The San Francisco Chronicle ran a very clever newspaper article on October 22nd 1969 challenging the Zodiac Killer to issue another cryptogram that would surely contain his name. However, they did this hoping that the Zodiac Killer would create a cipher down the path they had guided him towards. By dropping the name Edgar Allan Poe into their challenge, they were relying on the Zodiac Killer choosing a cipher technique described in the essays of the American writer and poet, thereby increasing their chances of solving it.

​The murderer of five not only responded by employing the first cipher technique described in Poe's A Few Words on Secret Writing to create the 340 cipher, but also inserted one of Poe's poems into the message. Here is a portion of the newspaper article: "Dr 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. Zodiac has not told the truth in his cipher messages to the Examiner, the Chronicle and the Vallejo Times-Herald. Zodiac has not done this, because to tell the complete truth in relation to his name -in cipher code - would lead to his capture. I invite Zodiac to send The American Cryptogram Association a cipher code - however complicated - which will truly and honestly include his name".  

The first section of Poe's essay mentioned the encryption technique of using scytala to conceal a message. In cryptography, a scytale (also transliterated skytale), is a tool used to perform a transposition cipher, consisting of a cylinder with a strip of parchment wound around it, on which is written a message. This online scytale decoder can be used to unearth the message in the Zodiac Killer's 340 cipher, which used a period 19 shift. Quite the coincidence that the Zodiac Killer would employ a similar technique from the very first portion of the essay 'A Few Words on Secret Writing'. This alone is not evidence of a connection between the newspaper article, Edgar Allan Poe and the Zodiac Killer, but the following observations may change your mind.     

Five months later, the Zodiac Killer would then mail the "My name is" cipher on April 20th 1970, apparently responding to Dr. Marsh directly, with "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is...."  In the essay 'A Few Words on Secret Writing', the second cipher technique described by Poe involves splitting the alphabet into two parts of 13, A to M, and N to Z. The Zodiac Killer's code this time contained 13 characters, beginning with A and ending with M.

But what is really interesting, is that the essay then suggests the notion of a perpetually shifting alphabet by creating two concentric circular pieces of pasteboard, with one placed inside the other and fixed, while the other can rotate. On each, the alphabet would be written (or random characters). By shifting the outer circle a certain number of spaces, different letters can represent others in the message. Bearing in mind the Zodiac Killer created three circled 8's, I considered the idea of placing Zodiac's 13 characters in two concentric circles with the characters aligned. In other words, A on the outer circle aligned with the A on the inner circle ,E on the outer circle aligned with the E on the inner circle, N on the outer circle aligned with the N on the inner circle, etc. Then I just shifted the outer circle 8 spaces clockwise, so that the 8's aligned with three new characters. Those characters were ME and the Zodiac crosshairs (shown above in the red boxes). 

Ordinarily, this would appear a little crude and unconvincing, if it wasn't for the fact the Zodiac Killer mailed the Exorcist letter on January 29th 1974, switching from his usual crosshairs equalling his victim total, to "Me" corresponding with his victim total. He often allotted SFPD=0, while giving himself the latest victim total (10 in the April 20th 1970 letter). If "Me" corresponds to a victim total and his crosshairs correspond to a victim total, then "Me" corresponds to the crosshairs (and Zodiac). The shifting of the 13 character cipher by a factor of 8 to create the message "Me (crosshairs), would be similar to the period 19 shift employed in the 340 cipher.

The Zodiac Killer must have known that by creating a 13 character code, he was making it practically unsolvable using standard cryptographic methods. By using this method, employing a simple "shift of 8" technique, we at least get a crude message that he used later in the Exorcist letter: "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Me (crosshairs)"   

The Zodiac Killer likely mailed this communication knowing it would arrive at the San Francisco Chronicle offices on April 21st 1970, which tallies with the only date supplied in the essay 'A Few Words on Secret Writing'. The Chronicle stated on April 22nd 1970 that "in a letter received yesterday, Zodiac claims he has killed again". A letter dated April 21st was noted by Edgar Allan Poe after a challenge had been laid down in Graham's Magazine. The responder to the challenge stated "In the April number of your magazine, while reviewing the translation by Mr. Walsh of “Sketches of Conspicuous Living Characters of France,” you invite your readers to address you a note in cipher". This was reminiscent of the direct challenge given to Zodiac by Dr. Marsh, to encode his name in cipher form.  

The Zodiac Killer would almost certainly have been aware that Edgar Allan Poe was a poet, so it would be rather fitting had Zodiac incorporated one of Edgar Allan Poe's poems into one of his ciphers or codes. We had to wait 51 years to find the answer to this question. In December 2020, David Oranchak, Sam Blake and Jarl Van Eykce cracked the 340 cipher, which ended with the likely message of "I AM NOT AFRAID BECAUSE I KNOW THAT MY NEW LIFE IS DEATH. LIFE WILL BE AN EASY ONE IN PARADICE". The moving epitaph to his recently deceased wife, written by Edgar Allan Poe, was delivered in the form of poetry and entitled "To One in Paradise". 

​Are all these connections to Edgar Allan Poe a coincidence?  

