Zodiac Discussion Forum - Recent Topics

Proposal for a Z13 Symmetric Autokey: The Role of the Symmetrically Placed N Symbol on Both Ends and the K-Axis

Marclean — Mon, 07 Sep 2026 21:10:28 +0000

Hey everyone! Analyzing the structural patterns of the Z13, I wanted to propose a new line of reasoning focused on graphic symmetry to solve the problem of orphan symbols (those not found in the traditional Z340 or Z408 tables).

Observing the layout of the cipher, we have a striking detail: the symbol N is positioned completely symmetrically on both ends of the code (on both the left and the right sides).

The K-Axis Dynamics and the Self-Generated Sequence

If we treat the K symbol as our central axis, the symmetric expansion of the reading behaves as follows:

Moving left from K, we pass through L and reach N.
Moving right from K, we pass through L, M, and N, ending at O.

This symmetric distribution maps out precisely the four unknowns that usually generate discrepancies in Z13 decoding attempts (resulting in the letters L, L, N, O highlighted in blue in the projection). Instead of trying to fit letters arbitrarily or forcefully, treating these remaining symbols as a sequence self-generated by a spiral or palindromic rotation key (N-M-L-K-L-M-N-O) brings an impressive mathematical cohesion to the arrangement.

This would solve the mystery of the Z13 "orphan" symbols by utilizing the internal symmetry of the Zodiac's own graphical chaining. What do you think of this approach? Has anyone else tested whether this symmetric logic fits with the alphabetical inversion pattern or generates other coherent readings across the rest of the line?

Before anyone gets too carried away trying to force anagrams like "ALLEN" or "LEANDRO" out of these letters: let's be real, forcing anagrams is a massive stretch. My name is Marcelo Leandro, and for the record, I am definitely not the Zodiac Killer. If mathematical ciphers start spelling out my grocery list or personal info next, I'll be sure to send my billing address to the police.

Validating the Z13 Solution: How a Palindromic Key Reinforces Dr. Ryan Garlick’s Hypothesis

Marclean — Sun, 06 Sep 2026 06:13:36 +0000

alidating the Z13 Solution: How a Palindromic Key Reinforces Dr. Ryan Garlick’s Hypothesis

Hey everyone,

I wanted to share a structural analysis I’ve been working on that provides mechanical backing for Dr. Ryan Garlick’s proposed solution to the Z13 cipher ( on Dave Oranchak’s channel).

While Dr. Garlick derived the historical context from 1960s newspaper publications and assigned the letters P-R-T to fill the short cipher's missing slots, my goal here is to demonstrate the geometric shift mechanism that validates this exact substitution.

1. Historical Context: Taunting the 1960s Academic

Around the time the Z13 was mailed (prefaced by "My name is..."), a 1960s academic and cryptography expert publicly challenged the Zodiac in local newspapers to provide a cipher containing his actual name.

As analyzed by Dr. Garlick, the Zodiac’s response wasn't his real identity, but a dark taunt directed at that scholar:

The Railway "Torpedo": In 1960s railroad parlance, a "torpedo" was a small explosive cap strapped to train tracks that detonated with a loud bang when rolled over by a train wheel to warn the engineer.
The Response: By combining characters solved via the Z340 and assigning P-R-T to the unmapped symbols of the short Z13 code, the plaintext resolves into DREATATORPEDO ("Dr Eat a torpedo") — a sarcastic "eat an explosive" response to the scholar who dared him.

2. Structural Validation: The Palindromic Rotation Matrix

To show that the assignment of P-R-T holds mechanical backing and isn't arbitrary, I applied the mirrored shift vector ZYXWVUTSRQPONMNOPQRSTUVWXYZ across two parallel tracks anchored around the central pivot M:

Layer / Track	Sequence & Structure	Function in Code
1. Z13 Ciphertext (Symbols)	`A E N ⊕ ⊗ K ⊗ M ⊗ ⅋ N A` `M`	Ciphertext anchored at central pivot M
2. Revealed Plaintext	`D R E A T A T O R P E D O`	Decoded plaintext ("Eat a torpedo")
3. Upper Key Track	`Y X W V U T S R Q` `P` `O N` `M`	Regressive shift sweep towards center M
4. Lower Key Track	`Z Y X W V U` `T` `S` `R` `Q P O N`	Phase offset validating missing P-R-T values

Sliding the key leftward creates a symmetrical rotational shift that naturally maps the Z13's unknown symbols directly into P, R, and T.

