Independently Enciphered Duplicates

Important dispatches were often sent in duplicates to ensure the delivery of a message. When the message is in cipher, it would be easy to make a copy of an enciphered dispatch. But there are cases in which duplicates are independently enciphered. I added such examples in "Finding the Keys to Philip II's Cipher Letters to Juan de Vargas Mexia".

Practice in Use of Ciphers in the Time of Catherine de Medici

I added a section "References to Cipher in the Correspondence of Catherine de Medici" in my article about French ciphers during the reigns of Charles IX and Henry III. It consists of excerpts of Catherine de Medici's letters mentioning a cipher. They are about instructions to use a cipher, delivery of a cipher, handling a cipher personally, forwarding of letters deciphered or to be deciphered, etc. They may be nothing new, but may allow a glimpse of practice in use of ciphers.

Trevanion's Cipher Still being Sought

Sir John Trevanion was a prisoner at the Colchester Castle during the English Civil War, but managed to escape thanks to a letter which hided a message "PANEL AT EAST END OF CHAPEL SLIDES", which showed him an escape route.
Although this episode is famous as a spectacular feat of steganography, nobody seems to know a primary source of this episode, as I pointed out in 2012 in "Quest for 'Trevanion's Cipher'".
I made some additions to the page (references from 1878 and 1925 and some peripheral information).

Zodiac Killer's Cipher Z340 Broken after 51 Years

Earlier this month (December 2020), Zodiac Killer's Cipher known as Z340 was solved by David Oranchak, Sam Blake, and Jarl Van Eycke. Although I have not paid much attention to this cipher, the puzzle is so well-known that I felt obliged to cover it in a new article in Japanese. (In English, I believe there will be plenty of articles out there.) I also added an entry for this in "Unsolved Historical Ciphers.", which also covers recently solved ciphers. 

 

Ciphers in Catherine de Medici's Correspondence

Some weeks ago, I added ciphers used in the correspondence of Catherine de Medici. (When I said it was the first time I came across ciphers used in her correspondence, I did not remember I already described in the same article a cipher used in a letter from Foix to Catherine de Medici in the reign of Henry III.) Now, I added more ciphers used in letters of the Queen Mother during the reign of Charles IX. As for as the specimens I encountered this time, the Queen Mother used the same cipher as Charles IX. (Not that they did the ciphering themselves. The letters are undersigned by a secretary of state.)
I also made one addition (Tournon?) in "French Ciphers during the Reign of Henry II of France" and another [Hurault?] in "Unsolved Historical Ciphers".

Letters Deciphered by John Wallis Sold at Auction for £29,000

It is well-known that a collectioin of fifty-two letters deciphered by John Wallis was deposited at the Bodleian Library, Oxford. Wallis actually made multiple copies of the volume, and on 7 October 2020, one (possibly Wallis's own) was sold at an auction for £29,000. It even includes a fifty-third letter not included in the copy at the Bodleian Library. I added a reference to this in "John Wallis and Cryptanalysis", and also made a few additions from Philip Beeley's paper (2016) referenced by the auction site.
The auction site has some images.
One is Charles I's letter to his son in February 1647, which I already covered in "King Charles I's Ciphers".
Another is a letter from French agent Graymond to Cardinal Mazarin. The cipher used seems to be the same as Graymond's cipher I recently reconstructed from another source and presented in "Ciphers Early in the Reign of Louis XIV".
Another is a letter from the Earl of Lauderdale to the Countess of Carlisle. I now added this in "King Charles II's Ciphers during Exile".
According to the auction site, nearly half of the collection are "from royalist agents in Breda to Dutch and English merchants and other contacts in London: dating from 1650, these relate to the negotiations by which the exiled Charles II was offered passage to Scotland and a means of recovering the throne in England, in return for accepting the authority of the Scottish kirk and parliament." These may include a key between Charles II and the Duke of Hamilton used in some undeciphered letters. I noted this possibility in "Unsolved Historical Ciphers".