The point was made in an earlier article that the immediate murder with a Zodiac connection after the "latent homosexual" suggestion was floated in the San Francisco Chronicle, where the Bay Area murderer's pseudonym was found at the crime scene, was the murder of gay man, Robert Salem, on April 15th 1970 in San Francisco. The Zodiac Killer's 13-Symbol cipher was argued as being contemporary in nature, with his April 20th 1970 letter being mailed the same day this murder was published in the newspapers. Homosexuality and acceptance has been a continuing struggle for gay activists to this day, but the 1960s and 1970s were arguably more difficult times, with newspaper coverage on this topic less than acceptable. Many religious people were unwilling to accept individual rights, claiming that homosexuality was the mark of the beast, and was an abomination in the eyes of God. The writing in blood on Robert Salem's apartment wall stating "Satan Saves" must have had some meaning to the killer - so was it in any way connected to the sexual preferences of Robert Salem? This writing was accompanied by an Egyptian ankh, adopted by Coptic Christians as early as AD 200. If the 13-Symbol cipher was based on the murder of Robert Salem, one could argue that the writing on the apartment wall, along with the murder of Robert Salem, may have featured in this extremely short code.  

The only other time the Zodiac Killer mailed a cipher in connection with a brutal knife murder, was when he mailed the 148 character cipher shortly after the arrest and interrogation of Karl Francis Werner for the murders of Kathie Snoozy, Debra Furlong and Kathy Bilek on August 3rd 1969 and April 11th 1971. In the 148 character cipher the Zodiac Killer encrypted "I will skin three little kids and make a suit from the skin", and wrote "I will send a patch of human skin if their is some left over" in the message of the accompanying letter. Bearing in mind the killer removed Robert Salem's left ear and took it from the crime scene, I considered the possibility that the word "skin" may feature in the 13-Symbol cipher, alongside the word "satan" (or an extension of it), taken from the apartment wall. In other words, the encrypted message was related to the murder scene of Robert Salem. The dash after "My name is" in the April 20th 1970 letter, being the withheld name, with the 13-Symbol cipher being the message. 

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ASSOCIATED ARTICLES:
ANCHORS AWEIGH
ROBERT SALEM-A ZODIAC MURDER?
A CONTEMPORARY CODE ON APRIL 20TH 1970
THE ZODIAC KILLER-DRIVEN BY DEVIANCY     

The 408 cipher mailed on July 31st 1969 could be considered an introductory cipher by the Zodiac Killer, laying out his plans to collect more slaves for his afterlife and warning police of more murder to come. The 340 cipher, solved by eminent cryptographers David Oranchak, Sam Blake and Jarl Van Eycke in December 2020 was contemporary in nature, and effectively called out Eric Weill who telephoned into the Jim Dunbar TV Show on October 22nd 1969, that initiated the response of Zodiac just over two weeks later, who stated "That wasn't me on the TV show". The 32-Symbol cipher was also contemporary in nature, threatening to detonate a bomb in San Francisco & Vicinity soon after the Zodiac Killer had referenced the Park Police Station bombing (on April 20th 1970) which killed San Francisco police officer Brian McDonnell. The Zodiac Killer also called out Karl Francis Werner shortly after his arrest and interrogation for the murders of Snoozy & Furlong on April 29th 1971, again encoding a contemporary message stating "stop listening to phonys". This message (plural in nature) was not only labelling Karl Francis Werner as an imposter, but included Eric Weill from the Jim Dunbar Show - and effectively bound the 340 and 148 character ciphers under the banner of one author.

This should make you think, when you consider the April 20th 1970 letter arriving after 121 days sf silence from the Zodiac Killer, mailed on the same day his Zodiac pseudonym was reported in the San Francisco Chronicle as being written in blood on the wall of murder victim Robert Michael Salem, stabbed to death in his 745 Stevenson Street apartment. Was this just sheer coincidence after four months, or was the letter a rushed response to the breaking news in the Chronicle newspaper on the same day (with an AM postmark)? If you play the odds, the chances that this was coincidence, may appear unlikely. If the April 20th 1970 letter was a response to the San Francisco Chronicle article, then the cipher and bus bomb diagram were literally created in a matter of hours. Of course, the 13-Symbol code could have been designed in advance and added to his letter - but if not - the message contained within the code could likely be a reaction to the latest news about Robert Salem, or at the very least, be extremely contemporary in nature if his other three ciphers are anything to go by.

In fact, if you believe the 148 character cipher and letter in 1971 as genuine Zodiac material (as I do), then there will never be any reasonable chance of the Zodiac Killer ever revealing his real name in any code or communication, because the Zodiac Killer comprehensively stated in the 1971 letter that "I will never give my name because you don't understand". The offering of an alternative name in the Z13 seems equally unlikely, because its lack of ciphertext characters lends itself to thousands of possibilities, rendering any alternative name a pointless exercise when it cannot be verified. There appears two ways forward: [1] either the Zodiac Killer fashioned a code based on the Robert Salem murder or its column inches, so contemporary in nature, that it would carry great significance when unearthed, or [2] It isn't necessarily contemporary in nature and the answer or key lies in subsequent communications. The Zodiac Killer would almost certainly have known a code of just 13 characters was practically unsolvable, so the notion of a solve so contemporary in nature as to cement its validity, appears a justifiable avenue to explore. 

