Professor D.C.B. Marsh told the San Francisco Examiner on October 22nd 1969: "The killer wouldn't dare, as he claimed in letters to the newspapers, to reveal his name in the cipher to established cryptogram experts. He knows, to quote Edgar Allen Poe, that any cipher created by man can be solved by man. Zodiac has not told the truth in his cipher messages to the Examiner, the Chronicle and the Vallejo Times-Herald. Zodiac has not done this, because to tell the complete truth in relation to his name - in cipher code - would lead to his capture. I invite Zodiac to send The American Cryptogram Association a cipher code - however complicated - which will truly and honestly include his name". According to Edgar Allen Poe, any cipher created by man can be solved by man. Which is why Zodiac created the apologetic "sorry no cipher".

The video has a minor error - the "rope" in the bottom right quadrant should look like the image on the left. Click to enlarge.

The following will be extremely speculatory and should not to be taken too seriously, but I wanted to examine the prompt by Professor D.C.B. Marsh who told the 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 Allen Poe, that any cipher created by man can be solved by man. Zodiac has not told the truth in his cipher messages to the Examiner, the Chronicle and the Vallejo Times-Herald. Zodiac has not done this, because to tell the complete truth in relation to his name - in cipher code - would lead to his capture. I invite Zodiac to send The American Cryptogram Association a cipher code - however complicated - which will truly and honestly include his name".

When recently promoting the notion of a killer providing us with all the solutions to his ciphers in Three Months After the Mount Diablo Code, it was considered that the Zodiac Killer did respond to Dr. Marsh, but he certainly wasn't going to be as forthcoming as to provide us with his full name as Dr. Marsh had honestly requested. Hence the idea that he did give us his name, albeit in the abridged version of his initials which he supplied to us in the October 5th 1970 '13 Hole' Postcard. When this was slotted into the April 20th 1970 '13 Symbol' Cipher it read like so: "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Fk, I'm crackproof". The Zodiac Killer had in effect answered the request of Dr. Marsh, although in a rather devious manner. However, Dr. Marsh issued this challenge on October 22nd 1969 and the 340 Cipher came before the 13 Symbol Cipher.     

One of the most prominent features in the 340 Cipher is the sixth line where he corrects a forward facing K to a backwards facing K, similar in nature to the way he reversed the "Fk, I'm crackproof" phrase on the 13 Hole Postcard. The proximity of F and K can be noted in these two outstanding features - and possibly the Zodiac thought it mildly amusing to provide his name to Dr. Marsh in the extremely "complicated" manner of reversing his name or initials. Everybody was searching for a stunningly complicated solution to the 340 character cipher as Dr. Marsh had requested, so the Zodiac Killer gave us the complete opposite.

The connection between the 13 Hole Postcard and 13 Symbol Cipher was not only bound in the "Fk, I'm crackproof" solution, but the two phrases he used in each communication didn't go unnoticed either. The Zodiac Killer inextricably tied the two correspondences together using similar phraseology, such as "What is the price tag now" and "how much money you have on my head now". On January 29th 1970, the Yellow Cab Company put up a thousand dollar reward for any information leading to the arrest of the Zodiac Killer. In addition, the Teamsters Union which represents the Yellow Cab Company were reported in the San Francisco Chronicle to be considering offering a further reward on February 8th 1970 in the case of Paul Stine and Charles Jarman (another taxicab murder victim). This news was likely what prompted the Zodiac Killer to open this communication with the words "I am mildly cerous as to how much money you have on my head now".  Or could there be another more subtle clue in these phrases with regard to his name?

Where on the April 20th 1970 letter and throughout much of his communications to date (including the 340 Cipher) could money or a price tag be found on a head? The 13 Symbol Cipher letter carried a dated 1966 Franklin D. Roosevelt stamp, where indeed "money" or a "price tag" could be found 'on' the head of Franklin D. Roosevelt. Was this a subtle hint to his first name of "Franklin" or "Frank". This would satisfy the F part of "Fk, I'm crackproof" - but as stated earlier,  very speculative to say the least.

Another communication where he promised us his name was the October 27th 1970 'Halloween' Card, in which he gave us an odd-looking symbol and placed it on the left side of the envelope and the Halloween Card inner, followed by the letter Z. The correct way to address an envelope is to write the sender's name and address in the top left corner of the envelope, shown here on a Youtube video, and the recipient address (in this case Paul Avery) in the center of the envelope. Therefore, this strange symbol could equate to the sender's name. Since we are looking for the initials of the Zodiac Killer (which may be reversed for a third time), it is extremely promising that we have an F looking character on the right side yet again. I don't like too much manipulation and the use of mathematics anymore, but on this occasion I will choose the path of least resistance and take the 7 and 4 dots to equal 11 (K being the 11th letter of the alphabet) - and therefore give us a joined K and F for his name on the return section of the envelope. Unfortunately, manipulation such as this always leads to the possibility of multiple solutions, so we have to be guarded to any conclusions we make. Finally, I would like to take a look at the sister card to the Halloween Card mailed in the December of 1990. It too promised us his name.       

The greeting card was again from our Secret Pal just like the Halloween Card twenty years earlier - it began with the message "FROM YOUR SECRET PAL CAN'T GUESS WHO I AM YET? WELL, LOOK INSIDE AND YOU'LL FIND OUT". Then promised to keep us guessing on the card inner.

All the Zodiac Killer added to the card inner was a Xerox copy of some "keys". It really couldn't be any simpler. The card outer stated "From your secret pal, can't guess who I am yet? Well, look inside and you'll find out" followed by "keys". This may very well be the final really complicated answer to the challenge laid down by Dr. Marsh all those years earlier. The surname of Keys, Keyes or Keays would satisfy the K of FK, from the phrase "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Fk, I'm crackproof".

This mocking response to Professor D.C.B. Marsh, who requested that the Zodiac Killer "send The American Cryptogram Association a cipher code - however complicated - which will truly and honestly include his name" was probably befitting of the Zodiac Killer. The answer may have been simpler than we could ever of imagined. Return to sender: Franklin Keys (or alternate options above).

Of course, I am not claiming this to be the answer regarding the identity of the Zodiac Killer, but it would be rather appropriate for the Zodiac Killer to have begun his letter writing campaign with Franklin on the stamps of his July 31st 1969 trinity of communications, and ended with his surname of Keys in 1990 - and thumb a finger to all the cipher experts trying vainly to crack his extremely complicated ciphers, when the answer was literally staring us in the face all along. 

The Zodiac Killer gave us the answers to his six unsolved ciphers by March 13th 1971 without ambiguity, but effectively gave us all the answers by October 27th 1970. It is important to read Three Months After the Mount Diablo Code to understand all of the following, but I shall give a very brief recap. The Zodiac gave us the answer to the Mount Diablo code (32 symbol Cipher} in the Little List Letter on July 26th 1970. In fact, he gave us the answer word for word, in the form of Radians and 5 inches along the radians (all we had to do was add the number 5 where he placed the arrow and hashtag}. The 13 Hole Postcard on October 5th 1970 gave us the answer to the 13 Symbol Cipher word for word, in the form of Fk I'm crackproof. The Halloween Card on October 27th 1970 gave us the answer to the 340 Cipher word for word, in the form of Paradice and Slaves. No mathematics was required and no manipulation was needed - all we had to do, was use the three phrases that Zodiac provided us with in three consecutive communications, to answer the three previously unsolved ciphers. But that wasn't all. The Zodiac gave us the answer to both the Fairfield Letter codes of December 7th and 16th of 1969, again word for word using the Halloween Card. The 18 unsolved characters in the 408 cipher he again gave us the solution word for word, using the trinity of communications on July 31st 1969 and following letter on August 4th 1969, when he revealed his pseudonym to the world. However, there is even more.

The Zodiac Killer's 408 Cipher was effectively a written message that he enciphered into characters. When you take a look at the decoded message, it isn't structured and organized - because one line or row bleeds into the following. The Zodiac Killer didn't contain his words within the confines of one row. For example, when he opened the cipher with "I like killing people", the letter E is positioned at the beginning of the second row. This randomness is not displayed in the answers to his remaining six unsolved portions of code. The answer to the 18 unsolved characters, the 340 Cipher, the two Fairfield letters, the 13 Symbol Cipher and the 32 Symbol Cipher are all organized and deliberately structured, where every single solution and word is contained within each line - and does not leak from one row to another. Let us take a look at the 13 Symbol Cipher that exhibits symmetry within its design.             

I don't have to explain the above, because its structure and symmetry is there for all to see. The Zodiac Killer had already responded to prompts by Vallejo Police Chief Jack Stiltz to send more details to prove the letter writer and killer were one and the same. The more the Zodiac Killer wrote, not only lessened his time for killing, but may have provided additional clues to detectives regarding his identity. This tactic was likely adopted by Professor D.C.B. Marsh in the October 22nd 1969 San Francisco Examiner newspaper article by Will Stevens, which laid down a challenge to the Zodiac Killer to reveal his name. The newspaper stated Dr Marsh told the Examiner today: "The killer wouldn't dare, as he claimed in letters to the newspapers, to reveal his name in the cipher to established cryptogram experts. He knows, to quote Edgar Allen Poe, that any cipher created by man can be solved by man. Zodiac has not told the truth in his cipher messages to the Examiner, the Chronicle and the Vallejo Times-Herald. Zodiac has not done this, because to tell the complete truth in relation to his name -in cipher code - would lead to his capture. I invite Zodiac to send The American Cryptogram Association a cipher code - however complicated - which will truly and honestly include his name".

The above invitation by Dr. Marsh, quoting Edgar Allen Poe, was met with the 13 Symbol Cipher that mirrored a code used in Poe's A Few Words on Secret Writing. The alphabet being split A to M, and N to Z. The 13 Symbol Cipher began with A and ended with M. So it was logical to place the alphabet alongside the 13 Symbol Cipher and see if any patterns emerged by counting the numerical difference between corresponding characters. This resulted.