Ciphers of Charles IX and Queen Mother, Catherine de Medici

I added a section "Ciphers of Charles IX and Queen Mother, Catherine de Medici" in "French ciphers during the Reigns of Charles IX and Henry III", now renamed from "French ciphers during the Reign of Henry III of France". (I thought separate treatment of the reigns of these brother kings was not necessary.)
As far as I remember, this is the first time I came across ciphers used in the correspondence of Catherine de Medici. The same ciphers were used in letters to the King and Queen Mother as far as these specimens are concerned.
I have been wondering whether Catherine de Medici brought something new to the French cryptography, but these specimens show no such evidence.

Earliest Known French Ciphers

The earliest known specimen of French ciphertext is from January 1526 (or possibly September 1525). This is a few months earlier than the earliest mentioned in a scholarly paper (2018). This and other French ciphers during the reign of Francis I are described in the new article "French Ciphers during the Reign of Francis I".
It includes some undeciphered ciphers, which are now mentioned in "Unsolved Historical Ciphers".

Two Ciphers Broken by George Lasry

Two of unsolved ciphers presented in "Unsolved Historical Ciphers" have been solved by George Lasry.
One is a ciphertext (Senecey to Archbishop of Lyon) left undeciphered by François Viète (see "Ciphers Broken by François Viète").
The other is an Italian letter in the French archives (see "Undeciphered Letters in BnF fr.4715").
Senecey's cipher employs as many as 79 symbols in a relatively short ciphertext, and was very hard to break even with his sophisticated computer algorithms, which appear to have solved the Italian letter in an instant. I look forward to a paper detailing his method.

Regent Marie de Medici's Cipher

I found undeciphered passages in Marie de Medici's letters (1610) in BnF fr.3789 and included it in "French Ciphers during the Reign of Louis XIII" and "Unsolved Historical Ciphers".
The same source also included Villeroy's letter in cipher. The latter cipher turned out to be the same as one I previously reconstructed from BnF fr.15578 presented in "French Ciphers during the Reign of Henry IV of France".

Cipher between Emperor Charles V and Juan Perez (1527)

I added an unsolved cipher in a letter from Juan Perez, ambassador in Rome, to Charles V and another from Charles V to an unnamed recipient in "Ciphers during the Reign of Emperor Charles V" and added references to these in "Unsolved Historical Ciphers".

Venetian Ciphers with Superscripts

I uploaded a new article "Venetian Ciphers with Superscripts" about 16th-century Venetian ciphers. I added a reference to an unsolved cipher (1528) in "Unsolved Historical Ciphers".

Deciphered Letter to Emperor Charles V

In 2018, I solved a cipher in a letter (1529) to Emperor Charles V from Suarez de Figueroa, Spanish ambassador in Genoa and reported it in "Codebreaking of a Spanish Cipher with Vowel Indicators". Since I don't know Spanish, the deciphered text was no more than preliminary. Now, thanks to Demetrio Martín Vilela from Argentina, I made many corrections to my preliminary deciphering. I believe now it is almost a decent text in Spanish (though some parts are puzzling even for the native Speaker of modern Spanish). Martín even provided a quick English translation.

Another Code from the Age of Louis XIV

I added another code as item (11) in "French Ciphers during the Reign of Louis XIV".
Unlike other ciphers at the time, it employs numbers up to 100 (not 99) as well as other letter-letter or figure-letter combinations such as "aa" (Avantage), "2a" (bla), "bc" (la), "maniere" (bl).

French Ciphers in Henry II's Time

I added Duke Marcantonio of Paliano's cipher in "French Ciphers during the Reign of Henry II of France".
I also found an actual letter (1556) in the cipher no.15 presented in "Duke of Guise's Ciphers (1556) in BnF fr.20974" and mentioned it accordingly.

A Cipher of Henry of Navarre before Accession to the French Throne (1587)

I uploaded a new article "A Cipher of Henry of Navarre before Accession to the French Throne (1587)", which presents a cipher used in a letter of Henry of Navarre to Buzenval. This is the only cipher I know of Henry IV before his accession to the French throne. Interestingly, it is a figure cipher, consisting of two- or three-digit figures. In France, such a figure cipher was not yet common at the time, though there were other sporadic examples as I wrote in the last post.

