Empress Eugénie's Cipher Telegrams to Napoleon III Broken by Two

Again, two people independently achieved codebreaking with AI almost at the same time. They decoded telegrams between Napoleon III and Empress Eugénie in June 1859.

Geoge Lasry notified me of his solution (one in a batch of no less than 56 solutions) on 10 October 2026 and I published his results here on 12 October 2026. Jimmy Apples had published his results on X on 5 October 2026 and provided me with details on 13 October 2026. I now mentioned him in my report of George's results.

Two of the decoded telegrams are from Eugénie to Napoleon and the others are from the Emperor to the Empress.

Eugénie's telegram on 23 June 1859 reads:

Je suis désolée de vous avoir fait de la peine. Ce n'était pas mon intention. Ne vousinquiétez pas du petit, il va à merveille. J'écris aujourd'hui par la poste.
(I am so sorry to have caused you pain. It was not my intention. Do not worry about the little one, he is doing wonderfully. I am writing today by post. (Apples' translation))

The short telegram of the Empress is about personal matters, though the Empress acted as regent during the Emperor's absences in 1859, 1865, and 1870 (Wikipedia). In 1859, Napoleon III was with the army in the Italian campaign, which culminated in the Battle of Solferino on 24 June.

In terms of cryptanalysis, this is interesting in two points.

(1) No plaintext is found and this is a ciphertext-only achievement.

(2) One telegram has a sequence in which many figures occur only once:

677(je) 1074(re) 310 925 357(des) 381 708(le) 81 1099 123 495 656 257 914(par) 439(ennemi)

Apples succeeded in filling these:

677(je) 1074(re) 310([cueille]) 925([partout]) 357(des) 381([do]) 708(le) 81([ances]) 1099([relatives]) 123([aux]) 495([exact]) 656([ions]) 257([commises]) 914(par) 439(ennemi)

The readings identified for these code groups fit in appropriate places in the alphabetically ordered code list. So this is not just a fabrication from nowhere. But it is not straightforward to find out whether this is the only candidate.

 

Dutch Ciphers with Table Switching

It has been known from Karl de Leeuw's work that Dutch diplomatic ciphers provided multiple substitution tables.

Now, in deciphering a ciphertext in Thurloe State Papers, Paolo Rosson found it switches among five tables in one letter. Though the plaintext was found in a Dutch publication, the scheme he found out is interesting.

The ciphertext is something like "113. 10. 26. 13. 13. 19. 29. 29. 26. 11. 222. 31. 17. 21. 22. 23. 23. 22.13. 30. 20. 18. 22. 23. 15. 13. 24. 22. 13. 24. 22. 17. 10. 15. 25. 23. 13. 329. 28. 15. 22. 20. 25. 20. 15. 25. 27. 28. 20. 27. 27. 20. 22. 17. 20. 15. 527. 16. 20. 21. 12. 19. 21. 29. 26. 20. 16. 27. 16. 19...." Although the specimen is a bit short, I thought solving this would not be difficult.

As it turned out, this short letter switches tables multiple times. No wonder it couldn't be solved with ordinary attacks. (I said the plaintext might not be in Dutch but in French. Some may have been misled by this.)

The first digit of three-digit group indicates one of tables 1-5.

I uploaded a new article about this, "Table Switching in Dutch Diplomatic Ciphers".

Trithemius' Cipher Deciphered and Re-enciphered Polyalphabetically in the 17th Century (Heidel Cipher)

It is well-known that the cipher in the third book of Trithemius' Steganographia was solved in the 1990s. But it was only recently that I learned the cipher was broken in the seventeenth century by one Wolfgang Ernst Heidel, who declared it in his 1676 book but re-enciphered his solution in his own polyalphabetic cipher!

Thomas Ernst, who had solved Trithemius' cipher, deciphered Heidel's cipher and thus proved that Heidel indeed had the solution of Trithemius' cipher. Since Heidel's cipher had apparent word boundaries, a breakthrough was made when he identified the matching ciphertext for "gaza frequens libicos carthago duxit triumphos" known from the solution of Trithemius' cipher.

Thomas Ernst had succeeded in deciphering Trithemius cipher in 1993 and published it in 1996. In 1998, Jim Reeds independently solved it and then found it was already solved before him. Cryptologia (1998, issue 4) carried Jim Reeds' paper together with Thomas Ernst's brief English summary of his original paper in German.

