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

It was common for the Zodiac Killer to compose letters and cards inspired by newspaper articles he had recently read, so it wouldn't have been out of the ordinary for the murderer of five to have been a regular consumer of the San Francisco Chronicle, including the games and puzzles section. On November 8th 1969 the Zodiac Killer mailed his infamous 340 cipher, unsolved for 51 years, until it was cracked by David Oranchak, Sam Blake and Jarl Van Eycke in 2020 using a knight's move (period 19) decryption technique. Could the Zodiac Killer have had an avid interest in chess, followed the popular column by George Koltanowski in the San Francisco Chronicle and incorporated a shift move into his encoding of the 340 cipher, that required a knight's move to unlock its secrets half a century later? Did the individual outlined below have an influence on the Zodiac Killer? The answer may lie in a newspaper article in the San Francisco Examiner on July 16th 1978, announcing the upcoming World Chess Championship beginning on July 18th 1978 with a match between ​Anatoly Karpov and Viktor Korchnoi, covered by guest speaker George Koltanowski at the Paul Masson Vineyard in Saratoga, Santa Clara County. A county where only 3 months earlier, the Zodiac Killer may have mailed the April 24th 1978 "I am back with you" letter from.   

George Koltanowski, the legendary grandmaster of chess who wrote more than 19,000 chess columns for The San Francisco Chronicle with the same ease with which he dispatched countless opponents in a career that spanned 10 decades, died Saturday (February 5th 2000) in a San Francisco hospital after a brief illness. He was 96. His column, which appeared in The Chronicle every day without interruption for 52 years, was the longest-running daily chess column in history.

He was also the world champion of a form of the game known as blindfold chess, in which the player commits the game to memory and does not look at the board or touch the pieces used by opponents, who play in the normal fashion. Mr. Koltanowski's 1937 feat of playing 34 opponents simultaneously while blindfolded without losing a game has never been equaled. Koltanowski was the former president of the U.S. Chess Federation, which bestowed upon him the title of "Dean of American Chess." He served during the years after the Bobby Fischer boom of 1972, when interest in chess soared to record highs after the mercurial American grandmaster won the world title. Koltanowski seized the momentum of those heady days to install chess clubs in countless schools, community centers and even at San Quentin Prison. San Francisco Chronicle.

Among his countless chess feats, Mr. Koltanowski was well-known for performing the Knight's Tour, where random bits of information such as names and phone numbers would be supplied by audience members and written in the 64 squares of a giant chessboard. In seconds, Mr. Koltanowski would commit the entire hodgepodge to memory. Then, while blindfolded, he would call out the intricate path required for a chess knight to make its series of L-shaped hops around the board -- by recalling the scraps of information in order.  ​If the Zodiac Killer had a liking or fascination with chess and puzzles, he would very likely have known about the knight's tour challenge, a mathematical problem where you have to move a knight around a chessboard (8 X 8 grid) and visit all 64 squares without landing on a square more than once. The Knight's Tour is very well-known, recognized as a classic, over-thousand-year-old mathematical puzzle and graph theory problem, first appearing in 9th-century Sanskrit texts and later analyzed by Leonhard Euler, becoming famous for its complexity and links to magic squares, popularizing it through chess history and computer science as an illustration of algorithms. ​

To commemorate the opening of the World Chess Championship in the Philippines on July 18th 1978, George Koltanowski appeared at a chess tournament in the Paul Masson Vineyard in Saratoga, Santa Clara County, which offered $15,000 in prize money and was open to 700 players. A chess tournament was held there annually in the late 1970s and early 1980s. The San Francisco Examiner newspaper reported on July 16th 1978 that it had not yet been decided whether George Koltanowski would be performing his mind-blowing Knight's Tour chess puzzle while blindfolded, or would be taking on the Controlled Data's computer in St. Paul Minnesota, while sitting in the shade of the sycamore trees in the Paul Masson Vineyard in the mountains of Saratoga.

Whatever the case, the day after the World Chess Championship began (and while George Koltanowski was giving his performance in Saratoga), the Zodiac Killer mailed a letter to the San Francisco Chronicle on July 19th 1978, stating "But maybe you play chess with me. I have several cheap sets in closets all over. I have my name on the bottom of the lid with the scotch tape....My tape is waiting for me all over California". Clearly this was no coincidence, especially when you consider that this Zodiac letter was probably composed on July 18th 1978, the day the World Chess Championship began, the day that George Koltanowski gave a talk in Saratoga about the opening chess match between Anatoly Karpov and Viktor Korchnoi, and the same day that the Santa Cruz Sentinel (and numerous others) reported on this very same chess game, with a Zodiac Killer newspaper article right next to it, entitled "SF Chief Says Inspector Didn't Write Zodiac Letter". A newspaper article on July 18th 1978 about David Toschi who had been demoted to pawn detail, followed by a Zodiac letter on July 19th 1978 inviting the former inspector to "maybe play chess". 