French Figure Ciphers in the 1580s

I added a figure cipher (1586) in "French ciphers during the Reign of Henry III of France" (called "Anonymous Figure Cipher (1586)"). It is similar to a cipher (1579-1584) of Paul de Foix, ambassador in Rome in use of randomly arranged two-digit figures. Ciphers mainly consisting of Arabic figures were not common in France at the time, though more examples can be found in the Nevers Collection.

More Ciphers from Louis XIII's Time

I made several additions to "French Ciphers during the Reign of Louis XIII", of which one undeciphered item (Coquet's) has also been included in "Unsolved Historical Ciphers".
Apart from specific ciphers, an observation by Desenclos (2017) that the cipher (1612) of Sainte-Catherine, resident in the Palatinate, was based on a cipher (1589) for Guillaume Ancel, resident to the Emperor, was interesting for me.

An Unsolved Cipher to Cardinal Mazarin? (1649)

I added an unsolved letter from Henri Brasset, a French resident in The Hague, to "Vostre Eminence" (Mazarin?), in "Unsolved Historical Ciphers". The figures with diacritics probably represent syllables alphabetically arranged and some words and names, as with other ciphers at the time (see here).
There are many interesting patterns, but my attempt has not been successful.
For example, there are many instances of "S 7:" (in my transcription). I guessed this might be "qu e". If so, "S 7: 34 S 7:" is "quelque". "n+", which appears some characters after "mesmes" in clear, might be "s". The pattern AxyA may be "de ma n de" or "re n d re" etc. All these guesses led nowhere.

Another Code from Napoleon III's Time

When googling, I came across a French code from Napoleon III's time, which I added in "Codes from the time of Napoleon III" (now renamed to the plural "Codes").

Four More French Diplomatic Ciphers Using Figures with Diacritics (1647-1649)

I added four ciphers in "Ciphers Early in the Reign of Louis XIV". They are all homophonic substitution ciphers, with a nomenclature employing Arabic figures with diacritics. Now, it seems certain that this is a standard type of French diplomatic ciphers in at least 1611-1676. The first specimen of this type known to me is Beaumont's cipher (1602) in Henry IV's time (here).

Henry IV's Cipher from 1590

I added a referene to Savasse (1997) in "French Ciphers during the Reign of Henry IV of France". He reconstructed one of the ciphers of Hurlaut de Maisse, ambassador in Venice. My reconstruction used letters in 1592, while his reconstruction is based on letters from 1590, making it the earliest specimen of Henry IV's ciphers described in this page. (I know one earlier example. I plan to post it some day.) I have quoted Savasse (1997) in the context of Spanish and Florentine ciphers. At that time, this particular cipher did not catch my attention because the name of de Maisse was not familiar to me.

¿Alguien podrá descifrar las cartas secretas de Felipe II con las llaves que encontré?

(This entry was created by using machine translation. The original post in English is here.)

Recientemente subí un nuevo artículo, "Finding the Keys to Philip II's Cipher Letters to Juan de Vargas Mexia".
Encontré las claves de cuatro cifras utilizadas en las cartas de Felipe II a Juan de Vargas Mexía, embajador en París, que datan de 1577 a 1580 en BnF es.132. Se considera que este volumen incluye materiales interesantes para los historiadores, pero las letras cifradas no se han descifrado (al menos hasta 2012). Las teclas que encontré permiten leer las letras del volumen, pero no puedo hacer el trabajo yo mismo porque no sé español. Espero que las personas versadas en español encuentren lo que escribió el Rey (y Antonio Pérez en algunos casos).
Mi desciframiento preliminar de una carta (16 de diciembre de 1577) está publicado en Academia.edu.

Will Anyone Decipher Philip II's Secret Letters with the Keys I Found?

I recently uploaded a new article, "Finding the Keys to Philip II's Cipher Letters to Juan de Vargas Mexia" and made related changes in "Spanish Ciphers during the Reign of Philip II" and "Unsolved Historical Ciphers."
I found the keys of four ciphers used in Philip II's letters to Juan de Vargas Mexia, ambassador in Paris, dating from 1577 to 1580 in BnF es.132. This volume is considered to include interesting materials for historians, but the letters in cipher have not been deciphered (at least as of 2012). The keys I found allow reading the letters in the volume, but I cannot do the work myself because I do not know Spanish. I hope people versed in Spanish will find what was written by the King (and Antonio Perez in some cases).

