Historical ciphers: what has been deciphered, by whom and how. https://cyphersolver.com/ 2026-11-07T22:56:52Z Daniel Bourdeau and contributors https://cyphersolver.com/pigeongrammes1870.html2026-11-07T22:56:52Z2026-11-07T22:56:52Z

A pigeon telegram from the director general of telegraphs at Tours to the director of telegraphs in besieged Paris, in the telegraph inspectors’ code mixed with clear words, from Alexandre Pillon’s collection: 736 coded groups, 437 clear words. The table is an alphabetical lexicon (13 syllable values fit their positions to about 0.015, a random mapping 0.33) and names spelled between beacon groups decode (Steenackers, Mercadier, pigeons, Trochu), but only 20 hand-assigned entries are supported, 12.5% of 608 coded groups; an acceptance engine rolled back its false acceptances and accepted nothing, and no second text exists to test on.

https://cyphersolver.com/gonzaga1542.html2026-11-07T14:41:55Z2026-11-07T14:41:55Z

A letter of the Emperor to his viceroy of Sicily, catalogued as an unread numeric cipher: no money for the infantry, the galleys and La Goleta, the Turkish fleet, and the French effort coming to Perpignan. Prabal Gupta found the key from the sign statistics of the letter alone: a consonant sign with a small digit that adds the vowel. 94% of the cipher words read.

https://cyphersolver.com/branicki1757.html2026-11-07T14:41:55Z2026-11-07T14:41:55Z

Four cipher letters of the Branicki family archive in Warsaw, listed as unsolved: Hetman Branicki’s plan of a manifesto (22 March 1757), a field report from the Russian army, a fund of 146,000 francs to buy the Lithuanian dietines, and a bloody dietine at Brest. Prabal Gupta found a reciprocal alphabet of twelve pairs from the ciphertext of the first letter, and the same key reads the others; 97.5% of the cipher words read, 1398 only in part.

https://cyphersolver.com/sforza1597.html2026-11-07T14:04:56Z2026-11-07T14:04:56Z

A long Italian letter entirely in about 60 graphic signs from the Sforza chancery box in Milan. Shuffled-token controls give Italian, a sign reader and a key estimated from the ciphertext alone reach 24% dictionary-word coverage, and a hand correction of the sign boxes adds only a point: the DECODE scans are too small (signs 15–25 px) for a reading. The 115 key sheets in the box are 19th-century reconstructions and do not fit.

https://cyphersolver.com/arabia1916.html2026-11-06T22:29:52Z2026-11-06T22:29:52Z

A German cipher telegram on the sinking of the Arabia, passed to Count Bernstorff through the American embassy in Berlin and the State Department. The file copy keeps only Grew’s cover and the words “(Quote German cipher)”: the groups were delivered to the ambassador, and no digitised source has them. Not solved.

https://cyphersolver.com/limantour1909.html2026-11-06T21:45:39Z2026-11-07T00:00:00Z

A cipher letter from a friend of General Reyes, governor of Nuevo León, at the moment he was being pushed aside before the 1910 election. Alberto Garvía García found the numerical key from two telegrams with plaintext (28 values), checked here on the images: the letter reads as Spanish (enemigo, te pronuncies, temor, calma y prudencia, clubs de Guadalajara) and the note of 29 July names Limantour. 88.8% of the groups read.

https://cyphersolver.com/piccolomini1646.html2026-11-06T20:55:05Z2026-11-06T20:55:05Z

Two letters in a cipher whose vowels are odd digits, never read: a student thesis of 2017 deciphered their neighbour and printed the key. WAINUT applied it unchanged to the other two, from photographs of a microfilm-reader screen: about 65% of the words decode verbatim, but most sentences have holes, so neither letter counts as read.

https://cyphersolver.com/mazzinghi1478.html2026-11-06T17:43:35Z2026-11-06T17:43:35Z

Two bare cipher letters from Rome to the Medici in the winter after the Pazzi conspiracy, the first of them warning of a bull annulling the Church’s privileges and of a plot named by two Pistoiese. The key was fitted on the contemporary decipherment of a sibling letter and checked by an independent ciphertext-only break: 76.1% of 1,647 signs read, the key partial.

