Charles I of Spain (Holy Roman Emperor Charles V) became King of Spain in 1516, when he was yet to be sixteen, by the death of his maternal grandfather Ferdinand the Catholic. His succession to his paternal grandfather as Holy Roman Emperor in 1519 resulted in a vast dominion known as "the empire on which the sun never sets." While he realized Spain was the pivot of his power (CSP, Further Supplement, Preface) and spent most of his life in Spain, he was never totally assimilated. Born and brought up in Flanders, he was fluent in French and Flemish but he only acquired an acceptable command of Spanish, which was required by the Castilian Cortes as a condition for becoming King of Castile. (Wikipedia)
The present article describes ciphers under the reign of Charles V to study development of Spanish ciphers.
Charles' claim to the crown of Spain came from his mother, daughter of Ferdinand and Isabella. Although his mother Juana was still alive when Ferdinand died, he was recognized as king jointly with his mother because of mental instability of the latter. Such a technicality persisted until the death of Juana the Mad in 1555.
The exact nature of Queen Juana's condition had to be kept secret. Her father Ferdinand put her in strict confinement, debarred from all communication with the outer world, and her son Charles saw fit to continue the close watch on the Queen. Charles reiterated that point to Cardinal Jimenez de Cisneros, regent of Castile in his behalf, in a letter in cipher dated 30 April 1516 with a subscription "By the order of the King, P. De La Mota".
When Charles came over to Spain, he appointed the Marquis of Denia as master of the household of the Queen in 1518. Of the numerous letters of the Marquis of Denia, those to be seen by the Privy Councillors avoided positively stating that the Queen was mad, while those for the eyes of Charles alone were written with less reserve. Such secrecy even to the councillors was in accordance with Charles' positive order: "you shall neither talk nor write to any person about the affairs of Her Highness, except to myself, and always (send the letters) by trustworthy messengers." (Charles V to Marquis of Denia, 19 April 1518).
The Marquis found distress of the Queen but the discovery only confirmed the necessity of secrecy and the Marquis asked the Emperor to have a cipher "for writing certain things." (Marquis of Denia to Charles V, October? 1519?)
In January 1519, when Charles had been in Spain for little more than a year, his grandfather and Holy Roman Emperor Maximilian died and Charles was elected as successor. He left for Germany in 1520, leaving his mentor Adrian of Utrecht as his regent.
Adrian of Utrecht, tutor to Charles since he was seven, had been sent to Spain shortly before the death of Ferdinand the Catholic to secure succession to Charles. He was made Bishop of Tortosa in 1516 and cardinal in 1517. When Charles left Spain in 1520, riots broke out against the foreign rule. The rebels upheld the authority of Juana and even controlled Tordesillas, where Queen Juana resided.
Adrian reported the situation in Spain to Charles. His letter of 8 October 1520 used cipher for a few words and he later used cipher occasionally. The rebels kept watch on the roads to arrest and search couriers and Adrian was aware of the need to "protect and secure myself against bad consequences by writing in cipher" (Adrian to Charles V, 21 October 1520). When his letter was actually intercepted in the following year, he felt a certain security because "a portion of it was written in cipher."(Adrian to Charles V, 22 January 1521)
Adrian was elected to the papacy in 1522 as a compromise between the Spanish and the French factions. Soon after Charles returned to Spain after the business in Germany (including facing Martin Luther at the Diet of Worms) and visiting England to consolidate an alliance with Henry VIII, Adrian departed for Rome.
Despite the suspicion of the French that Adrian might be a tool of the Emperor, Pope Adrian VI was determined to reign impartially and refused to ally himself with the Emperor against France. The Duke of Sessa, imperial ambassador in Rome, once reported that when the Pope read the Emperor's despatch in cipher, the Pope was so angry that he was nearly suffocated with rage. (Duke of Sessa to Charles V, 17 October 1522)
Adrian complained of hostile attitudes of imperial soldiers and ambassadors in cipher letters to the Emperor. (Adrian VI to Charles V, 21, 22 November 1522; 2 March 1523) His cipher correspondence with Spanish ambassadors in London is also known (Ambassadors in England to Charles V, 5 February 1523; British History Online).
Adrian VI, the last non-Italian Pope before the twentieth century, earnestly desired to bring about a general peace among the Christian nations and counter-reformation of the Church. He died in September 1523 after a brief tenure without achieving his objectives.
Margaret of Austria, Charles' aunt and widow of the Duke of Savoy, was Governor of the Habsburg Netherlands since 1507. She was relieved when Charles claimed majority in 1515 but was reappointed in 1519.
A fragment of a cipher letter from a Nassau to Margaret of Austria, dated Achembourg, 13 April 1519, is transcribed in Vesin (1857), p.56. The subject appears to be the imperial election held in June 1519 after the death of Maximilian I in January 1519. Count Henry of Nassau-Breda (Wikipedia) was a close confidant of the young Charles and, in 1519, he was part of the delegation that obtained election of Charles. (In 1530, his son inherited the title of Prince of Orange through his wife, which then passed to his nephew, William the Silent in 1544.)
This is a simple substitution cipher with homophones.
Charles V used cipher in correspondence with his ambassadors and viceroys.
The alliance of Charles V and Henry VIII against France resulted in many letters in French, occasionally in cipher, despatched to and from the imperial ambassador in England, Louis de Praët from Flanders.
Margaret, Governor of the Habsburg Netherlands, appears to have had officials who had the key of the cipher between the ambassador and the Emperor.
