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 

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

It is almost impossible to forge a solid connection to the Zodiac Killer from the Riverside communications, despite some interesting parallels, such as the trinity of letters mailed to the Riverside Press-Enterprise, Riverside Police and Joseph Bates in 1967 (and the Confession letters), foreshadowing a similar methodology in the Bay Area of northern California, with communications to the Vallejo Times-Herald, San Francisco Chronicle and San Francisco Examiner. Both sets of letters possibly containing the letter "Z" and giving us a common thread to "The Most Dangerous Game" and Count Zaroff of yesteryear.

​The two Confession letters mailed in 1966 stated "I am not sick. I am insane. But that will not stop the game" and "I am stalking your girls now", and offered us a message reminiscent of the flawed character traits of Count Zaroff and Erich Kreiger (A Game of Death, 1945), who were insane, heartless, and psychopathic men with a thirst for stalking and hunting human beings. The question being, were the Confession and Bates letters a precursor to the arrival of Zodiac on July 31st 1969, who boasted that "it was more fun than killing wild game in the forest because man is the most dangerous animal of all". A "game" that was played in Riverside, Benicia and Vallejo - and would continue into the middle half of 1971, with the "Z" of Count Zaroff seemingly never far away. 

The Zodiac Killer should have been unaware of the Bates letters in 1969 (and what some believe is a stylized "Z" signature), had he not been the author, so it may be noteworthy to point out the possibility of the 408 cipher being signed with the identity of "Z", present on the ring of Count Zaroff in "The Most Dangerous Game" (1932). The Zodiac Killer used the exact phrase uttered by Merian C. Cooper, the associate producer of the movie, when interviewed just prior to its release, by encoding the the words "man is the most dangerous animal of all" in his 408 cipher. So would it really be that unusual if he also encoded the letter "Z", taken from the main protagonist and big game hunter, in a story of unbridled madness? 

It is fairly clear that the Zodiac Killer made an error when taking his draft 408 message and separating it into three parts, missing out one complete row of seventeen characters when moving between his letters to the San Francisco Examiner and San Francisco Chronicle. The message on rows 17, 18 and 19 all began with the plaintext letter "E", so it is perfectly easy to comprehend how the Zodiac Killer accidentally skipped one row and left himself with 18 unwanted spaces rather than one. This is where I believe he intended to place his identity of "Z", synonymous with the villainous Russian aristocrat, Count Zaroff, who also enjoyed killing people for nothing more than entertainment.

On the left is the message he likely intended to encode, leaving us with "AFTERLIFEE" at the end of his cipher. The Zodiac Killer placed a dotted circle in the 391st position to give us the extra "E" in afterlife, so one could argue this was supposed to originally complete the 408 cipher and be the signature we had to work out. Only when the cipher key was understood, did it become apparent that the initial ciphertext character to represent the letter "E" in his cipher key was "Z". Whether this was the Zodiac's thinking is unclear, but the evidence is fairly compelling that he never intended to leave us a garbled message of 18 characters, that nobody has come close to explaining in over half a century. The massively interpretative quality of 18 jumbled letters should absolutely tell you that no definitive solution could ever be satisfactorily proven to be the correct answer - and as such - was never the intention of the Bay Area murderer, who was certainly no dummy. But the letter "Z" was, without doubt, an identity he would employ in later communications, with one additional key ingredient always present. This would show itself on October 27th 1970, when the Zodiac Killer selected his Halloween card with a specific message.       

The author of the typed Confession letters on November 29th 1966 claimed their insanity would "not stop the game" of murder, with the Zodiac Killer on July 31st 1969 bragging that killing people was "more fun than killing wild game in the forest", by taking his cues from "The Most Dangerous Game" (1932), where the letter "Z" both down south and up north, may have been the signature. Then came the Halloween card on October 27th 1970, in which the Zodiac Killer addressed Paul Avery and selected a card with the message "But, then why spoil our game", while visibly adding the letter "Z" to a communication for the first time, just 20 days prior to the Paul Avery article on November 16th 1970, informing us of the Bates letters from 1967 with a Z-like signature. Seven months later, another letter and cryptogram of 148 characters would be mailed to the San Francisco Chronicle newspaper, carrying the message "man is the most prized game", taken straight from the playbook of General Zaroff and "The Most Dangerous Game". This letter was signed with a sun cross, the ciphertext character representing the letter "Z" in the cipher. The Zodiac Killer only utilized the word "game" in three communications, on July 31st 1969, October 27th 1970 and May of 1971, with the letter "Z" plausibly embedded in the coding of two, and clearly present in a third. If the Zodiac Killer authored the communications in Riverside, it's possible he added a fourth - and may very well have been correct when he stated his insanity would "not stop the game", as many investigators had the misfortune to find out. 

