A shift cipher with circled numbers (often seen in puzzles like escape rooms) relies on a Caesar cipher, where the secret shift key is represented by numbers wrapped inside circles, such as the three number 8's present on the simple Z13 code mailed on April 20th 1970. A shift cipher replaces each plaintext letter with another letter located a fixed number of positions down the alphabet. When you hit the end of the alphabet, the count would wrap around to the beginning. In the case of the Z13, the count of 8 would travel in a right shift and wrap around to the beginning (this would apply to the second two 8's).

This was just a continuation of the technique adopted in the 340 cipher---at the time unsolved---in which the Zodiac Killer employed a positive nine and negative eight shift to encode his message---that could be decoded with a period 19 shift. He also encoded errors into his 340 cipher using a nine shift, that became apparent as diagonal patterns across the second half of this cipher. The April 20th 1970 letter was very likely triggered by the morning newspaper reports of the Robert Salem murder in San Francisco on the same day (with Zodiac scrawled in blood on his apartment wall). A letter that had a morning postmark, so was likely created in haste with very little regard for complex cipher techniques. It is not certain that the Zodiac Killer was inspired to resume his letter writing campaign because of the Robert Salem murder, but it had been four months since the Melvin Belli letter on December 20th 1969, so this letter coinciding with his pseudonym appearing at a murder site, is probably not coincidental. 

The November 8th 1969 and April 20th 1970 letters were very likely prompted by Professor Donald C. B. Marsh, who told the San Francisco Examiner on October 22nd 1969: "The killer wouldn't dare, as he claimed in letters to the newspapers, to reveal his name in the cipher to established cryptogram experts. He knows, to quote Edgar Allan Poe, that any cipher created by man can be solved by man. Zodiac has not told the truth in his cipher messages to the Examiner, the Chronicle and the Vallejo Times-Herald. Zodiac has not done this, because to tell the complete truth in relation to his name - in cipher code - would lead to his capture. I invite Zodiac to send The American Cryptogram Association a cipher code - however complicated - which will truly and honestly include his name".

​That is because Edgar Allan Poe's lengthy essay "A Few Words on Secret Writing".held all the ingredients to the design of the Z340 and Z13, including the splitting of the alphabet into two halves, and the cipher wheel which adopts the forwards and backwards shifting method of encryption and decryption, involving two concentric, independently rotating circles. The bottom line is that the Zodiac Killer likely didn't have much time to dazzle us with complex cryptograms on April 20th 1970, so created a simplistic code of 13 characters in which the three circled 8's became the engine room to the solution, where we had to circle around the code to produce the joke reply to "My name is" of "ME ⊕".  

This is the answer he gave us on October 27th 1970, highlighting the word "ME" twice on the Halloween card by the clever positioning of the word "BOO", preceded again by the promise of his name through the selection of a card with the introductory message of "I feel it in my bones you ache to know my name. And so I'll clue you in". The comedic answer was "ME"--- now given to us three times. The fourth time was in plain sight on January 29th 1974, when the Zodiac gave us his "pseudonym" or "name" as "Me-37".

A further fifth clue could be found by looking at the next line in the "Tit-Willow" verse he provided in 1974. The wording "My name is" can be extrapolated from the "The Mikado" text---thereby returning us back to the April 20th 1970 letter and ""ME" once again. We have now gone full circle back to the three circled eights. We effectively have four examples of "ME" through three communications---all but one of which are sitting in plain sight. The only one hidden from view can be easily found in seconds using a simple right shift the Zodiac Killer had previously employed. The Zodiac Killer mailed at least seven ciphers during his reign of terror, but it is safe to say that the four most commonly talked about ciphers have now been finally resolved.
​
FOUR AND A HALF YEARS OF ME             THREE INNOCUOUS EXCLAMATION MARKS

On June 2nd 2026 David Oranchak completed his 3-part destruction of yet another hopeless and deranged offering, which this time attempted to link the Zodiac Killer with the Black Dahlia murder from 1947. It is another excellent video series from David Oranchak, whose presentation skills are superlative in every aspect, as he comfortably annihilates the most recent of dumb theories. Massively respected in the Zodiac community by almost everybody, his services will no doubt be called upon in a year or two when the next chancer comes along, who will undoubtedly put forward more half-baked nonsense that captures the attention of an immoral mainstream media only concerned with generating money over truth.