Since it may take time before I have time to study further details, references are given below:

Thomas Ernst, "Schwarzweiße Magie: Der Schlüssel zum dritten Buch der Steganographia des Trithemius", Daphnis: Zeitschrift für Mittlere Deutsche Literatur, 25/1 (1996), pp. 1-205

Thomas Ernst, "The Numerical-Astrological Ciphers in the Third Book of Trithemius’s Steganographia", Cryptologia, XXII/4 (1998), pp. 318-341

Jim Reeds, "Solved: the Ciphers in Book III of Trithemius's Steganographia", Cryptologia, XXII/4 (1998), pp.291-317

Thomas Ernst's information about Heidel is on a wordpress-site: Restoring the Steganographia of Trithemius

Thomas Ernst analysed a forged manuscript of the "Steganographia" presumedly from 1521: "Anatomie einer Fälschung: ‘Johannis Trithemij [...] Steganographiæ Lib· 3. cum Clave, tàm generalj, quàm specialj [...] M.D.XXI’", Daphnis: Zeitschrift für Mittlere Deutsche Literatur und Kultur der Frühen Neuzeit (1400–1750), 30/3-4 (2001), pp. 513-595

"Hieronimo Ranzo" Cipher Solved by AI

A cipher with superscripts with word elements are now solved by Paolo Rosson. A few hours after his email, I received a report of solution from George Lasry.

This is what I listed as "Venetian? Cipher with Superscript Digits (1528)". As it turned out, the writer was a Genoese with the pseudoonym "Hieronimo Ranzo", apparently different from "Hieronimo Ranzo" known in history. Only yesterday, I gave this one that remains intractable by AI!

I uploaded a new article about this, "A Cipher with Superscripts for Word Elements ("Hieronimo Ranzo") Solved by AI".

 

Anatomy of AI Codebreaking

I uploaded a new article, "Codebreaking with AI".

In the past month, I received many solutions for pieces in my list of unsolved ciphers. I suppose most of them were achieved with the assistane of AI.

Although I'm not versed in technical details, I tried to sort out what AI did in these achievements.

Possibly Manual Solution of a Very Short Numerical Ciphertext: Ormonde-Maltravers Cipher (1634-1635)

While Daniel Bourdeau is known to have solved many ciphers by using AI, his simulated-annealing homophonic solver didn't work for Ormonde-Maltravers Cipher (1634-1635). The ciphertext looks too short for ordinary algorithmic analysis. His solution seems more like human ingenuity. It can be seen as an interesting example of good old codebreaking. (Github records are difficult for me to decipher, and I don't know how far he was helped by AI in this.)

I uploaded a new article to describe his solution: "Ormonde-Maltravers Cipher (1634-1635)".

Did François Viète Break a Polyphonic Cipher?

I reported Paolo Rosson's full decipherment of two letters in a polyphonic cipher in a new article, "An Intercepted Report of Henry IV's Upcoming Attendance at Mass in a Polyphonic Cipher". When I identified the key from deciphered materials back in 2017, I reported these as undeciphered. The fresh decipherment reveals reporting of the prospect of Henry IV's attending Mass.

Rosson noted that these were among the intercepted letters but were recorded as left undeciphered. Probably, because the letters to the Pope and the Bishop of Lizieux from the same date were deciphered, deciphering these was not considered important. Since Rosson provides the full text, I hope someone will compare it with the known letters to see if there is some new content. (Maybe AI can do such a specific task?)

From the viewpoint of cryptography, it is wondered who deciphered the letters to the Pope and the bishop. It is exciting to speculate whether it was François Viète.

 

Enigma Messages Solved by AI

A wave of codebreaking by/with AI now hit unsolved Enigma messages. Three people independently reported solutions of Enigma messages on a list of Enigma messages in Frode Weierud's CryptoCellar. (Some messages used for his coauthored paper (Olaf Ostwald and Frode Weierud (2017), "Modern breaking of Enigma ciphertexts" (Cryptologia)) are here.)

(1) A message dated 10 July 1941 with a discriminant (Kenngruppe) MVUEH was broken by Carter Leffen (X), who used OpenAI GPT-6 Astra. He communicated his solution to Weierud on 15 September 2026 (see Weierud's report).

As with the case of Vals AI's solution of Cyphral Distich reported yesterday, Leffen only told AI to see if it could break any of the unbroken Enigma messages on the CryptoCellar web page. All by itself, AI picked up Nr.172 (MVUEH) and assumed that its content might be related to the known plaintext of Nr.173 (SIPVX) from the same date. After many failed attempts, AI took up the repeated place name ROSENOW ROSENOW as a crib. AI then autonomously developed necessary Python and C++ software for an Enigma simulator and an Enigma Bombe and finally it successfully identified the key. Its plaintext turned out to be almost identical with Nr.173 (SIPVX). Actually, the SIPVX key had been tried before but it didn't work. As it turned out, the MVUEH key is completely different from the SIPVX key.

