01 The record and the register
DECODE R1854 “Mantova enciphered letters” has five images (I8411–I8415), catalogued as “unknown” with graphic signs. Each sheet has an archivist’s note at the top: “1428 · 22 ap(ri)le Roma” (stamped 23), “1428 · 9 Ag.to Roma” (24), “1428 · 6 novembre Forlì” (26), and so on. The images are not in the public domain, so none is reproduced here.
| Image | Date, place | Sender | Language | Cipher signs | State |
|---|---|---|---|---|---|
| 1 | Rome, 22 April 1428 | Pandolfo Malatesta, archbishop of Patras (signed) | Latin, three cipher runs | 262 | not read |
| 2 | Rome, 9 August 1428 | unnamed agent (a lozenge mark) | Latin, all in cipher | 1,802 | read, 96.6% |
| 3 | Forlì, 6 November 1428 | “famulus et servulus Ricc. de Mutiliana” | Italian, clear and cipher | 894 | read at the time; re-deciphered, 97.2% |
| 4 | Rome, 13 February 1430 | Francesco de’ Cattanei | Latin, all in cipher | 1,537 | read, 96.7% |
| 5 | Rome, 21 February 1430 (verso) | Francesco de’ Cattanei | Latin, three lines | 199 | read |
The companion record R1853 “Mantova keys” is the Gonzaga chancery register of ciphers, begun about 1401. Its first folio lists “Zifra cum Malatesta d(omi)ni Pandulfi”, “Zifra nova cum fratribus de Malatestis” and two keys “cum Karolo de Malatestis”, and later folios have keys dated 1406–1419 (one for Carlo Malatesta, 8 December 1417). All are simple substitutions in letters and digits, and none gives sense on these letters. The other Mantua records on DECODE (R7858–R7888, Archivio Gonzaga E.I.2 busta 423) are sixteenth- and seventeenth-century keys.
02 Rome, 9 August 1428: a marriage for the Gonzaga
The whole letter is in cipher: 37 lines of graphic signs and digits, dated in clear “Rome die viiii augusti”. It uses about forty letter signs, a dozen nulls, syllable signs for con, et and -rum, and two word codes, one of them twice in “in domo [·] Senensis” and “cum prefato [·]”, that is, the cardinal of Siena. The opening, as deciphered:
Heri Iohannes de Orlandis, quam primum me vidit, dixit michi quod ser Victorius eomet die venit ad ipsum dicens dominam comitissam velle facere id totum quod placet et Iohanni predicto. Verum quia ipse incipiebat tunc prandere, dixit se ad eum reversurum et dicturum latius de ista materia. Postea cum heri sero plures essemus congregati in domo [cardinalis] Senensis pro quodam actu scolastico et cenaturi cum prefato [cardinali] …
Ser Vittorio goes on to report the countess’s answer: as far as she is concerned she agrees to the match of her daughter, but her subjects are not content, “quia dominatio vestra nimium distat, si ibi contingeret aliquod sinistrum; et quod Carolus est nimis iuvenis ad talia”. The bridegroom under discussion is Gianfrancesco’s son Carlo, then eleven. The cousins of domina Palma and Antonio Colonna, the pope’s nephew, appear as parties to the negotiation. The full text, with the doubtful spans marked, is in reading_p2.md.
03 Forlì, 6 November 1428: the Malatesta, Urbino and the pope
This letter is in Italian, clear text interrupted by cipher runs. Over every sign a contemporary hand has written the plaintext letter in small faint script, and three word signs are glossed as names: el signor Malatesta, li fioli del signor marchese and el papa. About two-thirds of the gloss is legible. Thirty values of signs attested in it (each two to fifty-six times), plus a handful of rare signs fixed from context, decipher all 894 signs:
… a ciascuno pare che questo acto sia molto dannoso a le signor Malatesta et cusì, perché [el] dà ad intendare a molti che el papa fia cum loro. Se la S.V. havesse da papa fare questa impresa insieme cum lo signor Malatesta [e] conte d’Urbino, la S.V. se faria una grande signore in pocho tempo. Bene che el signor Malatesta è riputato così povaro, molti se copriano per lui …
The informant reports that the governor secretly favours the marquess’s sons, and that Guidantonio da Montefeltro, count of Urbino, is in secret contact with Giovanni de Ramberto, which has aroused suspicion. Full text: reading_p3.md.
04 Rome, February 1430: Francesco de’ Cattanei’s news
Cattanei’s letter of 13 February is again wholly in cipher, a third homophonic system with signs for et, con and -rum; he writes x as “cx” (dicxit, reducxit). It is a newsletter. The magnificent lord Carlo speaks of a marriage alliance with King Louis. A galley of Giovanni de Orlandis (the man in the 1428 letter) took a Catalan ship and was itself taken at Gaeta, a loss of five thousand ducats. The king of Castile presses Aragon. An envoy of the lords of Rimini left without obtaining anything. Then:
dominus a[rchi]episcopus de Patrasio cum licencia domini nostri dare volebat temporale dominium dominio Venetorum, et illud defenderet ab infidelibus. Dominus noster fecit proponere cardinalibus. Responderunt melius est perdere quam Venetis tradere, quia una vice recuperabitur; set si Veneti haberent, recuperare nunquam esset possibile.