"Cipher with Don Juan de Borgia (1579)" Turned Out to be the One Reconstructed by Devos

The cipher I reconstructed some years ago and call "Cipher with Don Juan de Borgia (1579)" turned out to be the same as the one reconstructed by Deovos (p.414). I reflected this finding in "Spanish Ciphers during the Reign of Philip II".
So many different ciphers were in use in history, and it is hard to find out whether a cipher one is dealing with is already known elsewhere. I myself have noted multiple times that one cipher found in one source is the same as another cipher in another source. When I reconstruct a cipher, I always check whether it is already among the known ciphers (collected on my website), but this one slipped my check.

Two New Unsolved Ciphers

I added two unsolved ciphers in "Unsolved Historical Ciphers".
One is Juan de Idiaquez Olazabal y Pedro Gonzalez de Mendoza to Philip II (15 March 1557).
The other is Fra Guglielmo Vizani's letter (8 October 1637).

Ciphers from Louis XIII's time

I uploaded a new article: "French Ciphers during the Reign of Louis XIII".
I pointed out in 2019 that code elements with figures with diacritics used early in the reign of Louis XIV (1661, 1675, 1676) had already been in use during Henry IV's time. Most of the specimens of ciphers from Louis III's time presented in the present article follow this pattern.

Two More French Ciphers from Henry IV's Time

I added Salignac's Cipher and Lisle's Cipher in "French Ciphers during the Reign of Henry IV of France".
They are similar to other ciphers at the time, but the 1607 specimen of Lisle's cipher uses two-digit figures not used in the 1606 specimens. It is wondered whether the figure symbols were added, or Lisle simply didn't use figures in 1606.

Cardinal Richelieu's Cipher (1641) Identified

I mentioned a recent solution (by Norbert) of Cardinal Richelieu's cipher letter from 1641 in "Unsolved Historical Ciphers". While Richelieu is said to have used the Cardan grille, this is the first specific cipher used in Richelieu's correspondence known to me. Basically, it is a homophonic substitution cipher that has numbers, letters, and other symbols to represent the letters of the alphabet.

Complementing Transcription of Ambassador Vivonne's Letter by Decipherment

Old handwriting is hard to read. Crypto-people often find deciphering a ciphertext is easier than reading its decipherment.
Now, I added my decipherment of an enciphered passage from a letter from French ambassador Vivonne to King Henry III dated 17 September 1586 (BnF fr.16045, f.244) in "French ciphers during the Reign of Henry III of France". The letter is printed in a scholarly article, but the transcription of the ciphertext from the decipherment in the margin is incomplete. My decipherment from the ciphertext complements the reading (albeit yet not complete).

By the way, I'm glad to find that my transcription of cipher symbols can be used to read actual ciphertext.

Unsolved Ciphers in BnF fr.4712 (ca.1592?)

I added references to BnF fr.4712 in "Catalogue of Ciphers (Mainly Related to Duke of Nevers) in BnF fr.3995" and "Unsolved Historical Ciphers". The volume contains some cipher letters, of which some are undeciphered. I found one cipher with interlined decipherment is no.71 of the Nevers Collection.

Duke of Guise's Ciphers (1556)

I uploaded "Duke of Guise's Ciphers (1556) in BnF fr.20974". It includes some undeciphered ciphertexts. I solved one cipher, but two remain unsolved. I added a section on this in "Unsolved Historical Ciphers".