One more amazing thing about this solution gleaned from the log is that AI discovered relevant documents in the archives by itself, though it is not yet clear how far AI used the archival materials.

(2) Solution of Nr.285 (FMNGI), dated 31 July 1941, by Jack Willis using Anthropic's Claude Opus 5 was reported to Weierud on 21 September 2021. Unlike the case of MVUEH, this solution was "more directed and relied on strong human guidance" (see Weierud's report).

AI made the transcription of the message and used an already broken message ALQFI between the same two stations as a control to check the transcription.

Several messages (including ALQFI) from the same sender suggested a crib XHARTJENSTEINX (the sender was SS-Obersturmbannführer, Friedrich Hartjenstein). Variants of this name had already been given in Geoff Sullivan and Frode Weierud (2005), "Breaking German Army Ciphers", Cryptologia (pdf).

As it happened, Weierud had found a plaintext in July 2026 and put a notice of it on his website but not the plaintext itself. So the solutioin did not use the known plaintext.

(3) Solution of messages Nr.187 (AWTZK) and Nr.189 (ZNLZT) from 11 July 1941 by John Woodhouse (pdf) using Anthropic's Claude was reported to Weierud on 26 September 2026 (Weierud's report).

Again, a crib was the key to the success. Twelve cribs, harvested from messages with close dates, were "tested with a Bombe-style search that tolerates one garbled letter." The fifth crib XOSTROWXOSTROWX (again, a repeated place name) succeeded for ZNLST, and the key obtained therefrom could read AWTZK.

The search was helped by an observation from 1941 key sheets that "no wheel sits in the same slot on cnsecutive days". This reduced 60(=5*4*3) wheel orders to 14 for 11 July because 10 July employed V-II-I and 12 July emplyoed II-V-IV.

(By the way, I learned of this topic by newsfeeds in Japanese: GIGAZINE, netlife.)

AI's Solution of Urquhart's Cyphral Distich Verified

A short numerical ciphertext called Cyphral Distich in an edition of Logopandecteision by Sir Thomas Urquhart was solved by AI (Claude Fable 5.1), as announced by Geby Jaff (Vals AI) on 31 August 2026.

It is remarkable that Fable 5.1 was simply told to solve an unsolved cryptogram (one that is deterministic and not ultra-hard) and autonomously picked up this and solved it without any human intervention. What looks like an ordinary numerical cipher turned out to be a book cipher.

Right after the announcement, sceptics pointed out that the ciphertext is not present in the 1653 edition available online and the decryption could not be reproduced.

Actually, the ciphertext is found at least in an 1834 edition and using its text (different from that of the 1653 edition) reproduces the decryption. This was pointed out at least by Jozef Krajčovič（facebook, 5 September 2026), kjfriedo (comments on Bruce Schneier's blog, 9 September 2026), AI時短ラボ (17 September 2026). But because sceptic views continued to be professed, I prepared my own verification here, and uploaded a new article in Japanese, "AIが人間の介在なしに17世紀の暗号Cyphral Distichを解読したのは本物だった".

Urquhart also left a second ciphertext called Cyphral Octastich and solved it in a similar way. Daniel Bourdeau, who also used Fable 5.1 to solve many ciphers including those on my list, verified the solution. He independently applied the rule found by Vals AI to reproduce the announced reading, though some numbers were "one word off".

kjfriedo (comments on Bruce Schneier's blog, 10 September 2026) had also partially verified the solution.

Walsingham's Pigpen Cipher (1586-1587)

I uploaded a new article about a pigpen cipher used in letters from Thomas Wilkes to Sir Francis Walsingham. See "Walsingham's Pigpen Cipher (1586-1587)"

I wrote the most part of this some weeks ago but I didn't have time to complete it until now.

 

A Numerical Cipher in an Italian Letter to Francis I (1530)

During the sixteenth century, numerical ciphers were not common in France. One letter from London to Francis I (1530) is the earliest French numerical cipher I know, though, as expected, the letter is in Italian.

For a long time, I have been wondering what kind of cipher this is. Now Daniel Bourdeau deciphered it. I uploaded a new article about this, "A Numerical Cipher in a Letter to Francis I (1530)".