In the Zodiac Killer letter postmarked July 19th 1978, it stated "I am the ZODIAC and I am in control of all things. I am going to tell you a secret. I like friction tape. I like to have it around in case I need to truss someone up in a hurry....I have my real name on a small metallic tape. You see, while you have it in your possession, I want you to know it belongs to me and you think I may have left it accidentally. I am athletic. It could be swim fins, or a piece of scuba gear. But maybe you play chess with me. I have several cheap sets in closets all over. I have my name on the bottom of the lid with the scotch tape....My tape is waiting for me all over California. Do you know me? I am the ZODIAC and I am in control". You will notice that the letter mentions Scotch Tape, invented in 1930 by 3M engineer Richard Drew in St. Paul, Minnesota (and manufactured there). The very location of the computer being challenged by George Koltanowski at the time the Zodiac Killer letter arrived at the San Francisco Chronicle, mentioning chess. Designed as a moisture-proof sealant for food packaging, it quickly became popular during the Great Depression for repairing household items. The Zodiac Killer informed us that he had his name "on the bottom of the lid with the scotch tape", leading many to believe that the Zodiac Killer's name may have been "Paul", contained within the location of St. Paul, Minnesota. 

Is it possible that the Zodiac Killer attended this chess tournament at the Paul Masson Vineyard in Saratoga as a competitor or spectator? This location is situated 2 miles (by crow) from where Kathy Bilek (18) was stabbed to death on April 11th 1971 in the woods of Villa Montalvo, whom the Zodiac Killer claimed responsibility for on July 13th 1971 by mailing the "Monticello" card, stating "Near Monticello Shought Victims 21 ...... In The Woods Dies April". Saratoga is close to San Jose, which has consistently featured in the Zodiac Killer story.

The company (3M) that produced Scotch Tape also invented Post-it Notes (sticky notes) in 1974. George Koltanowski famously used sticky notes (or small pieces of paper) as part of his demonstration of the "Knight's Tour" during his exhibitions. During his demonstration of the knight's tour, George Koltanowski would ask audience members to call out random words, names, or numbers, which were written on sticky notes and placed on each of the 64 squares of a large demo chessboard. He was then blindfolded, and another person would select a random square. Starting from that square, Koltanowski would recite the text on the note and continue to call out the contents of every other square in sequence, without error, following the path of a knight's tour until all 64 notes were removed. A knight's move that was required to solve the Zodiac Killer's 340 cipher, mailed to the San Francisco Chronicle where George Koltanowski had a chess column. The audience members sometimes had their names placed on sticky notes, not unlike the Zodiac Killer, who claimed his name was on Scotch Tape all over California. 

The Scotch Tape letter upon first reading makes little sense, but everything contained within Zodiac communications usually have their foundation in Bay Area newspapers, which the Zodiac Killer borrowed from and inserted, often cryptically, into his writings to the San Francisco Chronicle (and occasionally others). Whether this extended to the 340 cipher through an interest in chess, is open to question.    

FURTHER READING: A PAWN IN A GAME OF 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 

Thanks to the brilliance and determination of David Oranchak, Sam Blake and Jarl Van Eycke, the 340 cipher was finally cracked after 51 years on December 5th 2020. However, with the exception of a few people, little has been done to find the inspiration for a killer who created a cipher that required the knight's move in chess to reconfigure the ciphertext and allow the message to be broken using homophonic substitution. The 340 cipher needed a one down, two across system to make the cipher easier to crack, with the Zodiac Killer's errors creating a further roadblock. Ciphers are mathematical, relying on algorithms, modular arithmetic, and complex equations for encryption and decryption, evolving from simple letter shifts to advanced concepts in number theory and abstract algebra for modern digital security. They use mathematical procedures to transform readable text (plaintext) into unreadable text (ciphertext) and back, making them a core part of cryptography, which sits at the intersection of math and computer science.