The cipher between Louis de Praët and Margaret of Austria apparently was not shared by Charles de Lannoy, the vicerooy of Naples since 1522 and commander of Imperial armies in Italy since 1523 (Louis De Praët to Margaret of Savoy, 18-20 December 1524). (On the other hand, the cipher of the next ambassador was shared by the viceroy (Charles V to Iñigo de Mendoza, 29 July 1527).)
After the complete failure of the campaign of 1523, Cardinal Wolsey became cold towards the alliance with the Emperor and sought peace with France. Distrust of the ambassador made him seize de Praët's despatches in February 1525 and accuse the ambassador of making remarks against his reputation. On the very day (9 March) a new French ambassador was to be received, however, news arrived that the French army was completely defeated at Pavia and the King of France was captured. The English court changed their attitude at once. (CSP, Spain, Further Supplement, Preface)
While De Praët could no longer continue his role in England and was soon recalled, Margaret of Austria had happened to send commissioners with instructions, dated 28 January 1525 and partly in cipher, to further the military cooperation against France.
When the commissioners were about to return, a packet arrived from the Emperor, including instructions in cipher for de Praët or whoever might be in his place. The commissioners, having no deciphering key (de Praët had carried away the key with him), had to forward the instructions to Margaret and begged to have them returned as soon as deciphered and know her wishes. In order to avoid suspicion of Wolsey, who was aware of the packet, the commissioners explained the situation. The commissioners had the deciphering in eleven days.
The following report describes the confusion about the cipher. (By the way, the cipher appears to be as simple as can be learnt by heart.)
Praët was soon appointed by the Emperor as ambassador in France. The Emperor's letter mentions providing him with a cipher.
Galende Díaz (1992) deals with ciphers used by Lope de Soria. Lope de Soria was sent to Genoa as ambassador to the Doge soon after the town was relieved from the French occupation in 1522 (CSP, Spain, Vol.3 Part 1, Introduction). He served in the post till 1529, when he was succeeded by Gomez Suarez de Figueroa (Henar Pizarro Llorente, "Un embajador de Carlos V en Italia: don Lope de Soria (1528-1532)", p.125, 140). Lope de Soria later served as ambassador in Venice (Pizarro Llorente, p.155), until he was succeeded by Don Diego Hurtado de Mendoza in 1539.
Galende Díaz (1992) and Galende Díaz (2006) print different fragments of a cipher letter of 2 August 1523 from Charles V to Lope de Soria. The deciphering is printed in Corpus documental de Carlos V, Vol.1 p.85 (Google).
The cipher key is printed in the paper of 1992, pp.497-499 (an image of the original is found at RTVE). Apparently, the basic form of cipher was inherited from the ciphers of Ferdinand and Isabella (another article). The cipher alphabet assigns two or three arbitrary symbols to each letter. Double letters rr, ss, and ll are assigned special symbols. Five symbols and four code words "bene", "mejor", "mus", and "par" are nulls. The nomenclature represents words and names with a two- or three-letter codes. For example, the code for Genova is "cop."
Another cipher with the Emperor is similar to this (ibid., pp.499-504).
The ambassador used a similar but different cipher with Charles' brother Ferdinand, King of Hungary and later Emperor Ferdinand I (ibid., pp.505-512). His cipher with the Count of Borrello, viceroy of Sicily is similar, though codes consist of two letters (ibid., pp.512-515). His cipher with Antonio de Leyva is singular and will be described separately below (ibid. pp.515-519).
Iñigo de Mendoza (Wikipedia) succeeded Louis de Praët's embassy in London.
England was changing sides from the Emperor to the King of France, who had been freed from captivity in March 1526, and invasion of Flanders was feared. At such a junction, the Emperor thought the cipher with the ambassador, which appears to have been updated in 1526 (CSP, Spain, Vol.3 Part 2), was safer than that with Margaret, Governor of the Netherlands.
One cause of estrangement between Henry VIII and the Emperor was Henry's relation with his Queen, Catherine of Aragon, who was aunt of Charles V. In 1525, Henry was enamoured with Anne Boleyn and, seeing that she would not become a mistress, sought an annulment of the marriage with Catherine from the Pope. At that time, however, Pope Clement VII was a prisoner of Charles V after the Sack of Rome by the soldiers of the Imperial army in May 1527.
When Charles heard of the situation from the ambassador in England and the Queen herself, he replied that he would do all he could in her favour. At the same time, Charles thought the affair should not be public and he enclosed in a despatch to the ambassador a letter of kind remonstrance to Henry VIII without letting any member of the Privy Council know of it. He even took the task of enciphering upon him.
Charles made clear his support of his aunt.
In April 1527, England was officially allied with France. In February 1528, Cardinal Wolsey went so far as to arrest the ambassador. The officer in charge demanded him in the King's name that he should give up all his letters and papers as well as the key of the casket containing them, as otherwise it would be broken open. Seeing this, the ambassador gave his key to his secretary, who contrived to make his escape and took out all the letters and ciphers relating to the Emperor's affairs and put them in a secure hiding-place, so that when the officer and the escort arrived, all the papers were out of sight. (CSP)
Unable to achieve the King's divorce, Wolsey lost favour and died in 1530. The ambassador asked the Emperor to recall him and was allowed to leave England in May 1529.
Eustace Chapuys (Wikipedia) took over the post in England in September 1529.
While one measure after another was taken to curtail the power of Rome in England, in May 1533, the new Archbishop of Canterbury Thomas Cranmer declared Henry VIII's marriage with Catherine of Aragon null and void and confirmed the marriage of Henry and Anne Boleyn. The ambassador, who had championed the cause of Catherine, was in a difficult position.
