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Applying the Combined Cipher Decoding Methodology to the Four Zodiac Ciphers
Below, I use the detailed, unified cipher-solving process outlined earlier on each of the Zodiac Killer's four main ciphers. For the two solved ciphers (Z408 and Z340), I summarize how the process works and why it succeeded. For the unsolved ciphers (Z13 and Z32), I describe how the same process would be applied and what obstacles remain.
1. Z408 Cipher ("I LIKE KILLING PEOPLE...")
Cipher Type: Homophonic substitution
Process Applied:
Acquire Cipher: The cipher was split into three parts, each a grid of symbols.
Frequency Analysis: Analysts noted multiple symbols for common letters (e.g., "E" had seven symbols).
Segmentation: Each part was treated as a separate block.
Homophonic Substitution: Donald and Bettye Harden matched symbol frequencies to English letter frequencies, using cribs like "KILL" and "SLAVES."
No Transposition: The cipher was a straightforward substitution, so no grid rearrangement was needed.
Result: The plaintext was revealed as the killer's message about killing for fun and collecting slaves for the afterlife.
Remaining Mystery: The last 18 letters ("EBEORIETEMETHHPITI") did not fit the pattern and remain unsolved—possibly a meaningless addition.
2. Z340 Cipher ("I HOPE YOU ARE HAVING LOTS OF FUN...")
Cipher Type: Homophonic substitution + transposition
Process Applied:
Acquire Cipher: 340 symbols in a 17x20 grid.
Frequency Analysis: 63 distinct symbols, with multiple symbols per letter.
Segmentation: The grid was split into segments, including a special "LIFEIS" segment, based on mathematical criteria and pattern analysis.
Homophonic Substitution: Initial symbol-to-letter assignments were made based on frequency, then refined.
Transposition: The solution required a "1,2-decimation" transposition, skipping the "LIFEIS" segment and reading other parts in a specific order.
Computational Heuristics: Tools like AZdecrypt and custom algorithms tested billions of permutations, using English language scoring and cribs to guide the solution.
Result: The plaintext was revealed, matching the Zodiac's taunting style and confirming the killer's authorship.
3. Z13 Cipher ("My Name Is...")
Cipher Type: Short homophonic or mixed substitution (13 symbols)
Process Applied:
Acquire Cipher: 13 symbols, possibly letters, numbers, and astrological signs.
Frequency Analysis: Limited by short length; frequency analysis is not effective.
Segmentation: Not applicable due to short length.
Homophonic Substitution: Attempts to map symbols to letters using possible Zodiac-related cribs (e.g., "ZODIAC," "KANE," "ALLEN").
Transposition: With so few symbols, transpositions yield too many possibilities for meaningful brute-force analysis.
Computational Heuristics: Dictionary and name-matching algorithms have been tried, but no solution has been confirmed.
Result: Remains unsolved, likely due to its brevity and possible use of a private or one-time cipher key.
4. Z32 Cipher ("Map/Bomb Cipher")
Cipher Type: Short homophonic or mixed substitution (32 symbols)
Process Applied:
Acquire Cipher: 32 symbols, possibly letters, numbers, and astrological signs.
Frequency Analysis: Limited effectiveness due to short length.
Segmentation: Some researchers have tried splitting the cipher based on the map grid or possible geographic clues.
Homophonic Substitution: Attempts to map symbols to letters using possible bomb-related cribs or Zodiac phrases.
Transposition: Some have tried rearranging the symbols based on the map's coordinates or grid.
Computational Heuristics: Automated tools have tested thousands of key possibilities, but no coherent English message has emerged.
Result: Remains unsolved, possibly due to brevity, a one-time pad, or a non-standard cipher method.
Summary Table
Cipher Solved? Method Used Outcome
Z408 Yes Homophonic substitution, cribs, frequency Full plaintext revealed except last 18 letters
Z340 Yes Homophonic substitution, transposition, computational heuristics Full plaintext revealed after 51 years
Z13 No Homophonic substitution, cribs, heuristics Unsolved—too short, possibly a name or code
Z32 No Homophonic substitution, transposition, heuristics Unsolved—possibly map-related, too short
Conclusion
The combined methodology—frequency analysis, segmentation, homophonic substitution, transposition, cribs, and computational heuristics—has proven effective for long, patterned ciphers (Z408, Z340), but is limited by the brevity and possible nonstandard construction of the shorter ciphers (Z13, Z32). For Z408 and Z340, the process revealed the Zodiac's chilling messages. For Z13 and Z32, the same approach has not yielded a solution, likely due to insufficient data and/or unique cipher design.
If you want to run a specific custom cipher or have further details about your own cipher pattern, I can help you apply this process step-by-step to any Zodiac cipher text.