GPT-6 Astra Solves a WWI German Radio Cipher
GPT-6 Astra Decodes a WWI German Radio Cipher
The German science portal Scienceblogs.de maintains a well-known registry of 50 unsolved ciphers, featuring everything from the enigmatic Voynich manuscript to cryptograms left by serial killers.
Among these mysteries is a collection of World War I German radio transmissions encrypted via the ADFGVX method.
Understanding the ADFGVX System
The ADFGVX cipher is a fractionating transposition cipher. To illustrate, consider the word HOUSE as the encryption key:
| A | D | F | G | V | X | |
|---|---|---|---|---|---|---|
| A | H | O | U | S | E | A |
| D | B | C | D | F | G | I |
| F | J | K | L | M | N | P |
| G | Q | R | T | V | W | X |
| V | Y | Z | 0 | 1 | 2 | 3 |
| X | 4 | 5 | 6 | 7 | 8 | 9 |
In this grid, each character is represented by a pair of coordinates. For instance:
AAHADODAB
Consequently, the word PRINZ would be encoded as: FX GD DX FV VD. Note: Changing the key word would completely alter the resulting table.
The Unsolved Message
While experts like George Lasry have decoded hundreds of these messages using known keys, over a dozen remained stubborn. One such message was transmitted on November 27, 1918.
The Breakthrough
GPT-6 Astra successfully cracked this cipher. The model identified the original German text as:
EIN ENGLISCHER KREUZER EINLIEG X SEWASTOPOL X S4STEN X EIN GESCHWADER DER X ALLIIERTEN FOLGT 26STEN X
English Translation: "An English cruiser arrived at Sevastopol on the 24th; an allied squadron follows on the 26th."
Technical Execution
Astra determined that the encryption key was TRUPPENVERSCHIEBUNG (referenced in Rives Childs's The History and Principles of German Military Ciphers, 1914–1918).
The Decryption Workflow
The process involved these specific steps:
- Alphabetize the key
TRUPPENVERSCHIEBUNG. - Write the 170-character message in rows of 19 (8 full rows, 1 row of 18).
- Determine column lengths (18 columns of 9, 1 column of 8).
- Extract characters based on the key's alphabetical rank.
The Mathematics of Column Extraction:
For the letter T (the 16th alphabetically), there are 14 columns of 9 and 1 column of 8 preceding it:
Thus, the 135th symbol in the message is the first character for T, which is A.
For the letter R (the 13th alphabetically), there are 11 columns of 9 and 1 column of 8 preceding it:
The 108th symbol is V.
Using the table, the pair AV maps to the letter E, the start of the word EIN.
Verification and Analysis
Astra hypothesized that this message remained unsolved because TRUPPENVERSCHIEBUNG was officially adopted as a key on December 9, 1918, whereas this message was sent earlier, on November 27.
To verify the historical accuracy, Astra cross-referenced naval logs:
- HMS Canterbury (English cruiser) arrived in Sevastopol on November 24, 1918.
- An allied squadron arrived on November 26.
This result serves as a compelling demonstration of the analytical capabilities of the GPT-6 Astra model.
Post Metadata:
- Author: prinz
- Date: Sep 17, 2026
- Engagement: 23 Likes, 1 Restack, 5 Shares
- Commentary: Sal Daher | Aging Fit
noted: "This is a great result."
