In the previous article I covered William Frederick Friedman and the "CSP 888" cipher machine, a highly secure, electromechanical rotor-based cipher machine used for top-level communications during World War II. Friedman was instrumental in leading the Army's cryptologic services during the 1920s and 1930s, which set the stage for the development of secure machines like the CSP 888. There is much reason to connect Edgar Allan Poe to the design of the Zodiac Killer's Z340 and Z13 through his cryptographic works, such as Poe's July 1841 essay "A Few Words on Secret Writing", which William Friedman mentioned in his 1937 bulletin entitled “Edgar Allen Poe, Cryptographer”.

​In Poe's essay, the alphabet was split A through M and N through Z, which was seemingly adopted by the Zodiac Killer on April 20th 1970, beginning and ending his ciphertext characters with the letters A and M, in an array of characters totalling thirteen (half an alphabet). To then find the three circled 8's present in the cipher and possibly mimicking the cipher machine "CSP 888", was extremely interesting (whether deliberate or accidental). Especially when you consider that William Friedman and Edgar Allan Poe are bound together by the words in “Edgar Allen Poe, Cryptographer” (1937), written by Friedman, whose career in the field of cryptology was originally inspired by Edgar Allan Poe. Was the Zodiac Killer influenced by the cryptographic work of William Friedman, who drew upon his knowledge of this individual when he was challenged by Donald C. B. Marsh of the American Cryptogram Association inviting the Zodiac Killer to mail a cipher which truly included his name?  A challenge published in the San Francisco Examiner on October 22nd 1969, just 17 days before the Zodiac Killer mailed his infamous 340 cipher on November 8th 1969, which may also have been influenced by the works of William Friedman.

The 340 cipher was finally cracked in December 2020 by David Oranchak, Sam Blake and Jarl Van Eycke, who discovered that the cipher was a combination of substitution and transposition (using frequency analysis). The Riverbank Publications is a series of pamphlets written by the people who worked for millionaire George Fabyan in the multi-discipline research facility he built in the early 20th century near Chicago. They were published by Fabyan, often without author credit. The publications on cryptanalysis, mostly written by William Friedman, with contributions from Elizebeth Smith Friedman and others, are considered seminal in the field. In particular, Publication 22 introduced the Index of Coincidence, a powerful statistical tool for cryptanalysis. 

​William Friedman's work on transposition ciphers at Riverbank Laboratories (circa 1916–1920) established foundational, mathematical techniques for solving complex reordering ciphers. Notably, Riverbank Publication No. 19, Formulae for the Solution of Geometrical Transposition Ciphers, provided analytical methods to solve transposition, which he compared to reassembling jigsaw puzzle pieces. It's quite ironical that the title of Friedman's work was called Riverbank Publication No. 19, Formulae for the Solution of Geometrical Transposition Ciphers, when a period 19 shift was required to break the Zodiac Killer's 340 transposition cipher. This was a fraction of the work issued by William Friedman. But was he the inspiration for the Zodiac Killer, who employed this type of cipher on November 8th 1969? 

​Unfortunately, there is one final intriguing aspect to this story - and sadly it's very final. Just six days before the 340 cipher was mailed on November 8th 1969, William Frederick Friedman died of a heart attack at the age of 78. He passed away on November 2nd 1969, about a week before the Zodiac Killer's transposition cipher arrived at the San Francisco Chronicle. He was buried with full military honors at Arlington Cemetery on November 5th 1969. 

THE 888 CIPHER MACHINE USED IN WORLD WAR II

The Zodiac Killer was riding high in October 1970, currently sitting on four unbroken ciphers he had mailed on November 8th 1969, December 7th 1969, April 20th 1970 and June 26th 1970. On October 6th 1970 the Zodiac Killer would mail the 13-Hole "Punch Card" with thirteen holes punched through the fabric of the card, while simultaneously declaring himself "crackproof". His use of the words "crack" or "cracked" were usually chosen when referring to his ciphers, so one could conclude that the thirteen punch holes in the card, having been mailed 5 1/2 months after his 13-Symbol cipher on April 20th 1970, which contained the words "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is....", could be related.

​Creating thirteen punch holes in the card (previously used in coding machines), in combination with the word "crackproof", may suggest a link between the two communications mailed on April 20th 1970 and October 6th 1970. Especially when you consider no cipher was included in the card mailed in October. It has previously been shown that the 13 punch holes were positioned in a 10:3 configuration, with the 3 punch holes placed directly below where they sat in the 13-Symbol cipher on April 20th 1970 (see below). If these two communications were linked together, we need to examine the Zodiac Killer's decision to use punch holes, his choice of the word "crackproof", and his selection of the three circled 8's in his 13-Symbol cipher, to see if we can connect all three to one encipherment technique or coding machine.  

The Zodiac Killer was "about 40" years of age in 1969 according to the three sets of eyewitnesses at Presidio Heights, so he would have been around 16 (or possibly slightly older) at the time World War II ended. If he had an interest in cryptography, he would almost certainly have known about Alan Turing, a British mathematician who led the crucial World War II effort at Bletchley Park, England to crack the German Enigma machine, an electromechanical rotor device used for secure military communications. This cipher machine is arguably the most famous cipher machine in the world, but it was far from unbreakable. 

It was clear to US cryptographers well before World War II that the single-stepping mechanical motion of rotor machines (e.g. the Hebern machine) could be exploited by attackers. In the case of the famous Enigma machine, these attacks were supposed to be upset by moving the rotors to random locations at the start of each new message. This, however, proved not to be secure enough, and German Enigma messages were frequently broken by cryptanalysis during World War II. William Friedman, director of the US Army's Signals Intelligence Service, devised a system to correct for this attack by truly randomizing the motion of the rotors. His modification consisted of a paper tape reader from a teletype machine attached to a small device with metal "feelers" positioned to pass electricity through the holes. When a letter was pressed on the keyboard the signal would be sent through the rotors as it was in the Enigma, producing an encrypted version. In addition, the current would also flow through the paper tape attachment, and any holes in the tape at its current location would cause the corresponding rotor to turn, and then advance the paper tape one position. In other words, the punch holes were a key ingredient to the encipherment process. link.