The archbishop is Pandolfo Malatesta, the sender of the first letter. Patrasio is the city’s name as the signs spell it, a Latin form of the Italian Patrasso: the two signs after Patras, read i and o with the key, are its ending, not a separate word (corrected 30 September 2026; earlier versions printed them as an unread “io”). Patras fell to the Palaiologoi in 1430. The rest of the letter concerns the chancellor of Niccolò da Tolentino, an abbot freed from excommunication, and six citizens of Bologna expected in Rome, “duos de maioribus, duos de mediocris, et duos de diminutivis”. The three cipher lines on the verso of the second letter (21 February) report the Rimini envoys: “dominus Astorgius et dominus Bartolomeus anbasiatores dominorum de Arimino die lune comparuerunt coram comisariis et producxerunt mandatum et certas copias bullarum auctenticatas … credo parum iuvabit”, and in clear, “denarios non habeo pro expensis”. Full text: reading_p4.md.
05 Pandolfo Malatesta, 22 April 1428: not deciphered
The first letter opens in clear with the news, just arrived in Rome, of the peace between the duke of Milan and the league (the peace of Ferrara, 19 April 1428), “licet nondum publicatam”. Pandolfo writes that he has conceived plans “valde utilia” for his brother-in-law, and the secret parts follow in three runs: after “decrevi ne” (58 signs), after “quo modo valeat” (70) and after “nolit rem ipsam negligere” (134). The signs are letter-like (ſſ, η, ʒ, H, cc, ∩, I, ƀʒ, v, ꭏ), with separators strewn between them at random.
They would not decipher. The index of coincidence is 0.056 with 29 sign types and about 44% vowel-like signs, which points to a near-monoalphabetic system. Yet annealing in Latin and in Italian (fifteenth- and sixteenth-century and modern models), with and without word spaces, with costed nulls, with vowel and consonant classes, reversed by line, by word and globally, and with digraph signs split or merged, gave nothing. The same solver solves a synthetic 266-letter Latin text in a monoalphabetic cipher even with 12% of its signs corrupted. A second, sign-by-sign transcription corrected three misreadings and made no difference. The register’s Malatesta keys share several shapes with these signs (ſt, H, Λ, v, ꭏ, ƀʒ) but not their values. The best lead is Pandolfo’s letter of 1 March 1438, nearly all in cipher (ASMn, AG, b. 1081, c. 159–160), whose contemporary Italian translation survives (b. 840, c. 95) and is printed by Anna Falcioni. If its cipher is the same family, that pair would give the key. Its images are not online.
06 Method
All transcriptions were made from the DECODE images, in crops at 4–13×. For the August 1428 letter the triangle sign is followed by sign 17 in 21 of its 29 occurrences, which fixed q and u. A homophonic annealer on the project’s shared Latin model then produced Latin words, and per-sign and per-occurrence rescoring separated nulls and look-alike glyphs, confirmed on the image: a bold ∇ is s while a thin dotted ∇ is a null, and a tailed circle is p while a plain circle is h. Cattanei’s key was recovered the same way. A second transcription pass checked every sign against the image with the key in hand and made 209 corrections, splitting look-alikes (a slanted and a rounded b, i and o; η and 9). For the Forlì letter the key comes from the contemporary gloss, and every run was deciphered from its signs rather than from the faint gloss.
07 What remains uncertain
- Pandolfo Malatesta, 22 April 1428: 262 signs in three runs, not deciphered (no key; see above).
- Rome, 9 August 1428: the word code in “in filium [·]” (once), and about 60 signs in doubtful spans on lines 15, 19, 26, 28 and 31–35 (for example “habet [in] num[ero] de ve[..]”); grades M–I.
- Forlì, 6 November 1428: two unglossed signs (one of them twice) and about 25 signs in doubtful words (“de Ianus(?) ubi(?)”, “dice cavad(?)”).
- Rome, 13 February 1430: “leonebi … re[∂]bs” (l. 4), “a-mhi episcopus” (l. 14, expected archiepiscopus), “debert onorio” (l. 20), “domicus” (l. 22); names decrypted letter by letter but not identified: Trrusius(?), Berardelus, Bonifacius de Meana(?), Canedulum(?).
08 Sources
- DECODE R1854 (the letters, 5 images) and R1853 (the Gonzaga cipher register, 14 images), de-crypt.org/decrypt-web/RecordsView/1854. Images © Archivio di Stato di Mantova; not reproduced here, since publication needs the archive’s permission.
- Anna Falcioni, “Pandolfo Malatesti e il concilio ecumenico di Ferrara (1438)”, with an appendix printing the 1438 letter from ASMn, AG, b. 840 c. 95 and b. 1081 c. 159–160; and A. Falcioni, “La crittografia e le cifre diplomatiche della cancelleria di Sigismondo Pandolfo Malatesti”, Quaderni dell’Accademia Fanestre 3 (2004), 187–190 (not seen).
- “Malatesta, Pandolfo”, Dizionario Biografico degli Italiani (Treccani), which cites his partly ciphered autograph letters in ASMn, AG, E.XXVII.2, b. 1081.
Transcriptions, keys, solver and readings are in the repository folder targets/r1854/.