At a glanceKey from external plaintext · complete
- The letter
- Juan de Eraso, Spanish ambassador at Genoa, to Philip IV, 18 January 1643, signed duplicate. Opening and closing in clear, one paragraph in cipher.
- Where
- Archivo General de Simancas, Estado, leg. 3598 no. 44 (PARES 3555178, image 1). The plain original (no. 42) is not online: the PARES record for no. 42 shows the images of no. 41. It is item 755 of this project’s catalogue, whose 1638 letters (a different table) are a separate target.
- The cipher
- The 1643 table of the Genoa embassy: syllabic series of five numbers (27 fa, 32 ta, 37 as, 42 na …), disguised bigrams and trigrams, single letters and code numbers (270 Vuestra Majestad, 223 república, 180 Francia).
- How it was read
- Key K4b learned by EM alignment on the pairs 3598,38/37 and 41/40 and frozen. First held-out test (3598,15 against 14): 0.816 of characters, 0.750 of words, below the criterion fixed in advance and reported. Main test, 3598,291 against 290: 0.881 and 0.834, against 0.298 and 0.121 at the 99th percentile of 200 permuted keys.
- What it says
- The Grand Duke defers to orders he will send his resident in Madrid; Eraso notes that he “will enjoy the benefit of time”.
- Still open
- Codes 149 and 210, found only here. Sixteen restored code words await a reproduction of the plain original.
- Credit
- Brice Dudout (Europe chiffrée, with Claude): key, held-out tests, transcription, Spanish text and English translation. Contributed by email on 29 October 2026 (branch dudout/bundle-spain-italy).
01 The letter
In January 1643 Tortona had just been retaken, the war with France weighed on the Milanese, and Madrid pressed the Italian princes bound to Spain to send troops. Eraso had forwarded the King’s letter to Ferdinand II de’ Medici. The next item in the bundle (3598,43) is the Grand Duke’s answer in Italian, Florence, 1 January 1643, which refers to the care he must take of his own states. Eraso explains in cipher what this means: the matter goes to Spain, and the delay is the Grand Duke’s gain.
Of the ten cipher items of 1643–51 in entry 755, nine have their contemporary plain text in the same bundle; this is the one whose plain text is not online. The 1638 Genoa letters (target genes1638, still on an open pull request) use another table.
02 The cipher
Series of five numbers give syllables (27 fa, 32 ta, 37 as, 42 na, 47 ja, 52 al, 57 da, 62 an); disguised bigrams (ax = la, at = sa, ha = ma) and trigrams (sal = ra, gan = ca, tes = ve) stand for letter groups; single letters and a few code numbers complete the table. The transcription has 261 symbols.
03 The reading
Of 137 enciphered words, 115 are certain, 4 probable, 16 restored from the sense and 2 unresolved: 135 read, 98.5%. The restored words are word codes seen nowhere else (con que, órdenes, España, respuesta, cuenta), fixed by syntax and by chancery formulas such as “dar cuenta a V. M.”; for 166 the same sense would follow from “Madrid” or “la corte”. The full text and translation are below. To our knowledge this is the first published decipherment.
04 What remains uncertain
- Code 149, before residente: perhaps a title or rank of the resident.
- Code 210, between llegue and antes este aviso: perhaps “a manos de V. M.”.
- Probable: Duque (130, attested nowhere else). Restored codes need the plain original 3598,42 (ff. 151–152) to be checked.
Full texts
The transcription and the decryption of every document on this page, so that the reading can be used and checked. Short files are shown here; all are in the repository.
Juan de Eraso to Philip IV, Genoa, 18 January 1643 (AGS EST,LEG,3598,44)
January 1643: Tortona has just been retaken, the war with France weighs on the Milanese, and Madrid is pressing the Italian princes bound to Spain to send troops. The ambassador at Genoa, Juan de Eraso, has forwarded the King’s letter to Grand Duke Ferdinand II de’ Medici. The answer comes back: the Grand Duke refers the matter to his resident in Madrid. Eraso tells the King, in cipher, that this is a way of playing for time.
Transcription
# AGS, EST,LEG,3598,44 (PARES 3555178), image 1: Juan de Eraso to Philip IV, Genoa, 18 January 1643 (duplicate).
# Tokens separated by spaces, one manuscript line per row. The opening ("En los dias que se ha detenido este correo por los
# malos tiempos, me ha llegado respuesta") and the closing ("y pueda V. M. servirse ... Genova 18 de enero 1643") are in plain text.
