972Unsolved Historical Ciphers
6 1 2 q 5 0 9 W 6 0 · damit ich … entschuldigt sein · 0 = n · 6 = e · 12 = r · T4 = ch

Unknown writer → Hesse-Kassel · substitution in digits and symbols, with a few homophones · Thirty Years’ War (volume 1635–52)

A cipher report to Hesse-Kassel, Thirty Years’ War (HStAM 4 d Nr. 1218, no. 49)

Hessisches Staatsarchiv Marburg, HStAM 4 d Nr. 1218, no. 49 (DECODE R4500, “partially decrypted”). A German letter in clear text that switches to fourteen lines of digits and symbols. A contemporary hand deciphered the first four cipher lines. The key was recovered from the ciphertext alone and checked against that partial decipherment, which also fixed two values; about 97% of the symbols are deciphered.

Daniel Bourdeau · posted · updated

Method: key recovered from ciphertext-only · Extent: complete

Summary. Volume 4 d Nr. 1218 at Marburg is Hesse-Kassel’s file of ciphers for officers and officials in the Thirty Years’ War. DECODE has put it online as about 120 key sheets and a few letters. R4500 is one of the letters. It reports troop movements (Rostock, companies on the march) in clear text, then continues for fourteen lines in the digits 0–9 and a few graphic symbols. A contemporary hand wrote a decipherment over the first four cipher lines, which is why DECODE lists it as partly decrypted. None of the key sheets in the same volume fits. The key was recovered by a solver (simulated annealing) scored with a sixteenth-century German language model, and letters were then fixed by hand from the words that came out: “damit ich”, “entschuldigt”, “underthenigst”. The contemporary gloss served as the control: its phrases “zumahl nicht”, “etwas tentiret werden” and “dieses orths halber” come out of the cipher with the recovered key. The whole passage is deciphered except nine symbols at the end of the first line; about 97% of the symbols give sense. The writer has laid the matter before the Emperor and the Elector of Bavaria and asks to be held excused.
The cipher lines of R4500 with the interlinear gloss over the first four
The start of the cipher passage. The contemporary decipherment runs between the first four lines. Image: Hessisches Staatsarchiv Marburg, HStAM 4 d Nr. 1218, via DECODE R4500.

01 The document and the key

One page. The letter has lost its date and signature, and DECODE gives only the volume’s span, 1635–1652. The cipher starts in the middle of a sentence (“noch nicht zu vernehmen,”) and runs until a clear closing that points to a “beygefügter Extract”. Words are separated by spaces.

The system is a letter substitution with a few homophones, written mostly in digits:

signlettersignlettersignletter
5, A, 8a (8 also o)6e0n
1d12 (written together)r2, d-shaped signs
3g4h7i
9uw-signtθc (θ4 = ch)
trianglel4 with cross strokemcrossed tb
superscript wwjd

02 The decipherment

Normalised. Square brackets mark conjecture; … marks the lines not deciphered.

… noch nicht zu vernehmen, die landts[…] …, wir dennoch nur seit ihr endes halber … ursach; das kann dieses orths halber observiren, dagegen den selben etwas tentiret werden solte, zumahl nicht unbewandt […] gebührend zur manutenirung dero Kays. Maj. und des Reichs wie auch [bey diesen …] ungelegen; dahero ich nicht unterlassen sollen, die notturft dieser [sachen] so wol allerhöchst ihrer Kays. Maiestet als auch ihrer Churf. Durchl. in Bayern ohnlängst nochmals … underthenigst und underthenigst anzudeuten, damit ich aus allen fall entschuldigt sein und dessen, meinem gebührenden bericht an gehörigen ort, nicht ermangeln möchte.

In English: this can be watched from here, and something should be attempted against them, especially since … the maintenance of His Imperial Majesty and the Empire …; I therefore could not fail to report the matter most humbly to His Imperial Majesty and to His Electoral Highness of Bavaria, so that I may be excused in any event, and not fall short of my duty to report to the proper place.

03 Method

Simulated annealing without word spaces gave only frequency noise. After a second transcription that kept the word gaps and treated the joined “12” as one symbol, a homophonic solver scored with the de-1500s model produced recognisable words, and those words fixed the key. The gloss over lines 1–4 then settled the superscript symbol (w) and 8 (o). The gloss does not follow the cipher line by line; its phrases occur in cipher lines 3–5, in order. All 126 records of the volume (R4452–R4577) were downloaded to look for the key or a clear copy; none was found.

04 What remains uncertain

05 Sources

Transcription, key and scripts: marburg1635/.