Marcelo

My z32 candidate

Northkey — Tue, 01 Sep 2026 14:58:56 +0000

I want to present this as a working hypothesis, not as a proven unique decryption of Z32.

My candidate is:

AT SIX SIX INCHES FROM MOUNT DIABLO PIT

Without spaces:

ATSIXSIXINCHESFROMMOUNTDIABLOPIT

It is exactly 32 letters.

Z32 contains only three repeated-symbol identities:

1 = 26

2 = 32

6 = 14

The candidate gives:

1/26 = A/A

2/32 = T/T

6/14 = S/S

All three fit.

What is interesting, however, is what happens if we do not insert PIT beforehand.

I tested a deliberately restricted map grammar based on what Zodiac actually gave us: Mount Diablo as the origin, the dial positions 0 / 3 / 6 / 9, distances written ONE through TWELVE, and the form:

AT INCHES FROM MOUNT DIABLO

The destination word was left unknown.

Within this defined model, SIX / SIX is the only direction/distance combination that can fill a 32-letter text while satisfying the Z32 constraints 1=26 and 6=14.

The result before the destination is determined is:

AT SIX SIX INCHES FROM MOUNT DIABLO ???

The known part occupies 29 positions. The Z32 constraint 2=32 then requires the final letter to be the same as position 2, namely T:

AT SIX SIX INCHES FROM MOUNT DIABLO ??T

This is an important distinction. We did not start with a gravel pit and then construct a 32-letter phrase that hit it. Within this map grammar, SIX / SIX / MOUNT DIABLO / ??T comes first. P and I in PIT are not cryptographically forced; if correct, they must come from the geography.

This is also not a claim of global uniqueness. Z32 is too short and contains too little repetition to force a single plaintext without external information.

The map operation

Zodiac wrote on the Mount Diablo map:

“0 is to be set to Mag. N.”

In the Little List letter about a month later, he wrote:

“P.S. The Mt. Diablo Code concerns Radians & # inches along the radians.”

This gives a natural angle-plus-distance operation.

Set 0 to magnetic north.

The first SIX is read as position 6 on the oriented dial. Six lies directly opposite zero:

6 o’clock = 180° from 0 = π radians

This does not mean six radians. 6 radians ≈343.8°, which is a completely different direction.

The second SIX belongs to:

SIX INCHES

and specifies the linear map distance along the ray defined by position 6.

The Phillips 66 inset used by Zodiac has the printed scale:

“ONE INCH EQUALS APPROX. 6.4 MILES”

The nominal 1970 operation is therefore:

6 inches × 6.4 miles/inch = 38.4 miles

I am therefore not using the Phillips 66 branding as the source of the words SIX/SIX. It is not necessary for the mechanism. The operative elements are the Z32 construction, the 0–3–6–9 dial, and the map’s printed scale.

Source check:

Search: "9-QQ-1219-S" Zodiac

Search: "Original Untouched '69 Phillips 66 Map"

The large original scan shows both the map code 9-QQ-1219-S and the printed 6.4-mile scale.

As a modern cross-check — not as the 1970 method — we can compare Mount Diablo with the published locality reference for Near/Neary Quarry.

The reference points give approximately:

Distance: 38.380 miles

Printed-scale equivalent: 5.997 inches

Initial true bearing: 197.236°

If dial position 6 is magnetic south, that bearing would correspond to a declination of approximately 17.236° E.

That value must not be confused with the historical value. A historical calculation for Mount Diablo on June 26, 1970 gives approximately 16°53′ E = 16.9° E. The difference is only a few tenths of a degree.

The quarry coordinate is also a locality reference with a stated accuracy of about 100 metres, not a survey-grade target point. I therefore do not use 38.380 versus 38.400 as a “32-metre precision” argument. The point is only that the nominal SIX-INCHES distance and direction are highly consistent with the historical quarry area.