I don't want to labor the point again, so for a full explanation please visit the article Embedded Symmetry  Suffice to say, that when the Zodiac's solution or answer to the 13 Symbol Cipher was inserted into the code above, it showed an organized and structured pattern without a word bleeding from one end of the cipher to the other. The Zodiac Killer gave us the cyclical solution of Fk I'm crackproof on October 5th 1970, and followed this up with the line "This is the Zodiac speaking Like I have allways said, I am crack proof" on March 13th 1971. But in the Los Angeles Letter you will notice he separates "crackproof" to "crack proof", exactly how it is found in the 13 Symbol Cipher. It does not bleed from the end of the cipher to the start.

The first 8 begins FK. The second 8 begins IM. The third 8 begins CRACKPROOF. But CRACK and PROOF are separated, without either word being fragmented. The FK and IM also fit nicely around the existing K and M in the cipher. The cipher solution maintains an organized and symmetrical appearance. The introduction on the April 20th 1970 letter now read "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Fk, I'm crackproof". He was leading us into the belief these were his initials.

The Paradice and Slaves configuration from the Halloween Card to the 340 Cipher also exhibited form, with Paradice exactly bisecting the columns of the 340 Cipher, and Slaves exactly bisecting the rows of the 340 Cipher in a 17 X 17 pattern. Each word contained within a row or column. The Halloween Card envelope providing us with "sorry no cipher" in a cross formation, not only telling us that the 340 wasn't a standard cipher, but the design of the 340 was to be found in a cross formation.

The 32 Symbol Cipher also adhered to a solution where no word bled from one row to another. The 32 Symbol Cipher contained two rows of 17 and 15 characters - obviously created this way for a purpose. When we discovered that the number 5 was to be inserted into the cipher using the arrow and hashtag, the answer of Radians and 5 inches along the radians again fell perfectly into the 32 Symbol Cipher with no word extending from one line to another. You will notice that when the Zodiac Killer provided us with the answer in the July 26th 1970 Little List Letter, he self-contained the answer on a separate line, with the first Radians beginning with a capital letter. This was the beginning of the code solution.

"PS. The Mt. Diablo Code concerns Radians and # inches along the radians" was in fact Radians and 5 inches along the radians. When this is placed into the 32 Symbol Cipher, you will notice that once again it retains separation, with "inches" ending line one, and "along" beginning line two. Each word is contained within the line. This organization and structure flies in the face of the solved portion of the 408 Cipher and implies a deliberate and calculated design. But we need to take it even further.

Explained in greater detail in the article The Answer to the Z38 Code, the structure of the Zodiac 38 character cipher was pointed out. The code below has been structured with different character counts on each line (unlike the 408 and 340 ciphers), but is instead arranged in a formation of 12 characters on line one, 7 characters on line two, 5 characters on line three, 6 characters on line four and 8 characters on line five. This may suggest that the words are contained separately on each line, without running from one line to another. We would expect Slaves and Paradice to be grouped together - and the last two lines satisfy this character count of 6 and 8. We then have three lines remaining of 12, 7 and 5 characters. By Gun satisfies the 5 characters, By Knife satisfies the 7 characters, and By Fire, By Rope satisfies the 12 characters. This forms the basis of the completed 38 character code solution, mimicking the second Fairfield Letter design and the exact wording on the Halloween Card configuration. Furthermore, no word extends from one line to another, exactly as displayed in the above codes.

So far (including the Tim Holt comic book unearthed by Tahoe27), every single solution or answer to the ciphers can be achieved using the exact words employed by Zodiac from three consecutive communications spanning July 26th 1970 to October 27th 1970. [1] Radians and 5 inches along the radians [2] Fk I'm crackproof [3] Paradise and Slaves, and [4] By Fire, By Gun, By Rope, By Knife, Paradice and Slaves. And none extend or bleed into another line, or from end to beginning in the 13 Symbol Cipher. That is five ciphers down with one to go. 

The Zodiac Killer claimed that his 408 Cipher contained his identity or pseudonym. What was important to the Bay Area murderer was the structure exhibited by all the above codes. The characters he used were of no particular significance, because they weren't designed to be solved without future Zodiac input. This input came towards the end of his letter writing campaign, when he supplied us all the answers in just three consecutive communications. He was effectively wrapping up business. There was no way a man with such an inflated ego and inability to resist writing to the newspapers, could keep the secret to his ciphers for upwards of five decades. The answer to the 408 Cipher was given to us in just four days, contained in the trinity of July 31st 1969 letters and the August 4th 1969 'Debut of Zodiac' Letter. He claimed his identity was in the 408 cipher - and we know his identity was "Zodiac" because he gave us his pseudonym. All we then had to do, was fit Zodiac around the declaration of who he was. 

Initially, the Zodiac Killer had intended to leave 12 characters at the base of the 408 Cipher, but his accidental omission of the word "people" when he encoded his message, inadvertently left him with 18 unsolved characters. However, this was of no consequence - it was an easy adjustment. You will notice again, that the unsolved 18 characters are split into an ungainly 1 and 17 configuration. If we are to hold true to single words not bleeding from one line to another, then the single character must stand for I or A. We know that the Zodiac Killer was an egotist, beginning the 408 Cipher with "I like killing people because it is so much fun". He also began two of the July 31st letters with "I am the killer". So it wouldn't be any great leap of faith to believe that the isolated singular character on line 23 was "I". Coupling the "Zodiac" with "I am the killer" to produce "I am the Zodiac Killer" satisfies his declaration of identity and the 18 characters at the base of the 408 Cipher. We again have used only the words written by the Zodiac Killer - and no word extends from one line to another. The third of code containing his identity was mailed to the San Francisco Chronicle, which is why he began that introduction with "This is the murderer". He was reserving "I am the Zodiac Killer" for the base of the 408 Cipher.  

We now have six unsolved portions of code answered, using only the words written by the Zodiac Killer in a total of four communications. Every single answer was organized and structured to remain within each row, line and column with no manipulation whatsoever. We can wait another 50 years for these codes to be "solved" - or believe they were all answered by October 27th 1970 from the pen of the Zodiac Killer.

A pasted card, mimicking the 13 Hole Postcard was mailed to the home address of Dr. Edward C. Adams at 102 Camino Don Miguel, Orinda, California, postmarked October 17th 1970 from Berkeley. Edward C. Adams was a psychiatrist. The card read

"Mon Oct 12, 1970. Edward Adams. The Zodiac is going to change the way of committing murders. I shall announce when I shall commit my murders, The Adamses are Next. you taught me to mean it. ADAMS YOU ARE NEXT. Zodiac".

The Gladman Hospital where Richard H. Adler worked is today listed as a Psychiatric Health Facility in Oakland. Telecare was founded by psychiatrist, Art Gladman in 1965. The Gladman Hospital was a traditional psychiatric hospital back in 1976,  extremely interesting and noteworthy, bearing in mind the FBI file concerning the Edward C. Adams Letter (shown below), which indicates Dr. Adams informed Inspector David Toschi of his belief that the threatening letter he received was sent by a former psychiatric patient who resided in Berkeley. The city of Berkeley lies on the east shore of San Francisco Bay in northern Alameda County, adjacent to Oakland.

"Edward C. Adams spent most of his life in the Bay Area where he attended the University of California Berkeley for his undergraduate work and Stanford University for his medical degree. His residency in psychiatry was received at the Menninger Clinic, Topeka, KS. During the Korean War he was an instructor in the Medical Field Service at Fort Sam Houston, San Antonio, TX. After retiring from an active practice in Psychiatry he devoted his energies to travel, fly fishing, the study of poetry and the enjoyment of his family and many friends. During the time spent at his Carmel home he volunteered as a docent at the Robinson Jeffers Foundation. He was a member of the San Francisco Psychoanalytic Society and an active supporter of many environmental groups".  SFGATE.COM.

The San Francisco Center for Psychoanalysis was organized in 2007, combining the San Francisco Psychoanalytic Institute & Society, founded in 1941, with the San Francisco Foundation for Psychoanalysis, founded in 1991. The Center provides an extensive training program in psychoanalysis. The Center also sponsors a large, vibrant Extension Division which offers classes and seminars to mental health professionals as well as to the general public. The San Francisco Psychoanalytic Society and Institute is a facility for psychoanalytic research, training, and education located on 2420 Sutter Street in San Francisco, California. It is situated in Lower Pacific Heights, approximately one mile from the intersection of Washington and Cherry.

It can be seen on the map below that Gladman Hospital (Mental Health Rehab) is only 6.5 miles from Orinda, 6.3 miles from Berkeley and 12 miles from 2420 Sutter Street. In summary, we have two communications sent six years apart, containing the phrases "You are next" and "You're next", both likely to psychiatrists, who lived and worked in close proximity to one another, and who both were addressed by the name "Zodiac" in the message. And one had the initials R.A. 

Edward C. Adams and Richard H. Alder may have crossed paths in their profession of psychiatry, either at the San Francisco Foundation for Psychoanalysis or their places of work, and the personal ad stating "Your partner is in deep real estate" may have been referencing Edward C. Adams as a man in deep trouble, using the word partner as "business partner", or in a more loose term, as a "partner in the same profession". Bearing in mind the almost identical threat six years earlier to somebody in the same profession, this seems a distinct possibility.

In a previous article we showed with a high degree of probability that the 13 Hole Postcard mailed on October 5th 1970 was connected to the as yet unpublished Little List Letter through its wording, and therefore both were authored by the Zodiac Killer. Most people accept that the Little List Letter is authenticated Zodiac correspondence, so by extension, if the October 17th 1970 Edward C. Adams Letter and "Deep Real Estate" Letter were authored by the same person, and we can connect the two pasted letters in October 1970, then we can verify Zodiac was responsible for all. This would mean that Edward C. Adams suspicions that the letter mailed to his home address in Orinda by a former psychiatric patient who resided in Berkeley, could have been the Zodiac Killer.        

On the flip side, Richard H. Adler may have been addressing Zodiac, or somebody claiming to be the Zodiac Killer.