Undecoded Chinese Telegrams (1916 and ca.1938)

I added undecoded Chinese telegrams to "Unsolved Historical Ciphers":
Telegram to Sun Yat-sen (1916)
Telegram from Huang Xing to Lin Hu and Li Genyuan (1916)
Telegrams Found in a Sunken Ship Zhongshan (ca.1938) (sorry, this is hearsay)

Chinese Cryptography: 1871-1945

I uploaded an article on Chinese cryptography from 1871 to 1945 in Japanese and English. When I wrote about Chinese telegraphic codes in 2014 in Japanese and English, it was commonly believed that there was nothing to discuss about Chinese cryptography during this period. Since then, new light has been shed on this neglected field by materials published in 2014-2018.
Five points I learned from these new materials:
(1) Revisions of Dianxin Xinfa (電信新法) (not to be confused with Dianbao Xinshu (電報新書) or Dianbao Xinbian (電報新編)) were used as official secret codebooks.
(2) Before the "Ming mi" (Plain/Secret) format of a 1908 codebook published by the Commercial Press, a similar format "Mi zhi" was used in official secret codebooks.
(3) There were many versions of official secret codebooks with different ordering of characters. (About the character ordering of the Zhou Code (1900 or 1902), there are conflicting descriptions, and it is desired to re-check the original copy.)
(4) Secret codebooks were used with the conventional (public) codebook (see the examples of "Qing Mi" and "Liang Mi" (1930-1931)).
(5) Official secret codebooks had long used the word dianma (電碼) in the title before 1929.

Codebreaking as opposed to Cipher-breaking (1926)

Codebreaking through logical reasoning would be the most exciting topic for crypto-enthusiasts. But breaking code, as opposed to cipher, cannot be achieved by techniques such as letter frequency analysis. I'm collecting specimens of breaking codes in "How to Break a Code (Not a Cipher)".
I now added a specimen of solving a Peruvian diplomatic code (1926) described by Yardley.

Crypto-Movie: "The Red Machine" Reviewed by NSA

Among several movies depicting codebreaking, The Red Machine (2009) is unique in dealing with the Japanese RED machine. This movie focuses on a story (1935) of the US Navy's slipping into the Japanese naval attaché's luxurious apartment in Washington, DC, to obtain information on the cipher machine. My article in Japanese "映画紹介：The Red Machine（「レッド暗号機」） " introduced this movie to the potential audience in Japan. I was hoping that the public interest might lead to this indie movie's release in Japan, which, to my regret, has not come true.
While I exlained in the article the general historical background of this story, I recently found that David A. Hatch pointed out many historical inaccuracies in Cryptologic Quarterly 2015-01. I updated the article by taking notice of his comments.
Most importantly, he says one documented "black-bag-job" (called "second-story cryptanalysis" by one former NSA senior) against a Japanese consular residence was for an earlier Japanese Navy Codebook called "Red Code", not the Red Machine (p.60-61). Of course, photographing of the Red Codebook in the 1920s is known, separately from the 1935 episode depicted in the movie. (Budiansky (2000), Battle of Wits, p.83, describes both episodes separately, but, significantly, does not show a primary source for the latter episode.) If I remember correctly, Layton (1985), And I Was There described the episode as apocryphal. We need to check if the episode can be traced earlier than Ladislas Farago quoted in Deavours and Kruh (1985), Machine Cryptography and Modern Cryptanalysis p.218. Smith (2000), The Emperor's Codes describes US breaking of the Japanese naval attaché's ORANGE machine by quoting Stafford, L.F., History of Japanese Cipher Machines, NARA RG 457 HCC 2344. I wonder whether this source describes the episode.

Even if the episode is not supported by a primary source, it is mentioned in many crypto-books, and it is understandable that filmmakers took up the episode.
We should remember that Hatch belongs to NSA and he wrote the review in the hope that "filmmakers will avoid showing [the government's cryptanalysis] in ways that have a negative impact on the community" (p.63).

Updated Links to International Telegraph Regulations

When my historical cryptography website is more than ten years old, it's inevitable that there are many dead links. The other day, I needed to consult the 1879 revision of the International Telegraph Regulation, and I followed a link in "Telegraph Regulations and Telegraph Codes", which no longer worked. I was at a loss, because somehow I could not find the relevant page by Googling. Now, I found the pages were not removed, but moved to different URLs. Now, I fixed the links, hoping that the URLs would not be changed so often.