Chapuys used different ciphers. He used a different cipher (unsolved) in his letter to Granvelle of 11 February 1534 (CSP). A cipher (unsolved) used in his letter of 8 November 1542 to Mary of Austria, Governor of the Netherlands, was one quite different from the one he generally used (CSP). His "own cipher" for the most important communications with the Imperial ambassador in France is mentioned in a letter of 14 October 1532 (CSP). The cipher used in Chapuys' letter to the Emperor dated 6 September 1543 was entirely new, and does not resemble that of Chapuys' ordinary despatches (CSP).
In 1541, Chapuys succeeded in bribing a man in the French embassy and obtained the cipher key. The deciphering of letters to and from the French ambassador in London was a valuable source of information (CSP, Spain, Vol. 6, Part 1, Part 2 in passim). In July 1543, the English ministers intercepted a letter of the French ambassador to his master and, as the letter was written in cipher, it was sent to Chapuys to decipher (CSP). (Similar forwarding of a French cipher letter was also done in 1553 in the reign of Mary I, though the letter at this occasion could not be deciphered. (CSP, ibid.). On the other hand, deciphering by Mary's government is also recorded (CSP).)
In 1545, Chapuys was relieved by his successor Van der Delft and thereafter lived in Louvain. The Emperor asked him to give advice to the new ambassador. The following is one of Chapuys' first letters from Louvain.
Charles' wife Isabella was an able woman and served as regent of Spain during the Emperor's absences. In 1529, the Emperor left for Italy for coronation. The Emperor and secretary Covos used cipher in writing to Isabella during her regency from 1529 to 1532.
CSP includes letters for Isabella partly in cipher from Charles (30 August 1529, 10 March 1531) and Secretary Covos (28 December 1529).
When Charles, born and brought up in the Low Countries, came over to Spain, his younger brother Ferdinand, born and brought up in Spain, was taken to the court of his aunt, Margaret of Austria. He became King of Hungary and Bohemia in 1526 and ruled the Holy Roman Empire as his brother's deputy. In 1531, he was formally elected King of the Romans to succeed to the imperial crown.
Germany was backward in cryptology compared to Italy, France, England, or even Spain. CSP has references to Ferdinand's correspondence in cipher with Martin de Salinas, his ambassador to the Emperor (CSP, Spain, Vol. 4, Part 1). Such use of cipher was probably the Spanish tradition, for Salinas as well as other secretaries of Ferdinand were natives of Spain, who were not even sufficiently acquainted with the German language (ibid., Introduction). Indeed, a cipher used between Lope de Soria and Ferdinand is similar to ones between Lope de Soria and Charles V, as mentioned above.
Martin de Salinas reported from Barcelona to the King of Hungary that Louis de Praët, now appointed extraordinary ambassador to Rome, would take as much care of the King's affairs as if they were the Emperor's and that, being uncertain of the fidelity of the King's resident in Rome, he would take a "new cipher and alphabet", a copy of which Martin de Salinas sent to the King's Secretary (8 July 1529, CSP).
In October 1529, when the Emperor was in Piacenza during his stay in Italy for coronation, Salinas received a letter in cipher from Ferdinand's secretary, which reported retreat of the Ottomans, who had been laying siege on Vienna. The Emperor was delighted to hear the news and requested him to read the letter in Council.
Ferdinand's cipher letter in Spanish to Antonio de Leyva of April 1534 is also recorded (CSP).
Mary of Austria, Queen Dowager of Hungary, governed Hungary in the name of her brother Ferdinand and took over the governorship of the Netherlands in 1531 after her aunt Margaret of Austria died.
She often received information in cipher from Chapuys, ambassador in England, and others and she used cipher in writing to ambassadors, the Emperor, and Prince Philip. Chapuys occasionally relied on her to relay his information to the Emperor. In May 1542, she forwarded a new cipher to Chapuys.
It is well-known that Spanish ciphers during the reign of Philip II included a class of ciphers called general ciphers (cifra general), which were used between the King and his governors and ministers in general (see another article; cf. Devos p.62). Similar common ciphers were used in the reign of Charles V.
Antonio de Leyva (Wikipedia) had contributed to the victory at the Battle of Pavia by sustaining the long siege of Pavia by the French. For this service, in 1525, he was made commander-in-chief of the Imperial army in the Duchy of Milan and in 1535, when the last Duke of Milan died, appointed the first Governor of Milan under the Habsburg rule.
Two letters partially in cipher are in BNE MSS/20212/43/1-12.
Carta 9 is Leyva's letter of 7 July 1525. Its substitution alphabet is similar to Ferdinand/Isabella's Cipher (ca.1500-1502) (see another article) in that symbols with one or two additional strokes represent the same letter.
Carta 12 is Leyva's letter of September 1527. The symbols of this cipher look like geometrical figures. This is the earliest cipher with vowel indicators known to me (see another article).
A cipher between Lope de Soria and Antonio de Leyva, printed in Galende Díaz (1992), (called Leyva's cipher herein for convenience) has two distinguishing features compared with the other ciphers of Lope de Soria described above.
(i) Not only single letters are given two or three symbols but also syllables are assigned their own symbols. Symbols for ba, be, ..., ho, hu follow what is called a vowel indicator system in another article dealing with ciphers in the next reign. That is, syllables be, ce, de, fe, ge, and he are assigned special symbols and the other syllables are represented by these base symbols plus some stroke to indicate a vowel. Syllables p*, r*, s*, v*, x*, and z* (where * is a vowel) are also represented by a combination of a base symbol and an additional stroke for indicating the vowel but the vowel indicator is not uniform. For example, for s*, an additional stroke like "4" indicates the vowel e but for v*, "4" corresponds to o. Syllables m* and t* are simply represented by two-letter combinations: ma (code "us"), me ("as"), ta ("or"), and te ("ur"). Such inconsistency per se is by no means a defect in ciphers in that any regularity would help codebreakers. However, such a cipher would be unwieldy.
