Prospero Santa Croce to Cardinal del Monte, 1553

Summary. Catalogue item 245 was five DECODE records of ciphered despatches from Prospero Santa Croce, nuncio in France, to Cardinal Innocenzo del Monte in Rome, with "what the cipher hides is not known". Every one of them was deciphered when it arrived. The volume holds the decifrati, and J. Lestocquoy's Correspondance du nonce en France Prospero Santa Croce (1552–1554) (Acta Nuntiaturae Gallicae 9, 1972) prints all five letters with the cipher already deciphered. George Lasry attached a scan of that edition and his reconstruction of the letter key to each record on DECODE in October 2020. The letters here run from 26 March to 23 December 1553; they are not from 1552. Lasry's key was applied to the 2016 volunteer transcriptions, and the decrypts agree with the printed text wherever the transcription is clean. One passage is not in the book: three lines of cipher under the letter of 14 December 1553, struck through with crosses. Decrypted with the key, they are the postscript that the secretary then wrote out in clear beneath them: the royal fleet that sailed for Corsica has met a storm, no one knows where it is, and there is no word from Piero Strozzi. Every passage of substance in the five records has a decipherment. The code groups were not given values, because the print gives the words they stand for.

01 The documents

The five records are leaves from Santa Croce's first French nunciature. In each, a letter in clear Italian moves into figures for its sensitive passages.

DECODE	Folio	Letter	In Lestocquoy 1972
R6	117r–v	Poissy, 26 March 1553; decipherment fol. 118v	no. 67, p. 157
R7	128r–v	Poissy, 5 April 1553; decipherment fol. 129–130v	no. 71, pp. 162–163
R8	230r	Abbaye d’Ourscamp, 28 September 1553	no. 112, p. 218
R9	248r (stamped 256)	Paris, 14 December 1553 (the edition gives fol. 254–258v, another foliation)	no. 124, p. 240; the cancelled cipher is not printed
R10	263r	Paris, second letter of 23 December 1553	pp. 243–244

02 The cipher

Lasry's reconstruction, as filed on the records, is a homophonic alphabet of one- and two-digit elements: a = 28, 38 or 8; e = 24, 34 or 4; i = 2, 22 or 32; o = 26, 36 or 6; t = 07, 76 or 86; u = 02, 04, 06 or 08; r = 03 or 56; s = 05 or 66; and single values for the other letters (b 48, c 58, d 68, f 44, g 54, h 64, l 42, m 52, n 62, p 46, z 96). The digit 1 is a null that mostly falls between words. Code groups for names and common words begin with a dotted digit. Element boundaries are not marked, so a run like 2 2 8 can be split in several ways. The decoder in the repository resolves the splits with a sixteenth-century Italian language model.

03 The printed letters, checked

For R6, R7, R8 and R10 the text is Lestocquoy's, and the decrypts confirm it. For example, R6 decrypts to "ci è maneggio stretto col [duca di Ferrara], non so se sia per haver denari con promesse di mercanti et avvantaggio d’esso Duca o pur per qualche lega o per haver artigliaria con la scusa che ha usato il [duca di Firenze] a Siena". That is the text on p. 157, word for word. R8's "Il Re Chr.mo resta mal contento dell’impresa di Corsica … credo che si risolverà di mantenerla" agrees both with p. 218 and with the interlinear decipherment on the leaf. R7 (Ferrara as "generale supremo di Italia con vinti mila scudi", the Naples enterprise) and R10 ("Molti persuadeno S.M. di havere a far guerra in Italia") match pp. 162–163 and 244.

04 R9: the cancelled postscript

Foot of f. 248r: three lines of cipher figures crossed through, with the Italian postscript written in clear beneath and Santa Croce's subscription — f. 248r (R9), Paris, 14 December 1553. Three lines of cipher struck through, and below them the same postscript in clear: "L’armata regia che partì per Corsica ha havuto fortuna et non si sa come né dove sia et non credo ci sia aviso del Strozzi". Image: Archivio Apostolico Vaticano, Segreteria di Stato, Nunziatura di Francia 3 f. 248r, via DECODE R9.

Lestocquoy prints the letter of 14 December and its clear postscript (p. 240) but not the struck-through figures above the postscript. The figures were transcribed through the cancellation strokes and decrypted with the key. Long stretches match the postscript:

line 1: 46 6 03 86 = port…, and 58 6 56 05 2 … 58 28 = Corsi…ca
line 2: 44 26 03 [07] 02 62 8 = fortuna; 58 6 52 4 62 4 = come ne; 68 6 02 4 = dove
line 3: 28 06 2 66 36 = auiso; 68 4 42 = del; 05 07 03 6 96 96 2 = strozzi

So the cancelled cipher is the postscript itself: l’armata regia che partì per Corsica ha havuto fortuna et non si sa come né dove sia et non credo che ci sia aviso del Strozzi. In English: the royal fleet that left for Corsica has met a storm, no one knows how or where it is, and I do not think there is any news of Strozzi. The secretary began to encipher it, gave up, struck the figures out and wrote the sentence in clear.

05 What remains uncertain

The code groups (dotted elements such as [57], [43], [63], [99]) were not given values. The print supplies the words, so nothing depends on them.
In R9, a few digits between the aligned stretches are illegible under the strokes. The alignment rests on the stretches listed above (grade C for the passage as a whole, H for the aligned words).
The volunteer transcriptions have gaps (underlined figures untranscribed, a few doubtful digits), so the decrypts are imperfect in places. The printed text is the authority.

06 Sources

DECODE records R6, R7, R8, R9, R10: images, 2016 volunteer transcriptions, and George Lasry’s reconstructed key (24 October 2020).
J. Lestocquoy (ed.), introduction by F. Giannetto, Correspondance du nonce en France Prospero Santa Croce (1552–1554), Acta Nuntiaturae Gallicae 9 (Rome and Paris, 1972). A scan is attached to the DECODE records.
Archivio Apostolico Vaticano, Segreteria di Stato, Nunziatura di Francia 3.

Notes, decoder and the R9 decryption: santacroce1552/.

Prospero Santa Croce to Cardinal del Monte, 1553: five ciphered despatches, deciphered on arrival and printed in 1972