https://cyphersolver.com/majesty1624.html2026-11-06T16:56:52Z2026-11-06T16:56:52Z

A German report on Bethlen, the peace with the Emperor and money for 24,000 men, in a mixed cipher deciphered between the lines at the time. Brice Dudout rebuilt the letter key from those glosses and read four of the six unglossed runs; there is no held-out part, so the key is not validated, and the addressee is probably not the Emperor.

https://cyphersolver.com/lannoy1527.html2026-11-06T08:43:34Z2026-11-07T00:00:00Z

The imperial ambassador in Genoa writes to the viceroy of Naples eight weeks before the Sack of Rome, with about a hundred lines in a cipher nobody had read (Biblioteca Estense, Autografoteca Campori, Lettera L, cc. 9–12). Its key was recovered here from the ciphertext alone: letter signs by simulated annealing on a model of 1520s Spanish, code groups from context; 95.5% of the cipher tokens read. Genoa will arm galleys if Charles V pays half, asks for the six imperial galleys at Naples, and fears the Pope’s truce will leave Savona to France.

https://cyphersolver.com/contucio1446.html2026-11-06T07:43:07Z2026-11-06T07:43:07Z

One of Sforza’s envoys at Venice reports his audience with the Signoria in clear, with nine lines in cipher (BnF italien 1583 f. 148, DECODE R7911). The envoys’ own key, an 18th-century copy in Milan headed with their names (cart. 1597 no. 14, DECODE R5314), reads 225 of the 226 cipher signs, and a decipherment of the time over the lines on the back agrees. Venice and Florence wanted to settle “the destruction of the Duke of Milan” and Sforza’s losses, and Cosimo de’ Medici advised what to offer.

https://cyphersolver.com/delcarretto1576.html2026-11-06T07:12:44Z2026-11-06T07:12:44Z

A letter of the marquis of Finale to his agents in Milan, its first eleven lines in a homophonic cipher with no decipherment of the time. Brice Dudout broke the key on eight lines and validated it on the other three (0.961 against 0.263): 95.6% of 182 cipher words, on Count Spinola and a man sent to His Majesty as trustworthy.

https://cyphersolver.com/dahku1715.html2026-11-06T07:12:44Z2026-11-06T07:12:44Z

Seventeen lines of graphic signs in a Polish letter from Cracow, catalogued with no decipherment. Brice Dudout broke the substitution on the ciphertext alone and measured it on held-out lines (0.444 against 0.083, key partial): the Sandomierz deputies ask that the Crown army support their levée of 9 October 1715. 84% of 63 cipher words.

https://cyphersolver.com/deboli1787.html2026-11-06T07:12:44Z2026-11-07T00:00:00Z

Fourteen cipher despatches of 1786–87 from the Polish legation at St Petersburg, in the one-part code of 1783 whose key survives in the same fonds. Brice Dudout transcribed the key and read the pieces blind, without opening the cabinet’s clear texts: 81.8% of 7,040 words, on the Russian regiments in Poland and the Empress’s journey to the Crimea.

https://cyphersolver.com/farnese1541.html2026-11-06T06:05:34Z2026-11-06T06:05:34Z

The companion of Vatican Challenge Part 5 (DECODE R91, catalogue 262), in another key: Meister’s 1906 key no. 2, “the last cipher with Mons. Poggio”, never before tied to this letter. Read polyphonically and corrected in five places on the letter (02 for b/c, co 26 not printed), it gives 80% of the 2,965 figures as Italian (67% certain) after an image re-read and four reading passes, the last allowing for the clerk’s slips. Paul III will not brand the King of France the Turk’s ally for Charles V. The letter, catalogued as of December 1541, is of 7 August 1542; a readable copy is in Chigi L III 65, not online. Corrosion and codes outside the printed table keep the rest open.

https://cyphersolver.com/smolensk1633.html2026-11-06T00:59:38Z2026-11-06T00:59:38Z

An appeal for relief from the officials and citizens shut in Smolensk by the Muscovite army, to the Lithuanian field hetman (AGAD, Archiwum Radziwiłłów dz. II nr 1116). The cipher is a simple substitution on digits told apart by where a cross stroke sits. The key was rebuilt from the cipher, with the clear close’s W.X.Mci as the first crib; 95.0% of the 1,856 signs read as written and one word is open.