(ii) Another characteristic of Leyva's cipher is in the nomenclature. Apart from a few three-letter codes and a special symbol, most words and names are represented by a left-pointing arrow with a triangular or square arrowhead having an Arabic numeral over it.
(iii) In addition, for the syllables "sa", "se", ..., and "va", "ve", ..., Arabic numerals are used to distinguish the vowels. This feature was not common in the next reign but is seen in some other ciphers at this time.
Four letters betewen Lope de Soria and Antonio Leyva are known from 1527, 1528, and 1536, of which one dated Milan, 11 July 1528, is in cipher, not deciphered ("Catálogo de los documentos del archivo de Lope de Soria, embajador del emperador Carlos V" (Biblioteca Virtual)). Inspection of the manuscript will reveal whether this cipher is used.
At one time, I favoured the dating of this cipher at 1528, but I now prefer a more conservative dating of 1528-1535 from internal evidence. Duke Francesco of Milan reigned from 1521 to 1535 (Wikipedia). "Embaxador Figueroa" (Gomez Suarez de Figueroa ) became ambassador no earlier than in 1529 (see below). Previously, I thought "El Principe de Oranjes" referred to the Prince of Orange Philibert (Wikipedia), who died in 1530 and was succeeded by an eleven-year-old boy. But the latter cannot be definitely excluded.
A cipher (Galende Diaz (1995), FIG.47), used in a letter from Count of Cifuentes (Wikipedia) to Lope de Soria dated 19 August 1536, has symbols for syllables. The image below shows tentative assignment of symbols by the present author.
Later, I found the same cipher is used in a letter of Suarez de Figueroa to Antonio de Leyva, dated 23 August 1533 (PARES). The longer specimen allowed recovering more symbols, which show some interesting characteristics:
(i) In some cases, a letter is represented by a symbol consisting of two letters; in other cases, a two-letter combination (syllable) is represented by a single glyph.
(ii) Homophones are provided not only for single letters but also for syllables.
(iii) There are irregularities in correspondence between plaintext letters and cipher symbols. This is good for security against cryptanalysis but would have been inconvenient for authentic recipients.
Devos (1950) records a particular cipher Cp.44, undated, for use by the King with "Diego de Mendoça, embaxador en Venecia." While Devos attributes this to the second half of the sixteenth century rather than the period of embassy of Diego Hurtado de Mendoza, ambassador in Venice from 1539 to 1547 (Wikipedia), the following background (where entries of the nomenclature are in boldface) points to the period 1531-1546, in particular 1536-1539.
Hayreddin Barbarossa ("Barbaroxa") (c.1478-1546) (Wikipedia), an admiral under the Ottoman Empire, was the most dreaded of the Barbary ("Berberia") corsairs. He dominated the Mediterranean for decades and, in 1534, captured Tunis ("Tunez") and expelled the King ("rey de Tunes"). The King appealed to Charles V, who personally led an expedition and recaptured the town in 1535 after fierce fighting for the strategic fort of La Goulette ("Goleta") at the mouth of the port. (Later in the century, in 1570, Tunis was again occupied by the Ottomans and the King of Tunis (the son of the above) was deposed (Answers.com).)
In 1537, an Ottoman force under Barbarossa captured islands belonging to the Republic of Venice and raided Corfu ("Corfu"), which marked the beginning of a war sometimes called Ottoman-Venetian War (1537-1540) (Wikipedia). Urged by the Venetians, the pope arranged the Holy League ("liga") of 1538. The combined fleet of the Holy League, however, was defeated by Barbarossa at the Battle of Preveza in 1538. Dominance of the Ottomans over the Mediterranean lasted until the combined Christian fleet under another Holy League won a decisive victory at the Battle of Lepanto in 1571.
One area of contention was the Morea ("La Morea") (the Peloponnese peninsula) under the Turkish rule since the invasion by the Spanish under Andrea Doria in 1532. When the Venetians made peace with the Ottomans in 1540, the Ottomans were in possession of the whole peninsula. (The history of Greece under Ottoman and Venetian domination, pp.82-85 Google)
Ayas Pasha ("ayas bassa") (Wikipedia) was a Grand Vizier of the Ottoman Empire from 1536 until his death in 1539.
In the sixteenth century, the title of the King of the Romans ("Rey de Romanos") was held during 1531-1558, 1562-1564, and 1575-1576 (Wikipedia).
I have not been able to identify "rey Jean". Although there was a John III on the throne of Portugal in 1521-1557, the King of Portugal is listed as "rey de Portugal".
This cipher has one striking resemblance to the cipher between Lope de Soria, predecessor of Diego Hurtado de Mendoza in embassy in Venice, and Antonio de Leyva. The codes for names and words starting with a in the nomenclature consist of a left-pointing arrow with a circular arrowhead having an Arabic numeral over it. Names and words in the b to e sections are represented by similar symbols. The other sections use combinations of a base symbol and a superscript numeral etc.
The cipher alphabet assigns two or three symbols to each letter.
Syllables are represented by a regular vowel indicator system, though the vowel indicator for a for x*, y*, z* are slightly different. The indicators for vowels "i" and "o" are Arabic figures "2" and "3."
Symbols for double letters and nulls are defined.
This is an undated cipher for use with the ambassador in Venice "Don Lopez y usala Don Diego, Desta se usa." While Devos attributes this cipher to the second half of the sixteenth century and mentions Iñigo Lopez Hurtado de Mendoza, again, the following background may point to 1530s, during the missions of Lope de Soria, Lope Hurtado de Mendoza, and Diego Hurtado de Mendoza.
