Paper 2023/982 Original: eprint.iacr.org/2023/982 ↗

On the 32-Character Zodiac Cipher

Abstract

A possible new approach to the Zodiac Killer's 32-Character Cipher (Z32) is proposed based on the strengths and weaknesses of previous approaches and novel interpretations. This approach does not assume the use of anagrams or similar complex transposition methods; does not assume the identity of a particular Zodiac suspect; and assumes the use of homophonic substitution (as in Z408 and Z340), and simple transposition (as in Z340). Assumptions are clearly defined and tested with sensitivity tests. With Mount Diablo as the pole of a plane polar coordinate system, the instruction "set to Mag. N." is interpreted by setting the hour and minute hands of a watchface to the magnetic declination of the Bay Area circa 1970. Sensitivity tests reveal the exact year and location have little impact on the declination in this case. The hour and minute given by the hands are interpreted as the radial coordinate r and the angular coordinate theta, as in "Radians & # inches along the radians". The hand corresponding to each coordinate is tested, as are 12- and 24-hour interpretations. Impossible or improbable coordinates are excluded leaving one coordinate as a possible solution. This coordinate is explored as the possible plaintext for Z32 using the Z340 transposition method. Further exploration of the proposed method is necessary.