SIGABA (also known as the ECM Mark II) was primarily developed by a team of American cryptographers in the mid-1930s, with key contributions from William Friedman. The device was an electromechanical rotor-based cipher machine developed in the late 1930s in the United States as a joint effort of the US Army and US Navy  At the time it was considered a superior cipher machine, intended to keep high-level communications absolutely secure. It was used throughout WWII and was so reliable that it was used well into the 1950s, after which it was replaced by newer machines like AFSAM-7 (KL-7). As far as we know, SIGABA was never broken by Axis powers. In other words it was the primary encryption technique used in World War II by America - and to the best of our knowledge - remained "crackproof" throughout its service.

This gives us the "punch holes" in paper and the "crackproof" elements, but where do we find the "888" present in the 13-Symbol cipher, that was possibly highlighted in the 13-Hole "Punch Card"? The U.S. Army called the cipher machine SIGABA or Converter M-134. The U.S. Navy called the machine the CSP-888 (Cryptographic Security Publication) and CSP-889. The machine has three banks of 5 rotors each. The main bank (at the rear) holds 5 rotors with 26 contacts each. These are the main cipher rotors. They work in a similar way as the rotors of the con­temporary German Enigma machine.

The 13-Symbol cipher on April 20th 1970, many believe was a response to the challenge by Donald C. B. Marsh, who 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". 

By invoking the name of Edgar Allan Poe, it was probably hoped that the Zodiac Killer would use one of the cryptographic techniques described (or used) by Poe in his famous works, such as "A Few Words on Secret Writing", which contained all the ingredients used in the decryption of the 340 cipher and the design of the 13-character code, including the scytale method of decryption, the splitting of the alphabet, A throgh M and N through Z, and the cipher wheel, which uncovers a potential message in the Z13 code. The SIGABA cipher machine has room for three rows (or banks), of five cipher wheels each.

​In total, we have 13 punch holes and 13 ciphertext characters, a famous "crackproof" cipher machine and the same declaration by the Zodiac Killer on October 6th 1970, the 10:3 configuration on the "Punch Card" possibly highlighting the position of "888" as the key in the April 20th 1970 letter, the CSP-888 cipher machine used by the U.S. Navy in World War II, the cipher wheel explained by Edgar Allan Poe in July 1841 in A Few Words on Secret Writing, prompted by cryptographer Donald C. B. Marsh in a newspaper article on October 22nd 1969, and the signature of "ME⊕" revealed in the Z13 by using three right shifts of 8, which was also present in the Exorcist letter on January 29th 1974. The other possibility, is we have nothing. 

`` Edgar Allan Poe (1809–1849) popularized cryptography in the 1840s through stories like "The Gold-Bug," prompting a young William Friedman (1891–1969) to pursue the field. While Friedman became a legendary U.S. Army codebreaker who valued Poe’s role as a catalyst, he famously critiqued Poe’s actual cryptanalytic skills as amateurish in his 1936 analysis, "Edgar Allan Poe, Cryptographer". Could we therefore have a crossover between the cipher machine CSP-888 and the essay of Edgar Allan Poe, A Few Words on Secret Writing, manifesting itself on April 20th 1970? A Few Words on Secret Writing is mentioned by William Friedman on page 146 of his analysis (see below).  

​​William F. Friedman on Edgar Allan Poe
THE FRIEDMAN LECTURES ON CRYPTOLOGY

FOLLOW UP ARTICLE: A FEW DAYS AFTER DEATH 

For five years, since the 340 cipher was cracked by David Oranchak, Sam Blake and Jarl Van Eycke, people have been under the misconception that the Zodiac Killer made many mistakes when encoding his 340 character message, but the reality is almost certainly different, with only eight mistakes yet to be fully explained in his cipher. I have found only four mistakes in the first 9 rows, and the same number in the second 9 rows, giving us eight mistakes in 340 operations during the encoding process, which is a success rate of 97.65%. The Zodiac Killer upped the level of difficulty from the 408 cipher to the 340 cipher, probably in response to the speed his first offering was cracked. However, no one likely expected the Zodiac Killer to ramp up the difficulty level from the first 9 rows to the second 9 rows in this one cipher. He clearly overestimated its complexity, because the message he masked behind a wall of ciphertext was of a contemporary nature, intended to be read in 1969 or 1970, not half a century later. The notion purveyed of a killer who bumbled his way through the 340 cipher, losing concentration numerous times during the encipherment process, can now be utterly dispelled. This cipher was as devious as it comes.  

The Zodiac Killer made the 340 cipher more difficult by using a combination of substitution and transposition to disguise his message, but he added a third layer in the second 9 rows of the cipher by adding 14 deliberate spelling mistakes in an organized pattern 9 spaces apart (running diagonally across the cipher). The Zodiac Killer not only hid his message by using a 9 shift (and negative 8 shift) technique shown here, but he would further complicate matters for codebreakers by baking in these spelling mistakes using the same 9 shift technique. If you thought that was the last hurdle codebreakers had to overcome you would be mistaken, because a fourth layer was added, also 9 spaces apart. The Zodiac Killer placed the phrase "LIFE IS" into his message, inserted deliberately into certain positions so that it would appear at the end of the 10th row of the original 340 cipher when the key was applied. Below are the 14 deliberate spelling errors he placed into his message, running diagonally across the grid (black rectangles). The four green circles, I believe, are the accidental errors made by the Zodiac Killer. These concepts were fully explained in the previous article No Cipher Mistakes by Zodiac. 

Below is the Zodiac Killer's encoded message with the spelling errors rectified (in brown). There is absolutely no way the Zodiac Killer accidentally made these 14 mistakes in such an organized pattern. If you add the "LIFE IS" phrase into the mix (blue rectangles), it gives us 20 deliberate "errors" by the Zodiac Killer, all organized diagonally 9 spaces apart.