The last Duke of Milan ("Duque de Milan") from the House of Sforza died in 1535 and Milan was claimed by Charles V as an imperial fief (Wikipedia).
Alessandro de' Medici ("el duque Alexandro") was made hereditary Duke of Florence in 1532. In 1533, he married Margaret of Austria, natural daughter of Charles V ("la duquesa nuestra Infanta"). He was assassinated in 1537, upon which Lope Hurtado de Mendoza was sent to Florence (CSP).
Admiral Andrea Doria (el principe Doria) was created Prince of Melfi in 1531. (In August 1530, the Prince of Orange, Philibert of Chalon, who held the title of Prince of Melfi had died (Wikipedia).) The title was inherited by Gian Andrea Doria and his successors. (Wikipedia)
The Marquis of Vasto ("el manques del Gasto") (1502-1546) (the name was variously spelled Basto, Vasto, Gasto and Guasto (CSP, Spanish, Vol.3, Part 2, Introduction n.35)), captain of a Neapolitan family, is occasionally mentioned in CSP from 1525. He was appointed a third governor of Milan in 1538 after the death of the first Governor, Antonio de Leyva (Wikipedia). In 1539, he was sent to Venice for some negotiations (CSP, Spain, Vol. 6, Part 1, Index). (Vasto's cipher with Giovanni Matteo Castaldo, bishop of Puzzuoli (near Naples) from 1542 to 1586, is found in Meister, p.204. It represents each letter of the alphabet with one or more arbitrary symbols or figures. The letter "e" is assigned four symbols. Double letters "tt", "ss", and "ll" are assigned figures "18", "17", and "15", respectively.)
For the King of the Romans ("el Rey de Romanos"), see above.
The cipher alphabet of Cp.45 assigns two symbols to each letter.
Syllables generally follow a vowel indicator system but combinations "*u" (where * is a consonant) are often assigned special symbols. Cp.44 and Cp.45 both use Arabic numerals for some of the vowels.
The nomenclature uses Arabic numerals 1-88 and 711. Unlike Cp.44, the entries are not arranged alphabetically.
Num.7 of Alcocer (1934) is a monoalphabetic substitution cipher of Alonso de Cordoba, Count of Alcaudete (Wikipedia), in Oran, Algeria, dated 28 April 1544.
Num.6 of Alcocer (1934) seems to be a fragment of a cipher representing syllables "ba", "ca", "da", ..., "gra", "pla" with letters with an overdot. This is related to a letter of Lope Hurtado de Mendoza (Wikipedia) dated Lisbon, 22 March 1548.
In 1542, war broke out again between the Emperor and France. In a campaign of 1544, when the imperial army invaded France, cryptology played a role in a siege of St Dizer, a strategically vital town on the route to Paris.
Despite the presence of the Emperor himself, the town was still in a condition to hold out longer even after five weeks of siege. Then, Granvelle, the Emperor's chief minister, having intercepted the key to the cipher used in communication between Sancerre, commander of the garrison, and the Duke of Guise, forged a letter in the name of the Duke that authorized the commander to capitulate because the King, though satisfied with his gallant defence, thought it imprudent to hazard a battle for his relief. When this letter came to hand, the commander agreed to capitulate if he was not relieved in eight days. (Robertson, William, The history of the reign of the Emperor Charles the Fifth Vol 2, p.390 (Internet Archive))
In August, the town surrendered but, due to the unexpected delay in the siege, the Emperor abandoned his plan of proceeding to Paris and made peace with France in September.
Genoese admiral Andrea Doria (Wikipedia) sided with the French during the war between France and the Holy Roman Empire and his fleet under the command of his nephew defeated a Spanish squadron in April 1528. However, dissatisfied with the French king's treatment, he joined the Imperial side and entered Genoa in September 1528, overturning the French rule from the previous year and re-establishing the republic (Thomas Allison Kirk, Genoa and the Sea (Google) p.19; 塩野七生『ローマ亡き後の地中海世界』下).
His letters to Charles V from October 1528 to April 1529 used a cipher based on a vowel indicator system. Although a similar system was employed in Leyva's cipher about this period, this Doria-Charles V Cipher (1528) is formed more systematically (hence weaker). In particular, the assignment of base symbols for syllables (e.g., "c" for "ba, be, bi, bo, bu"; "d" for "ca, ce, ci, co, cu") exhibit a regularity not seen in similar later ciphers such as Figueroa-Philip Cipher (1543) and Doria-Figueroa-Philip Cipher (1548).
This cipher is used at least in the following letters:
Doria to Charles V, 1528-10-26 (PARES) *used in the reconstruction
Doria to Charles V, 1528-10-29 (PARES)
Doria to Charles V, 1529-2-7 (PARES)
Doria to Charles V, 1529-3-3 (PARES) *used in the reconstruction
Doria to Charles V, 1529-3-14 (PARES)
Doria to Charles V, 1529-3-15 (PARES)
Doria to Charles V, 1529-4-24 (PARES)
After April 1529, Doria wrote in clear to Charles V, while the newly appointed ambassador Suarez de Figueroa used cipher in writing to the Emperor (see below).
Gomez Suarez de Figueroa was ambassador in Genoa since 1529, succeeding Lope de Soria (Pizarro Llorente p.140; CSP, Spain, Vol 3., Introduction, Vol.5, which mentions three persons of the name "Gomez Suarez de Figueroa" at this period). Several ciphers are used in his correspondence preserved in the Spanish archives.