LATEST UPDATE, INCLUDING POLICE REPORTS & PHOTOGRAPHS

On December 3rd 2020 David Oranchak, Sam Blake and Jarl Van Eycke unlocked the mystery to the 51-year-old 340 cipher, mailed by the Zodiac Killer on November 8th 1969. On December 7th 1969, the Zodiac Killer mailed a communication from Fairfield containing a 38 character code, yet to be broken. In recent years I have had little doubt that this letter was genuine Zodiac material, but the solving of the 340 cipher put to rest any lingering doubt regarding its authenticity.

​The author of the 38 character code prominently featured two sections of the 340 cipher, that included the beginning 4 ciphertext characters of the 340 cipher, and the last 5 ciphertext characters of the 340 cipher. The only logical reason for the Zodiac Killer to have done this, would have been to give us a clue to the solving of the 340 cipher. When the code key is applied to the 340 cipher before any period 19 (diagonal shift), the first 4 plaintext characters of the 340 cipher spell IRON. The last 5 plaintext characters spell DEATH. As previously pointed out, a hoaxer would have had to be extremely lucky to keep the beginning and ending of the 340 cipher intact, to the tune of 4 & 5 characters (when creating the Z38), that just happened to create two English words in these notable positions. One would have expected a lazy hoaxer to replicate ciphertext characters 333 to 338 in the 340 cipher, because these characters were close to the spelling of "Zodiac". But the author of the December 7th 1969 letter refrained from doing this, choosing to separate these 6 ciphertext characters, so as to form the word DEATH at the end of the 38 character code. 

After the solving of the 408 and 340 cryptograms in 1969 and 2020, there is a strong argument to be had, that the Zodiac Killer's remaining unbroken codes also contain a message, which includes the Z38 mailed just one month after the 340 cipher. I have attempted to tackle the Z38 code, but it needs an expert in code breaking to take a look at this encipherment, such as Dave Oranchak, who I believe could shed more light on this small code. The message beneath - at the very least - should provide a little more insight into the thinking of the Zodiac Killer during this crucial period. 

Did the Zodiac Killer create the 38 character code so soon after his November 8th 1969 offering as a prompt to the solution of the 340 cipher? I hope Dave Oranchak will take a look and possibly correct some of the incorrect assumptions I may have made. Thanks to Druzer, a regular contributor to both main Zodiac forums, for his assistance in this matter.
CLICK HERE FOR UNOBSTRUCTED VIEW OF CODE.

Professor D.C.B. Marsh told the San Francisco Examiner on October 22nd 1969: "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. Zodiac has not told the truth in his cipher messages to the Examiner, the Chronicle and the Vallejo Times-Herald. Zodiac has not done this, because to tell the complete truth in relation to his name - in cipher code - would lead to his capture. I invite Zodiac to send The American Cryptogram Association a cipher code - however complicated - which will truly and honestly include his name".

​The Zodiac Killer responded on November 8th 1969 by using the scytale method of decryption featured at the top of Poe's essay A Few Words On Secret Writing. Or should I say, it can be used to crack the 340 cipher encrypted message, that contained the wording "one in paradice" just like Edgar Allen Poe's poem to his dead wife entitled "To One In Paradise". The next method of encryption in Poe's A Few Words On Secret Writing involved splitting the alphabet A to M and N to Z (two sections of thirteen) mirroring the Zodiac's 13 character code which began with A and ended with M - and because of the distinct lack of characters in this code - it has been considered unsolvable using standard cryptographic methods.

​The Zodiac seemingly didn't supply us with a key to this code in later communications, leading me to believe that the key or answer lies in the Edgar Allen Poe essay mentioned above. I believe the answer to the code is ​"This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is....Fk, I'm crackproof, in which each element of the phrase is begun by each of the circled eights, thereby creating an infinite circular cipher (hence the circled 8's which represent infinity and a new beginning). The Zodiac Killer may have supplied us with the answer to the Z13 code in the 13-Hole postcard on October 5th 1970 in which he configured the punched holes in an arrangement of 10 to 3, pinpointing the position of the three eights, and supplying the answer of Fk, I'm crackproof. Using Edgar Allen Poe's reasoning in A Few Words On Secret Writing, I can now place five letters in the correct position within the 13 character code, albeit not to my complete satisfaction.  

Here is a section of reasoning from Edgar Allen Poe's A Few Words On Secret Writing where A can represent N and vice versa, where B can represent O and vice versa, and where C can represent P and vice versa. But he also makes a point of saying A might stand for P (or vice vera). This is where I shall jump into the code using a trial and error approach. 

If A can stand for P, I shall place P above the A in the beginning of the Z13 code like so:

If A can stand for P, and P can also represent C, then A can also stand for C. So let us insert the letter C above A in the Z13 code.

If A can represent N and vice versa, B can represent O and vice versa, and C can represent P and vice versa, then E can represented R. So let us place R in the Z13 code.

Edgar Allen Poe stated that N can represent A, so let us place A above the second N in the Z13 code:

If A can stand for P, and P can also represent C, then A can also stand for C. This means that if M can stand for X, and X can represent K, then M can also stand for K (just like A stood for C). So let us insert K into the Z13 code:

If the K and M between the three eights are representative of themselves as I have previously surmised, then we have the beginning of the answer to the Z13 code. But without this assumption, we have five letters inserted that mirror the previous solution I have suggested - all reasoned from Edgar Allen Poe's essay. It's not perfect, but it's a start.