 

A Cipher between Louise of Savoy and Nicolas Raince (1525)

Louise of Savoy, mother of Francis I, acted as regent from 1525 to 1526 when the king went to war in Italy and during his captivity in Spain (Wikipedia).

I learned from Ryan Turner that a letter to her (25 October 1525) from Nicolas Raince, secretary of the French ambassador to Rome, in Dupuy 452 used Nicolas Raince's cipher (1526) I reconstructed in "French Ciphers during the Reign of Francis I" and that the letter is printed in Jacqueton (1892), La politique extérieure de Louise de Savoie, XXXIII, pp.366-370 (Internet Archive). He points out that this identification shows that the 1526 cipher had been used as early as 1525 (his github). Although it is now known that cipher was used in France much earlier than this (see my blogpost), the year 1525 is interesting because nonsporadic records in cipher start to appear in 1525.

 

BnF Dupuy 452 includes the following letters partly in cipher, all using the same cipher and printed in Jacqueton (1892):
f.20 Alberto Pio de Carpi to Louise of Savoy, Rome, 22 October 1525, deciphered on f.22
f.24 Nicolas Raince to treasurer Florimond Robertet, Rome, 24 October 1525, deciphered on f.25
f.28 Nicolas Raince to Louise of Savoy, Rome, 25 October 1525, deciphered on f.31

 

Turner also published reading of some letters mentioned in my articles by using the respective keys mentioned:
Gramont's letter from BnF fr.2980 I mentioned in "French Ciphers during the Reign of Francis I" (his github); and
Danzay's letter to the Cardinal of Lorraine I mentioned in "Danzay's Ciphers: Ciphers of a French Diplomat with a Long Tenure" (his github)

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Use of Cipher in Cardinal Schiner's Letter to Henry VIII (1516)

The earliest users of cipher in England include Catherine of Aragon, John Stile, Thomas Spinelly, and Cuthbert Tunstall (see "Earliest English Diplomatic Ciphers"). To this may be added Richard Pace (Letters and Papers, Henry VIII, vol.2 (BHO), Wolsey's envoy.

On the receiving side, Brian Tuke is mentioned as the one who deciphered Spinelly's letters to Henry VIII or Wolsey (ibid. (BHO)). The cipher in a letter, dated 14 June 1516, from Matthew Schiner, Cardinal of Sion, to Henry VIII (ibid. (BHO) no.2044-2045) may also have been deciphered by Tuke.

I learned of the latter letter in a write-up by Daniel Bourdeau, who found that the letter is printed with decipherment in A. Büchi (ed.), Korrespondenzen und Akten zur Geschichte des Kardinals Matth. Schiner, vol. II (1516-1527), Basel 1925. It is amazing how his bot searches many sources to find a specific letter in a relevant volume, though it cannot get inside sources with "a bot check".

According to Bourdeau, Büchi tells in the preface that the volume includes 29 letters partly in cipher and names five kinds of cipher used by Schiner and his agents "above all in dealings with England". Inspection of the original materials is desired to see exactly what kind of ciphers were used in these. (At least, the original of some letters by Schiner and Pace are preserved in Cotton MS, Vitellius B XIX.)

It will shed light not only on possible influence on the earliest English ciphers but also on Vatican ciphers at this early stage. One letter addressed to Schiner in 1520 was written as a continuous stream of digits similar to, but much simpler than, later Vatican ciphers (see "An Early Vatican Cipher (1520)"). It would be interesting to know whether schiner's official correspondence used such a simple cipher.

Three Ciphers between Adrian of Utrecht and Charles V (1520-1523)

It has been known that Adrian of Utrecht and Chares V used cipher as early as 1520. When I saw a cipher between them in 1522-1523, after Adrian became Pope, reconstructed by Olga Kolossova (Ko.4) is a typical Spanish cipher, I wondered whether the cipher used in 1520 was so complex as this.

Now, I find that Adrian and Charles used a simple homophonic cipher in 1520 by cryptanalysis by Mikel García Larragan.

Also, the cipher used in October-December 1521 mentioned by Daniel Bourdeau appears to be the same as Ko.4. If so, it indicates that Adrian and Charles V used the same cipher before and after Adrian became Pope in January 1522. Inspection of the original images is desired. (I couldn't locate PTR 2/1/94, 99, 100, and 101 in PARES.)

Daniel Bourdeau also found that a letter jointly sent by Adrian and two other governors of Castile in December 1520 was deciphered in the nineteenth century by Claudio Pérez Gredilla. From his write-up, we see this is a typical Spanish cipher with three-letter code. I suppose Adrian learned this type of code in Spain.