The first dated letters of Suarez de Figueroa found in EST,LEG,1362 of Archivo General de Simancas are two letters to Charles V dated 24 May 1529. One (PARES) has undeciphered text (though the strikeout indicates a decipherment was made at the time). The other (PARES) in clear does not seem to correspond to its plaintext but I succeeded in solving the cipher myself (see another article).
As expected, the cipher (called the Figueroa-Charles V Cipher (1529) herein for convenience) is similar to the Doria-Charles V Cipher (1528) even in the regularity in assignment of base symbols for syllables (e.g., "d" for "ca, ce, ci, co, cu"). Use of superscript numerals is an additional feature but it is pretty much obvious that the sole superscript "2" would be nothing more than another subscript numeral.
Apparently, Suarez de Figueroa found this cipher too complex. He soon switched to a much simpler cipher, which he used in many letters for a decade.
The following simple cipher is used in Suarez de Figueroa's letters to Charles V in 1529-1538.
This cipher is used at least in the following letters:
Suarez de Figueroa to Charles V, 8 June 1529 (PARES) *This supplied some symbols in the above key.
Suarez de Figueroa to Charles V,18 June 1529 (PARES) Undeciphered. The beginning of the cipher reads "solicitar la venidade ,,,"
Suarez de Figueroa to Charles V, 23 June 1529 (PARES)
Suarez de Figueroa to Charles V, 26 June 1529 (PARES)
Suarez de Figueroa to Francisco de los Cobos, secretary of the Council of State, 26 June 1529 (PARES)
Copy of chapters of letters of Antonio Leyva to Suarez de Figueroa about his economic needs, 4 July 1529 (PARES)
Suarez de Figueroa to Charles V, 16 July 1529 (PARES)
Suarez de Figueroa to Charles V, 22 July 1529 (PARES)
Suarez de Figueroa to Charles V, 7 October 1529 (PARES)
Suarez de Figueroa to Charles V, 19 March 1530 (PARES)
Suarez de Figueroa to Charles V, 1 October 1530 (PARES)
Suarez de Figueroa to Charles V, 11 November 1530 (PARES)
Suarez de Figueroa to Charles V, 17 November 1530 (PARES)
Suarez de Figueroa to Charles V, 6 January 1531 (PARES)
Suarez de Figueroa to Charles V, 24 January 1531 (PARES)
Suarez de Figueroa to Charles V, 14 March 1531 (PARES)
Suarez de Figueroa to Charles V, 16 March 1531 (PARES)
Suarez de Figueroa to Charles V, 26 April 1531 (PARES)
Suarez de Figueroa to Charles V, 1 June 1531 (PARES) Undeciphered. The cipher passage begins "del prior de Barleta que ..."
Suarez de Figueroa to Charles V, 5 June 1531 (PARES)
Suarez de Figueroa to Charles V, 19 July 1531 (PARES) Undeciphered. The cipher reads "de Antonio Doria ...."
Suarez de Figueroa to Charles V, 5 August 1531 (PARES)
Suarez de Figueroa to Charles V, 17 August 1531 (PARES)
Suarez de Figueroa to Charles V, 15 September 1531 (PARES)
Suarez de Figueroa to Charles V, 1 October 1531 (PARES)
Suarez de Figueroa to Charles V, 8 October 1531 (PARES) Undeciphered. The cipher reads "conprendidos en la capitulacion ...."
Suarez de Figueroa to Charles V, 20 October 1531 (PARES)
Suarez de Figueroa to Charles V, 14 November 1531 (PARES)
Suarez de Figueroa to Charles V, 22 November 1531 (PARES) Undeciphered. The cipher reads something like "esto con lo demaude lau prohibiciones ...."
Suarez de Figueroa to Charles V, 27 January 1532 (PARES)
Suarez de Figueroa to Charles V, 9 September 1532 (PARES)
Suarez de Figueroa to Charles V, 3 August 1533 (PARES), undeciphered (the strikeout of the ciphertext seems to indicate there is a decipherment in a separate sheet)
Suarez de Figueroa to Charles V, 9 August 1533 (PARES), undeciphered (the strikeout of the ciphertext seems to indicate there is a decipherment in a separate sheet)
Suarez de Figueroa to Charles V, 15 February 1534 (PARES)
Suarez de Figueroa to Charles V, 2 July 1534 (PARES) (used in the reconstruction)
Suarez de Figueroa to Charles V, 6 September 1534 (PARES), undeciphered
Suarez de Figueroa to Charles V, 28 September 1534 (PARES)
Suarez de Figueroa to Charles V, 7 March 1536 (PARES)
Suarez de Figueroa to Charles V, 11 March 1536 (PARES)
Suarez de Figueroa to Charles V, 20 August 1536 (PARES), undeciphered (the strikeout of the ciphertext seems to indicate there is a decipherment in a separate sheet)
Suarez de Figueroa to Charles V, 28 January 1537 (PARES)
Suarez de Figueroa to Charles V, 3 February 1537 (PARES)
Suarez de Figueroa to Charles V, 15 January 1538 (PARES)
After the outbreak of the war with France, the Emperor left Spain in 1543, which was the beginning of what was to become the longest period of absence of fourteen years. Prince Philip, about to be sixteen, was named regent in his absence. Officials in Spain and abroad started to report to Philip (Kamen p.14-15). Chapuys, who usually wrote in French to the Emperor and Mary of Austria, wrote his first one "with my imperfect knowledge of Spanish" on 12 July 1543. He later used cipher in writing to Philip at least from 18 January 1544. St. Mauris, the Imperial ambassador in France, Mary of Austria, and the Emperor also used cipher in writing to him.
