Published January 22, 2026 | Version v1

Preprint Open

Description

The 32-character ciphertext ("Z32") mailed by the Zodiac Killer in June 1970 has historically been resistant to standard cryptanalysis due to its low unicity distance. This paper presents a solution derived by reframing the cipher as a Geographic Constraint Satisfaction Problem (GCSP). By restricting the search space to the author’s explicitly stated polar coordinate nomenclature ("radians and inches") and enforcing strict homophonic repetition constraints, we isolate a dominant candidate plaintext: "IN THREE AND THREE EIGHTHS RADIANS TEN".

When projected from the Mount Diablo anchor using the 1970 magnetic declination (17°E), this vector triangulates to coordinates 38.10995° N, 122.18535° W. Remote sensing analysis reveals that these coordinates align within the margin of manual plotting error (0.02 inches map-scale) to a distinct, 100-foot equilateral triangular crop mark. This anomaly exhibits hydrological signatures consistent with deep subsurface soil disturbance (excavation) and has been verified via historical photography to exist across multiple decades. Furthermore, the location serves as the geometric centroid of the killer’s activity radius and exhibits a high-fidelity topographical match to the "Death Machine" schematic. We argue that the independent convergence of cryptographic, geometric, and archaeological vectors onto a single point renders the hypothesis of coincidence statistically untenable.

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Stampher_2026_Z32_Geometric_Constraint_Satisfaction.pdf

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