Difference between revisions of "Solved 340-character cipher (old version)"
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[[File:Sfchron340cipher.png|thumb|Cipher as it appeared in the SF Chronicle on Nov 13, 1969 (Credit: Deborah Silva, who posts as Seagull on the Zodiac forums)]] | [[File:Sfchron340cipher.png|thumb|Cipher as it appeared in the SF Chronicle on Nov 13, 1969 (Credit: Deborah Silva, who posts as Seagull on the Zodiac forums)]] | ||
+ | *[[Encyclopedia of observations]] - A collection of observations about the cipher text | ||
*[[Comparison of cipher alphabets]] | *[[Comparison of cipher alphabets]] | ||
*[[Comparison of character repetition rates]] | *[[Comparison of character repetition rates]] | ||
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*[[Quadrant analysis Part 2]] - An expansion of the previous quadrant analysis experiment. Is it possible to produce quadrant arrangements that increase the number and quality of homophones detected algorithmically? | *[[Quadrant analysis Part 2]] - An expansion of the previous quadrant analysis experiment. Is it possible to produce quadrant arrangements that increase the number and quality of homophones detected algorithmically? | ||
*Information theory (entropy, randomness, etc) | *Information theory (entropy, randomness, etc) | ||
− | *[[FBI analysis from Dan | + | *[[FBI analysis from Dan Olson]] |
*[[Cipher-related excerpts from case documents]] | *[[Cipher-related excerpts from case documents]] | ||
*[[Word frequency analysis]] (word frequencies derived from a corpus of Zodiac correspondences) | *[[Word frequency analysis]] (word frequencies derived from a corpus of Zodiac correspondences) | ||
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*[[Substring ranking]] - Can we apply measurements that give us a way to find interesting sections of cipher text for focused attacks? | *[[Substring ranking]] - Can we apply measurements that give us a way to find interesting sections of cipher text for focused attacks? | ||
*[[Catalog of repeating fragments]] - A comprehensive list of portions of cipher text that occur more than once in the cipher text. | *[[Catalog of repeating fragments]] - A comprehensive list of portions of cipher text that occur more than once in the cipher text. | ||
− | *[ | + | *[[Cipher Legitimacy]] - Are the Zodiac ciphers real, or are they hoaxes? |
+ | *[[Corpus Experiments]] - A collection of corpus-based experiments performed on the Zodiac ciphers | ||
+ | *[http://zodiackillersite.com/viewtopic.php?f=81&t=2617 Outline of ongoing work on Z340] | ||
+ | *[http://zodiackillersite.com/viewtopic.php?f=81&t=2916 Another outline of ongoing work on Z340] | ||
== Homophone sequences == | == Homophone sequences == | ||
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*[http://www.zodiackillerfacts.com/forum/viewtopic.php?p=22455#p22455 Reversible trigram patterns in the intersecting "pivots" of the cipher text] | *[http://www.zodiackillerfacts.com/forum/viewtopic.php?p=22455#p22455 Reversible trigram patterns in the intersecting "pivots" of the cipher text] | ||
*[http://www.zodiackillerfacts.com/forum/viewtopic.php?f=11&t=1282&p=21758#p21758 Experiment to estimate odds of two intersecting "pivots" occurring by chance] | *[http://www.zodiackillerfacts.com/forum/viewtopic.php?f=11&t=1282&p=21758#p21758 Experiment to estimate odds of two intersecting "pivots" occurring by chance] | ||
− | *[http:// | + | *[http://zodiackillerciphers.com/wiki/index.php?title=Pivots Experimental results of generating pivots from large collection of plain text] |
== Transpositions and other possible variations == | == Transpositions and other possible variations == | ||
− | Is the 340 cipher unsolved because it is not a simple homophonic substitution cipher like the 408 cipher? Here is | + | Is the 340 cipher unsolved because it is not a simple homophonic substitution cipher like the 408 cipher? I began an attempt to rule out specific encipherment schemes here: |
+ | |||
+ | [[Hypothesis Testing]] | ||
+ | |||
+ | Here is an older collection of considered possibilities: | ||
*[[Oxcart]] - Does the 340 cipher's plaintext follow an "ox cart" path; that is, does it read alternately from left to right, then right to left? | *[[Oxcart]] - Does the 340 cipher's plaintext follow an "ox cart" path; that is, does it read alternately from left to right, then right to left? | ||
*Vigenere | *Vigenere | ||
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*Bifid | *Bifid | ||
**[http://www.zodiackillerfacts.com/forum/viewtopic.php?p=22038#p22038 Bifid encipherment prior to homophonic substitution] | **[http://www.zodiackillerfacts.com/forum/viewtopic.php?p=22038#p22038 Bifid encipherment prior to homophonic substitution] | ||
+ | *Did the killer encipher the message, then [http://www.zodiackillerfacts.com/forum/viewtopic.php?p=24969#p24969 re-arrange its lines?] | ||
*Many-to-many (one cipher symbol maps to multiple plaintext letters) | *Many-to-many (one cipher symbol maps to multiple plaintext letters) | ||
*Multiple encryption stages (examples: homophonic that has been rehomophoned, homophonic that has been transposed) | *Multiple encryption stages (examples: homophonic that has been rehomophoned, homophonic that has been transposed) | ||
*Phonetic / nomenclator | *Phonetic / nomenclator | ||