https://cyphersolver.com/pawel1624.html2026-11-06T00:24:37Z2026-11-06T00:24:37Z

A report to the exiled King of Bohemia on Colonel Fuchs’s recruiting in Württemberg, its cipher deciphered between the lines at the time. Brice Dudout found that its letter cipher is the alphabet of the Johann Casimir–Camerarius letters moved by three, fitted the shift on one page and tested it on the next (13 of 13 letters). The content is the period decipherment; the key and the family of keys are the new part.

https://cyphersolver.com/casimir1629.html2026-11-06T00:06:03Z2026-11-06T00:06:03Z

Letters of Pfalzgraf Johann Casimir to Ludwig Camerarius whose cipher passages carry a decipherment written at the time. Brice Dudout rebuilt the key from the glosses of one letter and tested it once on another: 0.873 of characters against 0.170 for shuffled keys. The content is the period decipherment; the key is the new part.

https://cyphersolver.com/dormer1694.html2026-11-06T00:06:03Z2026-11-06T00:06:03Z

Number-cipher passages and a slip wholly in cipher, in letters from unnamed writers in Catalonia to the Aragonese chronicler Diego José Dormer during the French war. Brice Dudout recovered the simple substitution from the ciphertext and cribs, then measured it on two held-out sets (0.577 and 0.594, key partial): 91.7% of 290 counted words.

https://cyphersolver.com/burr1804.html2026-11-05T23:22:20Z2026-11-05T23:22:20Z

A week after the duel with Hamilton, Burr wrote to his son-in-law with ten lines in a cipher of figures and stroke signs (Gilder Lehrman GLC01523), catalogued as undecoded. It is a simple substitution, its key recovered here from the cipher alone, and all 132 signs read. Burr asks what Alston would advise if the coroner’s jury finds murder: to stand trial, to go to Europe, or what?

https://cyphersolver.com/burr1808.html2026-11-05T23:22:20Z2026-11-07T00:00:00Z

Two sheets of numbers filed as pages of Burr’s 1804 letter to Alston (Gilder Lehrman GLC01523) are three letters to his daughter from Baltimore, 31 January to 18 February 1808, in a six-place Vigenère over the numbers 1–26. The key was recovered here from the cipher alone; 969 of 973 numbers read. Hiding “incog.”, Burr plans a secret visit to The Oaks and waits for money for “the long voyage” to Europe.

https://cyphersolver.com/nassau1620.html2026-11-05T21:27:27Z2026-11-05T21:27:27Z

Three cipher letters and a postscript of Willem Lodewijk of Nassau, stadtholder of Friesland, to his brother Johann VII on the defence of the Palatinate, in a nine-cell shape grid whose key sits in the family key book. Brice Dudout transcribed and read them: 96.4% of 1,388 cipher words, the nomenclator signs still open.

https://cyphersolver.com/olivares1626.html2026-11-05T21:27:27Z2026-11-07T00:00:00Z

A letter of the Count-Duke of Olivares, wholly in cipher, to the Duke of Alba, viceroy of Naples, on the deaths in his family and the future of his son-in-law. Brice Dudout read it with Philip IV’s cipher A plus 20 values learnt on its first part: 95.2% of 1,001 words, with the key only partly confirmed.

https://cyphersolver.com/hatzfeldt1641.html2026-11-05T21:27:27Z2026-11-05T21:27:27Z

Five cipher pieces of the Emperor Ferdinand III to Field Marshal Hatzfeldt in 1641, among them the ciphered copy of a bond of the city of Aachen. Hermann Stützel printed the key in 1963 and no text; Brice Dudout transcribed and read the pieces, 94.1% of 859 cipher words.

https://cyphersolver.com/leticia1932.html2026-11-05T21:27:27Z2026-11-07T00:00:00Z

Seventeen cipher telegrams between the Colombian Ministry of War and the military chief of the Amazonas in the first weeks after the Peruvian seizure of Leticia. Brice Dudout read all the alphabetic ones with the Ministry’s own weekday key (787 words, 99.5%); one numeric telegram stays open.