This leads us to the Zodiac Killer's next "13-Symbol" cipher mailed on April 20th 1970, in which the Zodiac Killer introduced the code with the phrase "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is....". If we had cracked the last cipher he sent us, we would have known that the message was encoded behind a simple combination of 9 and 8 shift techniques, which if applied to the 13-Symbol cipher encodes the message of "ME ⊕" ("ME" followed by the Zodiac crosshairs). Simply traveling 8 positions to the right of each circled 8 and cycling through the 13​-Symbol cipher, gives us the "identity" of "ME ⊕". A signature twice highlighted in the Halloween card on October 27th 1970, and given to us directly by the Zodiac Killer in the Exorcist letter on January 29th 1974. All these three communications teased us with the promise of a name, and all can easily be shown to give us the signature of "Me" in their design. The personal pronoun of "ME" was synonymous with the pseudonym "Zodiac" and his "crosshairs", hence the use of "Me-37" in his Exorcist letter rather than "⊕-37", a format he usually chose. Was the Zodiac Killer playing one big joke on us all? See here.

The Zodiac Killer's 340 cipher was broken up into 3 parts of 9, 9 and 2 rows. This was the initial key to solving the 340 cipher. If we apply the same methodology across the Z13 and cycle through the code (9th, 18th and 20th positions), we get 888, the key to solving the Zodiac Killer's 13-Symbol cipher. See here.

The first 18 rows of the 340 cipher reads 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. It is clear that the first 9 rows of the cipher (in black) carried the important part of Zodiac's message, where he confirms that it wasn't him on the TV show, and he was not afraid of the gas chamber. However, the second part of his message (in blue) is pretty irrelevant drivel about "paradice" and "slaves", copying much of what was present in the 408 cipher. This may be the reason the Zodiac Killer created the first 9 rows of the cipher with less complexity and without the designed spelling mistakes present in the second 9 rows. He probably cared less about the second part of his message being deciphered. The amount of cleverness baked into the 340 cipher shows that the Zodiac Killer knew perfectly well that the design of the Z13 and Z32 codes were incompatible with normal cryptographic techniques using all the ciphertext, which is why anybody adopting this approach is quite frankly wasting their time. These two codes require a much more nuanced approach, along with an in depth knowledge of the Zodiac case spanning several years..

THE INSERTION OF THE CORRECT PLAINTEXT LETTERS BELOW WOULD RECTIFY 78% OF THE MESSAGE. ONLY FOUR ERRORS WOULD REMAIN (THE GREEN CIRCLES). 

BELOW ARE THE SECOND 9 ROWS OF THE ORIGINAL 34O CIPHER WITH THE CIPHER KEY APPLIED. THIS IS BEFORE THE PERIOD 19 SHIFT WAS USED IN AN ATTEMPT TO FIND A COHERENT MESSAGE. 

Many people have described the author of the Fairfield letter (with code) as a lazy hoaxer who just dragged two sections of ciphertext from the 340 cipher and plonked them in the Z38 code below. Not only would this be a pointless task, but if this person wanted to make the reader believe they were the Zodiac Killer, why would they adopt the approach of an obvious impersonator and imitate previous correspondence? The more realistic answer to this communication is that it was the Zodiac Killer giving us a clue to the workings of the 340 cipher. Before David Oranchak, Sam Blake and Jarl Van Eycke cracked the 340 cipher in 2020, nobody was aware that the first 4 and last 5 characters of the 340 cipher spelled "IRON" and "DEATH" when the cipher key was applied to it, yet the author of the Z38 code just happened to feature these two sections of ciphertext in their December 7th 1969 letter. Probably the most obvious thing for an impersonator to do, was to bring forth the "near Zodiac"  (ZO∆AIK) from the final row of the 340 cipher and drop it into this code, but this person snubbed that opportunity and broke it up to what we see in the second red rectangle below. An obvious feature in the 340 cipher that the impersonator failed to impersonate. This segment of code is also noticeably larger than the rest of the ciphertext, including the row it sits on.

After the cipher key was applied to the original 340 ciphertext we got the incoherent plaintext shown below. However, after the period 19 shift was applied, the word "DEATH" remained one of only three forward facing words to stay intact (the others being "WILL" and "EASY"). But "DEATH" stands out because it isn't surrounded on both sides by other plaintext, sitting in a prominent position at the end of the cipher. 

The ciphertext characters "H" and "+", not only begin and end the original 340 ciphertext, they begin and end the new ciphertext arrangement after the period 19 shift is applied to it. They also form the beginning two ciphertext characters on the first row of the new ciphertext arrangement. And begin and end the Z38 code mailed on December 7th 1969. If you apply a period 19 shift to the Z38 code above, you get the ciphertext characters "H" and "+" featuring for a fifth time. Because the cipher is 38 characters in length, if you continue the period 19 shift you will get a repeated "H+" sequence continuously. Sam Fisher, a Zodiac researcher, also pointed out that the plaintext letter "H" was represented by the ciphertext character "+" in the 148 character cipher mailed by the Zodiac Killer in May 1971.

Of course, this is all totally coincidental, created by a hoaxer who pleaded "I just need help" (not published in the newspapers) two weeks before the Melvin Belli letter arrived on December 20th 1969, stating "please help me". A December 7th 1969 letter mailed a matter of hours before somebody rang the Oklahoma City radio station KTOK, and made mockery of the Jim Dunbar TV show on October 22nd 1969, featuring attorney Melvin Belli. If we want to discover more about the Zodiac Killer, it's imperative we analyse every potential communication mailed in his name. The other option, adopted by many researchers, is to pay little heed to these communications and lazily believe what they have been fed by others in the Zodiac community, adopting an "Ignorance is bliss" type approach. Lazy individuals who believe in lazy hoaxers, who refuse to even consider that they may be wrong. 