On October 22nd 1969, the San Francisco Examiner newspaper published an article by Will Stevens, which laid down a challenge from Professor D.C.B. Marsh of the American Cryptogram Association (ACA) to the Zodiac Killer, attempting to coax him into revealing his name.

The newspaper stated "Dr 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 Allen Poe, that any cipher created by man can be solved by man. Zodiac has not told the truth in his cipher messages to the Examiner, the Chronicle and the Vallejo Times-Herald. Zodiac has not done this, because to tell the complete truth in relation to his name -in cipher code - would lead to his capture. I invite Zodiac to send The American Cryptogram Association a cipher code - however complicated - which will truly and honestly include his name".

Professor D.C.B. Marsh was probably hoping the Zodiac Killer would employ a cryptographic technique featured in the works of Edgar Allan Poe, thereby making any future cipher mailed by the Zodiac Killer easier to crack. As it turned out, the Zodiac Killer's 340 cipher mailed on November 8th 1969 could be solved using the scytale method of encryption detailed in Edgar Allan Poe's essay A Few Words on Secret Writing in the very first paragraph. This was covered extensively in the article The Inspiration Behind the Zodiac Killer's 340 Cipher. We have Professor D.C.B. Marsh of the American Cryptogram Association creating the trigger, by inserting Edgar Allan Poe into the mind of the Zodiac Killer. The Zodiac Killer then created the 340 cipher that could be deciphered using the scytale method featured in Poe's A Few Words on Secret Writing. What are the odds that one of Edgar Allan Poe's poems would partially appear in the solution to the 340 cipher?

I HOPE YOU ARE HAVING LOTS OF FUN IN TRYING TO CATCH ME - THAT WASN’T ME ON THE TV SHOW - WHICH BRINGS UP A POINT ABOUT ME - I AM NOT AFRAID OF THE GAS CHAMBER BECAUSE IT WILL SEND ME TO PARADICE ALL THE SOONER BECAUSE I NOW HAVE ENOUGH SLAVES TO WORK FOR ME WHERE EVERYONE ELSE HAS NOTHING WHEN THEY REACH PARADICE - SO THEY ARE AFRAID OF DEATH - I AM NOT AFRAID BECAUSE I KNOW THAT MY NEW LIFE IS LIFE WILL BE AN EASY ONE IN PARADICE DEATH.   

"To One in Paradise" was written by Edgar Allan Poe. This poem was first published as part of the short story titled "The Visionary" (later retitled as "The Assignation"). The poem was also published under the names "To lanthe in Heaven" and "To One Beloved". The title "To One in Paradise" was used in the February 25, 1843 Saturday Musuem. This poem was written after the death of Poe's wife. He writes that she was his life and he lived for her and now he looks forward to the future where they will be together again in death. link.

This is the image supplied to us by the Zodiac Killer on the Phillips 66 Mount Diablo map on June 26th 1970. By placing the numbers 0, 3, 6 and 9 around the crosshairs, akin to a clock face, and instructing us that 0 is to be set to Mag. N, the Zodiac Killer is telling us that we have to travel a certain amount of degrees around the clock face from point zero (set to magnetic north, which was 17 degrees in 1970).

The Zodiac Killer realized that the information he provided in the Button letter was insufficient to discover where he was planning to set the bomb. He also realized it was insufficient to solve the 32-Symbol cipher. That is why he placed two crosshairs in his next communication on July 26th 1970. One of the crosshairs contained the radians value, while the other crosshairs contained the inches value. Zodiac wrote:

"P.S. The Mt. Diablo code concerns Radians + # inches along the radians".

It was that simple, all we had to do was place the first crosshairs (shown on the right) over a compass rose. The center of the little black circle with SFPD next to it, landed exactly at 246 degrees, which is 4 radians and magnetic north. That is the answer to the radians value. The target was SFPD.

The second crosshairs had the phrase "P.S. The Mt. Diablo code concerns Radians + # inches along the radians" written over it. Why would the Zodiac Killer place an arrow pointing before the inches value, if he didn't intend for us to place a number here? The answer could only ever be 5 inches, because using the Phillips 66 map scale of 6.4 miles to the inch, only 5 inches falls over San Francisco (4 & 6 inches falls into the sea).
​
The target of SFPD was therefore 4 radians and five inches from Mount Diablo. The target (to a 97.5% accuracy) was the Southern Freeway by Ingleside Police Station, explained in greater detail here.

Druzer and I have recently been working on the Mount Diablo map code solution, using the measurements of four radians and five inches supplied by the Little List letter crosshairs. Druzer came up with a solution to the 32-Symbol cipher that satisfied the three repeating ciphertext characters in the code, giving us an estimate of where the Zodiac Killer was threatening to "set his bomb". The target was the Southern Freeway alongside Ingleside Police Station, stated in a previous article as 4.08 radians (4 radians} and 4.84 inches (5 inches) from Mount Diablo, indicating that the Zodiac Killer was rounding off his values and giving us an estimate.

It has been stated on this site and elsewhere, that the 32 character code is unsolvable using conventional cipher techniques without the killer supplying us with a key. There are 29 unique characters within the code, making any solution practically unprovable. The solutions offered by using the 408 and 340 keys have produced less than convincing results, particularly when we consider that this code contains an "anchor" and "omega" symbol, not used in the 408 and 340 ciphers. Attempting to correlate the letters used in the code to written text in both the Button letter (June 26th 1970) and Little List letter (July 26th 1970) also produces negative results. Therefore, it could be argued, that a code containing 29 unique characters must have an alternative meaning, in accompaniment to the code solution of "estimate:four radians and five inches".