See the new section I added in "Scholarly Studies on Ciphers in the Reign of Emperor Charles V".

Many Telegrams Related to Sun Yat-sen in Japanese Archives Deciphered

A few days after identifying the code condenser to decipher the telegram to Sun Yat-sen (reported the other day), Daniel Bourdeau found that the telegram was only part of a larger collection. He succeeded in deciphering many of them. One is a report of assassination of Chen Qimei (陳其美) sent the day after the event. I wonder whether these telegrams reached the recipient and are preserved for historians. If not, his achievements will shed new light for historians.

Two pieces of news for crypto people. First, Bourdeau found telegrams that cannot be read with the family of code condensers he found combined with the standard character code. I added this in my list of unsolved ciphers.

Secondly, I successfully determined the mapping between the character code and the three-kana code identified by Bourdeau.

See the new section in "Solution of Two Chinese Cipher Telegrams Archived in Japan (1916)".

Solutions of Ciphers in a Continuous Digit Stream

I have been interested in ciphers written in a continuous sequence digits without a break. To solve such ciphers, the first step is parsing the digit stream into cipher units. I uploaded a new article, "Solutions of Ciphers in a Continuous Digit Stream" to describe recent solutions of such ciphers .

Of these, the Soglia cipher solved by Daniel Bourdeau is one for which a reward was offered in 1848.

The Starhemberg cipher solved by by Andrew Aymeloglu employs a fairly complicated scheme, for which he found the key among numerous keys in the DECODE database.

Bishop of Worcester's Latin Cipher with Superscripts Reconstructed from Decipherment in Print

I was told by Andrew Aymeloglu that plaintext of two of the Bishop of Worcester's letters in cipher is printed in publications. When I put them in my list of unsolved ciphers, I thought there was not much to be done to complete the decryption. As it turned out, however, many of the unidentified symbols represent whole words. It would have been hard to identify them from scratch. See "Bishop of Worcester's Latin Cipher with Superscripts (1526, 1529)".

One anonymous letter seems to employ the same cipher but has many yet unidentified symbols, many of which would be nulls or words. I re-marked this as yet unsolved.

Two Diplomatic Ciphers of Marquis de Villars (1669, 1671)

Some letters from Louis XIV to Pierre Villars, Marquis de Villars, are put on auction at Spink (I thank Patrick Hayes for the information). They are interesting in the study of codes and ciphers early in the reign of Louis XIV.

One (1669) seems to use "Colbert-Croissy Cipher (1668-1674) (DE=68) but there still remain many unidentified symbols.

I reconstructed the cipher used in another (1671). As far as I know, it is the only French cipher that had no regularity in arrangement before Louvois' in 1676.

See "Two Diplomatic Ciphers of Marquis de Villars (1669, 1671)".

PS. Patrick Hayes also discovered a letter part of which is in "Cipher with Prince Rupert, Digby, and Ormonde (1644-1645)" ("King Charles I's Ciphers"). The letter is Digby to Prince Rupert, dated 12 July 1644. He provided additional elements:

83=.

87=:

h3=now

Many thanks for the info!

Louvois' Petit Chiffre (1690-1691) Solved

Daniel Bourdeau solved "French Cipher Despatch received by General Catinat (1691)" in my list of "Unsolved Historical Ciphers".

He has been solving so many items in the past few days (he told me he solved 26, with avg 1-2 hours per problem) that I cannot catch up in updating my list. So I put a notice in my list that people about to start working should first check his website. As far as I have seen, his solution and analysis are of very high quality.

For this particular case, automatic codebreaking by AI failed. He found another ciphertext in the same cipher with a paraphrased translation, in which matching ciphertext-plaintext portions could be found from recurring symbols.

See "Solution of Louvois's Petit Chiffre (1690-1691)" and his github quoted therein.

Two Chinese Cipher Telegrams (1916) Solved

Two Chinese cipher telegrams from 1916 presented in "Chinese Cryptography: 1871-1945" are now solved by Daniel Bourdeau.

The one is a telegram to Sun Yat-sen, for which he identified the code condenser (kind of superencryption) by brute force attack after cleverly narrowing down the search scope.

The second was not technically "unsolved" because the decryption is attached, but the encryption scheme has not been known. Bourdeau found it is a three-kana code. It still remains to be found out how the three-kana code groups are mapped to character numbers in a codebook.

See "Solution of Two Chinese Cipher Telegrams Archived in Japan (1916)" and Bourdeau's github pages quoted therein.