Source check for the coordinate/bearing/declination control:

Mount Diablo summit reference (USGS topo source via TopoQuest): 37.881702 N, -121.914268 W

https://topoquest.com/place/california/summit/mount-diablo/222343

Near Quarry (Neary Rock Quarry), Mindat locality 92281: 37.35000 N, -122.12083 W; stated MRDS location accuracy 100 m

https://www.mindat.org/loc-92281.html

NOAA/NCEI Historic Magnetic Declination Calculator

https://www.ngdc.noaa.gov/geomag/calculators/ushistoricForm.shtml

On the 32-Character Zodiac Cipher — Table 2 gives Mount Diablo, June 26, 1970 as 16°53′ E

https://iacr.steepath.eu/2023/982-Onthe32CharacterZodiacCipher.pdf

What is at the endpoint?

When this operation is followed from Mount Diablo, we arrive in the Los Altos Hills area.

A contemporary topographic map then gives us an independent geographic check.

The USGS Cupertino, California 7.5-minute quadrangle, original 1961, version/photorevision 1968 and print 1969, existed before Z32 was mailed in June 1970.

On the map, the area is explicitly labeled:

Gravel Pit

The USGS catalog itself confirms:

Product 307728

Scale 1:24,000

Version date 1968

Print date 1969

1961 historical map

Source check:

Search: USGS Cupertino 307728

This is why I propose completing the already constrained destination slot as:

??T → PIT

The USGS map does not decrypt the letters P and I. No part of the Z32 repetition pattern does that. The argument is instead:

Z32 + the map grammar gives a three-letter destination ending in T.

The map operation leads to an area that a map available before Z32 literally labels Gravel Pit.

PIT is therefore a geographic and semantic completion of ??T.

Section 6 – found after the endpoint

The next finding came after the quarry/pit endpoint had already been identified.

In California Journal of Mines and Geology, Volume 50, No. 2, April 1954, there is:

Table 6. Rock (crushed) operations in Santa Clara County

Row 44 reads:

Sondgrath Bros. (Neary)

T. 7 S.

R. 2 W.*

Sec. 6

West of Los Altos

The footnote to the asterisk says:

“Mt. Diablo Base & Meridian projected.”

We have now checked this directly against the original scan of Volume 50 at Internet Archive, not only against a modern web transcription. The Internet Archive copy was scanned from the University of California, Davis Libraries and is identified as volume 50 of California journal of mines and geology. The separate QuarriesAndBeyond reproduction, used with permission from the California Geological Survey, transcribes the same Sondgrath/Neary entry as Sec. 6, T.7S., R.2W., M.D.B.M. (projected), west of Los Altos.

Source check:

Search: "Sondgrath Bros. (Neary)" "Sec. 6"

Search: californiajourna50cali

This is methodologically important:

Section 6 was not used to find the quarry.

We already had the SIX-o’clock direction, the SIX-INCHES distance, and the gravel-pit endpoint before the Section 6 entry was found.

Only then did this possible secondary pattern appear:

6 o’clock

6 inches

Section 6

or:

6 – 6 – 6

with DIABLO as the origin name.

I am not claiming that this proves a deliberate 666 construction. The components are not statistically independent enough for us to assign any meaningful probability, and the finding is post-hoc.

But because Section 6 was not used as an input to select the endpoint, it is an interesting secondary historical control finding, not a parameter that was adjusted to create the match.

What the hypothesis actually claims

This is not a claim that we have found a proven, unique symbol-for-symbol key to Z32.

What I find interesting is this sequence:

Z32 repeated-symbol constraints + restricted map grammar

→ AT SIX SIX INCHES FROM MOUNT DIABLO ??T

0 set to magnetic north

→ SIX = position 6 = 180° = π radians

SIX INCHES + Phillips map scale

→ 38.4 nominal map miles

Pre-Z32 USGS map at the endpoint

→ Gravel Pit

??T + geography

→ PIT

and only after this had been found:

1954 mining record

→ Sondgrath Bros. (Neary), Section 6, T7S R2W, Mt. Diablo Base & Meridian

The candidate is therefore:

AT SIX SIX INCHES FROM MOUNT DIABLO PIT

For me, the interesting point is not one single coincidence, but that the Z32 structure, Zodiac’s radians/inches hint, the dial geometry, the printed map distance, the contemporary Gravel Pit map, and the later-discovered Section 6 entry can be assembled into one coherent operation.

But the distinctions must be preserved:

P and I in PIT are derived geographically/semantically, not cipher-forced.

Section 6 / 666 is secondary post-hoc support.

The Phillips 66 branding is not necessary for SIX/SIX.

