Encyclopedia of observations - Revision history

Admin: /* Z408 and Z340 */

2026-02-09T12:17:35Z

‎Z408 and Z340

2026-02-04T16:09:35Z

‎Z408 and Z340

2026-01-13T11:00:56Z

‎Observations related to the discovered plaintext and encipherment method

2025-12-20T21:27:31Z

‎Kasiski Examination

2025-12-20T21:20:53Z

‎Other observations

2025-12-16T21:17:07Z

‎Other observations

2025-12-16T21:16:45Z

‎Other observations

2025-12-14T16:30:45Z

‎Repeated symbols by columns and rows

2025-04-16T16:15:55Z

‎Observations related to the discovered plaintext and encipherment method

2024-09-05T10:47:56Z

‎The "Pivots"

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 * When written vertically, some symbols repeat in a pattern similar to the period-19 reading order used to decrypt the Z340 ([http://www.zodiackillersite.com/viewtopic.php?p=85261#p85261 Source: Marclean])
 * 17,20,24,340 and 408 are "[https://en.wikipedia.org/wiki/Evil_number evil numbers]". (Source: Jarl)
 = Z13 =

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 * Z408 and Z340 each have an alphabet size that is divisible by 9:  "9x7 = 63 Z340, 9x6 = 54 Z408.  Just for inclusion 7 symbols were dropped from Z408 and 16 were added for a net gain of 9 in Z340."  [http://www.zodiackillersite.com/viewtopic.php?p=48175#p48175 (Source: BartW)]
 * When written vertically, some symbols repeat in a pattern similar to the period-19 reading order used to decrypt the Z340 ([http://www.zodiackillersite.com/viewtopic.php?p=85261#p85261 Source: Marclean])
 = Z13 =

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 * The untransposed plaintext has a 13-character section beginning with A and ending with M.  Z13 also begins with A and ends with W.  [https://www.tapatalk.com/groups/zodiackillerfr/curiosities-t10780.html#p237455 (Source: cragle)]
 * If you count the letters in "life is" and the shifted letters "ratenyrnosrvs", they add up to 19 (the period required to transpose the plaintext) (Source: @timpsensky5181 on YouTube)
 == Other observations ==

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 * A Kasiski examination performed on unigrams in Z408 reveals a spike of 18 repeats at shift of 49
 ** Among 1,000,000 random shuffles, only 2.2% of them had a spike as good or better as the one observed in Z408 [http://www.zodiackillersite.com/viewtopic.php?p=48226#p48226 (details)]
-* The 408 at period 4 transposed or period 102 untransposed has an even more significant (than Z340's) doublet peak.  (Source: [http://www.zodiackillersite.com/viewtopic.php?p=73882#p73882 Jarlve])
+* The 408 at period 4 transposed or period 102 untransposed has an even more significant (than Z340's) doublet peak.  (Source: [http://www.zodiackillersite.com/viewtopic.php?p=73882#p73882 Jarlve (broken)]) [https://forum.zodiackillerciphers.com/community/postid/71367/ (fixed)]
 = Z340 =

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 ** [https://forum.zodiackillerciphers.com/community/postid/4816/ Working link]
 * Of the three letters sent to newspapers, only the Chronicle's letter said "In this cipher is my identity".  This could be interpreted as referring specifically to the cipher portion the Chronicle received, which is the end portion of the cipher which also contains the unsolved 18 characters at the end.  Perhaps Zodiac is implying his identity or name can be derived from this portion or the last 18 characters.  [https://discord.com/channels/996952324150931477/996952376894292018/1087499591651438612 (Source: Nicodemus)]
 == Kasiski Examination ==

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 * The plaintext solution has a shorter average word length than regular English (4 vs 5) (Source: [http://www.zodiackillersite.com/viewtopic.php?t=4204&p=68848#p68848 Jarlve and beijinghouse])
 * [http://zodiackillersite.com/viewtopic.php?p=84668#p84668 Comparison of Z408 key with Z340 key via shifts] (Source: upsampled)
-** [https://zodiackillersite.com/viewtopic.php?p=84668#p84668 Working link]
+** [https://forum.zodiackillerciphers.com/community/postid/4816/ Working link]
 * Of the three letters sent to newspapers, only the Chronicle's letter said "In this cipher is my identity".  This could be interpreted as referring specifically to the cipher portion the Chronicle received, which is the end portion of the cipher which also contains the unsolved 18 characters at the end.  Perhaps Zodiac is implying his identity or name can be derived from this portion or the last 18 characters.  [https://discord.com/channels/996952324150931477/996952376894292018/1087499591651438612 (Source: Nicodemus)]

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 == Repeated symbols by columns and rows ==
 * The 340 cipher has 9 rows that each contain no repeated symbols [http://zodiackillerciphers.com/images/z340-z408-repeated-symbols-by-rows-and-columns.jpg (Illustration.  Rows are marked in yellow.)]  In 1,000,000 shuffles, no shuffled cipher text had at least 9 rows with no repeated symbols [http://zodiackillerciphers.com/images/z340-shuffles-rows-without-repeated-symbols.png (plot of distribution)] [http://zodiackillerciphers.com/images/z340-shuffles-rows-without-repeated-symbols (raw data)]
 * If you split the cipher in half with a horizontal cut in the middle, the top and bottom halves each start with 3 lines that have no repeated symbols.  This symmetry is discussed in [http://zodiackillerciphers.com/wiki/index.php?title=FBI_analysis_from_Dan_Olson Dan Olson's analysis].
 * Every column contains at least one repeated symbol.

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 * The plus and filled in circle symbols repeat in the same positions relative to each pivot.  [http://zodiackillersite.com/viewtopic.php?p=81465#p81465 (Source: Mr lowe)]
 * In light of the known solution and transposition steps, the pair of pivots vaguely resembles arrowheads suggestive of the reading direction.
-* 9 out of 14 of the plaintext letters forming the pivots involve the letters A, E, or N.  In both the 340 and 408 keys, the backwards L symbol decodes to A, the N symbol decodes to E, and the D symbol decodes to N.  Those are the only symbols that decode to the same letter.  [https://www.reddit.com/r/ZodiacExtortion/comments/1f3hqsl/pivot_patterns_with_aen_symbols/ (Source: Sam Fisher)]
+* 9 out of 14 of the plaintext letters forming the pivots involve the letters A, E, or N.  In both the 340 and 408 keys, the backwards L symbol decodes to A, the N symbol decodes to E, and the D symbol decodes to N.  Those are the only symbols that decode to the same letter.  Also, Z13 begins with the same three letters: AEN.  [https://www.reddit.com/r/ZodiacExtortion/comments/1f3hqsl/pivot_patterns_with_aen_symbols/ (Source: Sam Fisher)]
 == Observations related to the discovered plaintext and encipherment method ==