Richard Connell book, The Most Dangerous Game (1924): "My dear fellow," said the general, "have I not told you I always mean what I say about hunting? This is really an inspiration. I drink to a foeman worthy of my steel--at last." The general raised his glass, but Rainsford sat staring at him. "You'll find this game worth playing," the general said enthusiastically." Your brain against mine. Your woodcraft against mine. Your strength and stamina against mine. Outdoor chess! And the stake is not without value, eh?"

Thanks to the recently unveiled FBI files regarding the disappearance of Donna Lass (25), last seen at the Sahara Tahoe Hotel & Casino on September 6th 1970 at 2:00 am, it is safe to say that Donna Lass was not abducted from the casino (or its parking lot) at the end of her shift, and didn't meet foul play by the hands of a random stranger, who intercepted her journey while she returned back to her apartment in the early morning hours (whether she was walking or in a vehicle).

Donna Lass had changed out of her nurse's uniform and into a navy blue slack suit shortly before her shift end at 2 am. These were the clothes the young woman was last seen wearing at the Sahara Tahoe Hotel & Casino, that were not found in her apartment by investigators, which may lead some to believe she never arrived home that morning. However, her purse (handbag for carrying personal items) was discovered in her apartment, containing money, her personal cosmetics and car keys, which almost certainly suggests she returned back to her home after leaving the casino. She may have walked home, or accepted a lift from somebody at the casino (or during her journey), but the important thing to remember here, is that her navy blue slack suit was missing, yet her purse wasn't.

Her 1968 Chevrolet Camaro was found outside her Monte Verdi apartments on 3893 Pioneer Trail Road by the South Lake Tahoe Police Department on September 13th 1970, which suggests, that had she met foul play that morning, we are still unable to rule out that she drove to work on September 5th 1970, and returned home in her car on September 6th 1970, knowing now her car keys were found in her purse inside the apartment. In absence of any confirmed sightings of Donna Lass after 2 am on September 6th 1970, the fact that her navy blue slack suit was never seen again, strongly indicates she didn't change out of these clothes after arriving home that morning. Especially when we consider a malicious phone call was received by the Sahara Tahoe Hotel & Casino on September 7th 1970, claiming falsely that Donna Lass had been called out of town for a family illness and would not be returning to work for a few days. This obviously means that Donna Lass met foul play between the time she returned to her apartment on September 6th 1970, to the time the malevolent call was made to the casino the following day (September 7th 1970). And it tells us that she never likely removed her navy blue slack suit and went to bed.

The private investigator's report stated that the mysterious caller identified himself as Mr. Davis (Donna's new landlord), which Nick Davis vehemently denied was him. It would have been extremely stupid to have murdered Donna Lass and then used your own name to excuse her absence due to family illness, that obviously would have been discovered in due course by investigators. If this was the case, the caller wasn't Nick Davis. But this detail about "Mr. Davis" was not mentioned in the FBI files, which only referred to the phone caller as an unknown male. Even if the caller mentioned no name, it is clear that this person was involved in the disappearance (and likely murder) of Donna Lass, who knew where she worked, and felt the need to buy time and phone the casino to excuse her absence.

A random killer (unknown to Donna Lass and living distant from her residence), who murdered her at the apartment or abducted her from it, has absolutely no need to make contact with the Sahara Tahoe Hotel & Casino and make a bunch of excuses. The only person who needs to buy time is somebody the police would have chosen to visit first, such as friends, neighbors  and work colleagues. Somebody who may have given Donna Lass a lift in the early hours of September 6th 1970, somebody who rode in her vehicle that morning, or somebody that visited her apartment after she arrived home from work. Somebody that killed or abducted her while she was still wearing her navy blue slack suit, who needed to confuse the timeline of her disappearance and murder. The clothes she left work in vanished alongside her, but her purse, that she almost certainly carried with her when she arrived at work on September 5th 1970, found its way back to her apartment on September 6th 1970.

​It appears as though Donna Lass met her demise shortly after leaving work and arriving home. Was it a co-worker or a resident at the Monte Verdi apartment complex at ​3893 Pioneer Trail Road? The final question is why did the "killer" make the phone call on September 7th 1970 and inform the casino that Donna had gone out of town, rather than phoning her workplace in the daytime hours of September 6th 1970. Was he aware that Donna Lass wasn't working on the evening of September 6th 1970, and had the day off? There can't be many other reasons why the perpetrator waited over 24 hours to phone the casino. If this was the reason, it may narrow the focus to somebody who was not only familiar with her profession, but to somebody who knew her work schedule, such as a friend or close work colleague. A person who didn't want this crime investigated as a murder and needed to make the body disappear.  

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