This publicity effectively creates "puppets" in the Zodiac community, who feel compelled to confront the latest claims and dedicate unbridled effort to correct the record and quell the most recent uninformed fervour. There appears an irresistible compunction to expend great resource in dismissing drivel, where shade is probably the best disinfectant. If individuals have that much of an uncritical mind that they blindly accept rubbish spewed from the mainstream media, then they probably aren't going to distinguish between reasonable and unreasonable. Providing a counterweight to this stupidity is an endless task that David Oranchak will have to revisit time and time again. David Oranchak, whose fantastic work alongside Sam Blake and Jarl Van Eycke in solving the 340 cipher on December 5th 2020, is a highly intelligent person, blessed with dedication, modesty and ethics that sets him apart from most. 

With that said, let's examine a statement made by David Oranchak at 11 minutes and 50 seconds into his latest video, which appears to contradict the approach adopted in the rest of the video. This statement is not the focus of the overarching message in the video and will undoubtedly present as nitpicking, but nonetheless, it is a statement without merit. David Oranchak is widely known and respected to not just accept things without evidence---he meticulously examines claims through dedicated and diligent research, that is often labor intensive and time consuming. David is not the sort of person to just repeat a narrative without careful evaluation of that claim. However, at 11m 50s into the video David casually makes a claim that he cannot possibly substantiate---but one that has been repeated endlessly by individuals over many years, who I dare say, have not dedicated any time whatsoever in examining their throwaway comments (or the letter itself).

David stated "He (Baber) also links the DC Freeway Phantom using this 1981 letter from a Zodiac copycat". This statement is factually incorrect, because irrespective of your thoughts on this letter's authenticity, nobody has physically identified its sender to prove it wasn't Zodiac. And if the claim that the letter is from a copycat has its foundations based solely on handwriting and tone---then that is another falsehood perpetuated by researchers unable to prove this concept. With handwriting alone, it is currently impossible to say whether the 1981 "Atlanta" letter was penned by the Zodiac Killer, or somebody mimicking the Bay Area murderer. Unless you can undeniably identify the sender of this communication, you cannot possibly claim it was mailed by a copycat. Unfortunately David Oranchak, in this instance, has just copycatted the narrative that this is a copycat---and fell into the trap of repeating a claim passed down through the years---in absence of any evidence to make such a claim. The diligent research exemplified in the rest of the video, is not repeated in this limited instance. It may be a minor point in an otherwise excellent presentation by David Oranchak, whose work I value greatly---but it appears that when it comes to the Zodiac communications, comprehensive research by most is not a requirement when making such assertions. 

AUTHENTICATING THE ATLANTA LETTER?

In an effort to confuse the decoders, the sender will sometimes place deliberate errors into ciphertext in a classic cryptographic technique known as nulls, trapdoors, or intentional noise, aimed at disrupting automated frequency analysis. The Zodiac Killer likely did this in his 408 cipher on July 31st 1969, but took this technique to a new level when placing 14 deliberate errors, running diagonally across the second 9 rows of his 340 cipher on November 8th 1969. These manufactured errors were all situated 9 positions apart (shown by the red squares below), as were the blue squares spelling "LIFE IS". This is explained in greater detail in the article "The 340 Cipher: The Final Conclusion". But if the Zodiac Killer was to confuse cryptanalysts further, it would have benefited him to replace higher frequency letters within his message. If we take a look at the letters he replaced in his second 9 rows, we may get an insight into his thinking.    

The individual 10 letters he replaced were A, E, H, N (2 times), O, R (3 times), S (2 times), T, V and Y. In the total count of 14 letters he replaced with misspellings, all but V and Y fall in the top nine most frequently occurring letters in the English alphabet. This means that 12 of the correct letters he replaced (to produce errors) could be found in the nine most frequently used letters in normal text. Only the letter "I" was not selected in the nine most commonly used letters replaced on any diagonal (it was replaced on the 10th row in position 14, when the Zodiac Killer used the letter "E" instead. But this was not on a diagonal). The four green dots in the images above (showing misspellings) have yet to be fully explained. The frequency table on the left was based on a sample of 40,000 words. This frequency of letters is pretty much replicated on Wikipedia.   

It could be of interest to go back to his 408 cipher on July 31st 1969 and examine which letters he chose to misspell in that instance. The majority of the letters replaced in the 340 cipher along the diagonal are of higher frequency in everyday text---but I cannot say whether this was a deliberate choice on behalf of the Zodiac Killer.