be completed by the end of the day and that the best time for the news release will be Friday.

Teased the pending release of the news.

Friday, December 11th 2020

• 06:00AM: Explainer video (Let's Crack Zodiac Episode 5) switched to Public. I posted the news on many social media outlets and forums, and emailed the LCZ mailing list.
  • Post on Tom Voigt's forum
  • Post on Mike Morford's forum
• 01:03PM: First news report by SF Chronicle, announced by long time Zodiac reporter Kevin Fagan
• 02:21PM: FBI San Francisco makes a public announcement of the solution on their twitter account.

Over the next several days, many news outlets reported on the solution. Click here for a compilation.