Listing Recurring Polygrams from Ciphertext

I uploaded a new article "Listing Recurring Polygrams from Ciphertext (with Perl)". It presents a script in Perl to list recurring polygrams from a ciphertext (or any text). Here, I define a polygram to be an n-gram where n>=LEN (e.g., 10).
Although tools for counting bigrams etc. are available, I couldn't find tools for listing recurring long n-grams. So, I wrote one myself. It has known limitations, but it serves for my immediate need.

Scytale Was Not a Transposition Cipher

I uploaded a reorganized summary version of "Scytale Not as a Transposition Cipher" at Academia.edu.
Today, a scytale is explained as a tool for transposition cipher for letters, but such a definition of scytale was established only around 1900.
The original version was posted in 2014, which has grown with sources of historical description of scytale. As a result, it is now something like a motley collection of documents. So, I had to reorganize the whole to make a readable summary version. In the process, I made some updates, so I believe the summary version is more focused about the issue.

Another Specimen of a Vatican Cipher with Ambiguous Reading Frames (1551)

I found another specimen of a cipher with ambiguous reading frames when Googling without purpose. J. Lestocquoy (1966), Correspondance des nonces en France: Dandino, Della Torre et Trivultio (1546-1551) (Google), p.43, presents a reconstruction of a cipher of papal nuncio Montemerlo in his correspondence with the Farneses in 1551. It represents letters with one or two digits: 0(-) 1(L) 2(N) 3(O) 4(A) 5(U/V) 6(I) 7(M) 8(B) 9(H) 17(D) 18(Q) 19(P) 21(T) 27(Z) 28(F) 29(C) 71(G) 72(E) 82(S) 87(R) and provides for some names (the pope, the emperor, the king, V.Exc.=Octave Farnese, ...). The author points out the ambiguity of reading frames with an example 387213=3(O)87(R)21(T)3(O) or 3(O)8(B)72(E)1(L)3(O). This cipher is somewhat similar to "Cifra con mons. Aurelio" and "Cifra con mons. Arnoldo di Maguntia" in Meister (1906), p.183, 184. See also "Variable-Length Symbols in Italian Numerical Ciphers" for similar ciphers.

Lestocquoy (1966) also presents a reconstruction of a cipher used by Dandino in 1546. It is a polyphonic cipher printed in Meister (1906), p.177. See "Polyphonic Substitution in Italian Numerical Ciphers" for examples of Vatican polyphonic ciphers.

Bloggerで「試行回数が上限を超えた」と言われ自分のブログから締め出された顛末記

（The following is my experience of being locked out of my own blog, and has nothing to do with cryptography.）

先日、突然自分のブログにログインできなくなり、数日間編集ページにアクセスできなかった。検索してもあまり参考になるサイトがなかったので、私の経験を記しておきたい。
gmailのメールアドレスを入力して、端末に記憶されているパスワードでいつも通りログイン……のはずが、端末が認識された端末ではないなどと言われて、電話番号の入力を求められてしまった。ケータイ番号を入力すればCメールで数字が送られてきて、それをパソコンで入力すればOKという「２段階認証」だろうと思い、番号を入力したのだが、一向に送られてこない。おかしいなと思いつつ何度も繰り返していると、次のようなエラーになってしまった。
「ログイン試行の回数が上限を超えました。ユーザー保護のため、現在ログインすることはできません。しばらくしてからもう一度お試しいただくか、別の端末からログインしてください。」

どうしてこんなことになったのか。思い当たることが二つある。
・直前にウインドウズ１０の更新をして再起動したので、端末が変わったと認識されてしまったのだろうか（？）だがこれまでも更新・再起動は何度もしてきたはず。
・他のアカウントのブログを別のタブで開いたまま、ログインしようとしたのがいけなかったのかもしれない。これまでは他のアカウントはログアウトしてからログインしていたのだが、今回たまたまそちらの作業中に別のタブを使ったのがいけなかったのかもしれない。

「しばらくしてから」ということはどれくらい待てばいいのか。数分後にやってもだめだったのは当然としても、１日半空けてやってみてもだめだった。
今になって、ブラウザーのキャッシュをクリアすればよかったかなと思ったが、他のブラウザーで試してもだめだったので、おそらく無駄だったろう。