The Zodiac Killer gave us an estimate of 4 radians, but the actual figure (shown above) was 4.084 radians. That is, 4.084 multiplied by one radian value (57.3 degrees) to equal 234 degrees. When we add in the magnetic north which Zodiac instructed us to do (17 degrees in 1970), we get 251 degrees and the location of Ingleside Police Station. Could the 32 character code contain the value of 234 degrees, which once set to magnetic north, now identified the exact location of Ingleside Police Station? If we resort to basic numerology where A=1, B=2, C=3 etc, and add up the values of the alphabetical characters in the Zodiac Killer's 32 character code, we arrive at a total of 234 (or 234 degrees). When set to magnetic north, it gives us the value of 251 degrees, which when subtended from the peak of Mount Diablo passes directly over Ingleside Police Station and the Southern Freeway. "The map (set to 17 degrees magnetic north) coupled with the code of 234 will tell you where the bomb is set".

On July 26th 1970, the Zodiac Killer mailed the Little List letter with the important clues to the Mount Diablo mystery, stating "PS. The Mt. Diablo Code concerns Radians & # inches along the radians". The answer would be about radians and inches. With the northern section of the map crosshairs positioned at zero and to be set to magnetic north, the Zodiac Killer gave us the value of 4 radians and magnetic north (246 degrees) by the placement of the bold, black circle within the first crosshairs on the Little List letter.

The target was the San Francisco Police Department at Ingleside (SFPD). The second set of crosshairs on the Little List letter contained the hashtag (number sign) in the phrase above, with an arrow placed underneath, beckoning us to insert a number before inches. Only 4 radians and magnetic north, coupled with 5 inches could ever fall over San Francisco, constrained by its land mass. No other values can meet the requirement of targetting SFPD. To an overall accuracy in excess of 98%, the location of the bomb was to be set on the embankment of the Southern Freeway just 274 feet from Ingleside Police Station. For the full story, read The Answer to the Mount Diablo Code.

My solution to the 32-Symbol code in the above article did not marry up the ciphertext to the plaintext adequately, however, Druzer, an invaluable contributor to both Zodiac Killer forums, supplied a solution that married up the three repeating ciphertext characters with corresponding plaintext characters. His solution took "PS. The Mt. Diablo Code concerns Radians & # inches along the radians". into "four radians and five inches" that satisfied the requirement of the Zodiac Killer's Mount Diablo code. This would ultimately provide us with 24 of the plaintext characters for the solution, leaving us 8 ciphertext characters to decode. Druzer came up with the answer, but how was this achieved?     

The problem that materialized, was where to place "four radians and five inches" within the 32-Symbol array. We needed an entry point. The clue had to exist within the ciphertext characters themselves. Two of the most notable ciphertext characters were the Anchor and Omega symbols (the latter of which had never been used before), so possibly it was this symbol that held the key of where to insert "four radians and five inches".

The Omega symbol can be written two ways (shown on the left), with a quick search on Wikipedia revealing information on the radian per second. The radian per second (symbol: rad⋅s−1 or rad/s) is the SI unit of angular velocity, commonly denoted by the Greek letter ω (omega). The radian per second is also the SI unit of angular frequency. The radian per second is defined as the change in the orientation of an object, in radians, every second. 

Using this as the entry point in our ciphertext characters, the word "radians" was placed at the beginning of the Omega sign in the code, hoping that the 24 plaintext characters of "four radians and five inches" would travel to the end of the code. Inserting "four" before "radians", It fell into the code seamlessly (as shown below).

Now we can add in the three plaintext characters represented by O, C and ∆ to the three repeating ciphertext characters in the first section of the code, like so.

Ingleside Police Station is actually 4.08 radians (4 radians} and 4.84 inches (5 inches) from Mount Diablo, so the Zodiac Killer was rounding off his values and giving us an estimate. As can be seen in the above diagram, the word "estimate" fits perfectly into the first eight characters of the code, giving us the final answer to the 32-Symbol code of "estimate: four radians and five inches". The Zodiac Killer was informing us that the answer to the Mount Diablo code of "four radians and five inches" was just an estimate to the location of the bomb at Ingleside Police Station (SFPD). The Merriam-Webster dictionary defines "estimate" as a rough or approximate calculation, which is exactly what it is.

Just over two weeks before the 340 cipher was mailed, Dr. D.C.B. Marsh of the American Cryptogram Association laid down a challenge to the Zodiac in the newspapers to reveal his name in a cipher, however complicated. The wording in the San Francisco Examiner on October 22nd 1969 invoked the name of Edgar Allan Poe, so possibly the designers of the article were hoping that the Zodiac Killer would invoke Edgar Allan Poe to give us his name, making any offering easier to crack. This appeared to influence the Zodiac Killer, because the first cipher mentioned in Poe's essay A Few Words on Secret Writing actually works in decoding the message in the 340 cipher. The second cipher technique in Poe's essay A Few Words on Secret Writing split the alphabet into two portions of 13 letters, so it was surprising that the Zodiac Killer's next code reduced dramatically to 13 characters just like Poe's design (beginning with A and ending with M). See here for essay.