On December 7th 1969 the Zodiac Killer mailed a letter and code from Fairfield just hours before he phoned the Oklahoma radio station KTOK, both times imitating the caller to the Jim Dunbar TV show on October 22nd 1969. The person who mailed the letter provided crucial information in the Z38 code that showed intrinsic knowledge regarding the mechanics of the 340 cipher and its use of the knight's move in chess. In other words, the person who mailed the December 7th 1969 letter knew how to solve the 340 cipher. They knew this because they were the Zodiac Killer. The following will show how I arrived at the plausible solution of  "TRYING TIMES. SO I NEED APPOINTMENT TO GET HELP". 

Bearing in mind that the phone call to Oklahoma and the letter mailed on December 7th 1969 to the San Francisco Chronicle, were both continuing the theme of the Jim Dunbar TV show and Melvin Belli fiasco, in which the hoax caller was pleading for help, there is a strong probability that the Z38 code may contain a message along the same lines. If it did, it would almost certainly have been something the Zodiac Killer read in the newspapers on this topic, such as the article in the Los Angeles Times newspaper on October 23rd 1969, the day after the television show.
​
In the 340 cipher message, decoded by David Oranchak, Sam Blake and Jarl Van Eycke on December 5th 2020, the Zodiac Killer used the headlines from the San Francisco Chronicle newspaper on October 24th 1969, which was titled over two pages, reading both "That Wasn't Zodiac, Say 3 Who Know" and "It Wasn't Zodiac, Say 3 Who Know". In his 340 message he stated "That Wasn't Me on the TV Show". The numerous references in the newspapers immediately after October 22nd 1969 about the caller saying "I don't want to go to the gas chamber", was replied to by Zodiac, who encoded "I am not afraid of the gas chamber". The Zodiac Killer would emphasize these two points in the first seven lines of the deciphered message.   ​

The news was abound with the failed meeting between the "Zodiac Killer" (Sam) and Melvin Belli at the Vincent de Paul thrift store in Daly City, later that day. The Los Angeles Times newspaper on October 23rd 1969 read "Attorney Melvin Belli in a phone booth at a San Francisco television station talking to caller who said he was the Zodiac Killer. Caller made an appointment but didn't keep it". This was the sort of the thing the Zodiac Killer may have mocked, after writing "I just need help" on December 7th 1969. There were two plus signs (+) together in the Z38 code, so I knew they had to represent the same plaintext letter, and gambled on the word "appointment". This would not only fill up a significant portion of the Z38 code, but would mean that the code ended with the plaintext letter "P". That was likely the last letter of "help", which also featured prominently in the Los Angeles Times newspaper and others. In fact, the title of the article was "I Want Help, Zodiac Caller Tells Attorney on Telephone". After placing "appointment" and "help" in the Z38 code, it allows us to form the word "to" immediately after "appointment" because of the double character (dotted circles). The phrase "appointment to get help" was then easy to work out. 

The first 18 ciphertext characters could then be filled in somewhat, with the dotted circle represented by the plaintext letter "T",  the circle with the single vertical line through it represented by the plaintext letter "I", the plain circle ​represented by the plaintext letter "E", the square represented by the plaintext letter "G", the triangle represented by the plaintext letter "O", and the slanted line​ represented by the plaintext letter "N". We were left with this.

The plaintext letters in blue on the top line looked like it could spell "times", followed by the word "so", thereby satisfying the double "L" ciphertext. So I took a gamble and placed the words into the message like so. 

The rest was pretty simple. After the word "so" I added the personal pronoun of "I", and "need" was the obvious next choice. The final part was filling in the blanks for the starting five plaintext letters ending in "G". Trying times" is a well-known phrase that one might experience, and necessitates the need for an "appointment to get help". This completed the Z38 code. Whether it is the correct solution I can't say for certain, but it satisfies the workings of a substitution cipher and has relevance to the contemporary events the Zodiac Killer was reading in the newspapers at the time, just like the message in the 340 cipher.

In cryptography, unicity distance is the length of an original ciphertext needed to break the cipher by reducing the number of possible spurious keys to zero in a brute force attack. That is, after trying every possible key, there should be just one decipherment that makes sense, i.e. expected amount of ciphertext needed to determine the key completely, assuming the underlying message has redundancy. For a simple substitution cipher, the number of possible keys is 26! = 4.0329 × 1026 = 288.4, the number of ways in which the alphabet can be permuted. Assuming all keys are equally likely, H(k) = log2(26!) = 88.4 bits. For English text D = 3.2, thus U = 88.4/3.2 = 28. So given 28 characters of ciphertext it should be theoretically possible to work out an English plaintext and hence the key. Wikipedia. 

• Simple Monoalphabetic Substitution Cipher: The theoretical unicity distance is about 28 characters. In practice, cryptanalysts typically need around 50 characters to perform reliable frequency analysis and achieve a definite solve.

FURTHER READING: "IRON" AND "DEATH" FEATURED IN TWO CIPHERS   

On October 22nd 1969 Will Stevens published an article in the San Francisco Examiner, in which Professor Donald C. B. Marsh urged the killer to contact him in code, stating "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"

Professor Donald C. B. Marsh, by invoking the name of Edgar Allan Poe, was probably hoping that the Zodiac Killer was going to use techniques mentioned or used by Poe, making any future offering by Zodiac easier to solve. The next two ciphers/codes mailed by the Zodiac Killer can be linked to Poe's 1841 essay "A Few Words on Secret Writing" from the July edition of Graham's magazine. The scytale method of decryption featured by Poe can solve the 340 cipher. The immediate next passage of  A Few Words on Secret Writing further describes cryptographic techniques, showing the splitting of the alphabet into ABCDEFGHIJKLM and NOPQRSTUVWXYZ, creating two portions of thirteen letters. The Zodiac Killer's April 20th 1970 communication was a 13-Symbol cipher beginning with A and ending with M. Edgar Allan Poe then describes a cipher wheel that can be used to give a credible answer to the Z13 code. But of course, it doesn't end there.