The modern coordinate check is a control, not the solution method Zodiac or a solver would have had to use in 1970.

That is why I present this as a Z32 solution candidate, not as a proven decryption.

Small note: I’m posting this from my phone while away on vacation, and the forum’s mobile attachment handling was a bit awkward. I’m not entirely sure all the images came through correctly, so if anything is missing or out of order, that’s the reason. The text and source order are unchanged

01_P66_Zodiac_MagN_Dial.jpg

Fallen Angel Letters - Tinsley Letters - Sikikey Letter - Gidget Letter Time Line

BREAKER — Sat, 18 Jul 2026 03:53:13 +0000

Not many people knew that the Zodiac Killer was a long running government sponsored operation. It was so successful that they had planned to continue their operations for years afterwards. Mostly as the CIA was involved in the development of the communications of their objectives, they had used the ciphers to instruct their Agents in the field. One team was from the American side, and the other the called the "East Team" would take root in NYC and Vermont, carrying out their operations throughout the 90's with the use of the CIA's Kryptos Art Installation at Langley's Headquarters.

Formed with a copper scroll attached to a piece of Petrified Wood, the left side was filled with ciphertext and the right side was filled with a Vigenere Tableau using the word Kryptos as the filler to create a shift, surrounded by a series of alphabets.

Noticing the right side was shifted to appear like a large letter Z, it would take on the illusion of a hidden series of ciphers that were said to be used to instruct 2 agents in the field, using a delayed drop of information that would be used to confirm their orders to continue the operations of the previous objectives with the Zodiac Ciphers.

Take a look at the layout of the puzzle, and you will see it was designed partly to appear exactly as if it was expanding on the look and feel of the Zodiac Halloween Card.

kryptos-cia-ribbon-Zodiac-Halloween-Comparison.jpg

Z408, the last 18: Testing the final-line 'pull-down' hypothesis (ChatGPT)

shaqmeister — Wed, 08 Jul 2026 18:04:04 +0000

Statistical Assessment of the Z408 Final-Line “Pull-Down” Hypothesis

1. Research question

The final 18 cipher symbols of the Zodiac Z408 cipher famously do not decode into meaningful plaintext under the established homophonic substitution solution. One proposed explanation is that at least some of these symbols were not enciphered text at all, but were generated by copying (“pulling down”) fragments of ciphertext from rows immediately above.

The question tested here was:

Does the final line of the Z408 exhibit a degree of vertical copying from previous rows that would be unlikely to occur by chance?

The purpose of the test was not to prove intent, but to determine whether the observed pattern is statistically unusual.

Zodiac Memes

BREAKER — Mon, 29 Jun 2026 04:19:00 +0000

Present your favorite Zodiac Memes for lulz

I'll begin

Bernies-Flava.jpg

Chewing the fat with ZGPT

shaqmeister — Tue, 23 Jun 2026 22:22:10 +0000

Are the current implementations of the GPT model strong enough yet to enable us to use them in evaluating in our own proposals regarding the case, and can we trust them enough to let us be guided by them in our research?

Let's take look at the following discussion with ZGPT, a custom GPT put together by user datadude316 and announced on the ZodiacKiller.com message board, here.

Prior to the following conversation I had been discussing some thoughts about potential solutions to the Z32, but then decided to return to the following contentious proposition:

“Turning back to the question as to how we are to interpret the instructions guiding us on what use to make of the Phillips 66 map and the code we were given in 1970, I find myself unable to accept that there exists any plausible alternative to merely accepting that “This map” together with the code will show you where the bomb is set. Once we later have the postscript clue that the encoded distance is in inches, how else are we to consider using “this map” other than to measure the inches on it?”

Let's see how this initial gambit played out.

The Zodiac's conceptualisation of his chosen symbol

shaqmeister — Wed, 17 Jun 2026 13:37:39 +0000

So, this:

variously interpreted by Zodiac researchers to represent a gunsight, to be a symbol merely copied (for no especial reason) from the branding of the Zodiac watch, as well as a number of other less readily accepted conceptualisations. But these start out from how we choose to conceptualise the symbol. What, then, of how The Zodiac himself perceived its 'meaning'?

I think we can get close to the author's conceptualisation through careful study of the two key instances where it is clear The Zodiac was using this symbol for a purpose other than as just his signature.

