Thanks to the fantastic work of David Oranchak, Sam Blake and Jarl Van Eycke, the 340 cipher was finally decoded in 2020, allowing others to look into the mechanics of its creation. David stated in his YouTube video that they were "extremely lucky to uncover the solution" because of the many mistakes of Zodiac in the second part of the cipher. However, the Zodiac Killer may have been a little bit more devious than we give him credit for.
It is now safe to say that the Zodiac Killer hardly made any mistakes (maybe none) when creating his 340 cipher, and the numerous spelling errors were deliberately engineered to make the cipher more difficult to solve. It turns out that the second nine rows of the cipher only contains four unexplained errors. The following analysis has not been approached from the standpoint of how the cipher was cracked, it has been looked at through the eyes of Zodiac and how he encoded the message in 1969.
Clearly, he has to begin his process by writing a message of 340 plaintext characters. This message can be written ordinarily or in grid form, because the same technique will be applied to mix up the message in both - a right shift of 9 until we complete a new row, and then we fall back 8 positions and begin the sequence over. See here.
It is now safe to say that the Zodiac Killer hardly made any mistakes (maybe none) when creating his 340 cipher, and the numerous spelling errors were deliberately engineered to make the cipher more difficult to solve. It turns out that the second nine rows of the cipher only contains four unexplained errors. The following analysis has not been approached from the standpoint of how the cipher was cracked, it has been looked at through the eyes of Zodiac and how he encoded the message in 1969.
Clearly, he has to begin his process by writing a message of 340 plaintext characters. This message can be written ordinarily or in grid form, because the same technique will be applied to mix up the message in both - a right shift of 9 until we complete a new row, and then we fall back 8 positions and begin the sequence over. See here.
If we apply the cipher key to the original 340 cipher, the phrase "LIFE IS" appears at the end of the 10th row, but in the message below it appears at the end of the 18th row. So how does the Zodiac move this phrase up to the top, so it lands in positions 12, 13, 14, 15, 16 and 17 and finishes the 10th row. He has to deliberately insert the six letters of "LIFE IS" into the positions shown by the white circles below, which are in positions 12, 13, 14, 15, 16 and 17 in the highlighted sections of the grid (9 places apart). In other words, he has to wilfully insert these six plaintext letters into the erroneous positions below and position them all 9 apart from one another, to get them to appear at the end of the 10th row of the 340 cipher in the correct sequence. I suggest this cannot be achieved by accident. I believe this was done purposefully to play games with the codebreakers. This means that his spelling mistakes were also likely positioned strategically within the grid.
THIS GRID WAS CREATED WITHOUT THE SPELLING ERRORS SHOWN BELOW
THE GRID BELOW IS THE CIPHERTEXT OF THE 340 CIPHER AFTER THE PERIOD 19 SHIFT
Above I showed that the phrase "LIFE IS" was separated by 9 positions in the misspelled message, and inserted in such a way that it would appear coherently at the end of the 10th row of the 340 cipher.. Excluding these as errors, the Zodiac Killer also added 18 spelling mistakes into this section of the message (shown by the black and green circles below). The spelling mistakes represented by the black circles are all positioned 9 apart (the only exception is from number 7 to number 8, which are 4 X 9 apart). So we have a message encoded using shifts of 9, the phrase "LIFE IS" separated by 9 positions to allow it to appear on the 10th row of the Zodiac Killer's 340 cipher, with 14 of his spelling errors positioned 9 apart. Again, can we reasonably be expected to believe this happened by chance?
BELOW I HAVE PLACED THESE ERRORS INTO THE GRID TO SHOW THE PATTERN
BELOW I HAVE PLACED THESE ERRORS INTO THE GRID TO SHOW THE PATTERN
The Zodiac Killer has put the bulk of his errors on the central diagonal, apart from the middle row. The remaining six errors (top and bottom) are 9 positions to the right and left of the central diagonal. The spelling mistakes represented by the green circles I cannot yet fully explain, but I have an idea. Below in the black squares are 14 of the spelling errors (9 apart) and the "LIFE IS" phrase shown in the blue squares, both highlighted in one grid. The pattern of these errors indicates that they were intentional and designed, not created by random mistakes while creating the message in the 340 cipher.
THE INSERTION OF THE CORRECT PLAINTEXT LETTERS BELOW WOULD RECTIFY 78% OF THE MESSAGE. ONLY FOUR ERRORS WOULD REMAIN (THE GREEN CIRCLES).
The above 14 plaintext letters (in brown) are the same plaintext letters identified by Jarl Van Eycke on the 15th row of the 340 cipher after the cipher key was applied. This was deemed to be the problematic row in the second part of the cipher. Watch this portion of the video.
FURTHER READING: "I KNOW THAT MY NEW LIFE IS DEATH"
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