Not only did the Zodiac Killer use the encryption techniques described by Edgar Allan Poe, he may have embedded two of Edgar Allan's poems in the mechanics of the 340 cipher. Notable words from these two poems were visible when the cipher key was applied to the 340 cipher (before the period 19 shift was used to acquire the message). The presence of the second Edgar Allan Poe poem in the 340 cipher (after the key was applied) was highlighted by the author of the Z38 code mailed from Fairfield on December 7th 1969, who was undeniably the Zodiac Killer.

But let us deal with the first poem that was plainly visible in the deciphered 340 message, that read: 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 25th 1843 edition of the Philidelphia Saturday Museum. 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. Now let's look for the second poem by Edgar Allan Poe. When the Zodiac Killer mailed the Z38 code on December 7th 1969, he repeated two notable segments of ciphertext from the 340 cipher. The first four ciphertext characters, and the last five ciphertext characters (shown below). 

This may not seem significant, until you consider that when the original 340 cipher was changed using the key, it created the words "IRON" and "DEATH" in these two exact positions (see below). Are we are expected to believe that when the author of the Z38 code selected these four and five sections of ciphertext from the 340 cipher, taken from the beginning and end of the cipher, he chose two legible words created by the 340 key by accident, which he should have had no knowledge of unless he was the Zodiac Killer. No hoaxer should have been aware of this fact and had the foresight to highlight these sections in the Z38 code. The person who created the Z38 code broke up the "Zodiac-like" pseudonym (ZO∆AIK) from the last row of the 340 cipher to create the word "death", something that would not have been expected from a hoaxer. The person who did this knew exactly what they were doing, because they created the 340 cipher.

It must be remembered that Edgar Allan Poe wrote "To One in Paradise" upon the death of his beloved wife, Virginia Eliza Poe. But how can "IRON" and "DEATH" introduce a second Edgar Allan Poe poem into the equation? Edgar Allan Poe wrote "To One in Paradise" about the death of his wife, but this wasn't the only poem written by Poe about the death of Virginia. The inspiration for the second poem, "The Bells", was reported as coming from his friend, Marie Louise Shew, who likened the sound of the Fordham University bell made of "iron", to "death".

​Edgar Allan Poe's poem "The Bells" uses different types of bells (silver, gold, brazen, iron) as powerful metaphors for the stages of human life, from the joy and playfulness of childhood (silver sleigh bells) through the harmony of youth and marriage (golden bells), to the panic and chaos of maturity (brazen bells), culminating in the inescapable melancholy and terror of death (iron bells). Written at the end of his life, the poem's shifting sounds and increasing length mirror the journey from youthful delight to the despair and inevitability of mortality, exploring the passage of time and its emotional toll. Edgar Allan Poe's poem "The Bells" was inspired by the sounds of bells from Fordham University's church while he lived nearby in the Bronx, New York, capturing the changing emotions of life, from youthful joy (silver bells) to despair and death (iron bells), a reflection of his own grief after his wife Virginia's passing.. Inspiration for the poem is often granted to Marie Louise Shew, a woman who had helped care for Poe's wife Virginia as she lay dying. One day, as Shew was visiting Poe at his cottage in Fordham, New York, Poe needed to write a poem but had no inspiration. Shew allegedly heard ringing bells from afar and playfully suggested to start there, possibly even writing the first line of each stanza.

I always wondered why these two prominent English words began and ended the 340 cipher after the key was applied to the original 340 ciphertext, and then highlighted by Zodiac in the Z38 code. The poems "The Bells" and "To One in Paradise" were written about the grief Edgar Allan Poe experienced upon the death of his wife, with "IRON", "DEATH" and "PARADISE" instrumental to both - which just happened to be present at the beginning and end of the Zodiac Killer's 340 cipher after the key was applied (although "one in paradice" was reversed at this point). Throw in the essay A Few Words on Secret Writing by Edgar Allan Poe, containing a technique that can solve Zodiac's 340 cipher (and a further technique that possibly influenced the design and solution of the Z13), and we have a story steeped in history. 

FURTHER READING: THE MECHANICS OF THE Z38 CODE 

​Many Zodiac researchers have contemplated whether the Z13 code mailed on April 20th 1970 contains a name or meaningful message, but extensive analysis of this cipher appears to show that neither are hidden beneath the ciphertext supplied by Zodiac. The first thing we notice when looking at the 13-character code is its symmetry. We have three alphabetical characters at the beginning and end. We have three circled 8's at positions 5, 7, and 9. And we have two non-alphabetical symbols four positions in from either side.

​This code can contain a valid name or message as shown by cryptographer David Oranchak. However, if the Zodiac Killer provided a genuine message or name of 13 plaintext characters, which creates the ciphertext scenario of three 8's, two A's, two M's and two N's, it must be considered highly unusual that when these ciphertext characters are placed alongside the alphabet (A through M) and we count the alphabetical difference between the two rows (as shown below), it produces yet further symmetry. Positions 1 to 4 and 9 to 13 gives us "03110" twice. The middle five positions gives us "05050". Therefore, we have a symmetrical ciphertext offering by Zodiac on April 20th 1970, that generates further symmetry in number form when placed alongside the alphabet.

​Using an identical technique in the 340 cipher, we took the pseudonym ZODIAC and placed it above the "near Zodiac" in the form of ZO∆AIK on the 20th row, and counted the alphabetical difference between the two rows. This generated the numbers 000888 that formed the basis of the three 8's in the symmetrical Z13 code, which produced further symmetry when placed alongside the alphabet. This was a 13-character code almost certainly inspired by the October 22nd 1969 newspaper article by Will Stevens, in which Dr. D. C. B. Marsh challenged Zodiac to give us his name in cipher form. An article in which Dr. Marsh invoked the name of Edgar Allan Poe, probably hoping that Zodiac would research and use cipher techniques outlined by Poe. The essay by Poe entitled "A Few Words on Secret Writing" contains all the ingredients used in the decryption of the 340 cipher and the design of the 13-character code, including the scytale method of decryption, the splitting of the alphabet, A throgh M and N through Z, and the cipher wheel, which finds the potential message in the Z13 code.
​
See    Cracking the Crackproof.   Same Methodology Between Z340 and Z13.   Effectively a 353 Character Cipher.
​

For the Z13 code to contain a random and/or spontaneous message, we would have to believe that all of the above scenarios were created by sheer happenstance. The only reasonable way the Zodiac Killer could have formulated these interlocking occurrences between the 340 cipher, 13-character code and Edgar Allan Poe, is if his message on April 20th 1970 was anything but random. It had to be a decipherment of simplicity, in which the majority of his ciphertext characters were chosen for the sole purpose of manufacturing this web of symmetry, not to create a plaintext message (or name) of 13 characters. 

