A Proposed Solution to Zodiac's
32-Symbol Cipher

by A.K. Wilks

I give here the way to solve the code — I leave out the months of frustration, blind alleys, false leads and wrong starts. Also, at the same time I was trying to go forward to solve the code, I also took all the names of the major suspects and tried to work backwards. Along the way, I started to intensely study the life, writings, acts and thoughts of the one and only suspect that proved to have a name in the code tied to a mathematical sequence — an 18 digit number that read the same forward as backward. Since almost everything with this suspect related to numbers, symbols, patterns and shapes, the insight I developed into his thought process helped me solve the code.

In 1969, some 40 years ago, Don and Bettye Harden solved the first Zodiac code. Since that time, the three other codes Zodiac sent to the SF Chronicle have remained unsolved. If one takes the Harden solution and general code solving principles and applies them to the unsolved codes, you get a string of letters with no apparent meaning. It seems clear that there is at least one more "step" needed to solve the codes. But what is it? And did Zodiac give us a clue as to what it might be?

If the next step involves a number, I thought it would be a number with meaning to the killer. The first probable Zodiac killing was of Cheri Jo Bates, in Riverside, California, on Devil's Night, 10/30/1966. One other killing had similar numbers — the murder of Cecilia Shepherd and wounding of Bryan Hartnell on 9/27/1969 at Lake Berryessa. In fact, Zodiac wrote a message on the victims' car door, the last part of which read "Sept 27 1969 6:30."

Why write the time? Looking at the common numbers, with the Bates murder date we have 30 (1)966 and with the door message we have (1)969 630. So we have possible numbers of 30 9 66 and 9 69 6 3 0. So we have common numbers of 0-3-6-9. And in Norse mythology, something we know Zodiac (and my main suspect) had knowledge of, the numbers 3, 6, 9 and 27 (which is 3 x 9 and also 2 + 7 = 9) have special meaning.

Using a clue on the cipher sent by Zodiac, the Phillips 66 Map Code, there is the Zodiac symbol and the numbers 0, 3, 6 and 9.

Once again, we have the numbers 0-3-6-9. In the context of the map, one would expect to see N, E, S and W, or perhaps 0, 90, 180, 270. Could the numbers 0-3-6-9 be a clue, a clue on how to break all the Zodiac codes?

There is a famous code system that used shifts of 3 letters. It is called a Caesar Code, as it was first used by the Roman Emperor Julius Caesar. For example, the message ATTACK would be encoded as DWWDFN. The person getting the message DWWDFN would then go backwards (or forwards) in the alphabet three spaces for each letter. Caesar used a shift value of three, but any shift value can be used. From Wiki:

In cryptography, a Caesar cipher, also known as a Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a shift of 3, A would be replaced by D, B would become E, and so on. The method is named after Julius Caesar, who used it to communicate with his generals.

For a quick 10 minute lesson on the Caesar Code, go to Wikipedia.

A variation of a Caesar Code was also used by the Confederate Army — at Wiki there is a picture of a Confederate decoding wheel, showing "C" lined up with "F", for example, as "F" is three letters after "C".

Since a classic Caesar Code is fairly easy to break, more complex versions were formed, some keyed to a book passage (Vigenere Cipher) or a sequence of numbers (Gronsfeld Cipher).

If we take the clue as a number sequence, what does that gives us? We would take the 32 first stage solution of translated letters, and then create a chart showing the letters that are 3, 6 and 9 spaces in front of and behind each letter. (See Chart below).

For the first stage solution, I used mostly the Don & Bettye Harden translation of Zodiac symbols. In fact, I think I only differed in a few symbols. The 13th symbol in the Map Code, an upside down horse shoe, does not appear in the code Harden translated.   I translated it, primarily by backward engineering and word solving, as an "X".  I note that in math an unknown is often represented by an "X".   The 12th symbol here, a shaded in triangle, was solved by the Hardens as a switch between "S" and "A". Let us use math again, as my main suspect had a PHD in and taught mathematics. "A" is the 1st letter in the alphabet, and "S" is the 19th. 19 – 9 = 10, and 1 + 9 = 10. The 10th letter in the alphabet is "J", so I solve it as a "J". And the 1st and 26th symbols here are "C", which does not appear in Harden, and I solve it as a "C". Other than that, I think I used the Harden translation, so of the 32 symbols, one I solve (sort of) differently then the Harden's did (J), and three did not appear so I make new solutions (X, C, C). The other 28 symbols are translated according to the Harden Key.  The first phase of the Map Code I translate as follows:

Then I apply a Caesar shift code — modified Gronsfeld Cipher. Using the "crosshair" Zodiac symbol on the Phillips 66 map with the given clue of 0-3-6-9 for possible shift values, I write out the translated letters, with the 3rd, 6th and 9th letters going forward and backward above and beneath each letter. This gives us the translated letter and 3-6-9 shift values above and below it. Numbers are used for their absolute value, i.e., distance from zero, thus –6 is treated the same as +6. So for the first letter, "C", I go forward three letters and write "F" above it, then "I" above that, then "L". In the same way, I write "Z" below it, etc.