The following article will coalesce several pieces of work from 2019 into one cogent story regarding a handful of communications mailed by the Zodiac Killer in 1970. For some, the following will be repetitive, for which I apologize. It will hopefully make the case that the Zodiac Killer was winding down his operations and ultimately revealing the answers to his Z340, Z32 and Z13 ciphers and codes, to which he knew were practically unsolvable without such a prompt. The Zodiac Killer was a narcissistic braggart, who boasted of his exploits and threatened all and sundry with the possibility of more murders and mayhem if his demands were not met, including the claim he had killed far more than could be accounted for. If we applied the same model to his ciphers and codes, we would have expected him to be unable to resist giving us the answers - or at the very least - some clues to break open his puzzles. The notion of a killer keeping deathly silent on the solutions to his codes for up to 50 years, runs contrary to everything we know about the Bay Area murderer during his brief but deadly reign. That is why I don't believe he did.

The story begins with the final thing he wrote on the July 26th 1970 Little List Letter, and finishes just two communications later with the October 27th 1970 Halloween Card. All the answers to his codes were contained in just three short months. The end of the Little List Letter read "PS. The Mt. Diablo Code concerns Radians and # inches along the radians". The Z32 was the easiest code to crack because the Zodiac Killer just gave us the answer above - the code concerned "Radians and inches along the radians". Why make it any more complicated than it has to be? A code of 29 unique symbols within a total of 32 characters is simply not solvable without a key - and there is insufficient wording on the 13 Hole Postcard, Halloween Card or Los Angeles Letter written in plain English to formulate any such key. The Z32 is even worse than giving us the English alphabet of 26 letters, replacing M with A, W with B and H with C and saying "now solve it". There is no transposition key present in the remaining three communications from October 5th 1970 to March 13th 1971, so if the Zodiac Killer was to be consistent in his inability to resist revealing his deeds, then the only realistic alternative is he gave us all the answers instead.

Not only did the Zodiac Killer give us the answer to the 32 character code on a separate line, he capitalized the first "Radians" to effectively tell us this was the beginning of the solution (he didn't capitalize the second "radians", so why the first). You need look no further than the Paul Stine police report to notice that the hashtag symbol is used in conjunction with a number. The Zodiac Killer by use of an arrow pointer underneath the hashtag, was telling us to replace the hashtag with a number value. The Mount Diablo map scale was 6.4 miles to the inch, so it is probably unsurprising that the "Mt Diablo code would concern inches". In this instance, I have placed the number 5 into place, giving us the answer to the code of "Radians and 5 inches along the radians" (which is 32 letters in length). The reason for 5 inches is self explanatory, because 4 or 6 inches from Mount Diablo to San Francisco would fall into the sea on the east and west side. The San Francisco element will be covered shortly. The Zodiac Killer also gave us a second set of crosshairs (shown below).

This was the first time the Zodiac Killer had ever placed an accentuated zero within his crosshairs alongside the acronym SFPD. This had to be the second clue to the location of the bomb. The hashtag and arrow signified the value of inches required, so this had to signify the radian value. By some massive stroke of luck (almost beyond belief), the bold, black accentuated circle fell over 246 degrees on a compass rose - which is 4 radians and magnetic north (17 degrees in 1970). Therefore, the target of his bomb must have been 4 radians and magnetic north, and 5 inches along the radians. 

All Zodiac's bomb threats were focused towards the San Francisco Chronicle and San Francisco Police Department, so placing this bomb location alongside the acronym SFPD should tell us that the threat was most likely focused toward a police station. By another massive stroke of luck, when we travel 4 radians and 5 inches from Mount Diablo, the target area for the bomb lies right by Ingleside Police Station. Allowing for a degree of flexibility of less than 1%, by the Zodiac Killer rounding off his radians and inches, along with the black circle diameter, no other San Francisco police station comes close. However, we need to find a location where a school bus would be traveling from north to south (with the sun to the east), that has an embankment on the right side (as displayed on the April 20th 1970 bomb diagram), with easy and covert access to that embankment, and within a few hundred feet from Ingleside Police Station. The Zodiac Killer certainly wouldn't have wanted to attract attention by parking on the road itself, but by accessing the incline from a secondary location - likely at the top of the embankment - he could achieve this task in relative anonymity. Fortunately for us, that location sits only 230 feet from Ingleside Police Station. The perfect location for the Zodiac Killer to target a school bus and thumb his nose at the San Francisco Police Department, with covert access to the top of the embankment via the car park of San Francisco City College.             

Then came the 13 Hole Postcard punched in the style of a 'Dick Tracy' code with a "red crucifix decoder". What are the chances that if we arranged the 13 holes into the shape of a cross and place it over the midsection of the 340 cipher both horizontally and vertically, it would reveal the wording "paradice" and "slaves"? Then, what are the chances that the Zodiac Killer would write "paradice" and "slaves" in his next communication in a cross formation on the card, accompanied by "sorry no cipher" in a cross formation on the inside of the Halloween Card envelope? - totaling three cross formations - but supposedly, all created for absolutely no reason whatsoever in just two communications. Isn't it more believable they were created for purpose. The Zodiac Killer could easily have written "sorry no cipher" just the once, but deliberately fashioned it this way to tell us that the 340 character cipher was not a cipher after all. It was simply a design of "paradice" and "slaves" as exhibited by the Halloween Card. Throw in a few bigrams, pivots and 'corrected sixth line', and hopefully it will look convincing. 

All these clues from the back end of the Little List Letter to the Halloween Card giving us the literal answer to both the Z340 and Z32 in "paradice" and "slaves", and "Radians and 5 inches along the radians". Could either the 13 Hole Postcard or Halloween Card give us the answer to the Z13 as well? Again, totally unsolvable because of its limited number of characters, the Zodiac Killer could either keep quiet for up to fifty years or give us the answer.

From a previous article: On January 29th 1970, the Yellow Cab Company put up a thousand dollar reward for any information leading to the arrest of the Zodiac Killer. In addition, the Teamsters Union which represents the Yellow Cab Company were reported in the San Francisco Chronicle to be considering offering a further reward on February 8th 1970 in the case of Paul Stine and Charles Jarman (another taxicab murder victim). The April 20th 1970 letter gave us the code and was immediately followed by "I am mildly cerous as to how much money you have on my head now". The October 5th 1970 postcard gave us the possible solution of "Fk, I'm crackproof" and was immediately followed by "What is the price tag now". These are the only two communications in which the Zodiac Killer asked the police the price of his capture. These two communications not only had a code and an answer that fitted the code, but both were followed by the exact same question. When the Zodiac Killer was designing his 13 Hole Postcard, it is very likely he had at his disposal a copy of his original April 20th 1970 letter, or the San Francisco Chronicle newspaper cutting below, to which he was now supplying the answer. This may have been the trigger that influenced him to repeat the phrase "how much money you have on my head now" into the very similar "What is the price tag now". The Zodiac Killer, in essence, had inadvertently bound both communications together through phraseology, as well as code and solution.   

The Zodiac Killer introduction would now give us his name (albeit his initials) in absence of his full name. It would also read fluently as a sentence, as follows: "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Fk, I'm crackproof". Nobody realistically believed he was going to supply his full name, but this way he satisfies the promise in a restricted format. Two communications mailed nearly six months apart, with a solution that satisfies the code, as well as a satisfactory introduction to the code - and both followed by the same question.    

The three 8's (representing Jesus Christ in gematria), along with the number 8 which symbolizes a new beginning, actually begins each element of the phrase Fk I'm crackproof. In addition, when we begin the phrase on the first 8, it fits perfectly around the existing K and M already present in the code and thereby creating a cyclical format, where the code ends and begins with the same letter. The Little List Letter provided the solution to the Button Letter and Mount Diablo code that preceded it. His next communication, the 13 Hole Postcard, provided the solution to the 13 Symbol Cipher before that, and finally the Halloween Card provided the solution to the 340 cipher. Three chronological solves to the three previous ciphers - and the only thing we had to add was the number "5", for which he inserted the hashtag and arrow. Why look for convoluted and excessively complicated solutions to these ciphers, when the Zodiac Killer gave us all the answers literally word for word.

This isn't a case of dragging wording from the entire Zodiac collection of cards and letters, but using just the two crosshairs of the Little List Letter, followed by the 13 Hole Postcard and Halloween Card. The bold, black circle and "PS. The Mt. Diablo Code concerns Radians and # inches along the radians" to answer the Z32. The 13 holes, red cross, "paradice" and "slaves", and "sorry no cipher" to answer the Z340. And finally, "Fk, I'm crackproof" to give us a shorthanded version of his name, while still retaining his anonymity. The alternative is that the codes are genuine, the designs on the 13 Hole Postcard and Halloween Card are devoid of any purposeful meaning, and the big-headed, braggart called Zodiac, kept his lips 'butoned' for however many years afterwards.  

FOLLOW UP ARTICLE:
THE ANSWER, ORGANIZATION AND STRUCTURE OF THE SIX UNSOLVED CODES

The 13 Symbol Cipher is simply too short for any meaningful decryption without a key or the answer. It is certainly possible to arrive at the correct solution using a key provided by Zodiac, but then you have to prove that the key you have found is the correct one, and your implemented methodology is plausible. The best way to find the solution to the Z13, as it was for the 32 Symbol Cipher, is to do absolutely no work whatsoever and just let the Zodiac Killer give us the exact answer. On this occasion, the Zodiac Killer designed the code and waited nearly six months to supply us with a verbatim solution.

The first thing to examine in the 13 Symbol Cipher is the circled triple 8 configuration. This is the feature that stands out in the code the most and where one would envisage the answer residing. Identify the meaning of the three eights and in what context they were chosen, and half the battle may be won. We can add the numbers up to create birth years and ages, but without instruction to do so, it could be argued that the idea rests in our head and not the Zodiac's. Therefore, we shall take the number 888 as one complete entity.

In Christian numerology, the number 888 represents Jesus, or sometimes more specifically Christ the Redeemer. This representation may be justified either through gematria, by counting the letter values of the Greek transliteration of Jesus' name, or as an opposing value to 666, the number of the beast. Wikipedia. This could indicate a Christian element to the code, especially when we consider the Zodiac's Celtic Cross, a form of Christian cross featuring a nimbus or ring that emerged in Ireland and Britain in the Early Middle Ages. The shape, usually decorated with interlace and other motifs from Insular art, became popular for funerary monuments and other uses. Then we have the tenth character in the code, likened to an upside down Aries symbol. However, when we consider the above and the Zodiac Killer's musings of an afterlife, another possibility emerges. Christians adopted the anchor as a symbol of hope in future existence because the anchor was regarded in ancient times as a symbol of safety. For Christians, Christ is the unfailing hope of all who believe in him: Saint Peter, Saint Paul, and several of the early Church Fathers speak in this sense. The Epistle to the Hebrews 6:19-20 for the first time connects the idea of hope with the symbol of the anchor. Wikipedia. This effectively ties five of Zodiac's characters under the Christian banner and the premise of an afterlife.   

