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Structural analysis of the D'Agapeyeff cipher (1939)

Structural analysis of the D'Agapeyeff cipher (1939)

by evaneykelen·Mar 14, 2026·3 points·0 comments

AI Analysis

●●SolidRabbit HoleNiche GemBig Brain

Esperanto quadgrams outscores English by 200+ points on this 85-year-old unsolved cipher.

Strengths
  • The 2-and-7 positional pattern discovery shows genuine mathematical insight into cipher structure
  • Esperanto hypothesis is non-obvious and consistently recovers vocabulary across independent runs
  • Combines geometric grid analysis with computational linguistics systematically
Weaknesses
  • Cipher remains unsolved—this is preliminary research, not a working solution or tool
  • Blog post format limits practical utility compared to actual cryptanalysis software
Category
Target Audience

Cryptography enthusiasts, security researchers, puzzle solvers

Similar To

Cryptii · dCode · Boxentriq

Post Description

I am working on the D'Agapeyeff cipher, an unsolved cryptogram from 1939. Two findings that I haven't seen published before:

1. All 5 anomalous symbol values in the cipher cluster in the last column of a 14x14 grid. This turns out to be driven by a factor-of-2-and-7 positional pattern in the linear text.

2. Simulated annealing with Esperanto quadgrams (23M char Leipzig corpus) on a 2x98 columnar transposition consistently outscores English by 200+ points and recovers the same Esperanto vocabulary across independent runs.

The cipher is not solved. But the combination of structural geometry and computational linguistics narrows the search space significantly.

Work in progress, more to come!

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