Charles had left reliable advisers to help Philip but the prince soon had to grow out of tutelage because his principal advisers died one after another from 1545 to 1547 (Kamen p.28).
A cipher used in the first year of Philip's regency can be reconstructed from an undeciphered letter of Suarez de Figueroa to Prince Philip, 20 November 1543 (PARES) by using the plaintext of the letter of 17 November 1543 (PARES). The Letter (preserved in decipherement, apparently in secretary's hand) of 25 October 1543 (PARES) may also have been in the same cipher.
The letter of 11 February 1544 (PARES) is also preserved only in decipherment. The letter of 22 February 1544 used the Imperial Cipher of 1544-1554 below.
The cipher, called Figueroa-Philip Cipher (1543) herein for convenience, looks similar to Leyva's Cipher above and the Doria-Figueroa-Philip Cipher (1548) below in using vowel indicators including some Arabic numerals.
There are also some code symbols: "so" for "galeras" (page 1, line 6 etc.) and "ap" for "princip" (page 2, line 6).
(Another article describes my initial attempt at codebreaking of this cipher as well as some notes on the text.)
Charles defeated protestant princes in the Schmalkaldic War in 1546-1547 and the Augsburg Interim was proclaimed at the Diet in May 1548. In September 1548, Charles married his daughter Maria to his brother Ferdinand's son Maximilian, who had an honorary title of King of Bohemia since April 1548.
While the couple settled in Spain, Prince departed for the Low Countries in compliance with the Emperor's wish to make arrangements for a secure succession to his son. In his absence, Maria and Maximilian acted as regents of Spain. Charles' wish to let Philip succeed to the Imperial throne after Ferdinand was met with objection from Ferdinand and Maximilian (the latter joined the family in Augsburg in December 1550). Philip returned to Spain in July 1551. Soon thereafter, Maximilian and Maria left for Vienna.
During their regency, Maximilian and Maria received letters in cipher from St. Mauris, Imperial ambassador in France, and the Emperor. When the Emperor wrote about financial issues in a cipher letter dated 9 July 1551, a few days before Philip and Maximilian separately arrived in Spain, it was addressed to Maria alone (CSP).
Later, when Philip went to England in July 1554 for the marriage with Mary I, his sister Juana was called back to Spain to be regent of Spain. Juana had married the heir to the King of Portugal but had been widowed. Among others, Philip had correspondence in cipher with her from England (CSP).
Suarez de Figueroa used the Imperial Cipher of 1555 below as well as Cg.1 of 1556 in writing to her (see another article).
Meister (p.212) prints a cipher of Ferrante Gonzaga with Charles V and Gonzaga's secretary Natale (called the Imperial Cipher of 1544-1554 just for convenience herein (called the Imperial Cipher of 1547-1553 for some time)). Gonzaga (1507-1557) served Charles V as a commander in many campaigns and as Viceroy of Sicily (1535-1546) and Governor of Milan (1546-1554) (Wikipedia). Natale is known to have carried Gonzaga's messages from Milan at least in 1547 (CSP, Venice).
As far as can be seen in Meister, the cipher consisted of the following elements:
(i) Symbols representing the letters of the alphabet, which include alphabetic letters and arbitrary signs.
(ii) Syllables represented with the vowel indicator system.
(iii) Symbols for double letters "ll", "rr", "ss", and "tt."
(iv) Eight symbols for nulls.
The vowel indicator system was widely used under Philip II but was not a novelty of his reign. Aloys Meister (1902), Die Anfange der Modernen Diplomatischen Geheimschrift: Beitrage zur Geschichte der Italienischen Kryptographie des XV Jahrhunderts, p.32, prints a cipher of Camillo Gilmo, a Milanese resident at the imperial court, as early as 1530, which uses vowel indicators.
(Notes Added on 13 February 2017) Bertomeu Masiá (2009) reconstructed a more complete version of this cipher. The cipher was used by Charles V, Prince Philip, Antoine Perrenot de Granvelle (Wikipedia), Ferrante Gonzaga, Diego Hurtado de Mendoza, and Fernando Montesa (a secretary of Diego Hurtado de Mendoza in his embassy in Rome) around 1547-1550 (p.151) in the context of the issue of Piacenza (Wikipedia). The following shows this reconstruction reorganized by the present author with reference to those of the original letters reproduced in the book. (Parsing "ω uo" as "e t" rather than "et null" is justified by the cipher printed in Meister.) Some variations in the handwriting are included.
It appears there are two series of syllable representation with different base symbols and different indicators, though Ferrante Gonzaga's two letters reproduced in the book use only one. This cipher is similar to the Imperial Cipher of 1555 below in having two series of syllable representation as well as in some specific symbols used.
(Notes Added in September 2018 and later) This cipher is used in the following letters in the Spanish archives:
Suarez de Figueroa to Philip, Prince of Asturias, 22 February 1544 (PARES)
Suarez de Figueroa to Prince Philip, 1 April 1544 (PARES)
Suarez de Figueroa to Prince Philip, 20 April 1544 (PARES)
Suarez de Figueroa to Prince Philip, 25 May 1544 (PARES)
Suarez de Figueroa to Prince Philip, 29 March 1545 (PARES)
Suarez de Figueroa to Prince Philip, 30 January 1546 (PARES)
Suarez de Figueroa to Charles V, 8 September 1547 (PARES), undeciphered
(That is, this cipher was sent from Diego Hurtado de Mendoza to the Emperor on 17 February 1547 (Bartomeu Masiá, p.151) but it had been in use by the prince before that.)