Of course this can produce a large number of names. I looked for more clues on the map. I notice the huge number of "6"'s all over the map — each Phillips 66 gas station is noted by a "66" symbol. Including the "66" logo that appears on the map, I count twelve "66" symbols. Each symbol equals 6+6=12, so 12 x 12 = 144, or, 24 x 6 = 144. So we have twenty four "6" 's on the map. The other given numbers on the map are the Zodiac symbol's 0-3-6-9, which equals 18. 144 + 18 = 162. Later, I will show a hidden cryptic "9" on the map. 162 + 9 = 171. So, perhaps the total value of all the shift values used also equals 171? And perhaps twenty four shift values of "6" are used?

I also notice the "9" on the Zodiac symbol. It appears right behind a "66" symbol and right in front of another "66". Looking at the map it reads " 66 9 66". There are parts of the map that are less cluttered. Why did Zodiac put his symbol here, which causes the large "9" to be right between two "66" symbols? It seems to be intentional. What if it is a clue? But do I go left or right? If I start at the "66" then go left to the "9", and keep going in a clockwise direction, I get a "66", another "66", then the "0" at the top of the symbol, and then the "6" at the bottom of the symbol. A nine digit sequence, "66 9 6666 0 6". See close up photo of the map above.

The Zodiac synbol is centered on Mt. Diablo. "Diablo" is Spanish for Devil. This suspect is fixated on numbers and symbols. The number for the Devil is "6 6 6", from the Bible passage that no man shall be able to buy or sell without the mark of the Beast, 666. So once again we have multiple "6" 's. Could the huge number of "66" 's that appear on the map (12 in all, for 24 "6" 's) indicate that the code generally will rely very heavily on the "6" shift value lines and perhaps use 24 "6" 's? That seems to be a strategy to try. But I do start with the idea of a possible "66 9 6666 06" for a clue to use for shift values, and to use 24 "6" 's for shift values.

Through trial and error, applying my analysis, discovered clues, ideas about Zodiac and general code principles, I start with and repeat three times the complex shift values of "669 666 606", at the start of the letter sequence begining "CIF", keep in mind the clues pointing to heavy use of a "6" for shift values, trying 24 "6" shift values, matching the map, and start to get results of a letter sequence. This is the number sequence of Caesar shift values to apply to the letter sequence starting with CIF, divided for clarity into groupings of three then spaced into four quadrants of nine, nine, nine and the left over five:

The clue sequence — 66 9 6666 0 6 — appears, EXACTLY, three times in order. It appears from the 1st to the 9th, from the 10th to the 18th and again from the 19th to the 27th. Also, from 7th to 9th, 16th to 18th, 25th to 27th and 30th to 32nd appears the same sequence of "606". Only the 15th, 16th, 18th, 28th and 30th numbers are a negative, i.e., "–6 –6 –6 –6 –6", and the 21st is a "–9". The –9 creates an "E" which is used in the suspect name I will reveal shortly. All the other negatives, the five "–6" 's, create an "A", "I", "I" "N" and "C", none of which are used in the suspect name, and all of which are used, grouped together, in two other words. All else are "9" 's, "0" 's and "+6" 's. In fact, it is mostly "6" 's — there are twenty four "6" 's — the EXACT same number as on the map - five "0" 's and three "9" 's. No "3" 's are used, though 64 letters are available on the "3" lines.

This equals, with the hidden "9" on the map I will show later, 171, the exact same number as all the combined numbers on the map. This gives us the following letters, grouped into threes for clarity with two left over, with their Caesar shift value numbers underneath them:

Now the third and final phase of the code solution is a word anagram. There are of course many words and names that can be formed out of the above. But the correct message would have a clear mathematical precision to it. Zodiac repeatedly said he would give us his NAME in the codes. And what if the "bomb" set to go off is "inside" the Zodiac himself, as he hinted in his 12/20/69 letter, talking about "this thing IN ME"?

I think about the clues and some of the commonly named Zodiac suspects, such as Arthur Leigh Allen, Richard J Gaikowski, Lawrence Kane, Bruce Davis, Rick Marshall and Theodore J Kaczynski. I can't get Arthur Leigh Allen because there is no "U", and no "L" 's. I can't get Gaikowski because there are no "W" 's or "G" 's.