On January 29th 1970, the Yellow Cab Company put up a thousand dollar reward for any information leading to the arrest of the Zodiac Killer. In addition, the Teamsters Union which represents the Yellow Cab Company were reported in the San Francisco Chronicle to be considering offering a further reward on February 8th 1970 in the case of Paul Stine and Charles Jarman (another taxicab murder victim). The April 20th 1970 letter gave us the code and was immediately followed by "I am mildly cerous as to how much money you have on my head now". The October 5th 1970 postcard gave us the possible solution of "Fk, I'm crackproof" and was immediately followed by "What is the price tag now". These are the only two communications in which the Zodiac Killer asked the police the price of his capture. These two communications not only had a code and an answer that fitted the code, but both were followed by the exact same question. When the Zodiac Killer was designing his 13 Hole Postcard, it is very likely he had at his disposal a copy of his original April 20th 1970 letter, or the San Francisco Chronicle newspaper cutting below, to which he was now supplying the answer. This may have been the trigger that influenced him to repeat the phrase "how much money you have on my head now" into the very similar "What is the price tag now". The Zodiac Killer, in essence, had inadvertently bound both communications together through phraseology, as well as code and solution.   

The Zodiac Killer introduction would now give us his name (albeit his initials) in absence of his full name. It would also read fluently as a sentence, as follows: "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is Fk, I'm crackproof". Nobody realistically believed he was going to supply his full name, but this way he satisfies the promise in a restricted format. Two communications mailed nearly six months apart, with a solution that satisfies the code, as well as a satisfactory introduction to the code - and both followed by the same question.  

THE ANSWER TO THE 32 SYMBOL CODE - STRAIGHT FROM THE HORSE'S MOUTH

This has been covered before, but I just wanted to expand in a little more detail without pinpointing a particular location.

How embarassing is the notion of a 50-year-old unsolved cipher, that we were given the answer to in just thirty one days? - and an answer that came straight from the horse's mouth. The 32 Symbol Cipher solution was served to us on a silver platter in the July 26th 1970 Little List Letter using the Zodiac crosshairs and six words. 

When the Button Letter was mailed on June 26th 1970, the Zodiac Killer gave us a map of San Francisco and Vicinity with his crosshairs centered over Mount Diablo, stating "the map coupled with this code will tell you where the bomb is set." If we were to find a perceived bomb, it is fairly obvious we have to travel a certain angle and distance from the top of Mount Diablo to find the location. Therefore, the 32 symbol code, if it served any purpose whatsoever, had to contain a measurement in the form of degrees and distance. The map scale was 6.4 miles to the inch - so that will be the distance the Zodiac Killer has to employ from Mount Diablo to make any sense. The degrees he used was radians, because he told us so in the July 26th 1970 Little List Letter. The Zodiac stated "P.S. The Mt. Diablo code concerns Radians + # inches along the radians". He is actually telling us that the 32 symbol code contains radians and inches in the solution.

"P.S. The Mt. Diablo code concerns (is about ) (has to do with) Radians + # inches along the radians". Any cipher expert such as David Oranchak, or quite frankly, any Joe Bloggs such as myself, will tell you that a 32 symbol code with only three repeating characters is unsolvable without a key. The Zodiac Killer was certainly no muppet - and clearly knew this when he concocted this jumble of random characters. But he gave us the key a mere 31 days later in the form of an arrow and a hashtag. He even gave us the answer of "Radians and # inches along the radians" on a separate line to distinguish the very fact. He then began the first "Radians" with a capital letter to emphasize this. We just had to key in the number. The symbol # is most commonly known as the number sign, The symbol is described as the "number" character in an 1853 treatise on bookkeeping, and its double meaning is described in a bookkeeping text from 1880. The instruction manual of the Blickensderfer model 5 typewriter (c. 1896) appears to refer to the symbol as the "number mark". Some early-20th-century U.S. sources refer to it as the "number sign", although this could also refer to the numero sign. A 1917 manual distinguishes between two uses of the sign: "number (written before a figure)"; and "pounds (written after a figure)". Mainstream use in the United States is as follows: when it prefixes a number, it is read as "number", as in "a #2 pencil" (indicating "a number-two pencil"). The one exception is with the # key on a phone, which is always referred to as the "pound key" or "pound". Thus instructions to dial an extension such as #77 are always read as "pound seven seven". Wikipedia.

All of Zodiac's bomb threats were mailed to the San Francisco Chronicle newspaper - even detailing the murder of San Francisco police officer Brian McDonnell on February 16th 1970, who suffered devastating and sadly fatal injuries when a bomb packed with fence staples exploded on an outside ledge of Park Police Station in the Upper Haight neighborhood of San Francisco. The Zodiac constantly signed off his communications with the barbed acronym SFPD = 0 and threatened "there is more glory in killing a cop than a cid because a cop can shoot back". If that wasn't enough, the Phillips 66 Road Map was labelled San Francisco and Vicinity.  Based on a map scale of 6.4 inches to the mile, only 5 inches would land in San Francisco (4 and 6 inches would fall into the sea, other than Treasure Island). Fortunately, the Zodiac Killer gave us the angle from Mount Diablo, courtesy of his bold, black circle on the Little List crosshairs. It fell 4 radians (and magnetic north) clockwise from his arrowed pointer, around the clock face he provided. Radians are usually measured counter-clockwise, but the Zodiac Killer placed the bold circle exactly 4 radians "set to Mag.N" clockwise.

The answer was now extremely simple. All we had to do was insert a number in place of the hashtag, shown by the big flashing arrow pointing us in the right direction. The hashtag conveniently preceded "inches", so it's here we will slot in the number 5 - and bingo - we have our answer to the devilishly difficult 32 Symbol Cipher: "Radians + 5 inches along the radians" or "Radians and 5 inches along the radians".  By some quirk of fate, this phrase with the addition of the number 5, just happens to be exactly 32 characters in length. What an absolute criminal mastermind the Zodiac Killer was, creating a code that we only had to add one character to. As with all the best puzzles, the answer is usually hidden in plain sight. There is a possibility that the code reads "4 radians and 5 inches along the radian", but because the Zodiac Killer inserted one hashtag, it is more likely this is the only addition required.        

In the Little List communication it is apparent that Zodiac Killer gave us two prominent crosshairs: [1] with the accentuated black circle with SFPD=0 alongside, and [2] the extra large crosshairs with "P.S. The Mt. Diablo code concerns Radians + # inches along the radians" scrawled across it. Attaching these important additions was clearly done for purpose, thereby informing us of the radian value required, and the correlation between the crosshairs on the Phillips 66 Map and the measurements of radians and inches. The importance of a second set of crosshairs and their position, regarding the solution of the 340 cipher on November 8th 1969 could be significant in that case also.

With 29 unique characters in a 32 character code, any correlation between the characters and alphabetical solution is going to be minimal. What we do have in the solution above, is no word running from one line to the next, with the letter C beginning the word radians at the start and end of the code. As with any cipher, the Zodiac Killer had the opportunity to provide us with a key in later communications, which he effectively did for cipher 2, 3 and 4 when he gave us the answers literally word for word. What we have to consider are the three "cryptic messages" he gave us in three consecutive communications from July 26th 1970 to October 27th 1970. The Zodiac Killer was giving us the solutions to the ciphers before his campaign ended, albeit he wanted us to put in a modicum of effort. He told us on July 26th 1970 that the Mount Diablo code concerns "radians and 5 inches along the radians" verbatim. He then gave us the cryptic "Fk I'm crackproof" that fortunately slots nicely into the 13 Symbol Cipher in a cyclical nature. And finally, he gave us "paradice and slaves" in a cross formation (17X17) that mimicked the 340 cipher formation exactly (adding sorry no cipher in the identical formation on the Halloween envelope inner). How can three consecutive "cryptic messages" just happen to seamlessly fall into each cipher with no effort required?

We can place thousands of names into the 13 Symbol Cipher and then attempt to justify why this is correct by providing additional information on the subject. There have been hundreds of "solutions" to the 340 cipher, when we know only one can realistically be correct. This demonstrates the subjectivity of the 340 cipher to conform to what you had already decided upon before the decoding process began. You have the predetermined answer in your head and work towards that goal to the exclusion of all others. Our own biases will govern the answer we require. The 32 Symbol Cipher is too character variable to be decoded using standard cryptographic techniques, and therefore can literally give rise to an infinite number of possibilities, requiring only three characters to match. What better way to solve the ciphers than straight from the horse's mouth. The Zodiac Killer supplied us with 32 characters in the Little List Letter, 14 characters in the 13 Hole Postcard (that began and ended in the same letter), and 13 characters in the Halloween Card - all of which required no 'square pegs in round holes' technique to land unadulterated into every cipher. The notion of a braggart remaining tight-lipped about his ciphers, while still staggering around the streets of America some 50 years later, deserves a book all by itself.  

THE CODE SOLUTIONS BY ZODIAC

The Zodiac Killer mailed us three parts of one cipher on July 31st 1969, to the San Francisco Chronicle, San Francisco Examiner and Vallejo Times-Herald. In his communication to the Chronicle he stated "In this cipher is my idenity". Bearing in mind this is the only portion of cipher with unsolved characters, it could be argued that any identity the Zodiac was offering would be found at the signing off phase in this cipher. It didn't really matter, because only four days later he gave us his identity in the form of "This is the Zodiac Speaking". The Zodiac Killer clearly made a mistake when taking his draught message into his 408 cipher, accidentally omitting the word "people" from the final offering. If we therefore conclude his original identity to be left was actually six characters shorter, it would have reduced the 18 unsolved characters to 12. Using the first-person singular pronoun of "I", his identity at the base of the 408 cipher would read "I am the Zodiac", to become "I am the Zodiac Killer" upon realization of his mistake. The Bay Area murderer literally gave us the exact wording to his unsolved 18 characters through his introductions in the Examiner and Herald letters (both communications began with "I am the killer"). Once we knew the pseudonym or identity as Zodiac on August 4th 1969, the conversion to "I am the Zodiac Killer" was the next logical step. This would become a habit for the Zodiac Killer, who would ultimately give us the exact wording to solve his remaining three ciphers. Not only would he give us the solutions to the codes, but his practice of using 'filler' with no apparent correlation to the solution would continue.  

