Great presentation doranchak and funny at the end.

Thank you very much for this excellent presentation! The selected topics were great and well arranged. The audience was obviously very courious and asked a lot of questions. I bet that brings new people into the forum and new ideas.

The presentation was excellent. Very good delivery. It sounded like you rehearsed it at least several times, and I was impressed by your ability to answer the questions and make adjustments to the presentation on the fly. It was particularly interesting to hear the questions from the audience. They were first time impression stream of thought, and I just really liked to hear them instead of reading discussion in writing. You did a great job answering those questions. I liked the introduction a lot. I really liked the idea that the three parts of the 408 could have been encoded separately, explaining the breakdown of the cycles. I never thought of that before. It makes me wonder about the 340 and the two possible halves. It could have originally been intended to be two halves, and he just didn’t cut them apart. It makes me wonder about the isomorphic patterns and first half versus second half, which we haven’t looked at I don’t think. Thanks for representing us there. You were the perfect person to do so. Good job.

Thanks for the comments everyone. Many of those ACA members are scary smart, so I really hope they will spend some time on the cipher and generate some new insights.

Very nice job! Lots of murmurs in the crowd, that’s a great sign your talk is a hit.

Nicely done oranchak, you made a technical subject fascinating and entertaining.

Because of doranchak’s video I have again been thinking about the hypothesis that Zodiac did something with the bigrams repeats of the 340 in response to the 408.

– How do you hide this intention?
– Surely you do not want to alter all of the bigrams repeats.
– Do you consider period 2 to period 5 bigrams repeats?
– How do you end up with 24 unigram repeats of a symbol in such a scheme?

There are some ways to go about it:

1) Do you keep a list as you apply the homophonic substitution?
2) Do you make a second pass and alter bigrams repeats that visually stand out?

I say that option 1 is most sensible, you keep a list of bigrams repeats as you apply the homophonic substitution. This list will grow quite extensive though.

What do you do with a bigram when it repeats too many times:

1) Remove the bigram repeat or part thereof.
2) Pick another symbol for that letter.
3) Replace it with a fixed symbol.
4) …

My realization was that you would likely end up with a cipher that has less repeating bigrams towards the later parts of the cipher and that this happens to be a observation we have "The top half of the cipher text, considered on its own, contains 9 repeated bigrams. However, the bottom half of the cipher text, considered on its own, contains only 1 repeated bigram".

The bigrams that are repeating more often are more likely to appear later in the cipher, and with the keeping of a list as you apply the homophonic substitution, these are the bigram repeats that are more likely to be altered. That is why there could be much less bigram repeats in the second half of the 340.

Add in that the altering of bigrams could also explain the disturbed cycles and it seems to me that this hypothesis deserves another look.

Good job doranchak, you are really good at explaining things in a simple way that makes it easier to understand.

While the whole video was interesting one specific part stood out. At 22:27 when you start explaining the two-step process "period column two" followed by "period 18" I couldn’t help but think about the bus bomb/death machine letter.

On page 4, the letter mentions the items needed in the construction of the device. It explicitly details two 18" cardboard tubes. This is listed right under the word "mirror".

18 inches is a strange size for cardboard tubes considering most paper towels are around a foot or less and toilet paper is much smaller. And to include this specific detail in the letter seems odd to me.

If we look closely there are a few hints that seem to correlate with the detail on page 4.

On page 5:
we have the "bomb" diagram.
First, you can see that the two 18 inch tubes are arranged as columns and have an arrow coming out hitting a mirror and going back into the other tube.

Second, in the top right corner we see a tube with arrows originating of the bus in two different directions.

On page 3:
the part marked out as "must print in paper". Notice that this also has two arrows going in opposite directions just like the tubes. It is even pointing at two black dashes that could be representative of the two tubes with the shoe polish on the outside. The words "must print in paper" are written perpendicular to these two black dashes (tubes).

Could this be some kind of hint at some step of the cipher? Something like writing the original plain-text up and down in columns of 18?

If you also look at the way the bus is traveling, it is perpendicular to these columns.