Radians, chosen by the Zodiac Killer for us to discover the location of his hidden (likely pretend) bomb, are fundamental to mathematics, serving as the standard unit for measuring angles, especially in calculus and physics, because they simplify formulas by relating angles directly to the circle's radius, making calculations for arc length, sectors, and trigonometric functions much cleaner than using degrees. Radians are essentially a unitless count of "radius units", making them a natural fit for mathematical expressions. This was another of Zodiac's puzzles that lay unbroken for 51 years until Zodiac researcher, Druzer, filled in the blanks on December 27th 2020. But what is another form of mathematics that may have inspired the Zodiac Killer to fashion the 340 cipher the way he did? A form of mathematics that Zodiac mentioned in his letters?​  

On July 19th 1978, a deeply controversial communication, that is almost certainly genuine Zodiac material, was mailed to the Los Angeles Times. It read: "I am the ZODIAC and I am in control of all things. I am going to tell you a secret. I like friction tape. I like to have it around in case I need to truss someone up in a hurry....I have my real name on a small metallic tape. You see, while you have it in your possession, I want you to know it belongs to me and you think I may have left it accidentally. I am athletic. It could be swim fins, or a piece of scuba gear. But maybe you play chess with me. I have several cheap sets in closets all over. I have my name on the bottom of the lid with the scotch tape....My tape is waiting for me all over California. Do you know me? I am the ZODIAC and I am in control". This letter probably formed the basis of Robert Graysmith's mentioning of Zodiac's crimes as an "outdoor game of chess".

Chess is deeply mathematical, relying on logic, patterns, probability, and combinatorics, even though it's not about traditional arithmetic; it's a game of finite states and algorithms with a vast solution space, making it a practical application of mathematical thinking. While you don't need advanced math skills to play, the underlying principles of strategic calculation, geometry, and problem-solving connect it directly to mathematics. Coming the day after the opening game in the World Chess Championship between Anatoly Karpov and Viktor Korchnoi on July 18th 1978, this letter told of a person who had "chess sets all over California" and suggested that David Toschi, who had been demoted to pawn detail, play a game of chess with him.

​If the Zodiac Killer really had an avid interest in chess and puzzles, he would very likely have known about the knight's tour challenge, a mathematical problem where you have to move a knight around a chessboard (8 X 8 grid) and visit all 64 squares without landing on a square more than once. The Knight's Tour is very well-known, recognized as a classic, over-thousand-year-old mathematical puzzle and graph theory problem, first appearing in 9th-century Sanskrit texts and later analyzed by Leonhard Euler, becoming famous for its complexity and links to magic squares, popularizing it through chess history and computer science as an illustration of algorithms. 

Ciphers are essentially algorithms (or sets of rules/steps) used for encryption and decryption, transforming readable text (plaintext) into unreadable ciphertext and back again, using keys to control the process. So did the Zodiac Killer use a knowledge of chess and the well-known puzzle of the knight's tour, and create a more complex 340 cipher that required the very same move to begin decoding his message on November 8th 1969? 

FURTHER READING: A PAWN IN A GAME OF DEATH   ​

​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.
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See    Cracking the Crackproof.   Same Methodology Between Z340 and Z13.   Effectively a 353 Character Cipher.
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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"     

The April 20th 1970 letter opens with "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is....". One of the takeaways from the mention of his previous cipher while beginning this communication, has been that something about that previous cipher may aid in the solving of the current Z13 code. Many have taken the code key from that now solved 340 cipher and tried to apply it to the Z13 code. While some of those attempts have produced interesting outcomes, they have all required some form of manipulation to generate a desired result, which leaves room for objection. But what if the answer or key lay in the unsolved 340 cipher at the time Zodiac mailed his Z13 code on April 20th 1970. Bearing in mind this latest letter was suggesting that the Z13 code would reveal a "name" or "identity", it is quite possible that his identity in the unsolved 340 cipher held the clue.

In the 340 cipher on the final line he appeared to give us his signature of ZODIAC from characters 333 to 338. However, he replaced the "D" with a blackened triangle, reversed the "I" and "A", and changed the "C" for a "K". Despite this, it's unmistakable presence is there for all to see. What if we took this identity to solve the Z13 code.  

