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What Does The Solved Z340 Tell Us About Zodiac?

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AK Wilks
Posts: 1407
Noble Member
Topic starter

We have all applauded the amazing work by Doranchak, Jarvle and Sam in achieving something the FBI could not do, which is solve the Zodiac 340. The only disappointment has been that so far the solved 340 has just shown more of the Z raving nonsense and not given us significant clues about his identity or name. But after more detailed examination does it tell us something about Zodiac, his traits & skills and maybe even point us towards a name?


I would argue that it does. The complicated Z340 which resisted a solution by the FBI or amateurs for 50 years was likely done by a very intelligent person with knowledge of mathematics and codes. As one poster here put it it is harder to accept a “Joe Six Pack” suspect like Allen or the parade of fathers and stepfathers. I know of nothing in the background of  any of the other suspects that makes me think they likely had the knowledge and intellectual ability to create such a code. I would argue that there is one major suspect who matches that profile, and fits other aspects of Z, such as the ability to design bombs, make bomb threats against mass transit, used .22 Super X ammo, had a gun with a flashlight attached, was a fan of opera, had a black hood, a hood with front chest piece bib, expressed a hatred and desire to kill couples,demanded his words appear on the front pages of newspapers or innocents would die, used over 30 words and phrases that Z used, etc. This suspect is TK, the only major suspect who is also a known murderer.


Also this excellent work by Jelberg shows the amazing similarities between the solved Z340 and the solved code of this suspect. Out of the hundreds and hundreds, even thousands, of potential code methods, both Zodiac and TK used Period 19, horizontal – vertical – diagonal sequences and Fibonacci number sequences.  See Jelberg’s work:


Jelberg: Just an observation. Notice any similarities? 340 Period 19 normal/mirror enlarge enlarge Matrix for Kaczynski’s “Code #1” Same pattern but with some type of cycling Fibonacci pattern. enlarge Nash Equilibrium applied to poker and other games generates the same type of pattern… enlarge *edit* more to the pattern… two on right = left (except @ the arrow?) enlarge The 80 (with the strangely bold 8) that doesn’t follow the sequence, directly splits the diagonal row into two length 15 halves. It is also 15 squares in from the lower left corner.

Doranchak does an excellent job showing the similarities between the solved Zodiac 340 and the solved Unabomber code here:




Posted : February 21, 2023 11:21 pm
Marclean reacted
Posts: 1
New Member

Hi @ak-wilks


I don’t have a good handle on Z’s skill at creating ciphers. He certainly created two valid ciphers, the second (340) being much more difficult than the first (408).

Z included contemporary information in the 340 cipher “THAT WASNT ME ON THE TV SHOW”, which makes me conclude that he thought the 340 was going to be relatively quickly – certainly not half a century later and using computing power unavailable at the time. What does this say about Z’s ability to estimate the difficulty of solving the 340?

Perhaps he was far better at creating ciphers than solving ciphers and did not possess the mathematical/cryptanalytical skills to do a back of the envelope-type estimation of the difficulty of solving the 340. If he had, perhaps he would have made the 340 significantly easier.


Regarding period 19. Z, for example, could not have made the first 9 lines of the 340 transposition period 18, as 18 is not coprime to 9*17 = 153, and so is not a proper decimation of 153. Nor could he have made it periods 3, 6, 9, 12, 15, 17, 18, 21, 24, 27, 30, 33, 34, 36, 39, 42, 45, 48, 51, 54, 57, 60, 63, 66, 68, 69, 72, 75, 78, 81, 84, 85, 87, 90, 93, 96, 99, 102, 105, 108, 111, 114, 117, 119, 120, 123, 126, 129, 132, 135, 136, 138, 141, 144, 147, 150 as none of these result in proper decimations of a length 153 string.

You can also generalise this analysis to 2D, where Z used a 1,2-decimation (1-down, 2-right), but he could not have used a 3,2-decimation (3-down, 2-right) as 3 is not coprime to 9. He had a lot more freedom with the horizontal component of the decimation, as 17 is prime. So perhaps he got lucky selecting a 9 by 17 grid and using period 19, or perhaps he played around with it until he found a period/decimation which resulted in a proper decimation (in either one or two dimensions), or perhaps (and I think this is far more unlikely) he had a good grasp of modular arithmetic and/or number theory and knew which periods/decimations he could use.




Sam Blake





Posted : March 27, 2023 12:09 pm
AK Wilks and IthinkIknow reacted
Russ Thompson
Posts: 268
Reputable Member

Tells us that Zodiac never encoded actual clues into cyphers. The codes were merely an anti-social attention game for him.

That was too much!

Posted : March 31, 2023 4:02 pm
IthinkIknow reacted
AK Wilks
Posts: 1407
Noble Member
Topic starter


That is a very interesting analysis.  But even with your analysis it shows Zodiac could have selected some different methods and number values to base his directional changes on.  Yet both the Zodiac and the Unabomber used a Period 19 encryption method with horizontal and diagonal routes. 

I would also make this point. The FBI Cryptanalysis and Racketeering Records Unit,  on a fairly regular basis over the years,  has broken complex codes of hostile foreign intelligence services,  drug cartels and terrorist groups. 

Yet the Zodiac 340 defeated all their attempts at a solution.  And they admitted that they probably would never have been able to break the complex code of the Unabomber had they not found the key in Ted Kaczynski’s cabin.  (See also the excellent video on the Unabomber codes on David’s YouTube channel).

Now it may be true that Z overestimated the ability of the FBI to break a complex code and underestimated how difficult the 340 actually was.  But IMO, based on the available evidence, I think we have to acknowledge Z, like Ted Kaczynski,  likely had considerable code making skill.


Congratulations again on the work you,  David and Jarvle did in solving the Z340 and your contribution to the case.




Posted : May 30, 2023 6:25 am
Posts: 1764
Noble Member

Seems hardly anyone hangs out here anymore, but I managed to reset my password and log on to the site.

I just wanted to say: congratulations, I’m absolutely thrilled for you guys. I remember saying (on this site) that I didn’t believe the thing would ever be solved. I was wrong! And you deserve so much credit and praise for your work, it really is an amazing achievement.

David, Sam and Jarl – fantastic!

I’m not sure who Sam is, actually, in terms of usernames on here (forgive me) – but I certainly interacted many times with both David and Jarl back when I was active (their usernames are a bit easier to, er, decipher).

Anyway, I learned about this very shortly after it was made public, but at that time I had been out of the Z loop for years, and…a lot of things were going on in my life. I would have liked – very much – to congratulate you all back then, in real time, but please accept my belated congrats (and immense respect for what you did) now.


Posted : February 19, 2024 4:19 pm
Posts: 2614
Member Admin

Hi @norse, welcome back!  Yes, this forum is my effort to preserve Morf’s old forum, because he decided to stop running his Zodiac site and forum.  I figured out how to import all the data over onto my site so we could at least preserve all the useful information contained here.

Thanks for the belated congrats.  It still seems surreal to me that Z340 has finally been solved.  It didn’t seem to say anything important but I sure as hell learned a lot about codebreaking in the many years we spent on it.



Posted : February 21, 2024 9:53 pm