Transposed the first block (17×9) according to a mathematical scheme

This isn’t a valid explanation. What scheme?
You are quick to dismiss a completely reasonable explanation as to how this cipher was constructed.

The scheme I am pointing to is the scytale .

Here is the post on how it was done.
viewtopic.php?f=81&t=5088&start=10#p83079

This method is not only clear systematically, it actually explains the mistakes made in the published version of the 340.

Part 2 is the section with more mistakes. But the correct scytale encryption lines up with what he was meaning to do.

Paul_Averly-

It is not the point of this thread to give a precise, detailed explanation of Zodiac’s exact methodology. That would be for another topic.

I am simply pointing out that in order to decipher a complex, multi-step encoding, it is absolutely required to reverse that process, which necessarily leads to a complex, multi-stage decipherment.

For example, had the 340 been only a substitution cipher like the 408, only finding the key would have been necessary. We know now, of course, that it was not.

There have been some comments on the recent 340 solution being convoluted, etc. I want to share my thoughts about why I believe this is so.

Let’s say that in constructing the 340, Zodiac

1) Wrote out a message (with some misspellings)
2) Broke it up into 3 parts, or blocks
3) Transposed the first block (17×9) according to a mathematical scheme
4) Added a short phrase into, and transposed the second block (17×9) according to the same scheme, with an encoding error
5) Left the last block (17×2) un-transposed, but reversed some words
6) Put the whole thing back into one 17×20 block
7) Created a homophonic substitution cipher from that

A fairly complicated process, but that is basically what I believe that he did. What would someone have to do to decipher that result?

1) Figure out the substitution key
2) Determine that the message was created in 3 blocks, isolate them, and treat each one separately
3) Un-transpose each block, according to whatever scheme gave readable text
4) Put it all back together into one message and…
5) SUCCESS!

Again, somewhat complex. But absolutely necessary, every single step, to undo what Zodiac did in creating the message.

And I believe that to be the essential sum of it. Anything further, such as spelling corrections, or determining if Zodiac meant "LIFE IS DEATH" or "DEATH IS LIFE" or whatever, are simply minor quibbles that can be discussed and argued over ad infinitum. None of those issues really make any difference.

The major breakthrough, and the success here, is the recovery of 340 characters of readable, plain English text. Something no one else has been able to do for the last 51 years. These are my thoughts on the matter.

Congratulations, again, to Dave, Jarl, and Sam for this outstanding effort.

-glurk

PERFECTLY SUMMED UP IMO!

Thanks glurk!

Paul_Averly: IMO, I don’t think he used scytale. I will address this in my next video.

Thanks glurk!

Paul_Averly, IMO, I don’t think he used scytale. I will address this in my next video.

Although some don’t think he used scytale, it does actually decode the message correctly as a continuous sequence in each section of 9 rows. I only bring this up because of the October 22nd 1969 Examiner article mentioning Edgar Allan Poe.

The newspaper stated Dr D.C.B Marsh told the Examiner today: "The killer wouldn’t dare, as he claimed in letters to the newspapers, to reveal his name in the cipher to established cryptogram experts. He knows, to quote Edgar Allan Poe, that any cipher created by man can be solved by man".

Poe details the scytale cipher extensively at the beginning of the essay A Few Words on Secret Writing. The next encryption technique described in this same essay involves splitting the alphabet into two lots of 13 (one beginning with A and ending with M), just like his third cipher.

The third decryption technique described in the essay involves the two concentric circles.

https://classic-literature.co.uk/a-few- … t-writing/

Thanks glurk!

Paul_Averly, IMO, I don’t think he used scytale. I will address this in my next video.

Although some don’t think he used scytale, it does actually decode the message correctly as a continuous sequence in each section of 9 rows. I only bring this up because of the October 22nd 1969 Examiner article mentioning Edgar Allan Poe.

The newspaper stated Dr D.C.B Marsh told the Examiner today: "The killer wouldn’t dare, as he claimed in letters to the newspapers, to reveal his name in the cipher to established cryptogram experts. He knows, to quote Edgar Allan Poe, that any cipher created by man can be solved by man".

Poe details the scytale cipher extensively at the beginning of the essay A Few Words on Secret Writing. The next encryption technique described in this same essay involves splitting the alphabet into two lots of 13 (one beginning with A and ending with M), just like his third cipher.

The third decryption technique described in the essay involves the two concentric circles.

https://classic-literature.co.uk/a-few- … t-writing/

Hi all. Long time lurker, first time poster here.

I read that piece and EAP is citing Æneas Tacticus and his twenty methods for cyphering.

Aeneas disk is this one:

More info here http://cryptowiki.net/index.php?title=Aeneas

Going back to Z, the Z13 starts with "AEN"

The FK letter has similar black dots

I know, human’s brain has a tendency to create similiraties where they are none but I wanted to add my thoughts from the last days.

The holes on this card are as best as I can recall placed in the exact position on a blank postcard that my poi (boyfriend) asked me to punch for him as his hand hurt. So it is possible (if my poi is guilty) that I am the one who punched the holes!

The time frame is correct. I asked him what it was all about and he said it had to do with some project he was working on in connection with his job and he couldn’t tell me as it was "classified."

He just told me to punch the holes however I thought they’d look good and he’d work around them or figure out the rest later. So at that time I just thought it was a little odd but went ahead and did it for him.

I think there is another postcard (Peek Through The Pines) that is similar. I just remember punching holes on a blank postcard once but it could have been twice. And if there are two cards, the ones I punched could be on the other one. I knew he liked symmetry and was going to punch them on each side of the card but asked what he was going to do with it as I was trying to figure out how much blank space he’d need.

When he’d ask me to write phrases such as "There Will Be More" and I’d ask "more what?" it was similar in that he never was clear and just brushed off as a joke he was playing on someone, it was work related, nevermind..he’d tell me later as we were on our way somewhere or become mildly irritated, telling me I should have been a detective. (I was working as a social worker).

So with these writings, I’d do it for him as they seemed totally harmless but just odd and I’d alter/disguise my normal handwriting or printing as I didn’t want to be involved with anything that wasn’t legit and did not like his vague non-answers.

"

7) Created a homophonic substitution cipher from that

The fact that the substitution comes last opens up the possibility that a word-game is overlain on the z340. Pick the symbol substitutions so that you can insert additional messages in the cyphertext itself. The nearly plain Zodiac signature at the end of the cyphertext, combined with the nearby reverse paradice in the clear text suggest a word game.

Thanks glurk!

Paul_Averly: IMO, I don’t think he used scytale. I will address this in my next video.

i agree skytale does not quite work, unless i am doing someting wrong..
i nearly had it worked out but had a drunken christmas break up party get in the way