The only constraints the Zodiac Killer faced when constructing the Z13 code, was beginning it with the ciphertext character A and ending it with the ciphertext character M, to allude to Poe. It was then a simple task of adding the three circled 8's, along with the ciphertext character E and the crosshairs, in such a position that a right shift of eight from each circled 8 (across and around the code) created the message of "ME ⊕". A message that was further explored in Four and Half Years of Me and The Identity in the Halloween Card. ​The A, M and three circled 8's all produced a numerical shift of zero when placed alongside the alphabet, allowing the Zodiac Killer to add the "E" and "⊕" (to complete the message) and manufacture the remainder of the code with symmetry in mind.

EXTRA READING: THE DEMON INSIDE OF ME 

One puzzling aspect of the Zodiac Killer's 340 cipher is his decision to separate the encipherment into three parts of 9, 9 and 2 rows, rather than simply dividing the cipher into two parts. The third section of two rows didn't follow the same technique as the other two parts. Therefore, one could conclude that it was important for the Zodiac Killer to separate the cipher into two equal parts of 9 rows, leaving the final 2 rows for an entirely different purpose, such as his signature on the 20th row. If we assert that the "near Zodiac" signature (ZO∆AIK) on the final row was a deliberate choice and not accidental, it may follow that this misspelling of "Zodiac" was purposely designed as a key.    

When we place the correct spelling of "ZODIAC" above the "near Zodiac" of ZO∆AIK, and count the alphabetical difference, the Z to Z requires a 0 shift, the O to O requires a 0 shift, and the D to ∆ requires a 0 shift, giving us three zero's. But when we look at "IAC" to "AIK", we require three shifts of 8, giving us three eight's (which when combined, gives us the three circled 8's seen in the Z13 code). Therefore, we have a 340 cipher split downwards into three parts of 9, 9 and 2 rows, with a "near Zodiac" signature on the 20th line that easily gives us three circled 8's.

​If we apply the same technique across the Z13 code, and cycle around the ciphertext to the 9th, 18th and 20th positions (9, 9 and 2), it again completes the 888 signature (shown below)..The 20th position of the Z340 and Z13 puzzles both highlight the 888 signature of Zodiac. When we apply the three shifts of 8 found by comparing ZODIAC to ZO∆AIK into the Z13 code, we get "ME ⊕" ("ME" followed by the Zodiac crosshairs)​. Two of the signatures used by Zodiac to identify himself in his letters. This has been pointed out previously by the use of "Me" as his signature within the Exorcist letter on January 29th 1974.  

In David Oranchak's excellent YouTube video entitled Let's Crack Zodiac, the 340 Cipher is Solved, he stated "The message doesn't really say a whole lot, it's more of the same attention seeking junk of Zodiac. We were disappointed that he didn't put any personally identifying information in the message, but we didn't expect him to. Maybe his name really is in the thirteen character cipher sent almost six months after the 340. Unfortunately there is not much hope of confirming any solutions for such a short cipher without getting lucky and discovering new evidence". 

I believe the personally identifying information in the 340 cipher is the "near Zodiac" on the 20th line, that gave us the three circled 8's present in the Z13 ciphertext, which produced "ME" and the "crosshairs" by employing a simple right shift of eight. The Zodiac psuedonym has been shown to be inextricably linked to the three 8's. thereby giving us "Zodiac", "Me" and the "crosshairs" in the Z13 code. The Z13 code is believed by many Zodiac researchers to be too short to solve, but by combining it with the 340 cipher it effectively becomes a 353 character cipher, where traveling 9, 9, and 2 downwards and across in both Z340 cipher and Z13 code, ultimately finds the key of 888. Which we can then apply using three right shifts of eight to reveal two further identities of "ME" and "⊕".


FURTHER READING: SAME METHODOLOGY BETWEEN Z340 AND Z13
                                     FOUR AND A HALF YEARS OF "ME"

In a recent article entitled Four and a Half Years of Me I came to the conclusion that the 13-character cipher was likely done in haste, and the Zodiac Killer jokingly provided his name as "ME ⊕" ("ME" followed by the Zodiac crosshairs), which I showed to be also present in the 408 cipher, Halloween card, Exorcist letter, and maybe was hinted at in the Eureka card. To achieve the "ME ⊕" identity, all we had to do was apply a "period 8" right shift to each circled 8 and cycle around the cipher, exactly the same methodology that was used in the 340 cipher five months earlier, where a "period 19" right shift was needed to decode his message.  .  

Many have speculated that the Zodiac Killer's opening wording in the April 20th 1970 letter of "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is....", indicated that we needed to solve the 340 cipher to give us a clue to decoding the 13-symbol cipher. I have put forward that the Z13 may have revealed two forms of Zodiac identity in "ME ⊕", by using the three circled ​8's in the cipher. But how can we prove that this was the Zodiac Killer's intention? How can we prove that this was the Zodiac Killer's key? Did the answer lie in the decoding of the 340 cipher?

If the 340 cipher had been solved before April 20th 1970, we would have known that the Zodiac Killer split his cipher into three parts of 9, 9, and 2 rows. These three parts were comprised of row 1 to row 9, followed by row 10 to row 18, and finally the last two rows up to the 20th line. The Zodiac Killer gave us the key to the 340 cipher by splitting it into a 9, 9, 2 configuration. We then had to apply the "period 19" right shift to make the message possible. This configuration of 9, 9, 2 went down the cipher, so let's apply the same methodology to the Z13 by going across the cipher.