Now I look at the name of the suspect who was most promising from other evidence and my "backward engineering" of this code. What if the "669 666 606" sequence is also an extraction method to produce the name? That sequence is given on the map, produced the letters when applied and now perhaps can also produce a name or message when used as an extraction sequence. Can I get a "T" with a value of "6"? I can and do. Can I get an "H" with the value of "6"? I do. Now, for this extraction method to be valid I need an "E" with the value of "9". It is there. Going through the "669 666 06" sequence as an extraction method, first forwards, then exactly backwards, gives me the 18 character name of a major Zodiac suspect. The solution I come up with is as follows:

Theodore J Kaczynski had a PHD from the University of Michigan, and was teaching at University of California Berkeley during 1967 through summer of 1969, a position for which he interviewed in the Fall/Winter of 1966. He was in California during the key period of Zodiac activity. He was in fact Doctor Theodore J. Kaczynski. From fall of 69 to fall of 1971 he was said to be domiciled at his parents home in Lombard, Illinois, but spent much of his time — by his own account — traveling "out west looking for land." He has no known alibi for Zodiac murder and letter mailing dates. Writer Doug Oswell referenced a source who wrote to Kaczynski's attorney asking for alibi dates and was told none could be provided. In all the known documentation on Kaczynski, no dates conflict with Zodiac dates.

As "FC", aka "The Unabomber", we know he was domiciled mostly in Montana with a few periods in Illinois, yet he traveled as far as Utah and Berkeley, California to place bombs, and to the SF Bay area to mail bombs and letters. Kaczynski as "FC" sent taunting letters to the police and victims, just like "Z", and used an elaborate cipher to code incriminating parts of his diaries. And "I F C Z" is an actual sequence on the Caesar Code shift values. Both were killers, both had an interest in bombs, both threatened to bomb mass transit (Z a school bus, FC an airliner; FC also put a bomb on an airliner out of Chicago). Both had a hatred for society and a mania to have their words published on the front pages of newspapers, on penalty of death for innocent people if not done. And we know that TJK knew about the Caesar Code — not only was he a code expert, he had a half dozen books about Caesar and Rome found in his cabin.

While Kaczynski posed as someone with a political grievance against technology (which is partially true), he admits in his coded diaries that he mostly acts out of a desire for "revenge" against society at large, and that doing, reading about and writing about the killings and maimings give him some kind of "release". And he placed a bomb on an airliner leaving Chicago, that could have killed hundreds of innocent civilians, just as "Z" had threatened to bumb a bus of children.

There are many, many other points of convergence, including handwriting and word usage matches.

See the work of Doug Oswell on similar writing style and word usage, and other points of interest, including handwriting.

KEY POINT: Looking just at the name, here are the shift values that produce it:

Look VERY CLOSELY at the extraction method formula that gives us the name. It is a perfect and precise sequence. It reads the same frontwards as it does backwards. And it EXACTLY matches the "66 9 6666 0 6" clue — with "Theodore J" going forward, and with "Kaczynski" going backwards. The EXACT same nine digit sequence. And the names share no letters in common. This simply cannot be a coincidence. It is not random. It is exact and intended. The odds of this happening by chance must be astronomical.

I also form words out of the remaining letters. They make sense and give a coherent message, but I am not as sure that they are the correct intended message. Remember that Zodiac spoke of the need to kill as "this thing IN ME".  With the other words we can get a message of:

Or, in horizontal order:

I hope this can be analyzed and confirmed. Using some variations and other clues and formulas, I have also applied the same basic cipher solution method (0-3-6-9) to the other unsolved Zodiac codes and get very interesting results, including in the 340, directions to a physical location in SF where items are buried. And this name — Theodore Kaczynski or Theo Kaczynski — appears in all the other decoded Zodiac ciphers.

As a side note, after I finished most of my code work, I wondered if Zodiac gave other clues on the Map on how to solve the code. Next to the Zodiac symbol and the 0-3-6-9, are the words are "is to be set to Mag. N.". In the context of the code solution I arrived at, that makes no sense, and the "Mag. N." is strange, as there is room to write "Magnetic North" if that is what he meant. It can be made into an anagram:

"TO GET NAME IS + 0 3 6 9" by getting the 0-3-6-9 from the symbol and the "T" in the first "TO" looks like a "+". Or, if you turn the map upside down you get "+ 0 9" from the "TO BE". This the hidden "9" I mentioned earlier. When we take the sume of all the numbers on the map and add this "9", we end up with 171, with equals the total sum of all the shift values used.

Text, analysis, code solution, cipher solution Copyright 2009 by AK Wilks.