Three years ago, it was suggested that the Zodiac Killer wouldn't again shy away from the challenge of giving us his name, having possibly given us it in an abbreviated format. That is why the cryptic reference of Fk, I'm crackproof caught my eye in the October 5th 1970 communication with 13 punch-holes in the fabric of the card. The punch-holes were separated into a 10 to 3 configuration, positioned in such a way that they mirrored the design of the 13-Symbol cipher. The only way to break the small code was to discover the entry point, and the three circled 8's seemed as good a place as any, especially when we consider Fk, I'm crackproof is split into three parts and fits around the existing K and M in the code. The crosshairs, anchor and Celtic Cross in the code are all religious symbols, with the number 8 representing rebirth, regeneration and a new beginning in Christianity. The figure 888 is also representative of Jesus Christ in Christian numerology. It was discovered that the first 8 began FK, the second 8 began IM and the third 8 began CRACKPROOF, which completed the circle of eternal life. The introduction to the April 20th 1970 letter was also completed, to "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Fk, I'm crackproof",

Anyway, this is to show that the Fk, I'm crackproof solution was found before the 340 cipher was cracked by Dave Oranchak, Sam Blake and Jarl Van Eycke on December 3rd 2020, along with its scytale links to Edgar Allan Poe's A Few Words on Secret Writing. This is extremely important when we consider the following. Edgar Allan Poe highlighted certain encipherment techniques in the essay regarding a split alphabet, which are outlined here: and, so placed, a might stand for n and n for a, o for b and b for o, &c. &c. This, again, having an air of regularity which might be fathomed, the key alphabet might be constructed absolutely at random. The next line was: Thus A might stand for P.

These examples can be summarized as;
[1] a might stand for n and n for a
[2] Therefore, r might stand for e and e for r
[3] Thus, a might stand for p (and vice-versa)
Using only these examples in the 13-Symbol cipher, I inserted the possibilities into the code, using the letters K and M as entry points, based on the aforementioned reasoning. The letters N, A and M (not boxed in blue) I have no explanation for. So the search goes on to discover whether the Zodiac applied something else to the encryption. Or whether a different technique was used entirely.

When you take into consideration that the Fk, I'm crackproof solution was suggested in 2017, before the scytale link of the 340 cipher to Edgar Allan Poe, coupled with the formation above using just Poe's examples shown in [1], [2] and [3], it shows a pattern receptive to the remaining letters in the solution. But the three remaining ciphertext characters would need explaining. 

The next encipherment technique described in A Few Words on Secret Writing were the two concentric circles (one fixed), where the outer wheel can be rotated around the inner wheel during the coding process. Here is a working cipher wheel.

On October 22nd 1969, Dr. D.C.B Marsh in alliance with investigators and the San Francisco Examiner, attempted to refocus the Zodiac Killer's attention toward creating a second major cryptogram and "reveal his name in the cipher to established cryptogram experts". Marsh would continue to press the killer throughout the article, stating "I invite Zodiac to send to The American Cryptogram Association a cipher code - however complicated - which will truly and honestly include his name". However, in order to crack any cipher the killer may send, it would have been wise to place certain triggers within the article to guide the Zodiac Killer into choosing a particular cryptographic technique. This may have been the purpose of dropping the name Edgar Allan Poe into the San Francisco Examiner article, thereby influencing the killer to choose a cryptographic technique highlighted by Poe in one of his essays. If the Zodiac Killer then responds with a second cipher, your first port of call would obviously be Edgar Allan Poe.

Although Dave Oranchak doesn't believe the Zodiac Killer used the scytale method of encryption in the recently decoded 340 cipher, this decryption tool does actually decode the message in the 340 cipher. If the Zodiac Killer responded to the prompt by Dr. Marsh and read Edgar Allan Poe's essay A Few Words on Secret Writing, he would have noticed that the first topic of discussion was the scytale cipher, which involves disguising a message by separation, avoiding the common left-to-right method of decryption. This is what the Zodiac Killer used in his 340 cipher. In further reading of A Few Words on Secret Writing, it became apparent that other encryption methods were discussed in addition to the scytale method, with the possibility existing that the Zodiac Killer may have adopted one of these techniques for his following 13-Symbol cipher on April 20th 1970. The most notable encryption methods discussed included separating the alphabet A to M, and N to Z, into two equal parts of 13 letters. This involved placing the alphabet into the following configuration.

Here is an excerpt from Edgar Allan Poe's A Few Words on Secret Writing: and, so placed, a might stand for n and n for a, o for b and b for o, &c. &c. This, again, having an air of regularity which might be fathomed, the key alphabet might be constructed absolutely at random. The next line was: Thus A might stand for P.

If we then represent the second ciphertext character N (11th position} with the plaintext character A shown in Poe's writing, we get the diagram shown below, with the circular Fk, I'm crackproof starting to emerge.

The relationship  between the remaining ciphertext characters of N, A and M, to the plaintext characters in the solution of O, C and K respectively, can be seen in the diagram below. These are never more than two apart in the alphabet. This is a work in progress.