On page 3 of letter we see "going from south to northwest"

and we also see "groups of barking/parking" which draws attention to the letter b/p and kind of looks like a 6.

The "bomb" diagram shows 5 Bombs with one bag each (= 5 lowercase b‘s?)
and the bus makes (6 lowercase b‘s total?)

Also notice on page one of the letter there is "up to the end" right above "at
her" and a "7 or >"
If we look at the northwest corner of the z340 the first four symbols are HER>

Could this be a hint at taking groups of some amount starting at the bottom of the cipher and traveling northwest? Or that the end of some process on the plain-text led up until ending at "HER>"?

Maybe there was some type of step where the cipher was originally drafted "up and down" columns of 18 and then read off in groups of five or six starting from the bottom right to the top left?
Both "up" and "down" are also conveniently mentioned at the beginning of the section that is marked as MPIP.

It is also interesting that there is a mention of "around the corner". Could this be a hint at the pivots??

The chapter on transposition from Codes and Ciphers – Secret writing through the ages – John Laffin (1964)
starts out with a few examples that are of a similar concept…

enlarge

I’m sure there’s much more that I’m not seeing, but it seems as though there’s way too much about this letter that coincides with attributes of the Z340.

With how insistent zodiac was on the publication of this letter and "all of the details" could the whole thing (including the bomb diagram) just be clues about how the cipher was constructed?

1) Do you keep a list as you apply the homophonic substitution?
2) Do you make a second pass and alter bigrams repeats that visually stand out?

Somehow I don’t believe in either of the two possibilities. It seems too much effort to me for someone who made so many mistakes in the first cipher and seems to work carelessly. There are so many easier ways to eliminate the main weakness of z408 (bigrams). Add occasional fillers to create fake bigrams, for example.
And even if I repeat myself here: If z340 uses a transposition, then there is no reason to hide bigrams. On the contrary, as bigrams would lead to a wrong track in this case anyway.
I still think that a much simpler option has been used that we just haven’t thought about yet. It has been shown that even the simplest manipulations can trick an autosolver and also randomly generate very interesting, but incorrect, statistics. For example 75% of the ciphertext is written in regular order, leaving gaps. Then the gaps are filled in a different order. There are about one Brazillion possibilities, which are extremely simple and yet very effective.

If one doesn’t get ahead with a problem, then one tends to complicate things. That could well have already happened. Perhaps it is indeed the case, as you have just suggested. I am not saying that I think that is implausible. However, in my current investigations I am increasingly moving towards simplification. Let us see where this leads. However, I will have much less time in the near future.

Jelberg:
I find your idea very creative and I like your descriptions. Making links between different letters can help quite a lot. Zodiac seems to like subtle notes. But also in this case I think that your guess is too complex. If you concentrate on such things only long enough, you see a connection in all possible details. For my part, I usually ask myself the question: "How likely is that?" Sure, I can be completely wrong about that. But the more effort you have to put into a thesis, the more I tend to reject it. I like to use the following principle (I already posted this a few weeks ago):

https://en.wikipedia.org/wiki/Occam%27s_razor

PS: Do you know this link? https://www.tapatalk.com/groups/zodiack … s3390.html It’s listed in the Encyclopedia of Observations.

Translated with http://www.DeepL.com/Translator

If one doesn’t get ahead with a problem, then one tends to complicate things.

So true. First try the simple things.

I completely agree & it is very likely that something simple could be the reason why the cipher hasn’t been solved in all these years.

What is fascinating -and I’ve just realized- is that one of the easiest ways to deceive would be to simply avoid the most simple solution/method for doing something.
I’m not saying that is what zodiac did, but I do wonder if that type of thinking was factored into his decision making.

Someone on Facebook responded to the presentation with this observation of symmetries:

I thought it was interesting. I wonder whether or not those kinds of symmetries of rotationally-equivalent symbols happen a lot by chance.

Hi there, I have been thinking a lot about the mirroring in the 340 as well and using your wonderful web toy to illustrate some of the these features. Though not precisely, there are mirroring aspects in multiple directions. He may have even tried to encourage the perception of a circle and cross hairs symbol.