If we travel from position 1 to 9, we land on the right circled 8. If we travel from position 10 to 18, we land on the left circled 8. If we travel from position 19 to 20, we land on the middle circled 8. The configuration employed in the 340 cipher gave us the key to its solving. Does the same configuration applied to the Z13 gives us a clue to its solving? It gives us the three 8's. Once the configuration (of three parts) was identified in the 340 cipher, the "period 19" right shift was applied. Once the configuration (of three parts) was identified in the Z13 cipher, the "period 8" right shift was applied to get the message. The "period 19" right shift in the 340 cipher was crucial in finding the message. The "period 8" right shift in the 13-symbol cipher was crucial to finding the message of "ME ⊕". A personal pronoun that is seen twice in the Halloween card, and clearly written as the Zodiac Killer's identity on January 29th 1974 in the Exorcist letter.

The Zodiac Killer may also have highlighted these three circled 8 positions in his 13 punch holes in the October 6th 1970 "Pace" postcard. 

ADDITIONAL READING: FOUR AND A HALF YEARS OF "ME"     

This is a further examination of the 18 characters at the foot of the 408 cipher mailed on July 31st 1969, and the reasoning behind the apparent filler that made little sense. It is fairly clear that the Zodiac Killer made an error when converting his draft message into ciphertext form when he transitioned from the San Francisco Examiner to San Francisco Chronicle portion of the cipher, inadvertently missing out one line of 17 characters. This left him with the option of maybe dumping something unplanned into the remaining 18 characters to play a joke on the audience, which I have explored in the April 20th 1970, October 27th 1970, January 29th 1974 and December 1990 communications, found in an article entitled Four and a Half Years of "Me". 

​The word "ME" can be reasoned to be present in all the above four communications, but is also noticeable within these 18 characters, albeit not currently supported by the most convincing of arguments. So let's examine the 408 cipher in more depth, because on August 4th 1969 the Zodiac Killer informed the police to "cheer up", who would, once they solved the code "have me". This is despite his message in the 408 cipher stating that "I will not give you my name". The notion being that the identity he supplied was "ME", just like he eventually gave us in the "Exorcist" letter on January 29th 1974 when writing Me-37. The Zodiac Killer may not have been lying when he told police they would "have me" when they cracked the code. Below in green I have highlighted the characters that have seemingly been sourced by the Zodiac Killer from the columns above the final line. This final 24th row has 12 characters from the above columns, with 5 characters absent from the above columns. That is a strike rate of 70.5%. So if the final row really was just filler, why did the Zodiac Killer abandon this technique nearly 30% of the time? ​

Using the full 18 characters, let us examine the 11 characters either side of the run of 7 characters boxed in green. The first 6 characters only have a strike rate of 50% from the columns above, with the final 5 characters having a strike rate of just 40%. So its fairly obvious that the Zodiac Killer wasn't stringently harvesting characters from the above columns in these sections of the cipher. Therefore, if we discount the seven characters in a row, the remaining 11 only generate an overall strike rate of 45% from the above columns. But of these 7 consecutive characters found in the above columns, it is the grouping of 4 on row 8 that carry the most significance. The grouping of 4 characters on the eighth row spelling METH contain the object pronoun of "ME", which is visible on the final row - and an "identity" that the Zodiac Killer promised to give us in the cipher when he wrote to the San Francisco Chronicle on July 31st 1969. One could conclude that a promise to give us his identity when writing to the San Francisco Chronicle and supplying us with the third portion of the cipher, meant we would find his identity in the final 8 rows of the 408 cipher (or possibly the final line). On August 4th 1969 the Zodiac stated "By the way, are the police having a good time with the code? If not, tell them to cheer up; when they do crack it, they will have me". The final 8 rows of the cipher did contain "HAVE", "ME" and "ME".

The phrase "yours truly" has two main uses in English: as a formal sign-off in a letter and, informally and often humorously, as a substitute for "I" or "me"..When used in conversation or informal writing, "yours truly" is an idiomatic expression used to refer to oneself, the speaker or writer, usually in a self-deprecating or ironically boastful way. It functions as a first-person pronoun substitute. This is why it's important to note the use of "yours truley" and "Me" as the Zodiac Killer's chosen identity in the Exorcist letter on January 29th 1974. He effectively gave us "Me" twice. After he wrote "Signed, yours truley" in the 1974 letter he gave us a "Tit-Willow" verse from "The Mikado", whose very next line contained the phrase "My name is", which was previously followed by a 13-character code on April 20th 1970. A code which can easily be shown to give us the personal pronoun of "Me" (and the crosshairs) by employing a simple right shift of 8 positions from each circled 8.  It can be argued that he gave us two identities on April 20th 1970 by supplying us with both the "crosshairs" and "ME".

We also had the visible presence of "ME" and "me" in the Halloween card on October 27th 1970, which was teed up with the introduction of "I feel it in my bones you ache to know my name. And so I'll clue you in". The Zodiac didn't give us his name on October 27th 1970, but he did give us the personal pronoun of "Me" twice. The third portion of the 408 cipher (shown above) stated that he would not give us his name, although he did, once again, give us "ME" two more times. Throw in the autobiography of Groucho Marx entitled "Groucho and Me" with respect to the Eureka card in 1990, and it appears that the Zodiac Killer may have been playing a running joke on his audience for upwards of twenty-one years. 

After noticing the presence (or inference) of "ME" at least six times on April 20th 1970, October 27th 1970 and January 29th 1974, all with the promise or suggestion of his name or identity, this has been a retrospective analysis of the 408 cipher, looking for the most reasonable way the Zodiac Killer inserted "ME" into the final portion of the 408 cipher, mailed to the San Francisco Chronicle on July 31st 1969, and followed with a promise by the Zodiac Killer to "have me" on August 4th 1969 when the code was cracked. This analysis of the 408 cipher is far from satisfactory, but I believe our focus should be squarely on the four consecutive characters on the eighth line, which appeared like a deliberate choice by the Zodiac Killer to drop into the signature line of his three-part cipher. However, I would be surprised if there wasn't more to it.