In respect to the Mount Diablo code, the Zodiac Killer gave us two clues to where his bomb was to be set, in the form of two crosshairs on July 26th 1970. The first crosshairs contained a bold, black circle positioned at 4 radians and magnetic north around its circumference. Next to this circle, the Zodiac Killer placed SFPD=0, indicating the target was a San Francisco Police Department. The second crosshairs were overwritten with the wording "P.S. The Mt. Diablo code concerns Radians + # inches along the radians". The hashtag (recognized as a number sign) was positioned above a pointing arrow, beckoning us to insert a number value before inches. The answer is five inches, because this is the only value that falls over San Francisco from Mount Diablo using the map scale of 6.4 miles to the inch. The bomb was to be set alongside Ingleside Police Station, on an embankment bordering the Southern Freeway. For further explanation in simplified form, please visit here, or for more extensive coverage read the article The Answer to the Mount Diablo Code.

Footnote: Ordinarily radians would be measured counter-clockwise, but the Zodiac Killer gave us crosshairs superimposed over Mount Diablo with an arrow pointer set in the north facing position, "to be set to Mag. N". He allocated it a zero position, with a 3, 6 and 9 in the form of a clock face around its circumference. This was to instruct us to travel clockwise around the circumference of the crosshairs in this instance. Which is why it was no fluke that the bold, black circle fell exactly at 4 radians and magnetic north.

The Blast Estimate of Zodiac (Part Two)

The discovery of the message in the 340 cipher has triggered a new debate on the intelligence of the Zodiac Killer, bearing in mind the greater complexity of the encryption used to disguise its contents. Creating an extremely difficult cipher is actually far easier than attempting to decode it, especially when the person who designs the cipher accidentally bakes errors into his cipher as shown by the Zodiac Killer.

However, Cragle on the Zodiac Killer Site forum made an astute observation regarding the Zodiac Killer's switch from describing his hidden messages as ciphers, to codes in the June 26th 1970 and July 26th 1970 letters. While not completely true, because the Zodiac Killer stated "By the way, are the police having a good time with the code?" on August 4th 1969, it does open up the broader point of the difference between codes and ciphers, which is effectively what Cragle was implying. Codes generally operate on semantics, while ciphers operate on syntax. A cipher is a system to make a word or message secret by changing or rearranging the letters in the message, whereas a code is a system of changing entire words or phrases into something else. Codes are not just secret messages, they can be any symbol or signal used to represent, or communicate, something else.

One could argue, that if the Zodiac Killer invested the time to construct a period nineteen cipher, then he was certainly aware that by creating the Z13 and Z32  codes of such brevity and variability, he was effectively creating an impossible task and any realistic possibility of a solution without ultimately providing a key to each code. The fact that the Mount Diablo code had 29 unique characters in a 32 character array, makes it practically unsolvable without that key, A key explaining these 29 unique characters in his remaining communications appears not to be the case. The Zodiac Killer stated that "the map coupled with the code will tell you where the bomb is set", so if we take this literally, then the Zodiac Killer by June 26th 1970 expected us to solve the 32 character code with nothing more than the Phillips 66 map he supplied alongside the letter. He did supply additional clues on July 26th 1970 in the form of "P.S. The Mt. Diablo code concerns Radians + # inches along the radians", but as of June 26th 1970 he fully expected us to decipher these 29 unique characters with nothing more than a map, lending credence to the notion that this encryption was designed as a code rather than a cipher. Finding corresponding alphabetical letters to 29 unique characters appears an unlikely proposition with the limited information he provided. A man with the patience to design the 340 cipher encryption must have known this.

Sam Blake, who contributed to the solving of the 340 cipher, made an extremely valid point when stating that the decoded message was contemporary. By the Zodiac Killer claiming that "it wasn't me on the TV show", he fully expected his 340 cipher to be decoded fairly quickly. This message was for the moment, not for 51 years later. The same is probably true for the Z13 and Z32. These codes were apparently designed with the promise of a hidden name and bomb at a time when newspapers were king. When the Zodiac Killer started fading from the newspaper headlines by 1971, the ongoing quest to decipher these two codes had equally faded into obscurity. This isn't the case today, with the internet endlessly keeping the mystery and speculation alive. But as the 1970s rolled forward these codes would have faded from the publics gaze, making these puzzles much more contemporary at the time they were designed. The Zodiac Killer could enjoy the speculation surrounding his unsolved puzzles and codes while they were still being discussed in the newspapers, but once the San Francisco Chronicle and San Francisco Examiner have moved away from featuring the Zodiac Killer, the feedback surrounding his unsolved codes would equally fade away. He probably expected these two codes to remain unbroken for a limited time only.

Therefore, as Cragle intimated, we might be better rewarded by looking at the Z13 and Z32 codes through the lens of codes rather than ciphers. The search for words or phrases, in accompaniment to the limited clues he supplied, quite possibly a much more profitable avenue to go down. The solving of the 340 cipher has inevitably switched the focus of attention toward the remaining unbroken codes, with every effort being made to follow up on the success of Dave Oranchak, Sam Blake and Jarl Van Eycke. However, adopting an approach using cipher-type encryption may possibly lead to another 51 years of blind alleyways and false beliefs, scattered with the graveyards of "solved solutions" that never were.