The Zodiac Killer was no master criminal in the style of Moriarty, but he was nobody's fool either. To make the false assumption he didn't understand ciphers or codes when creating his remaining three offerings to the San Francisco Chronicle, would be a misguided one. Even somebody with limited knowledge of coding, knows that giving us a 32 character code with 29 unique characters within its framework, is practically unsolvable without a key. You can literally fill in the blanks as you choose. Therefore, the only realistic solution to the two smaller codes can come in two forms: [1] The Zodiac Killer can give us a key to decrypt the code, or [2] He can simply give us the answer. The Zodiac Killer may well have chosen option two, and given us the entire solution to all his three unsolved codes in subsequent communications. In fact, the possibilty exists that he supplied us with all the answers in three consecutive communications from July 26th 1970 to October 27th 1970 - in the Little List Letter (07/26/70), 13 Hole Postcard (10/05/70) and Halloween Card (10/27/70). The Zodiac Killer was likely giving us all the solutions before slipping back into anonymity. The newspaper article on November 16th 1970 by Paul Avery, linking Zodiac to the Riverside murder of Cheri Jo Bates on October 30th 1966, likely drew one final breath from the Zodiac Killer through 1971, before his race was run.    

The "key" phrases for the four codes are *in this cipher is my identity", "the Mt. Diablo code concerns radians and inches",  "Fk, I'm crackproof" and "sorry no cipher". The 408 cipher we have examined, so we will now tackle the 32 symbol code.

The Little List Letter mailed on July 26th 1970, one month after the Mount Diablo code (06/26/70), told us the code "concerns radians and # inches along the radians". It was as simple as adding in two figures to complete the code (hence the hashtag symbol denoting a number). The Zodiac gave us the exact wording for the solution, detailed here in a previous article. As stated above, the 32 symbol code with 29 unique characters couldn't be solved without a key or the answer. The Mount Diablo map and crosshairs were the framework, onto which we "coupled" the code for the location of the bomb. The answer was likely "4 radians and 5 inches along the radian", thereby giving us the solution word for word. An alternative to this solution (where only the hashtag is replaced by the number 5), is "P.S. The Mt. Diablo code concerns Radians and 5 inches along the radians". The Zodiac didn't necessarily have to incorporate the number 4 because we already knew the radian value from the bold, black circle provided on the Little List Letter crosshairs.

The next solutions were given to us in the 13 Hole Postcard - that may ultimately become the most important communication of them all. By combining the "red crucifix" decoder and 13 punch-holes in true "Dick Tracy" style, the Paradice and Slaves formation would be revealed, bisecting the 340 cipher along its mid-section both horizontally and vertically. See the article 'The Dick Tracy 340 Cipher'. The Zodiac Killer would again push us in the right direction by revealing the 340 was "sorry no cipher", by way of a cross formation on the Halloween Card envelope just 22 days later. If that wasn't enough, he wrote Paradice and Slaves in the identical formation it could be found within the 340 cipher. Three clues within the space of three weeks. See the article 'Zodiac Admitted 340 Not a Real Cipher'.

The Zodiac Killer also gave us the phrase "Fk, I'm crackproof" (upside down) on the 13 Hole Postcard. Apart from an expletive, the other viable option here, is the Zodiac Killer exclaiming that he is crackproof, preceded by his initials. The reason for this line of thinking, is the Zodiac Killer's wording before the 13 Symbol Cipher on April 20th 1970. The code is designed symmetrically and looks contrived, with three circled 8's fashioned at its center. The Zodiac Killer couldn't have supplied us with his name with any expectation it would be solved, because the code was simply too short and capable of providing us with thousands of solutions. However, he could provide us a solution to the code by giving us his initials. By doing it this way, he is in a roundabout way, giving us his name and a solution to the code that satisfies the introduction that preceded it: "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you. My name is Fk, I'm crackproof".

This solution not only fits into the 13 Symbol Cipher, but reads continuously if imagined in circular fashion. The Zodiac Killer gave us three 8's within a circle (the symbol of infinity, and regeneration and rebirth within Christianity), with the letters K and M positioned ideally in the code to fit "Fk, I'm crackproof" around. There are three elements to this phrase: Fk, I'm, and crackproof. When the entire phrase is slotted around the letters K and M, the number 8 begins each element of the phrase (as shown below). As a side note, "Fk, I'm crackproof" can be spelled using the letters from the 32 Symbol Cipher characters, with only the F and K reversed.      

The Zodiac Killer had effectively given us the exact wording of "I am the Zodiac Killer", "Paradice and Slaves", "Fk I'm crackproof" and "radians and inches along the radian" - all of which can be inserted untouched into all four ciphers and provide us with solutions that don't require a key. The idea of a killer who constantly responded to the newspapers at every turn, somehow resisting the temptation to ever disclose the workings of his codes and ciphers is a difficult story to sell. If we are of the belief that the 32 and 13 character codes are simply too short and too variable to be solved, then without a key the Zodiac Killer likely supplied an alternative. In the case presented above, the "key" and "answer" could be described as exactly the same thing - and It was just a case of transferring the wording from one communication to another in at least three of the examples.

John Rose used Dave Oranchak's webtoy to create features of the Halloween Card in just an 81 character block around the center of the 340 cipher. Some have stated that the variability of the characters in this area of the cipher have allowed the freedom to manufacture such a result. While that may be the case, a larger pattern of Paradice and Slaves is replicated in a 17 X 17 formation along both same midsections, effectively mirroring the John Rose presentation. The fact that both are even achievable in the same cipher, is worthy of mention. The Bay Area braggart must have been itching to throw us a few clues to his unbroken codes and ciphers - so the notion that he didn't give us any before he disappeared into the twilight - is somehow difficult to swallow.   

In the history of cryptography, a grille cipher was a technique for encrypting a plaintext by writing it onto a sheet of paper through a pierced sheet (of paper or cardboard or similar). The earliest known description is due to the polymath Girolamo Cardano in 1550. His proposal was for a rectangular stencil allowing single letters, syllables, or words to be written, then later read, through its various apertures. The written fragments of the plaintext could be further disguised by filling the gaps between the fragments with anodyne words or letters. This variant is also an example of steganography, as are many of the grille ciphers. Wikipedia.

The Zodiac Killer began his letter writing campaign on July 31st 1969, when he mailed three portions of one cipher to the San Francisco Chronicle, San Francisco Examiner and Vallejo Times-Herald. However, it wasn't until October 5th 1970 that his communications took on a different appearance entirely, in which the Bay Area murderer began claiming he was "crackproof" and stated "sorry no cipher", with four out of the next five communications (if we include the Monticello Card) employing the notion of a grille cipher. The '13 Hole' Postcard, possibly using a "red cross" decoder (akin to the Dick Tracy red decoder) , to be punctured by the 13 holes on the card and overlayed onto the 340 character cipher. This would reveal the enciphered "paradice" and "slaves" bisecting the 340 cipher both horizontally and vertically along its mid-section. The "sorry no cipher" in a cross formation on the Halloween Card envelope, also overlayed onto the "paradice" and "slaves" on the rear of the card, to again point to the 340 cipher configuration and let us know that it was unfortunately "no cipher" (Zodiac's Halloween trick or treat reveal). This was explored in the Dick Tracy 340 Cipher article. 

The 13 holes overlayed onto the 340 cipher in a cross formation, taken from the '13 Hole' Postcard would reveal the hidden arrangement in the 340 cipher (similar to the depiction on the right, although portrayed with yellow squares as opposed to white punch-holes). This was the arrangement already present on the Halloween Card in reveal mode.

The '13 Hole' Postcard has 13 punch-holes in the fabric of the card, the Halloween Card has an eye peeking through the knothole in the tree, and the mask on the skeleton has two eyeholes. Then (if I am correct) we have one hole punched in both the March 22nd 1971 Pines Card and the July 13th 1971 Monticello Card, which when overlayed on a map by the Sierra Club of Lake Tahoe and the Villa Montalvo woods in Saratoga, would both reveal the name of the victim in both instances. The point being, we have a rudimentary grille cipher being employed or insinuated in four communications spanning through October 5th 1970 and July 13th 1971. The arrangement of "paradice" and "slaves" on the Halloween Card, and the punch-holes in every other card during this period, revealing something significant hidden beneath. The name of Donna and Kathy in the two 1971 postcards, and the hidden configuration in the November 8th 1969 340 cipher, derived from both October 1970 communications.

The grille cipher, even in its most rudimentary form, was implied or used through four of Zodiac's last five communications from October 5th 1970. I am completely confident that the Monticello Card is fashioned in exactly the same manner as the Pines Card, separated by less than four months, with the single punch-hole revealing the location of Donner Memorial State Park (Donna Lass) and Oak Hill Memorial Park & Cemetery (Kathy Snoozy) by the Monticello neighborhood of San Jose. Two locations, two victims and two names, all bound by two postcards. If these overlays didn't drop over these locations accidentally, then why should the cross design on the '13 Hole' Postcard and Halloween Card mimic the 340 cipher accidentally as well.

Was the Zodiac Killer inspired by the simple Dick Tracy grille cipher, or had he invested in the book The Codebreakers - The Story of Secret Writing by David Khan, released the year before the Zodiac attacks began on December 20th 1968? It is without much doubt, that the grille cipher featured heavily in his final two communications of 1970, even though one could argue that the single holes punched into the 1971 postcards are more representative of an overlay, rather than a decryption technique - yet in every instance, a message was revealed through the punch-holes.

