972Unsolved Historical Ciphers
δ8cʒ2ΛʒxʒwΛ xvxΛ · Protestatus abbas
w3vX · ewr F.G. · 48 = -en · ↓ = r · ω = e

Buda, Kraków, Rome, Pressburg → the Dukes of Bavaria · fourteen ciphertexts in at least six systems · 1529–1583

The Bavarian key volume: fourteen ciphertexts in Kurbayern Äußeres Archiv 4591

BayHStA Munich, Kurbayern Äußeres Archiv 4591 · DECODE R9291–R9427 · catalogue entry 161, “unknown sender to unknown recipient”

Separate letters in at least six systems, which DECODE catalogued as one group. Three are deciphered completely: one with the key filed in the same volume, two with a key recovered from their interlinear glosses. One leaf was deciphered at the time. Eight are partly deciphered, with keys recovered from contemporary glosses, taken from a key register in the volume, or in one case recovered from the ciphertext alone. One is blocked, one is attempted and open, and one is a key fragment, not a letter. No edition of the volume was found.

Daniel Bourdeau · posted · updated

Method: key recovered based on adjacent plaintext · Extent: partial

Summary. KAA 4591 is the Bavarian ducal chancery’s volume of cipher keys, with about a hundred key sheets from the 1520s to 1620 and fourteen ciphertexts bound in among them. DECODE catalogued the fourteen as one “unknown sender” group. They are separate letters in at least six systems. The Fulda note (R9325, 1576) is deciphered completely with the key filed five leaves earlier (R9324). Three letters of Hieronymus Łaski and King John of Hungary (R9322, R9323, R9417, 1529–30) are deciphered completely or nearly, with a key recovered from their interlinear glosses. A servant’s petition (R9416 f. 262) was deciphered at the time. Seven German reports of 1534–35 on Hungary, the Turks, Rincon and France are partly deciphered. The key of one (R9416 f. 263) was recovered from the ciphertext alone with a new sixteenth-century German language model, that of five (R9408, R9409, R9410, R9413, R9427) from one faint contemporary gloss on R9427, and one (R9367) was deciphered with a key in the volume’s own key register. The dot-grille of 1583 (R9319) is blocked because DECODE never imaged the cover letters it lies over, R9424 (1583) is attempted and open, and R9291 is a key fragment. No edition of the volume was found. Extent: partial. The working decrypts are machine output with gaps and are marked as such; none of the eight partial decipherments is yet a clean text.

01 The fourteen records

RecordFolioWhat it isKeyState
R9325129Latin note on the Fulda affair, 1576R9324, f. 124–127read
R9322121–122Łaski, Buda, 24 Nov 1529; King John to Duke Ludwigrebuilt from glossesread
R9417264Łaski, Kraków, 16 June [1530]sameread
R9323123Łaski to the dukes’ secretarysameread except four faint lines
R9416262a servant to his duke, “eritags nach Jacobi”interlinear deciphermentread at the time
R9416263the Pressburg talks, c. 1533–34ciphertext-only solveread in part
R9408236–239report of 1534 on Hungary and the TurkR9427 gloss keyread in part
R9409240–243intelligence report with articles and answersR9427 gloss keyread in part
R9410244–247report of 1535, France and the EmpireR9427 gloss keyread in part
R9413252–256three letters, June–July 1534 (Rincon, Constantinople)gloss key refittedread in part
R9427287newsletter of 24–25 April 1534its own glossread in part
R9367169a son to his father, 22 March 1535register R9423, block 2_4read in part
R9424274–277to Duke Wilhelm V, 12 June 1583, Cologne warnot foundattempted, open
R931996–114dot grille over a clear cover letter, 1583the cover lettersblocked
R929136a strip of cipher signs—key fragment, not a letter

02 The Fulda protest, 1576 (R9325)

The key sheet five leaves earlier (R9324) has the same six null signs as the note, which is how the two were matched. It is a letter alphabet with doubled letters and a nomenclator of the Fulda affair: Pope, nuncio, the Abbot, Chapter and Dean of Fulda, the Bishop of Würzburg, the Emperor’s councillors, the Duke of Bavaria. Every sign resolves:

Protestatus [est] abbas secreto coactum [se] ad litem acceptare Pontificis inhibitionem. Rogatus Pontifex ut contradicendo se interponat, declaret sive sponte sive vi contra canones esse. Si id fiat, Abbas agere cessat et cum Pontifice litigabit; … Consiliarii Caesaris iudicabunt, aut Pontifex tum facit quod iam voluit. Rogatus Dux Bavariae auxilio sit; Nuncius suadeat Pontifici ita ad protectionem via[m].

It is the deposed abbot Balthasar von Dernbach’s case: he protests that he was forced to accept the papal inhibition, and asks for the Pope’s declaration, the Duke’s help and the nuncio’s intercession.

03 Hieronymus Łaski and King John, 1529–30 (R9322, R9323, R9417)

A graphic monoalphabetic cipher with three word signs. Interlinear glosses over some lines gave 153 word pairs, and the key from them deciphers the unglossed lines. The word signs follow from context: the Sultan “will have [†] in no other place than that of his brother” (King John); “concord between [†] and [X]” (Ferdinand).

04 The German reports of 1534–35

R9416. Folio 262 carries a contemporary German decipherment over every line. A servant asks the duke for seven years’ unpaid pension and for the office of Oberrichter at Straubing. Folio 263 has no gloss past its first lines. Its key was recovered from the ciphertext alone by a solver (simulated annealing) against a language model built for this target from the Deutsches Textarchiv’s German prints of 1472–1609. The faint gloss on its first lines agrees word for word with the solver’s text: “…von beden kunigen zu entlicher handlung gen Pressburg gesetzt…”. It reports the Pressburg negotiations between Ferdinand and John, a Turkish embassy, Imre Czibak offering tribute, and “den hern Griti abgefertigt” (Alvise Gritti, killed September 1534). One sign still has to be set by hand: the sense requires ch where the solver gives s.

System A′. R9408, R9409, R9410, R9413 and R9427 share one sign family. R9427 has a faint gloss over ten lines. Aligned sign by sign, it shows that the commonest group w3vX is “ewr F.G.” (X is a code sign for Fürstliche Gnaden) and gives a homophonic key: 4 and ω e, □ and 8 n (“48” = -en), ↓ r, ÿ t, 5 a, π b/w, the slanted ‡ g, the upright H u/v, and so on. Every transcription was then re-checked sign by sign on the images, and look-alike signs that had been merged were split. A decoder applies the key and chooses d or ch for one ambiguous sign from context.

R9367, a son to his father, 22 March 1535, is deciphered with block 2_4 (“H. Wilh.”) of R9423, a chancery register copying out nineteen keys of the 1520s–30s. The ciphered passages say he was questioned and denied everything, fears for his safety, and reports the Turks coming up; the postscript names a Friedrich and “Schmalcz”. Three signs are nulls. One sign and six lines remain open.

05 What stays open

06 Sources

Bayerisches Hauptstaatsarchiv, Kurbayern Äußeres Archiv 4591, via the DECODE database (records R9277–R9428, login). The images are not in the public domain and are not reproduced. Keys used: R9324 (f. 124–127), R9423 (f. 272–273), the interlinear glosses of R9322, R9417, R9416 and R9427. Language model: Deutsches Textarchiv prints 1472–1609 (lang/ model de-1500s).

Transcriptions, keys, decoders and working decrypts are in the repository folder kaa4591/.