*Was the cipher intended for use [http://www.zodiackillerfacts.com/forum/viewtopic.php?f=50&t=1390&start=20#p24191 by its author only?] | *Was the cipher intended for use [http://www.zodiackillerfacts.com/forum/viewtopic.php?f=50&t=1390&start=20#p24191 by its author only?] | ||
+ | *[http://www.zodiackillersite.com/viewtopic.php?f=81&t=2435 Jarlve's tests] | ||
+ | **At the above link, Jarlve has documented the following variations: Cardan grille variant, stacked directional transformations, spirals, double spirals, column flips, double directional transformations, rail fence, row flips, and row flips in a 20 by 17 grid. | ||
+ | *[https://www.dropbox.com/sh/xlsjup1en6evq2o/AABHmixWHW9rdbWupupSC87sa?dl=0 Heiko's transposition ideas] [http://www.zodiackillersite.com/viewtopic.php?f=81&t=3093&p=48602 (more info)] | ||
== Halloween Card == | == Halloween Card == | ||
* Does the Halloween Card, mailed by the killer a year after the 340 cipher, contain clues about the 340? | * Does the Halloween Card, mailed by the killer a year after the 340 cipher, contain clues about the 340? | ||
**[http://www.kirps.com/web/main/resources/various/zodiac340/ Jos Kirps' article about interesting coincidences between the Halloween card and the 340 cipher] | **[http://www.kirps.com/web/main/resources/various/zodiac340/ Jos Kirps' article about interesting coincidences between the Halloween card and the 340 cipher] |
Revision as of 18:24, 26 June 2016
Zodiac, the serial killer who terrorized Northern California in the late 1960s, sent four ciphers to local newspapers. The first cipher was separated into three different parts and each part was sent to Vallejo Times-Herald, the San Francisco Chronicle, and the San Francisco Examiner. The combination of all three parts formed a 408-letter cipher, which was decrypted one week after it was received. Zodiac also sent a 340-letter cipher, mailed on a card on November 8 1969, that remains unsolved to this day.
Contents
Articles and information about the 340 cipher
- Encyclopedia of observations - A collection of observations about the cipher text
- Comparison of cipher alphabets
- Comparison of character repetition rates
- Comparison of sequence repetition rates
- Levenshtein distance analysis - A look at the occurrences of repeated sequences that are not exact matches.
- Quadrant analysis - Do the n-gram counts improve If we split the cipher text into four quadrants?
- Quadrant analysis Part 2 - An expansion of the previous quadrant analysis experiment. Is it possible to produce quadrant arrangements that increase the number and quality of homophones detected algorithmically?
- Information theory (entropy, randomness, etc)
- FBI analysis from Dan Olson
- Cipher-related excerpts from case documents
- Word frequency analysis (word frequencies derived from a corpus of Zodiac correspondences)
- Omnidirectional repetitions - An investigation into patterns that repeat in arbitrary directions by following "snake-like" paths.
- "Complexification" - Did the cipher author begin with a simpler set of cipher symbols, then "complexify" certain symbols to further flatten the symbol distributions?
- Substring ranking - Can we apply measurements that give us a way to find interesting sections of cipher text for focused attacks?
- Catalog of repeating fragments - A comprehensive list of portions of cipher text that occur more than once in the cipher text.
- Cipher Legitimacy - Are the Zodiac ciphers real, or are they hoaxes?
- Corpus Experiments - A collection of corpus-based experiments performed on the Zodiac ciphers
- Outline of ongoing work on Z340
- Another outline of ongoing work on Z340
Homophone sequences
- Detection of homophone sequences in the cipher text
- Jurgen Koller's "Two-Times Repetition" approach
- Computation of statistical significance of 6-symbol repetitions at the beginning of the cipher text
- Brute force search for homophone sequences - Shows sequences detected in the 408 and 340 ciphers by performing brute force searches for sequences involving up to 7 symbols.
The "Pivots"
- Reversible trigram patterns in the intersecting "pivots" of the cipher text
- Experiment to estimate odds of two intersecting "pivots" occurring by chance
- Experimental results of generating pivots from large collection of plain text
Transpositions and other possible variations
Is the 340 cipher unsolved because it is not a simple homophonic substitution cipher like the 408 cipher? I began an attempt to rule out specific encipherment schemes here:
Here is an older collection of considered possibilities:
- Oxcart - Does the 340 cipher's plaintext follow an "ox cart" path; that is, does it read alternately from left to right, then right to left?
- Vigenere
- Playfair
- Bifid
- Did the killer encipher the message, then re-arrange its lines?
- Many-to-many (one cipher symbol maps to multiple plaintext letters)
- Multiple encryption stages (examples: homophonic that has been rehomophoned, homophonic that has been transposed)
- Phonetic / nomenclator
- Was the cipher intended for use by its author only?
- Jarlve's tests
- At the above link, Jarlve has documented the following variations: Cardan grille variant, stacked directional transformations, spirals, double spirals, column flips, double directional transformations, rail fence, row flips, and row flips in a 20 by 17 grid.
- Heiko's transposition ideas (more info)
Halloween Card
- Does the Halloween Card, mailed by the killer a year after the 340 cipher, contain clues about the 340?