These occur, firstly, on the 'Death Machine' letter of 9 November 1969, as:

and, secondly, on the Phillips 66 map sent with the Z32 cipher on 26 June 1970:

death_machine_usage.png

phillips_66_usage.png

Revisiting a take on the Halloween 'symbol'

shaqmeister — Mon, 25 May 2026 11:19:01 +0000

This is not a wholly new idea, but I did want to revisit it and set it down in the relevant thread.

I'm intending to provide a run-through of some thoughts and observations I've had that might help us form a plausible interpretation of the otherwise mysterious 'symbol' that appears both inside, and on the envelope of, the Halloween card sent to Paul Avery in 1970. To start, then, here's the base symbol in question, as it appears inside the card:

The line that I am planning to take is one that essentially questions the symbol being mysterious at all. In fact, it should be noted from the outset that I shall not be thinking of it conventionally as, in fact, a symbol of any kind, but rather as a straight-up drawing or sketch of something, together with a number of annotations added for the purpose of conveying certain pieces of information—specifically, aspects pertaining to where we are to look for this 'something', and where to search on it, once we get there.

halloween_symbol.png

Modified Micheal Cole Z13 solution

letega — Thu, 21 May 2026 03:30:37 +0000

Modified Micheal Cole Z13 solution.

Well actually, i am going to ripoff, ermm, i mean riff off, Michael Cole's solution from 10years ago
Cole: https://zodiacrevisited.com/my-name-is-cipher-solution/

Micheal Cole presents his full solution as:
I AM . _ . X . _ M I X

~~~ The modification ~~~

As per Cole, the 1st underscore and the 'X' are the initials (forename, surname) of a name
So i think we can change the 2nd underscore to an 'a' resulting in:

I AM . . . aM I

then it links nicely to "I am mildly cerous" on the next line.

This solution responds to Dr. D.C.B.Marsh's challenge by giving Z's name initials yet also reveals nothing.

It keeps the glyph count 3 part symmetry of 4-5-4
Has its own symmetry of "I am", "am I"
Ties into "I am mildly cerous"
Reveals nothing about Z, just like the 408+340 (though this is a + point for Z, not for us )

Does not tie into "My name is ---" ( Though that long dash is peculiar )
No question mark after the proposed "am I"

~~ An expanded full solution ~~
split Z13 into 3 parts

AEN@ .K.M. *NAM
iam@ .K.M. amiM

Key = {A:i, E:a, N:m, K:K, M:M, *:a, },
@ = Zodiac glyph ,
* = Inverted Aries glyph

I am Zodiac am I Surname ?

--Zodiac , expanded form of Zodiac glyph
--? Should be in the cipher for grammar reasons, but is not
--K corresponds to letter initial probably a First name/ forename (culturally dependant)
--Surname corresponds to the 2nd initial, in this case 'M'

~~ Notes ~~
"My name is ---" could be the title of the cryptogram, specifically directing Prof D.C.B. Marsh to this cipher.

D.C.B. Marsh's name has 3 periods in it ... coincidence ?? I like to think its a reference to to D.C.B Marsh's name.

M.Coles says the 8-ball glyph is a taurus symbol and its unused elsewhere on all Z's ciphers
therefore it has a special significance - that is, it is a letter/word separator, like a space, period, etc.
None of Z's ciphers so far as is known use a letter/word separator except maybe this one.

Super speculative is the philosophical angle of "I am Zodiac ... am I Surname?"
Is Surname a character played by Zodiac ? Is Zodiac another personality of Surname ?
--In the "Death machine" letter dated November 9th 1969, Zodiac says;
"I look like the description passed out only when I do my thing, the rest of the time I look entirle different."
Is it only Zodiacs appearance that changes or does his persona change too?
Will the real Zodiac please stand up. 🙂

The envelope has a repeat of the word 'Editor' rotated 180 degrees.
https://zodiackillerciphers.com/wiki/index.php?title=Unsolved_13-character_%22My_name_is%22_cipher
--Could be a clue to this z13 or a clue to the z408 or nothing.
--Some of Z's other envelopes have peculiarities,
not sure if those peculiarities have been studied, they probably have.

To be clear i am not saying this is the solution, it's just another speculative attempt.

I kinda like the way it gives possible Name initials whilst at the same time gives nothing.
Credit to Micheal Cole, i just added a little tweak and made a messy post.