ネット検索したら２０日たってもだめだったという人がいて、その人はパスワードのリセットで解決したらしいのだが、私はそれもできなかった。うろ覚えだが、連絡できるメールアドレスを入力しろというので入力したら、そちらにコードを送ってきた。また２段階認証というやつだ。それを入力したところ、「連絡できるメールアドレスをご確認いただいてありがとうございました」という感じのメッセージが出ただけで、その先には進めなかった。たぶん、そのメールアドレスをあらかじめ登録しておかなかったのがいけなかったのだろう。（仮に悪者が私のアカウントにログインしようとしている場合、任意のメールアドレスを入力してロックを解除できるなら意味がない。）

ところがそのメールアドレスに「重大なセキュリティ通知」というタイトルで「ログインをブロックしました」というメールが届いていた。gmailにはログインできないものの、gmailで転送設定をしてあったようだ。 そのメールいわく、
「あなたのパスワードを使ってアカウントにログインしようとした人がいます。Google でブロックしましたが、アクティビティをご確認ください。」
ここで「確認」すればロックが解除するのではと淡い期待を抱いたが、「確認」するにはログインが必要で、結局何の解決にもならなかった。

仕方がないので「別の端末」というのを試してみることにした。おそるおそるタブレットでアクセスしてみると、あっさりログインできた。その状態でgmailにアクセスして「重大なセキュリティ通知」で、アクティビティを「確認」してみたが、それでもパソコンのほうのロックは解除されなかった。実は何度もはねられたので、「重大なセキュリティ通知」がたくさんあったらしい。それを一つ一つ全部「確認」したところ、ようやくパソコンからも自分のアカウントにログインできるようになった。

それにしても、携帯にCメールがこなかったのはなぜだろう。迷惑メールを防止するためにパソコンからの送信ははねるように設定しているからそのためだろうか。それにしても、コードが届くこともあるから、そういうわけではないだろう。今回はたしか、Cメールは役に立たず、音声通話で（機械から）携帯にかけてもらい、それでコードを取得できた場面があった。（ネット検索では音声が英語、という情報もあったが、今回は日本語だった。）

というわけで解決はしたのだが、本当の悪者が不正アクセスしようとした場合、せっかくブロックしても、悪者がスマホで再試行したら素通りになる、ということなのだろうか。

これまで「２段階認証」というのはどうもうさんくさいと思っていたのだが、これを機に登録することにした。

Polyphonic Challenge Part 2

Now I see polyphonic ciphers do not pose a serious problem to codebreaking. Part 2 of my "Polyphonic Challenge" has been released at MTC3 (Part 1 was reported here), and three people already solved it.
Part 1 and Part 2 have different characteristics. While the digits of Part 1 tend to represent two letters of similar frequencies, the digits of Part 2 tend to represent one high-frequency letter and one low-frequency letter. I think Part 2 is easier. Although frequencies of digits are somewhat flattened, considering a reduced alphabet consisting of only high-frequency letters may reveal some portions of the plaintext. (Anyway, I have not done it myself, and I hope someone will demonstrate solution of a ciphertext in a polyphonic substitution cipher.)

Spanish Codebreaker: Luis Valle de la Cerda

I uploaded a new article "Spanish Codebreaking under Phillip II", focusing on Luis Valle de la Cerda and mentioning three others.
I planned this article some years ago when I saw Marcos (2014), but had difficulty in reading the Spanish text. Now I have come to know sources in English and French, which allowed finishing this article (helped by much improved machine translation since then).

As a byproduct, I added the following entries in "Unsolved Historical Ciphers":
Venetian Letter in Spanish Archives (ca.1589)
Fragments in Novel Cipher Invented by a Milanese (ca.1599)

Ciphers Broken (and Not Broken) by François Viète

I uploaded a new article "Ciphers Broken by François Viète".
Apart from an overview of well-known facts about the French codebreaker Viète, papers deciphered by Viète in Cinq Cents de Colbert 33 are catalogued and some specific ciphers solved by Viète are identified. There appear to be three ciphertexts left undecifered (unbroken) by Viete, for which I also included a reference in "Unsolved Historical Ciphers".