https://cyphersolver.com/guarna1447.html2026-11-05T15:44:02Z2026-11-05T15:44:02Z

Sforza’s envoy at Milan reports an audience with Duke Filippo Maria Visconti: the state in danger, the plague, nine thousand ducats and no more money for a long while, and the Duke’s fervent wish that Sforza come at once. Brice Dudout rebuilt the key from another Guarna letter and its late clear copy and read 616 of about 852 cipher words (72.3%, the unread stretches estimated); the key is partial by our protocol, there is no fresh held-out block, and the end of the letter was already in clear on f. 156.

https://cyphersolver.com/aragon1676.html2026-11-05T15:33:11Z2026-11-05T15:33:11Z

One page of a letter in a mixed syllabic cipher (BNE Mss/2043, p. 0496), with a contemporary decipherment in the margin. Brice Dudout learned a key from 14 other pairs of the same volume, froze it, and measured it once on this page: 0.742 of characters against 0.422 for the best of 200 shuffled keys. 82 of 95 margin words read (86%); the cipher corrects the margin in three places.

https://cyphersolver.com/coloma1622.html2026-11-05T15:29:22Z2026-11-05T15:29:22Z

A letter of the Spanish ambassador in France to his colleague in London, in clear at the ends and cipher in the body. Brice Dudout rebuilt the key from the margin clears of the Duke of Feria’s letters to Coloma and read 375 of 425 cipher words (88.2%), but the key is only partly validated (two of four held-out tests partial, two failed) and about a third of the sentences read clean. Savoy, the Valtellina, a Lorraine garrison and Richelieu.

https://cyphersolver.com/ariosto1559.html2026-11-05T15:09:16Z2026-11-05T15:09:16Z

A letter of the duke of Ferrara to his secretary in clear Italian, with runs of Greek- and Latin-shaped signs under small raised vowel digits. Brice Dudout recovered the key from the signs alone, tested it once on held-out lines (0.605 of letters in Italian words against 0.155 for the best of 200 shuffled keys) and read 357 of 402 cipher words (88.8%). A countess claims arrears of rents; the duke refuses those that fell due during her husband’s rebellion.

https://cyphersolver.com/este1585.html2026-11-05T15:09:16Z2026-11-05T15:09:16Z

One page of BnF Cinq Cents de Colbert 338 (p. 523), wholly in the cipher of Cardinal Luigi d’Este, protector of France at Rome. Brice Dudout transcribed it and read it with Satoshi Tomokiyo’s published d’Este table, adjusted on glossed pages of the same volume: 177 of 200 words, 88.5%. A prince had asked the pope for the title of king and been refused; he turned to the emperor, and the writer was told the emperor alone gave Cosimo of Florence his grand-ducal title. The prince’s name and the key’s own test on this page stay open.

https://cyphersolver.com/gongmi1916.html2026-11-05T15:00:09Z2026-11-05T15:00:09Z

Nine telegrams of 10 June to 2 July 1916 between Huang Xing in Tokyo and the Shanghai group, intercepted in Japan and headed 0364 1378 = 共密 in clear. Brice Dudout recovered the key from the ciphertext alone with Claude (published 17 October 2026): the tens digit swapped through a table, the group subtracted from 9000. Satoshi Tomokiyo identified it as a renumbered 明密 code book. 96.2% of 555 groups read as sense; another telegram under the same prefix does not read.

https://cyphersolver.com/rongmi1916.html2026-11-05T15:00:09Z2026-11-07T00:00:00Z

Fourteen telegrams of June 1916 between Huang Xing’s circle in Tokyo and the Shanghai group, headed 1369 1378 = 容密 in clear. Brice Dudout recovered the key from the ciphertext alone with Claude (published 19 October 2026): a digit table for each place, then 0901 added. Satoshi Tomokiyo identified it as a renumbered 明密 code book. They cover Japanese arms for Zhejiang, a loan of a million and the bargaining over the 1912 Constitution; 95.9% of 1,306 groups read as sense.

