Prince of Conti's Keyphrase Cipher

A cipher used by the Prince of Conti at the time of the Fronde was broken by George Lasry, as was reported in HistoCrypt 2023. The cipher is what I would call a keyphrase cipher.
Since the keyphrase cipher is usually polyphonic, his paper is also interesting as a demonstration of solving a polyphonic cipher.
Now, I added a reference to this in "A Polyphonic Substitution Cipher of the Catholic League (1592-1593)", where I'm collecting specimens of polyphonic ciphers.

Ciphers during the Reign of Henry VIII

While working on Elizabethan ciphers, I came across a few ciphers from the first half of the century, which are now in a new article "Ciphers during the Reign of Henry VIII".

Concealment Cipher on "Ramune" Soda Candy Package

For a change, it's about a lighter topic today.
When I sat at the dining table the other day, I noticed a strange text on a package of "Ramune" soda candies (Morinaga), which read something like "It may be just me, but I'm too hungry that the area of a triangle somehow looks like nothing but a cake." The incoherent message seemed so out of place on a candy package. My son told me the real message appears when we pick up only characters in bluish color. It is supposed to be used with a red transparent sheet that students use to memorize stuff (Wikipedia (in Japanese)). 

Application of the sheet reveals the message "Don't give up."

Package says this is a special version with 10%-increased content for students studying for their entrance examination. Another version reveals a message "You can do it." 

 

 

Spanish Ciphers with Vowel Indicators Solved

The other day, I reported George Lasry's solution of several syllabary ciphers, two of which employed vowel indicators. Right after that, I received solution of those two vowel indicator systems from Carlos Köpte, who independently solved them. He designed a program to solve ciphers that employ consistent vowel indicators.
Now, Carlos sent in his solution of another vowel indicator system used in a letter from Juan de Idiaquez Olazabal y Pedro Gonzalez de Mendoza to Philip II. As it turned out, the cipher is the same as a cipher used in other channels.
Now, the achievement is recorded in "Spanish Ciphers during the Reign of Philip II" and "Unsolved Historical Ciphers".

George Lasry's Breakthrough into Syllabary Ciphers

Last week, George Lasry provided me with his solution of ciphertext in a letter from Henri Brasset (1649), probably addressed to Cardinal Mazarin, from my list of unsolved historical ciphers. Now, I uploaded the solution in "Ciphers Early in the Reign of Louis XIV".

George has solved many ciphers from my list (and of course other cipher challenges), including the batch presented in Decipherment of Hitherto Unsolved Historical Ciphers (by George Lasry). But this time, the achievement is more than just another cipher solved. Most ciphers broken up to now are homophonic substitution ciphers, in which a letter of the alphabet may be represented by one of multiple candidate symbols (homophones). In the last decade, solution of such homophonic ciphers by computer algorithms became a standard technique, and homophonic solvers are now readily found on the web. The technique is described in, e.g., Nils Kopal (2019), "Cryptanalysis of Homophonic Substitution Ciphers Using Simulated Annealing with Fixed Temperature" (which I mentioned here, and which seems to be still the state of the art, as attested by the citation in George's recent pulication for HistoCrypt 2023). As long as a major part of the ciphertext consists of symbols for individual letters, today's homophonic solvers would readily provide a solution (or at least give a breakthrough).

But codebreaking algorithms up to now have not been able to successfully solve ciphers when the ciphertext includes many symbols representing syllables, names, and other words. For the Brasset-Mazarin cipher, I had a brief email exchange with George back in 2021, but at that time, even his calibre couldn't break the cipher. There has been a widely shared desire for a solver algorithm for such ciphers including syllables.

It seems George has now developed a workable algorithm for handling such syllable ciphers, because he also solved several other syllable ciphers including two from the Spanish archives (Simancas, EST,LEG,1381,143 and 180, see here).

Solution of syllable ciphers does not merely involve larger search space than for letter-based ciphers. It would require some radical change in the scoring function, i.e., a measure of how plausible the plaintext obtained by a provisional key is. For letter-based ciphers, a syllable structure might give a measure of goodness. But when many symbols correspond to syllables, the provisional plaintext would include many plausible syllables, even if the assignment is random.
I hope George will publish some paper for this groundbreaking work in the history of cryptanalysis.

Castiglione-Schomberg Cipher: Vowel Indicator System (1527) Earlier Than Those Hitherto Known

I uploaded a new article "A Cipher with Vowel Indicators Used by Papal Nuncio Castiglione (1527)"
The cipher, which I call the Castiglione-Schomberg Cipher, is used in letters deciphered by Marcello Simonetta and Norbert Biermann.
The cipher employs a scheme I call a vowel indicator system, whereby syllables are represented by a base symbol indicative of a consonat combined with an additional stroke or a superscript figure indicative of a vowel.
Castiglione was an apostolic nunctio (ambassador) sent by the Pope to Emperor Charles V in Spain, and Schomberg worked for the Pope in negotiation with the Imperialists. It is desired to establish whether this cipher was provided by the Vatican, because some of the other early vowel indicator systems appear to belong to the Imperialists. If the Castiglione-Schomberg Cipher was Vatican's, a new question arises how come the same scheme began to be used by both the Vatican and the Imperialists about the same time. I included some preliminary discussion on the matter.
I also mentioned this in "Tracing the Origin of Vowel Indicators in Spanish Ciphers".