ADFGVX & WW1 Radio Cipher Cryptanalysis

Analyze, fractionate, permute, and crack historical military radio messages. Model Fritz Nebel's 1918 German field cipher, perform Index of Coincidence tests, and run automated columnar transposition recovery.

Intercept Input

Field Signal 1918

Preset Historical Intercept Radio Intercept Ciphertext (ADFGVX Stream) ADFGVX was chosen because Morse representations are distinct and acoustic errors are minimized.

Intercept Length

0 chars

Index of Coinc.

0.000

Transposition Key

Nebel Columnar

Columnar Transposition Keyword Alphabetical order determines the readout order of columns. Polybius Substitution Keyword Generates 36-char square (A-Z and 0-9).

Automated Key Discovery & Crib Dragging

Crib Test Pattern Highlight candidate match positions in decrypted stream.

Ready. Default 1918 Crimea Naval Intercept decoded successfully.

RECOVERED INTELLIGENCE STREAM

Fitness Log-Likelihood: -142.8

Recovered German Plaintext / Military Telegraph:

CRUISER IN SEVASTOPOL CRIMEA SQUADRON ARRIVING IN TWO DAYS

Historical Context: In 1918, German naval command transmitted encrypted field reports tracking Allied operations in the Black Sea following the Treaty of Brest-Litovsk. Modern machine intelligence (such as GPT-6 Astra) successfully reconstructed this long-lost transmission.

Polybius 6×6 Grid ADFGVX Coordinates

Columnar Matrix Permutation Key: KAISER (6 columns)

The ADFGVX Cipher (1918)

Introduced in March 1918 on the Western Front by German Army Lieutenant Fritz Nebel, ADFGVX was considered unbreakable at its debut. It combined two cryptographic steps:

Fractionation: Each plaintext character is replaced by two letters from the set {A, D, F, G, V, X} using a 36-cell keyed Polybius square.
Columnar Transposition: The fractionated coordinates are written into a matrix row by row and read out column by column according to a secret keyword.

Georges Painvin famously cracked the cipher during the 1918 German Spring Offensive by collecting messages sent with identical keys and analyzing transposed pair collisions.

Cryptanalysis & Automated Solving

This workbench reproduces Painvin's analytical techniques combined with statistical n-gram hill climbing:

Index of Coincidence (IoC): Raw fractionated ADFGVX produces an IoC near random noise (~0.038) because the alphabet is compressed into 6 symbols.
Column Decimation: Because each plaintext letter comprises two coordinates, an odd number of transposition rows creates parity shifts that cryptanalysts exploit.
Hill-Climbing Search: Swapping candidate column orders and measuring bigram/trigram log-probabilities rapidly recovers German military keywords.

ADFGVX & WW1 Radio Cipher Cryptanalysis

Intercept Letter Frequency (ADFGVX) Signal Balance

Decrypted Letter Distribution vs German Standard Chi-squared validation

The ADFGVX Cipher (1918)

Cryptanalysis & Automated Solving