https://cyphersolver.com/chenmi1916.html2026-11-05T15:00:09Z2026-11-05T15:00:09Z

Four telegrams of 3 to 13 June 1916 from Huang Xing’s household in Tokyo to the Hunanese group in Shanghai, headed 6591 1378 = 辰密 in clear. Brice Dudout recovered the key from the ciphertext alone with Claude (published 19 October 2026): the telegraph code with its pages counted backwards over numbers without a zero. Satoshi Tomokiyo identified it as a renumbered 明密 code book. All 239 groups read as sense, 232 without doubt.

https://cyphersolver.com/vaudreuil1760.html2026-11-05T13:10:26Z2026-11-05T13:10:26Z

The governor of New France reports to the minister, in 2,424 number groups, the British fleet and Amherst’s army converging on Montréal, the three ships and the frigate Machault at Restigouche, the loss of the lake flotillas, no powder and no food, and Murray’s circular against the paper money. Read with his own 1757 numerical table, which sat in the same volume of the Colonies archive and had not been tied to this letter; 33 cells were corrected from the letter. 96% of the groups read; 47 are lost in the binding and 24 legible groups in nine places are open.

https://cyphersolver.com/desnoyers1659.html2026-11-05T04:26:03Z2026-11-05T04:26:03Z

A short note in cipher, enclosed in a letter from the secretary of the Queen of Poland to the Paris astronomer Boulliau, on the Spanish marriage of Louis XIV and la Mancini. A contemporary hand, probably Boulliau’s, wrote the clear word above every cipher group, so the note was deciphered at the time and is not a new decipherment. Brice Dudout transcribed the 24 groups and the gloss and rebuilt the two-digit nomenclator with marks from the other glossed passages of the volume; 12 of 12 cipher words are given by the gloss and 8 are supported by the rebuilt table.

https://cyphersolver.com/cardona1517.html2026-11-05T04:26:03Z2026-11-05T04:26:03Z

Two letters of the viceroy of Naples to the young Charles I of Spain, of 5 October 1517 and 18 June 1520 (BNE MSS/20210/11/1 and /4), each with passages in cipher and no decipherment on the pages. Michael Brackx recovered most of the key from the ciphertext alone, with Claude Code: letter signs and three-letter code groups that stand for whole words, in the family of Lannoy’s Naples cipher. Two names confirm it, Borghese Petrucci and Giampaolo Baglioni; about half the sentences still have holes, so it is decoded, not read.

https://cyphersolver.com/geleen1633.html2026-11-04T21:41:33Z2026-11-04T21:41:33Z

A letter to the League general Gottfried Huyn von Geleen on the relief of Hildesheim and the army’s pay, with the sensitive words in two-digit numbers. Brice Dudout recovered the key from the numbers alone, tested it on five held-out lines (0.656 of letters in German words against at most 0.113 for shuffled keys) and read 186 of 221 cipher words. Nineteen words are lost in the binding of the microfilm, which caps the reading at 91.4%.

https://cyphersolver.com/dole1636.html2026-11-04T21:26:59Z2026-11-04T21:26:59Z

Letters from Dole, besieged by Condé, to the relief army of the Marquis of Conflans, June–July 1636, with one number per letter set between clear words. Brice Dudout learnt the key from the period gloss in the margin of one folio, tested it on a held-out block (0.907 of letters against at most 0.229 for shuffled keys) and read the unglossed letters: 124 of 128 words. The clear text was already printed by Longin in 1912.

https://cyphersolver.com/deboli1788.html2026-11-04T18:48:55Z2026-11-07T00:00:00Z

A cipher despatch of the Polish envoy at St Petersburg, one of two of 1788 with no cabinet decipherment, on a dinner for John Paul Jones and Russian talk of an alliance to be turned into a confederation. Brice Dudout read it with the 1789 key completed on 1788 pairs; on a held-out pair it reads 0.862 of groups as sense.

https://cyphersolver.com/buda1490.html2026-11-04T04:39:50Z2026-11-07T00:00:00Z

A four-page Latin cipher letter on the Sforza marriage alliance with the new king of Hungary, with the dowry raised from 150,000 to 200,000 ducats. Harrison Bornstein recovered the key from the clear minute kept in Milan and read 561 of 624 words (89.9%), under the 95% bar.