L01 58 15 1 salc 130 58 35 tt gan 42 ℓ
L02 ax pis 72 ex 38 K sil tis 213 sel hi 34 ax sel 52 58 270 10
L03 gin 63 60 ex tt 64 tt 32 c gin ℓ tt hec ℓ gun 59 38 et
L04 gon c ax 200 72 34 v 43 tin 52 168 58 ble 2 18 20 22 ax
L05 gon 18 2 ℓ 72 et sal gon c 38 32 58 ax pis 58 15 1 salc
L06 130 et 22 tis sal 270 58 ha c 52 22 tes 22 93 et 58 tt tis o
L07 58 hi 63 ax 59 tt 18 y 32 58 63 tis ℓ 22 ax 200 52 168
L08 sel et 22 tas c 60 et ℓ ax tt tun 38 72 57 sal ℓ ut 149 sel
L09 it 58 c 33 63 ha m sil m hec las 33 58 38 32 ha 33 sil ℓ 2 45
L10 tas ℓ 18 v 22 58 22 42 57 63 38 35 207 1 y 20 gan sal 58 15 tes 43
L11 29 gin 20 58 15 258 63 ax tt 133 tt 72 gan y at 53 sel hi 34 22
L12 38 33 lic ℓ 166 2 J ℓ tes 22 58 1 y ℓ 22 57 22 224 2 60 2 ux
L13 v 1 20 214 ℓ 270 58 ax 72 J v 33 44 60 58 15 1 salc 130 58 35
L14 tt gan 42 hec 15 ex 1 y v 210 62 33 tt 38 33 C̲Decryption
# Decryption of EST,LEG,3598,44 line by line with key_K4b.tsv (first value of each token; ‹x› = token without a value; ∅ = null). # The established text is in reading.md; notes on the marked words are in NOTES.md. L01 58 15 1 salc 130 58 35 tt gan 42 ℓ de l g ran g fo de to s ca na a L02 ax pis 72 ex 38 K sil tis 213 sel hi 34 ax sel 52 58 270 10 la ‹p› ‹i› ‹s› que le es c ri vi y g ‹3› re mi ti la re al de vuestramagestad g ‹0› L03 gin 63 60 ex tt 64 tt 32 c gin ℓ tt hec ℓ gun 59 38 et ci en do le s in s ta n ci a s me n a cu di es se L04 gon c ax 200 72 34 v 43 tin 52 168 58 ble 2 18 20 22 ax co n la gen que ti e ne obligacion al estado de ‹b› ‹l› ‹e› y p o r la L05 gon 18 2 ℓ 72 et sal gon c 38 32 58 ax pis 58 15 1 salc co p y a que se ra co n es ta de la ‹p› ‹i› ‹s› de l g ran L06 130 et 22 tis sal 270 58 ha c 52 22 tes 22 93 et 58 tt tis o g fo se r vi ra vuestramagestad de ma n al r ve r como se de s vi a L07 58 hi 63 ax 59 tt 18 y 32 58 63 tis ℓ 22 ax 200 52 168 de mi en la di s p u ta de en vi a r la gen al estado L08 sel et 22 tas c 60 et ℓ ax tt tun 38 72 57 sal ℓ ut 149 sel re se r ba n do se a la s ‹t› ‹u› z es que da ra a su g ji re L09 it 58 c 33 63 ha m sil m hec las 33 58 38 32 ha 33 sil ℓ 2 45 si de n te en ma d ri d me n tra te de es ta ma te ri a y no L10 tas ℓ 18 v 22 58 22 42 57 63 38 35 207 1 y 20 gan sal 58 15 tes 43 ba a p e r de r na da en es to pues g u o ca ra de l ve ne L11 29 gin 20 58 15 258 63 ax tt 133 tt 72 gan y at 53 sel hi 34 22 fi ci o de l tiempos en la s diligencia s que ca u sa el re mi ti r L12 38 33 lic ℓ 166 2 J ℓ tes 22 58 1 y ℓ 22 57 22 224 2 60 2 ux es te gocio a g un y h a ve r de g u a r da r r ‹4› y do y lu L13 v 1 20 214 ℓ 270 58 ax 72 J v 33 44 60 58 15 1 salc 130 58 35 e g o y g ‹4› a vuestramagestad de la que h e te ni do de l g ran g fo de to L14 tt gan 42 hec 15 ex 1 y v 210 62 33 tt 38 33 C̲ s ca na me n l le g u e y g ‹0› an te s es te aviso
Reading
# Juan de Eraso to Philip IV, Genoa, 18 January 1643: established text (Spanish)
Conventions: {x} = probable reading; ‹…› = unresolved group; [x] = restored from the sense; *italics* = written in plain text in the original. Spelling normalised; punctuation and accents added.