FOUR AND A HALF YEARS OF "ME"        THE AUTOBIOGRAPHY OF GROUCHO MARX

If you want to read an introductory article to better understand the following presentation, please click here. ​

When the Zodiac Killer mailed the "Little List" letter on July 26th 1970 he pretty much gave us the full solution to the Z32 by writing "P.S. The Mt. Diablo code concerns Radians + # inches along the radians". The solution contained "radians" and "inches", and all we had to do was precede each with a number, giving us the answer of "four radians and five inches". The location of his claimed bomb was never going to land on a round number, so the solution was just an estimate, giving us the complete answer of "estimate: four radians and five inches" (supplied by Andrew Gray). That is really all there is to it. 

In the "Button" letter mailed on June 26th 1970 the Zodiac Killer wrote "the map coupled with the code will tell you where the bomb is set". We have the code answer of "four radians and five inches", but we needed to couple it with the map "set to magnetic north" of 17 degrees in 1970. That is 4 X 57.3 degrees (one radian) + 17 degrees = 246.2 degrees. Therefore, the bomb was claimed to be set at 246.2 degrees from Mount Diablo (which was an estimate). The actual target was Ingleside Police Department by the Southern Freeway, which was positioned at 251 degrees  The margin of error over a 360 degree circle was just 1.3%. That is pretty damn accurate. The crosshairs with the bold, black circle on the "Little List" letter was set to 246.2 degrees and had SFPD aligned next to it, so it's clear that the target was a police station. 

The repeating ciphertext characters are now satisfied, but do we really believe that the extremely clever Zodiac Killer added the remaining 26 ciphertext characters by using random letters and symbols that meant absolutely nothing? The solution thus far gave us 246.2 degrees (which was an estimate), but what was the real value in degrees to pinpoint the exact target? What can we possibly do with 32 characters, of which 29 are unique? If you are approaching this based on techniques employed in the 340 and 408 ciphers, then the answer is absolutely nothing. Therefore, it's fairly obvious that the Zodiac Killer used a different approach. A simplistic approach as old as time. However, the only clues we had was "P.S. The Mt. Diablo code concerns Radians + # inches along the radians" and "the map coupled with the code will tell you where the bomb is set". We have already explained both of these messages from the Zodiac Killer, so one of them must have a double meaning with respect to finding the exact location the Zodiac Killer was claiming for his bomb.

If we look at the message in blue, we already have the "map" element of "17 degrees magnetic north" (as mentioned above), so did the Zodiac "couple" this with something other than four radians in the "code", to give us the remaining degrees and pinpoint the exact location of the proposed bomb. The only way to attempt this, is by attributing number values to the alphabetical letters (correctly aligned), of which there are 20 in the code. For example A=1, B=2, C=3, etc. What are the chances that these alphabetical letters would add up to 234 in the "code", to be "coupled" with 17 degrees from the "map", and give us 251 degrees to identify the exact location of the Ingleside Police Department (SFPD) from Mount Diablo? They did.

We have "four radians" in the code (229. 2 degrees) coupled with the map of 17 degrees magnetic north = 246.2 (estimate).
We also have 234 degrees in the code, coupled with the map of 17 degrees magnetic north = 251 (the exact target location).
​The idea that the Zodiac Killer gave us 29 different characters in the Z32 with seemingly no hope of a solution, should be flipped on its head. In other words, the fact that he deliberately engineered such an impossible code with no chance of a resolution, meant that there probably was one. I expect that he thoroughly enjoyed the notion of a "crackproof" code, when in fact, the solution was anything but.  If you look too deep into a problem, you will often overlook the shallow. 
​
ADDITIONAL READING: THE ANSWER TO THE MOUNT DIABLO CODE 

There may have been a change in the Zodiac Killer's approach to encrypting his ciphers/codes after the 408 and 340 cryptograms, in that the Z13 and Z32 were specifically designed with maybe just six characters forming the bedrock of each solution, but with a key of just three characters. The key characters in the April 20th 1970 letter were the three 8's, whereas the key characters in the "Button" letter Z32 code on June 26th 1970 were the three repeating symbols of C, O and the triangle. These three symbols (characters) were seemingly the key to unlocking both codes mailed on April 20th 1970 and June 26th 1970, with the remaining characters beyond the total of six possibly meaningless filler placed around them.

Once the Zodiac Killer had supplied us with the prompt of "The Mt. Diablo Code concerns Radians & # inches along the radians" on July 26th 1970, the placement of "four radians and five inches" into the Z32 from position 9 to 32, unlocked the answer of "estimate" from position 1 to 8, to identify the complete solution of "Estimate: four radians and five inches". There was a total of six characters at play here, but only three were key characters involved in the solution. The key characters in the Z13 on April 20th 1970 were the three circled 8's, but a total of six characters may also have been at play here. They were the three 8's, and the "M", "E" and "crosshairs". If the proposed solution of "Me⊕" for the Z13 is correct, then both the Z13 and Z32 codes follow the same template.   

It can be seen above in the Z32 that six characters are at play here, but only the three characters at positions 14, 26 and 32 are key to the solution. The characters at 14, 26 and 32 within "four radians and five inches", unlock the characters at positions 1, 2 and 6 to give us the word "estimate" and complete the full solution. In the Z13 below we again have six characters at play, but only three characters at positions 5, 7 and 9 are key to the solution of "Me⊕".    

This drives at the heart of the question, of whether the Zodiac Killer used redundant characters in 54% of the Z13 and 81% of the Z32 to change the methodology he employed in his previous ciphers. If the proposed solution to the Z13 is correct, then there is a good argument to be had that the Zodiac Killer used only six functional characters in both designs, of which, only three were key to each solution. That key being the three circled 8's in the Z13, and the C, O and △ in the Z32.