The Dick Tracy Magic Decoder was an integral part of American advertisements in the 1950s, encouraging children to eat their breakfast cereals while also capturing their interest in rudimentary code breaking. This was great for children, but likely a nightmare for parents, who were undoubtedly nagged into buying Post Sugar Crisp, Raisin Bran and Sugar Rice Krinkles to excess. The daily diet of codebreaking a fascination for many children growing up in mid twentieth century, post-war America. Fast forward to October 22nd 1969, when Dr DCB Marsh, president of The American Cryptogram Association, laid down a challenge to Zodiac. In the San Francisco Examiner article, Dr Marsh stated "The killer wouldn't dare, as he claimed in letters to the newspapers, to reveal his name in a cipher to established cryptogram experts. "Zodiac" had not done this, Marsh suggested, 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." Therefore, wouldn't it be just like the Zodiac Killer to send the newspapers the most uncomplicated cipher code he could find, based on a code found in children's cereal boxes. I believe he may just have done exactly that.  

In the picture above, the writing states "This is your Red Decoder. Punch out white holes to decode answers to Red "Crimestopper" messages on the package. Green questions requires a Green Decoder from other Sugar Crisp, Post Raisin Bran, or Sugar Rice Krinkles packages".  

Where have we seen a possible "Red Decoder" and "Punched out white holes" in one of Zodiac's communications before.
The '13 Hole' Postcard was mailed by the Zodiac Killer on October 5th 1970, just shy of the one year anniversary of the 340 cipher. In the postcard the Zodiac Killer provided us with his "red crucifix decoder" and "13 punch-holes" in the fabric of the card. This was his very own Dick Tracy descoder. Seagull, a contributor to the Zodiac Killer Site forum, was on the right path when she stated "If I were to attempt to try something like this, to find a hidden message, I think I would start with using the shape of the crosshair symbol for the template. The problem would be to determine a size and whether or not to round the shape or square it off. Even if you managed to hit on the right size and shape, the message could still be coded. But my totally untrained cipher gut tells me that if the 340 can be solved it's might be something as seemingly simplistic as this". It may very well have been this simplistic, with everybody expecting the Zodiac Killer to make his second cipher much harder, after his first cipher was cracked with relative ease. The Zodiac Killer taking the shape of the "red crucifix decoder" as the template, to be coupled with the 13 punch-holes he added to the October 5th 1970 postcard  All we had to do was arrange the 13 punch-holes in the shape of a crucifix, so when it was placed over the 340 cipher, a message was revealed. The Zodiac Killer did add a second tier of messages in the 340 cipher, to which he revealed in the following Halloween Card on October 27th 1970. Nobody at the time understood the secret message in the '13 Hole' Postcard, which is why he added the second layer just 22 days later.    

The 13 punched holes in the postcard was the initial attempt by the Zodiac Killer to show us that the "crackproof" 340 cipher  was a Dick Tracy style code. Arranged on the template of the "red crucifix", a message would be revealed in the 340 cipher. If this first step was achieved successfully, then the message in the 340 cipher would be obvious. The "Dick Tracy Red Crucifix Decoder" with 13 punch-holes, if placed bisecting the 340 cipher both vertically and horizontally and arranged correctly, would reveal the wording "Paradice" and Slaves" on the 340 cipher. This is shown by the 13 white circles on the diagram below. Whether the red crucifix was intended to be reversed in sinister fashion (keeping the correct proportions relative to Paradice and Slaves on the 340), as hinted by the reversed writing on the '13 Hole' Postcard, is open to conjecture.

Unfortunately, nobody appeared to understand the simplicity of his message, so he added a second crucifix (or cross) just three weeks later, when he mailed the Halloween Card on October 27th 1970. Here, he added a second layer, by giving us the second part of the message in the 340 cipher. The Zodiac Killer placed the wording By Fire, By Gun, By Rope and By Knife around the crucifix of Paradice and Slaves, and added the message "sorry no cipher" in the form of a third crucifix (or cross) to the envelope inner. The reason being, the 340 was "no cipher" - it was a simple Dick Tracy punched hole decoder style puzzle. The Halloween Card began with "From Your Secret Pal", so it's no surprise that it contained a secret message also. If you create the 37 punched holes in the style of a Dick Tracy Decoder (shown in the above right image) and place over the 340 cipher, the By Fire, By Gun, By Rope and By Knife wording is revealed - and derived from the Halloween Card. The respective 'method of death' remaining in each quadrant of the 340 cipher (9 by 10 and sharing the central column). 

The Zodiac Killer manufactured the Halloween Card to depict thirteen eyes, often suggested as the Eye of Horus. Funerary amulets were often made in the shape of the Eye of Horus. The symbol was intended to protect the pharaoh in the "afterlife" and to ward off evil. Ancient Egyptian and Middle-Eastern sailors would frequently paint the symbol on the bows of their vessels to ensure safe sea travel. This would certainly give us Paradice, Slaves and the Afterlife in one neat package.

Osiris, is the Egyptian god of fertility, alcohol, agriculture, the "afterlife", the dead, resurrection, life, and vegetation in ancient Egyptian religion. This normally wouldn't be relevant, but for the Dick Tracy Decoder Ring (designed to conceal messages or items) and the Dick Tracy Radio Show sponsored by Quaker Oats, which featured the The Black Pearl of Osiris, given to Dick Tracy to hide in the Decoder Ring. This ring had a specific design on its face, split into four quadrants just like the Paradice and Slaves configuration on the Halloween Card. In the top left quadrant is a Zodiac-like design, bearing some similarity to the crosshairs of Zodiac, along with a moon design in the lower left quadrant. "The Dick Tracy Premium was offered in exchange for five box tops of Quaker Puffed Wheat or Rice and one wonders how many uneaten boxes were dismembered by eager kids before the offer expired". See here at the Dick Tracy Depot. 

The Dick Tracy Decoder and Dick Tracy Ring were both targeted at chidren from the 1930s onwards - and both may have had an influence on the cereal munching Zodiac in his childhood years - the rudimentary coding of which may have spawned the inspiration in his design of both the '13 Hole' Postcard and Halloween Card in the October of 1970. Many people believed the Zodiac Killer, shaken by the ease to which his first cipher was cracked, devilishly formulated a far more impenetrable cipher the second time round. Yet, it may be the case, that the inspiration for the Bay Area serial killer in his design of the 340 cipher, may have been inspired by nothing more complicated than the cereal boxes of children. 

For more on this topic: Zodiac Killer Site forum and ZodiacKiller.com discussion forum.

Question marks have always hung over the October 5th 1970 '13 Hole' or 'Pace' Postcard as to whether the author was the Zodiac Killer or a copycat. This article will hopefully go a long way to convince people that the communication was indeed mailed by the Bay Area murderer. The Zodiac Killer wrote the lengthy 'Little List' Letter on July 26th 1970, beginning the correspondence with his intentions for his slaves in paradise, followed by the torture methods he was going to apply, before finishing with the plagiarism of Gilbert & Sullivan's The Mikado, from the Act As Some Day it May Happen. The crucial thing to remember here, is that this communication was withheld from the newspapers and public alike, so by October 5th 1970 when this postcard was postmarked, the author (if not Zodiac} was totally unaware to the contents of the Little List Letter. The Zodiac Killer could have been reemphasizing his victim total of thirteen, or a copycat could have been suggesting thirteen victims for the first time, unaware that the Little List Letter had ever been mailed. Therefore, this is no help in determining whether the author of the '13 Hole' Postcard was the Zodiac Killer or not. We need to look at the wording on both communications back to back.

The first thing to notice on the '13 Hole' Postcard is the crucifix and number 13 in close alliance - extremely relevant when we consider the Zodiac Killer using the phrase "I shall (on top of everything else) torture all 13 of my slaves that I have waiting for me in Paradice" in the Little List Letter. The crucifix, a symbol of Christianity and the progression from life on earth to the paradise of heaven, is further cemented by the October 27th 1970 Halloween Card where the Zodiac Killer actually combines all three elements. However, if you are also a skeptic of the Halloween Card, then we need to focus entirely on finding a link between the '13 Hole' Postcard and the previously unpublished Little List Letter, both eventually released in tandem with one another on October 12th 1970 in a newspaper article by Paul Avery. Below I have separated the Little List Letter into its constituent parts - his promise of torture, his methods of torture and the search for victims.            

The Zodiac Killer refers to his victims in the plural and in the future tense, beginning his torture methods with "Some I shall tie over ant hills and watch them scream + twich and sqwirm. Others shall have pine splinters driven under their nails + then burned. Others shall be placed in cages + fed salt beef untill they are gorged then I shall listen to their pleass for water and I shall laugh at them". He uses the word "some" to begin his rhetoric, then continues with his Little List of potential victims, sourced from As Some Day it May Happen, beginning with "As some day it may hapen that a victom must be found". Therefore, is it any great surprise that the Zodiac Killer having noted his lengthy communication was not published in the newspapers, would begin the '13 Hole' Postcard in the past tense, stating "The pace isn't any slower. In fact it's just one big thirteenth. 'Some of them fought it was horrible'".

The Zodiac Killer is effectively saying that he had now tortured his victims in paradice and "some of them had fought". He is telling Paul Avery and the San Francisco Chronicle newspaper he had made good on his promises. This strongly suggests that the author of the '13 Hole' Postcard knew the contents of the July 26th 1970 Little List Letter, thereby cementing the notion that the Zodiac Killer was the author of both communications. The alternative, is that a copycat just threw together a random postcard that not only continued the theme of the previous letter accidentally, but was adopted by the Zodiac Killer in the October 27th 1970 Halloween Card and the following March 13th 1971 letter, where the Zodiac Killer stated "This is the Zodiac speaking Like I have allways said, I am crack proof". The copycat scenario proliferated by many, a sensational subplot to discredit certain Zodiac communications and attacks, where no merit for such claims exist. 

The other notable element of the '13 Hole' Postcard is the Mon, Oct 5, 1970 attribution in the top right corner. The Zodiac Killer did recite the Gilbert & Sullivan Act As Some Day it May Happen. So was Monday, October 5th the day something happened - and the reason he added a specific date for the very first time?   