After two Zodiac attacks in close succession on September 27th 1969 and October 11th 1969, investigators must have feared an escalation in terror from the Bay Area murderer, so it would have certainly been in their interests to switch the Zodiac Killer's attention to communication instead of murder. On October 22nd 1969, Dr. D.C.B Marsh in alliance with investigators and the San Francisco Examiner, attempted to refocus the Zodiac Killer's attention toward creating a second major cryptogram and "reveal his name in the cipher to established cryptogram experts". Marsh would continue to press the killer throughout the article, stating "I invite Zodiac to send to The American Cryptogram Association a cipher code - however complicated - which will truly and honestly include his name". However, in order to crack any cipher the killer may send, it would have been wise to place certain triggers within the article to guide the Zodiac Killer into choosing a particular cryptographic technique. This may have been the purpose of dropping the name Edgar Allan Poe into the San Francisco Examiner article, thereby influencing the killer to choose a cryptographic technique highlighted by Poe in one of his essays. If the Zodiac Killer then responds with a second cipher, your first port of call would obviously be Edgar Allan Poe.

Although Dave Oranchak doesn't believe the Zodiac Killer used the scytale method of encryption in the recently decoded 340 cipher, this decryption tool does actually decode the message in the 340 cipher. If the Zodiac Killer responded to the prompt by Dr. Marsh and read Edgar Allan Poe's essay A Few Words on Secret Writing, he would have noticed that the first topic of discussion was the scytale cipher, which involves disguising a message by separation, avoiding the common left-to-right method of decryption. This is what the Zodiac Killer used in his 340 cipher. In further reading of A Few Words on Secret Writing, it became apparent that other encryption methods were discussed in addition to the scytale method, with the possibility existing that the Zodiac Killer may have adopted one of these techniques for his following 13-Symbol cipher on April 20th 1970. The most notable encryption methods discussed included separating the alphabet A to M, and N to Z, into two equal parts of 13 letters. Followed by a technique involving two concentric discs, akin to the Union Cipher Disk that held the number configurations of 000 and 888. These techniques show promise when we consider the design and structure of the 13-Symbol cipher. This has been covered in a much more extensive article, so it will not be covered any further here.  

Dr. Marsh, under the banner of Cipher Expert Dares Zodiac to Tell Name, would persist throughout the article into cajoling the Zodiac Killer to reveal his name by way of a cryptogram. This is why another passage in A Few Words on Secret Writing caught my attention - and may have resonated with the Zodiac Killer too. It concerned a reader sending in cryptograms to Edgar Allan Poe, but refraining from giving his name. The passage read "This challenge has elicited but a single response, which is embraced in the following letter. The only quarrel we have with the epistle, is that its writer has declined giving us his name in full. We beg that he will take an early opportunity of doing this, and thus relieve us of the chance of that suspicion which was attached to the cryptography of the weekly journal above-mentioned–the suspicion of inditing ciphers to ourselves. The postmark of the letter is Stonington, Conn".

This reminded me of the statement by Dr. Marsh when he challenged Zodiac, who he contended "had not told the truth in his cipher messages to the Examiner, the Chronicle and the Vallejo Times-Herald". He claimed "Zodiac has not done this, because to tell the complete truth in relation to his name would lead to his capture". Did the Zodiac Killer read this passage in A Few Words on Secret Writing and get some ideas?

The reader who mailed Edgar Allan Poe from Stonington, Connecticut, failed to supply his name, but did begin by placing a letter S, followed by a horizontal dash, similar to the Zodiac Killer's introduction on April 20th 1970, The Zodiac Killer began the introduction to his 13-Symbol cipher by stating MY NAME IS ---------. The sender of the cryptograms to Poe only signed his name at the bottom of the intoductory letter by use of initials, concluding with "I am yours, respectfully S.D.L." Not wanting to shy away from the challenge of Dr. Marsh a second time, I couldn't help thinking that the Zodiac Killer may have rose to the challenge and given us the initials to his name (or fictitious initials), just like the sender of the cryptograms from Stonington, Connecticut. Another thing to note, is that Dr. Marsh laid down this challenge on October 22nd 1969, so 182 days had elapsed before the Zodiac Killer's third confirmed cryptogram arrived at the San Francisco Chronicle on April 21st 1970.

Paul Avery wrote on April 22nd 1970, in an article entitled Zodiac Sends New Letter-Claims Ten, that "the killer who calls himself Zodiac has once again written to the Chronicle. In a letter received yesterday, Zodiac claims he has killed again". This letter was received by the San Francisco Chronicle on April 21st 1970, the exact day and month the letter from Stonington, Connecticut was postmarked from the anonymous sender to Edgar Allan Poe. This all may have been coincidence, but it would certainly be worth looking for the Zodiac Killer's initials as part of the answer to the 13-Symbol cipher.

That answer could be "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Fk, I'm crackproof", given to us in the Zodiac Killer's postcard five-and-a-half months later as a big hint to its decipherment. The 340 character cipher was split into rows of 9, 9 and 2 sections. The 13-Symbol cipher may have been split into 2. 2 and 9 sections, with the circled 8's beginning each section of the phrase. The letters K and M were already in place for a perfectly circular message, as highlighted in the October 5th 1970 communication by the Zodiac Killer, in which he supplied us with the phrase Fk I'm crackproof.   

On April 20th 1970, the Zodiac Killer mailed a 13-Symbol cipher to the San Francisco Chronicle, in addition to a bus bomb diagram threatening to blow up a school bus. Let's compare the 13-Symbol cipher to the 13-Hole postcard on October 5th 1970, in which the Zodiac Killer may have completed the introduction of "My name is" to "My name is Fk, I'm crackproof", again teasing us with a less than complete resolution to his real identity.