As stated previously, Professor Donald C. B. Marsh invoked the name of Edgar Allan Poe to challenge Zodiac to reveal his name on October 22nd 1969, hoping that the Zodiac Killer would utilize the cryptographic works of Poe to create any forthcoming ciphers. Taking one look at Poe's essay, "A Few Words on Secret Writing" in the July edition of Graham's magazine, you can see the scytale method of decryption that can be used to solve Zodiac's 340 cipher, the cryptographic technique of splitting of the alphabet A through M and N through Z, which Zodiac employed in his design of the Z13 code, and the cipher wheel explained by Poe, which not only decodes the "near Zodiac" on the final line of the 340 cipher to give us the key, but provides us with a resulting key that the Zodiac placed directly into his 13 characters on April 20th 1970, that generates an answer he would later reveal as his signature on January 29th 1974. That signature was "Me". 

The "near Zodiac" in the 340 cipher has simply been manipulated using a cipher wheel. When we compare the correct spelling of ZODIAC to the version supplied on the final line of the 340 cipher, we can see that Z to Z, O to O, and D to triangle generates no difference alphabetically (000). Whereas "IAC" to "AIK" generates a shift of 8 positions for each letter, producing 888. This provides us with 000888, the possible origin of the three circled 8's in the Z13 code. Visit the Caesar cipher wheel here and type in the number 8 (see below). The inner wheel will spin 8 positions clockwise so that the outer wheel "I" is represented by the inner wheel "A" (and vice versa). The outer wheel "K" is represented by inner wheel "C" (and vice versa). This is the bedrock of the switch from "IAC" to "AIK" in the spelling of ZODIAC. If we place the 13 characters from the April 20th 1970 letter within a cipher wheel (shown above), forming an inner and outer ring, and then spin the inner wheel clockwise by 8 positions, the three circled 8's land over "ME" and the "crosshairs". The signature he chose to use in the "Exorcist" letter on January 29th 1974, created by a technique described by Poe in "A Few Words on Secret Writing".    

But how do we know that the three circled 8's are the key to solving the Z13 code? In the April 20th 1970 letter the Zodiac Killer wrote "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is....", followed by 13 characters. The next time the Zodiac used the verb "to crack", is when he told us he was crackproof in the 13-Hole postcard at the beginning of October 1970, five and a half months later. The Zodiac Killer stated "Fk I'm crackproof" and punched 13 holes into the fabric of the postcard. But just like the April 20th 1970 letter featured three circled 8's in a configuration of 13 characters, the postcard in October separated out three punch-holes from the other ten. These three punch-holes were positioned almost directly below the positions the three 8's slotted into the Z13 code (see below). In other words, pull the three 8's downwards from the Z13 code and you get the 10:3 configuration shown in the 13-Hole postcard.  

Was the Zodiac Killer highlighting the three punch-holes (888) from the total of 13 to show that these were the key to solving the "crackproof" Z13 code on April 20th 1970? In total, we have the three circled 8's generated by a cipher wheel from the "near Zodiac" in the 340 cipher, placed into the Z13 code five months later, which by using a cipher wheel once again, generated the signature of "Me" from the Z13 code, that is present as the signature in the Exorcist letter on January 29th 1974. The Edgar Allan Poe essay "A Few Words on Secret Writing", featuring the cipher wheel, the scytale method of cryptography, and the technique of splitting the alphabet into 13 characters, which are all integral to the solving of the 340 cipher and the possible design of the Z13 code, may very well have been chosen because of the challenge by Marsh on October 22nd 1969. He wanted the Zodiac Killer to send a cipher to The American Cryptogram Association that would honestly include his name. The murderer of five may have given Professor Marsh more than he bargained for.

On January 29th 1974, April 24th 1978 and October 27th 1987, the Zodiac signed himself "Yours truley" or "Yours truly" as an added signature. "Yours Truly" simply means "Me". Both were used in the Exorcist letter on January 29th 1974. "Yours truly" originated as a formal sign-off for a letter, a shorter version of phrases like "I am truly yours". Today, it is mostly used in a conversational or informal context to refer to oneself in a playful, humorous, or self-deprecating manner. I believe that when the Zodiac Killer mailed the April 20th 1970 letter and Z13 code, he gave us the answer of "My name is....Me" as a playful joke. He was taking the piss.

A solution created by converting ciphertext into plaintext from just 13 characters could never be verified, which is probably why he employed a different technique, inspired by the writings of Poe in Graham's Magazine in 1841. Those three circled 8's may have stood out for a reason. 
 
FOLLOW UP ARTICLE: THE SAME IDENTITY IN THE HALLOWEEN CARD 
FURTHER READING: AN IDENTITY DISCLOSED IN TWO LETTERS