Unable to solve the 340 cipher and crack the message (in which I'm not alone), my only recourse is to try and prove that the 50-year-old cryptogram is unsolvable. I cannot do this on my own, so I need the Zodiac Killer to give me a hand and show me that it's not a valid cipher in his own words. The Zodiac Killer only gave us two visible 'crucifixes or crosses' (without the circle) in the cards and letters, throughout his entire correspondence with the newspapers. We can assume he did this for absolutely no reason whatsoever, or these two 'crucifixes or crosses' had a purpose. The two crosses were present in two consecutive cards - the '13 Hole' Postcard on October 5th 1970 and the Halloween Card on October 27th 1970. Both these cards also contained a hint that something was unsolvable. The '13 Hole' Postcard contained the phrase "Fk I'm crackproof", while the Zodiac Killer fashioned "sorry no cipher" in a cross formation on the envelope inner of the Halloween Card. If these statements are relevant to his ciphers, then we need to marry up the design of each card to his codes. Before we start, it must be noted that PARADICE and SLAVES in the cross formation is made up of 13 letters (the A pivotal to both words), but individually both words contain 14 letters - the total highlighted on each card. 

In the image below with respect to the '13 Hole' Postcard, you will notice that the Zodiac Killer has carefully positioned the cross beneath the number 13 - and we know Paradice and Slaves contains 13 letters in the cross formation. This is placed approximately in the center of the postcard with text either side. The 13 characters identified on the 340 cipher as Paradice and Slaves exactly mirroring this formation. Below the number 13 and cross on the postcard is the pseudonym Zodiac, accompanied by his crosshairs, almost mirroring the 340 cipher formation. The most notable feature on the 340 cipher is the corrected sixth line involving the letters F and K. Highlighted with a blue rectangle on the '13 Hole' Postcard we have "Fk I'm crackproof" written upside down. All we have to do now, is rotate the '13 Hole' Postcard 180 degrees clockwise to correct this text, so it can be read in the standard way. The corrected "Fk I'm crackproof" would now be present in the top right quadrant, just like the correctred FK in the 340 cipher.        

The Halloween Card also has the cross formation of Paradice and Slaves. This not only mirrors the "sorry no cipher" formation he provided on the envelope inner, but mirrors the 340 cipher formation also. In essence, the Zodiac Killer is telling us by extension that the 340 cryptogram is no cipher. Two consecutive communications, probably close to the anniversary he created the 340 cipher, and both designed to reveal the hidden crucifix or cross within the 340 cipher. Throw in the four By's in each quadrant and the pseudonym Zodiac from the '13 Hole' Postcard, along with "Fk I'm crackproof" and "sorry no cipher", and we have the Zodiac in his own words admitting the 340 character cryptogram has no solution. On the other hand, the Zodiac Killer is widely believed to be a liar - so maybe there's a message after all.

But just in case, let us stick "Fk I'm crackproof" into his third cipher and see if that's unsolvable as well.        

The Zodiac Killer again uses 13 characters/letters in his design, with the feature of three circled 8's. The circle and number 8 can be used to represent infinity or something of a cyclic nature. The cipher came with the handily placed K and M in the center of the code. All we have to do is place "Fk I'm crackproof" into place using these two letters (shown in blue), and in an unusual stroke of luck, the phrase is cyclic in nature. In addition, the three 8's (shown in green) just happen to begin each element of the phrase "Fk I'm crackproof" (Fk, I'm and crackproof). The Zodiac Killer may have twice told us his ciphers were unsolvable in the '13 Hole' Postcard and Halloween Card, but here he simply wouldn't shut up.

"This is the Zodiac speaking. By the way have you cracked the last cipher I sent you. My name is FK, I'm crackproof".

Professor D.C.B. Marsh, in the October 22nd 1969 San Francisco Examiner newspaper article by Will Stevens, laid down a challenge to the Zodiac Killer to reveal his name. The newspaper stated "Dr Marsh told the Examiner today: "The killer wouldn't dare, as he claimed in letters to the newspapers, to reveal his name in the cipher to established cryptogram experts. He knows, to quote Edgar Allen Poe, that any cipher created by man can be solved by man. Zodiac has not told the truth in his cipher messages to the Examiner, the Chronicle and the Vallejo Times-Herald. Zodiac has not done this, because to tell the complete truth in relation to his name - in cipher code - would lead to his capture. I invite Zodiac to send The American Cryptogram Association a cipher code - however complicated - which will truly and honestly include his name". It is highly unlikely the Zodiac Killer would have been suckered into providing a genuine cipher of any length knowing that 'any cipher created by man can be solved by man'. The 13 and 32 symbol ciphers mailed in 1970 proved this very fact - both effectively crackproof without a recognizable key. However, the Zodiac could certainly have sent us a rudimentary message within the 340 cipher utilizing the wording contained within his 408 cipher.

Paradice and slaves is a well-trodden theme in the Zodiac communications, and as I have stated before, the Halloween card mailed on October 27th 1970 (almost the anniversary of the D.C.B. Marsh challenge) actually admitted that the 340 cipher was "sorry no cipher". The Zodiac Killer had never apologized previously for not sending a cipher in his 'cipherless' communications, so why start now. Even if the "sorry no cipher" writing on the envelope inner was to inform us that in about two seconds we had no cipher, then just write "sorry no cipher" once. The fact it was fashioned into a cross formation that mimicked the paradice and slaves configuration on the card inner, seemed designed to suggest that this configuration would be found in a cipher that effectively had no solution. The sheer fact that this configuration can also be found in his 340 cipher, exactly bisecting the cipher vertically and horizontally (17 by 17), one would like to believe is a convincing argument to suggest that the Zodiac Killer was finally admitting the 340 cipher wasn't a cipher at all. Additionally, it did mimic the 408 cipher with its inclusion of the paradice and slaves reference. Although this may be interesting, it understandably isn't enough to convince certain quarters of the Zodiac community who are steadfast in their belief that the 340 cipher contains a cogent but elusive message. Regardless, one couldn't help thinking that this wasn't the only time the Zodiac admitted the 340 cipher was devoid of any meaningful solution. Fortunately, the answer came in the communication prior to the Halloween card.  

If I am correct, and the paradice and slaves (13 letters) configuration was intentional in the design of the 340 cipher, then this is a significant point of interest. Two other notable features stand out in the 340 cipher. Firstly, the corrected sixth line where the Zodiac Killer blacks out a forward K and replaces it with a backward K. Secondly, the distinct possibility that he placed his pseudonym on the final line of the 340 cipher. All these three features are present in the '13 Hole' postcard.

Despite the fact that Zodiac made many spelling errors in his design of the 408 cipher and his communications as a whole, he seemed conscientious enough to correct one character in his 340 cipher, that inevitably would have made no difference in it being deciphered, had it contained a genuine solution. The fact he spoiled an otherwise neat and tidy presentation appeared designed to convince us that it was a genuine cipher. After all, why would Zodiac correct a collection of gibberish, if not to convince us it wasn't. The correction seemed contrived in order to validate the authenticity of the cipher, to which he would allude to in the '13 Hole' postcard.        

Many have speculated on why the Zodiac Killer reversed the bottom section of text on the '13 Hole' postcard. He certainly didn't do this for absolutely no reason, as he didn't create the "sorry no cipher" configuration for no reason either. The Zodiac Killer pasted the lettering "Fk I'm crackproof" on the '13 Hole' postcard in a first attempt at showing us the 340 cipher had no solution. The definition of crack-proof is something that is unable to be cracked, or in the case of a cipher, unable to be decoded. He used this word in his April 20th 1970 letter, sarcastically stating "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you". He knew only too well that it hadn't been cracked, because it couldn't be cracked - and now was telling us it was crackproof by association to himself.

The Fk has been suggested as a shortened expletive or possibly a name - but what if we take it on face value, and the Fk actually means Fk and nothing more. It is like Ronseal and 'does exactly what it says on the tin'. The Zodiac Killer is essentially telling us that the corrected Fk on the 340 cipher was a ruse, because his cipher was crackproof. This is why the text on the '13 Hole' postcard is reversed, exactly the same as the reversed K on the 340 cipher. The K on the 340 cipher is not only reversed, but it is now much smaller than all the other characters on the 340 cipher, which is why the Zodiac Killer pastes "Fk I'm crackproof" rather than "FK I'm crackproof". ​ Crackproof, Fk and the reversal of text on the '13 Hole' postcard, coupled with the cross design of 13 (paradice and slaves), inevitably leads back to the 340 cipher. Either that, or he pasted "Fk I'm crackproof" upside down on the '13 Hole' postcard for no reason whatsoever.

What we effectively have, are two consecutive October 1970 communications stating ​"Fk I'm crackproof" and "sorry no cipher", both furnished with a cross design that mimics the appearance of paradice and slaves on the 340 cipher. It is my contention that the Zodiac Killer responded to the challenge of Professor D.C.B. Marsh, but he simply wasn't going to abide by the rules laid down by the cryptography expert, yet he stayed true to the paradice and slaves message in the 408 cipher, albeit in his own inimitable style. The paradice and slaves design in the 340 cipher (extending 17 rows down) still leaves the tantalizing prospect of three 'vacant' rows comprising of 51 unobstructed characters, that may harbor a second puzzle or message. With the Zodiac pseudonym almost appearing toward the end of the cipher, there may be a twist in the tail yet.       

In the last article 'The 340 Cipher-Trick or Treat?' we attempted to show how the Zodiac Killer used two xeroxed keys in the 1990 'American Greetings' card to intimate that the 340 cipher should be inverted or flipped, in order to begin the message with 'This is the Zodiac speaking'. The 'Halloween' card intersecting "sorry no cipher" key, was also used to show how Paradice and Slaves was pivotal to the design of the 340 cipher. But another cryptic communication arrived just 22 days before the 'Halloween' card, on October 5th 1970, entitled the '13 Hole' postcard. The Zodiac Killer could easily have drawn or photographed the keys in the 'American Greetings' card, but opted to xerox or photocopy them. The same could be said of "sorry no cipher", which he could easily have written once. This led to the notion that these two deliberate choices had a meaning or message. This brings us to the '13 Hole' postcard.