*En los días que se ha detenido este correo por los malos tiempos, me ha llegado respuesta* del Gran {Duque} de Toscana a la [carta] que le escribí, [con que] remití la Real de V. M., {ha}ciéndole instancias [para que] acudiese con la gente que tiene obligación al Estado de [Milán];
y por la copia que será con ésta de la [carta] del Gran {Duque} servirá V. M. de mandar ver cómo se desvía de mí en la disputa de enviar la gente al Estado, reservándose a las [órdenes] que dará a su ‹149› residente en Madrid [para que] trate de esta materia;
y no va a perder nada en esto, pues [gozará] del beneficio del tiempo en las diligencias que causa el remitir este negocio a [España] y haber de aguardar [respuesta]; y doy luego [cuenta] a V. M. de la que he tenido del Gran {Duque} de Toscana, [para que] llegue ‹210› antes este aviso,
*y pueda V. M. servirse de tomar la resolución que más tubiere por bien. Guarde Dios la católica y real persona de V. M. como la cristiandad y sus vasallos habemos menester. Génova, 18 de enero 1643.* *[Firma de Juan de Eraso.]*Translation
# English translation [In plain text: In the days this post has been held up by bad weather, I have received the answer] of the Grand Duke of Tuscany to the letter I wrote him, with which I forwarded Your Majesty’s royal letter, urging him to help the State of Milan with the men he is bound to provide; and from the copy of the Grand Duke’s letter, which will go with this one, Your Majesty will be pleased to see how he evades me in the dispute over sending the men to the State, deferring to the orders he will give his ‹…› resident in Madrid to deal with this matter; and he loses nothing by it, for he will enjoy the benefit of time in the steps that referring this business to Spain and waiting for an answer entail; and I at once give Your Majesty an account of the answer I have had from the Grand Duke of Tuscany, so that it may arrive ‹…› before this report, [in plain text:] and Your Majesty may take whatever resolution you think best. God keep the Catholic and royal person of Your Majesty as Christendom and your vassals have need. Genoa, 18 January 1643. [Signature of Juan de Eraso.]
Held-out validation letter: Eraso to Philip IV, Genoa, 15 October 1643 (AGS EST,LEG,3598,291 p. 1, with the contemporary plain original 3598,290) not prose
Transcription
# AGS, EST,LEG,3598,291 (PARES 3560822), image 1, 22 lines: held-out text for K4b, designated before it was opened; # transcribed and frozen (SHA-256 5edd454c...) before its contemporary plain copy 3598,290 (PARES 3560803) was opened. 58 tt 58 ax 18 v 22 59 57 58 lis c 45 J ℓ mul ho tis hi 63 35 gon c it 58 sal a ex 53 258 18 v 22 59 20 hu 67 200 63 ℓ 72 15 it 34 20 2 gan it 35 60 tt ox tt gan tos tt 58 15 169 J 62 72 57 60 63 28 22 ho tt 18 20 22 38 33 sel tt 18 v K 35 2 38 32 22 am 32 c 63 ox tt 18 sil c gin 18 2 40 58 15 2 tis v 22 45 et 18 y v 58 ( gon c 30 22 he ℓ 231 ) ut 18 65 v 22 72 18 20 22 38 32 gan 18 ℓ 42 64 33 c 33 53 158 20 las paf 63 58 sel at 18 v sol gon c 35 60 38 ot J v 63 33 c 59 60 18 20 22 pis tt 58 15 bla 58 tes ax 57 53 105 gon c 72 18 sol gun sal 18 65 v 22 63 tus v 42 30 22 ha ax tt 18 ax gan tt 72 18 y o 58 c 33 43 22 ha tt 64 he 59 ℓ 35 18 o ix 1 sol ax 58 lis c 43 gen it 32 tas 58 fan ha tt 200 58 ax 72 et J R̲ tas 58 c los 18 ℓ sal ut 58 28 c at 2 53 las tas 50 58 ox tt it 34 ℓ 60 tt 31 v 32 c gon c 34 46 20 72 gan y ot 198 mes 32 c 32 tt 63 28 22 he 57 58 tt 72 45 18 y 59 v solc 58 28 c 58 22 ha tt 258 ax 18 ax gan 53 tas solc 58 36 sel 42 58 et ℓ tos 15 tes 22 ℓ 180 a sel tes mes 2 it 38 35 31 38 et 64 tes 22 42 sil ℓ gon c ha tt 72t v 36 m 63 53 168 58 ble 33 ho 72 ax pof J ℓ 58 20 a ix 1 ℓ 22 52 158
Decryption
# AGS, EST,LEG,3598,290 (PARES 3560803), image 1: contemporary plain original (used only to score K4b; cut automatically # at the end of the deciphered passage). Despues de la perdida de Trin no ha hecho movimiento considerable el enemigo. Perdio mucha gente en aquel sitio y casi todos los cavos del exercito han quedado enfermos. Por este respeto y estar ya tan en los principios del invierno no se puede (conforme a razon) suponer que por esta campaña intente el enemigo otra ninguna empresa. Pero con todo esso he entendido por cartas del marques de Velada el cuydado con que procura poner en buena forma las placas que pueden tener mas inmediato peligro. La de Trin necessitava de mucha mas gente de la que se hallava dentro para su defensa, y el trabajo de los sitiados fue tan continuo que causo generalmente tantas enfermedades que no pudieron defender mas tiempo la placa. El Baron de Turena dessea bolver a Francia brevemente y si esto fuesse se invernaria con mas quietud en el Estado de Milan. Temo que la necesidad ha de obligar al
Key: key_K4b.tsv
05 Sources
- Archivo General de Simancas, Estado, leg. 3598 no. 44: PARES record 3555178, image 1; training and test pairs 3598,38/37, 41/40, 15/14 and 291/290 in the same bundle.
- Brice Dudout, Europe chiffrée, Eraso to Philip IV, Genoa, 18 January 1643.
Folder: targets/genes1643/ (notes, transcription, line-by-line decryption, key K4b, validation files, Spanish text and English translation, as contributed by Brice Dudout).