Just like the 'American Greetings' card, why does the Zodiac Killer punch 13 holes through the fabric of this card in a 10:3 configuration, rather than just fill in 13 circles like his ciphers? On the address side these holes can be found on the extreme left of the card, which then obviously switch position when the card is turned over. It can also be noted that the text at the bottom left of the card is also flipped over. It read ​"There are reports city police pig cops are closeing in on me. Fk I'm crackproof. What is the price tag now?" The 'American Greetings' card, it was suggested, used two keys to infer the 340 cipher code should be flipped - the bottom row becoming the top row and vice versa - allowing one of only two prominent 'words' on the 340 to settle on the top row, to facilitate the opening message of 'This is the Zodiac speaking'. The second prominent word of 'Her' (that begins the cipher) would now be flipped to the bottom line of the 340. The '13 Hole' postcard gives us the first clue to suggest the likelihood of this being the case.

The Zodiac Killer punched 13 holes into the card with a hole punch, A keypunch is also a device for precisely punching holes into stiff paper cards at specific locations as determined by keys struck by a human operator. Or in computing, a mechanical device whose keys are pressed, individually or in combination, to punch holes in punched cards or paper tape that correspond to particular characters. Programs or wording can be encoded onto a punched card. Did the Zodiac Killer encode a message in a 10:3 configuration using these punched holes, that would not only take 'Her' to the bottom line of the 340 cipher, but use the identical wording on the envelope of the 'Halloween' card to achieve it?    

The message the Zodiac Killer may have wanted to convey, was that "sorry no cipher" hypothetically written on the address side of the '13 Hole' postcard, would not only separate the word 'Her', but it would effectively be inverted or flipped over to the other side when the postcard was turned. The flipped text containing "Fk I'm crackproof" testament to the fact we have a 'Flipped key', despite the boast of Zodiac claiming he was "crackproof" because of it  The 'Her' has now switched sides, thereby giving us our third key to the workings of the 340 cipher. The Zodiac Killer used two keys in the 'American Greetings' card to flip the 340 cipher, and a hole punch here to project the same message. He even added a red crucifix with the number 13 above, to highlight the connection to the 'big thirteen' letters of paradice and slaves on the 'Halloween' card he was soon to mail. Inversion was at the heart of these three communications, using keys in all instances - and all pointing to a 340 cipher that should be turned on its head. 

Here we will revisit an article published by the San Francisco Examiner on October 22nd 1969, in which Professor D.C.B. Marsh, president of the American Cryptogram Association laid down a challenge to Zodiac. The words he chose to use in this article may be the bedrock to much of the subsequent Zodiac communications, beginning with the 340 cipher, mailed only seventeen days after the San Francisco Examiner article. Here are the crucial extracts from that article.

'Dr Marsh told the Examiner today: "The killer wouldn't dare, as he claimed in letters to the newspapers, to reveal his name in the cipher to established cryptogram experts. He knows, to quote Edgar Allen Poe, that any cipher created by man can be solved by man. Zodiac has not told the truth in his cipher messages to the Examiner, the Chronicle and the Vallejo Times-Herald. Zodiac has not done this, because to tell the complete truth in relation to his name-in cipher code-would lead to his capture. I invite Zodiac to send The American Cryptogram Association a cipher code, which will truly and honestly include his name". It is difficult to believe that Zodiac, an avid reader of the newspapers, could resist such a challenge, particularly as he had promised to reveal his identity in the 408 cipher two months earlier but failed to do so.  

The key section to note in the challenge by Professor D.C.B. Marsh is: "I invite Zodiac to send The American Cryptogram Association a cipher code, which will truly and honestly include his name". Seventeen days later, the Zodiac Killer duly obliged with the November 8th 1969 340 cipher. Could this cipher have included the killer's name, but not in the format envisaged by Professor D.C.B. Marsh?

In a previous article entitled 'Zodiac Admitted 340 Not a Real Cipher' we examined the idea that the 340 cipher was inextricably linked to the Zodiac's 'Halloween' card, mailed on October 27th 1970. One can notice that the word "By" is located in each of the four quadrants of the 340 cipher. The author of the cipher also placed the letters F and K adjacent to one another no less than seven times (situated in each quadrant). But of particular interest was the corrected section on the sixth line of the 340 cipher, where the author chose to scrub out a forward facing K and replace it with a backwards K, elevated above the blacked out section (shown in red rectangle}.

The Zodiac Killer was known for numerous spelling errors in his communications, so why was it seemingly imperative to correct this one mistake? Was this correction crucial to the interpretation of the cipher, or was he drawing our attention to the letters in this section of the cipher? Are the F and K characters the initials of the Zodiac Killer? This observation carries little merit on its own, so to bolster any argument for the initials of the Zodiac Killer being present in the 340 cipher, we have to explore the rest of his communications, particularly from around the time of the 'Halloween' card, in which we suggested was his admission that the 340 was unfortunately "no cipher". 

Linking the 'Halloween' card and 340 cipher through a Tim Holt comic book and explaining to us that the solution was "sorry no cipher" left us with the possibility that the 340 cipher was just a collection of puzzles, in which may have contained his name. The Zodiac Killer "wouldn't dare, as he claimed in letters to the newspapers, to reveal his name in the cipher to established cryptogram experts", but he may have given us the abridged version. We now enter the crucial phase of Zodiac communications, from the '13 Hole' postcard mailed on October 5th 1970, to the 'Exorcist' letter mailed on January 29th 1974. This critical period of four consecutive communications, is probably key to understanding the message the Zodiac Killer was trying to push. That the 340 was "sorry no cipher".    

In the '13 Hole' postcard the Zodiac Killer stated "There are reports city police pig cops are closeing in on me. Fk I'm crackproof. What is the price tag now?" This section of pasted letters was placed upside down. The question one should be asking is 'what is the purpose behind this'. If its significance had no relevance to the actual postcard, did it have relevance to another communication.

The wording "FK I'm crackproof" could indicate that the killer thought he was immune from capture, however, it could also be a reference to his 340 cipher once again. The word "crackproof" is something that is unable to be cracked. The 340 cipher would certainly be impervious to cracking, and certainly resistant to the attempts of The American Cryptogram Association had the killer devised a cipher not of conventional understanding, of which Professor D.C.B. Marsh was hoping when he laid down the challenge. The F and K text being flipped on the '13 Hole' postcard reminds one of the flipped K (next to F) on the only corrected portion of the 340 cipher. If FK were the Zodiac Killer's initials, then he certainly could be declaring that he was crackproof. 

​Professor D.C.B. Marsh stated  "He knows, to quote Edgar Allen Poe, that any cipher created by man can be solved by man. Zodiac has not told the truth in his cipher messages to the Examiner, the Chronicle and the Vallejo Times-Herald. Zodiac has not done this, because to tell the complete truth in relation to his name-in cipher code-would lead to his capture". However, the Zodiac Killer could give his name in the form of initials without any fear of revealing his identity, and without risking his immediate capture. This may have manifested itself when he mailed his following cipher on April 20th 1970, when he opened with the gambit "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you. My name is...."  The code placed underneath was likely an immediate rebuttal to this question. 

All he is probably doing, is stating "My name is FK," and once again telling us he is crackproof, just like the '13 Hole' postcard, which would be mailed five and a half months later. The phrase "FK I'm crackproof" fits perfectly in circular formation within the '13 Symbol' cipher - which itself contains a series of circled 8's. Structured in this fashion, the F and K yet again align, as does the K and M in both the cipher and phrase. 

Continuing with our four consecutive communications from October 5th 1970 onward, we now have the October 27th 1970 'Halloween' card promising to yet again reveal his name: "I feel it in my bones, You ache to know my name, And so I'll clue you in". Again we feel disappointed only to see the word "Boo" on the card inner - but we know the Zodiac Killer isn't going to make this a conventional and straightforward offering. He offers us the phrase "sorry no cipher," but can we find his name or initials within this communication. This is where it gets more difficult, nevertheless, we are aware that within the '13 Hole' postcard he reversed or flipped the text containing "FK I'm crackproof" and he flipped the K (next to the F) on the sixth line of the 340 cipher. So the obvious conclusion, is to look for flipped or reversed text within the 'Halloween' card.  

The only place that F and K exist within one word on the 'Halloween' card, is in the word "knife." either side of the reversed letter N. If we flipped the reversed N back to its appropriate position, the F and K of "knife" would be reversed yet again.

Now let us turn our attention to the peculiar configuration at the foot of the card inner. It would be extremely satisfying for the 'Halloween' card to read "I feel it in my bones, You ache to know my name, And so I'll clue you in... FK" - so that is what we will create, by manipulating this card to read whatever we want it to. The strange symbol, reading it as true as possible, appears like a number 7, followed by four dots and the letter F.
7+4=11=K (followed by F).

Without further ado, we shall move on to the next confirmed Zodiac communication on March 13th 1971, in which the Zodiac stated "This is the Zodiac speaking. Like I have allways said, I am crack proof. If the Blue Meannies are evere going to catch me, they had best get off their fat asses + do something. Because the longer they fiddle + fart around, the more slaves I will collect for my after life. I do have to give them credit for stumbling across my riverside activity, but they are only finding the easy ones, there are a hell of a lot more down there. The reason I'm writing to the Times is this, They don't bury me on the back pages like some of the others". You will notice that the Zodiac Killer refers to "crackproof" once again, parroting his October 5th 1970 communication five months earlier. However, he doesn't just state he is crackproof, he reminds us that he has always been telling us he is crackproof, and quite possibly we just haven't got the message.

Roll on the January 29th 1974 'Exorcist' letter, signed "yours truley," nearly three years later - giving us our final installment of FK contained within the array of symbols at the foot of the letter. On this occasion he mirrors the sixth line of the 340 cipher by elevating the K above the letter F, and to its left. In fact, five characters from the Exorcist letter can be found in and around the corrected sixth line of the 340 cipher, as shown here in a previous article. This was possibly the fourth consecutive communication inferring an FK link and the suggestion that the author was indeed "crackproof".
 
Was this a persistent and deliberate attempt to be true to the challenge laid down by The American Cryptogram Association and Professor D.C.B Marsh, by inserting his name (albeit initials) into the 340 cipher and subsequent communications, or just a case that my mind is F@@Ked after six exhausting years of looking for patterns where none exist.