Suarez de Figueroa to Prince Philip, 4 January 1548 (PARES)
Suarez de Figueroa to Prince Philip, 5 March 1548 (PARES)
Diego Hurtado de Mendoza to Granvelle, Rome, 29 May 1548 (BDH)
Suarez de Figueroa to Prince Philip, 13 August 1548 (PARES)
Suarez de Figueroa to Duke of Alba, 20 August 1548 (PARES)
Suarez de Figueroa to Prince Philip, 19 January 1549 (PARES)
Report to Secretary Francisco de Eraso, 21 January 1549 (PARES)
Suarez de Figueroa to Prince Philip, 14 February 1549 (PARES)
Suarez de Figueroa to Prince Philip, 20 February 1549 (PARES)
Suarez de Figueroa to Prince Philip, 2 April 1549 (PARES), Undeciphered.
Suarez de Figueroa to Prince Philip, 30 August 1549 (PARES)
Suarez de Figueroa to Prince Philip, 2 June 1551 (PARES)
Suarez de Figueroa to Prince Philip, 20 January 1552 (PARES) Undeciphered duplicate.
(duplicate) Suarez de Figueroa to Prince Philip, 30 January 1552 (PARES)
Suarez de Figueroa to Prince Philip, 30 January 1552 (PARES)
Suarez de Figueroa to Charles V, 5 January 1553 (PARES)
Suarez de Figueroa to Prince Philip, 19 February 1553 (PARES) Mostly undeciphered.
(duplicate) Suarez de Figueroa to Prince Philip, 16 May 1553 (PARES)
Suarez de Figueroa to Juan Vazquez de Molina, secretary of the Council of State, 28 May 1553 (PARES)
Suarez de Figueroa to Charles V, 5 July 1553 (PARES) (the strikeout of the ciphertext seems to indicate there is a decipherment in a separate sheet)
Suarez de Figueroa to Prince Philip, 29 August 1553 (PARES)
Suarez de Figueroa to Prince Philip, 30 August 1553 (PARES)
Suarez de Figueroa to Prince Philip, 16 September 1553 (PARES)
Suarez de Figueroa to Prince Philip, 20 September 1553 (PARES)
Suarez de Figueroa to Prince Philip, 27 October 1553 (PARES)
Suarez de Figueroa to Prince Philip, 30 January 1554 (PARES)
A cipher(?) used in some passages in a copy of a letter from Antonio de Leyva and the commissioners of the League for Suarez de Figueroa (24 September 1534) (PARES).
Undeciphered letter of 1551 (PARES)
Undeciphered letter of 24 August 1551 (PARES)
The cipher below (called the Doria-Figueroa-Philip Cipher (1548) for convenience herein(called the Imperial Cipher of 1548 for some time)) has been reconstructed from deciphered letters in the Spanish archives.
The cipher is used in the following letters:
Andrea Doria to Prince Philip, 3 April 1548 (PARES)
Suarez de Figueroa to Prince Philip, 4 April 1548 (PARES)
Suarez de Figueroa to Prince Philip, 10 April 1548 (PARES)
Suarez de Figueroa to Prince Philip, 25 April 1548 (PARES) (used in the reconstruction)
Suarez de Figueroa to Fernando Alvarez de Toledo, Duke of Alba, 10 June 1548 (PARES) (used in the reconstruction)
Suarez de Figueroa to Prince Philip, 4 May 1548 (PARES)
Suarez de Figueroa to Prince Philip, 14 June 1548 (PARES)
Suarez de Figueroa to Duke of Alba, 4 July 1548 (PARES), undeciphered (the strikeout of the ciphertext seems to indicate there is a decipherment in a separate sheet)
Suarez de Figueroa to Prince Philip, 9 August 1548 (PARES)
Suarez de Figueroa to Prince Philip, 20 August 1548 (PARES)
In Suarez de Figueroa's letters to Prince Philip, the above Imperial Cipher of 1544-1554 was used for a long time. This cipher, Doria-Figueroa-Philip Cipher (1548), temporarily replaced it but appears to have fallen in disuse in a few months. The last two specimens from August use less superscripts, which seems to show the writer felt it inconvenient for use.
The first specimen above is from Genoa, 3 April 1548. Early in 1548, Philip had been told by the Duke of Alva sent by Charles V that he was to join the Emperor in Flanders and on 4 April, informed the Cortes of Castile assembled in Valladolid of his departure. Philip sailed from Spain in November in a fleet of Andrea Doria. (Kamen p.34-36) This cipher may have been made in preparation for the prince's departure.
The following is the cipher used in a letter of Jean de Saint Mauris, imperial ambassador then in Dijon, to Granvelle, dated 5 July 1548 (BNE MSS/7913/127). The cipher is probably the same as the one identified by David L. Potter, "La fin du règne de François Ier et l'avènement d'Henri II d'après les dépêches de Jean de Saint-Mauris (1547)" (Cour de France.fr) but I could not find his "appendix 3" online.
(Reconstruction of this cipher was difficult because the decipherment in the margin is hard to read (as also observed by Potter). It should have been apparent that the third and fourth cipher paragraphs begin with "Le" and "Il", but I could not be sure of it until later because I was not aware of the difference between "8" for N and "8 with an open top" for L. The first clue was "de". One instance of "de" was found in the third cipher paragraph in "Le prieur de Capua", which I first took for "Le prince de Capua". Another instance was found after "poste", which I could not read but which I noticed also occur in the second cipher paragraph, which allowed me to identify the counterpart symbol for the plaintext "de".)
In 1547, death of two monarchs changed the outlook of the European situation. Charles' biggest rival Francis I of France died soon after Henry VIII of England was succeeded by a boy king Edward VI.
CSP calendars Charles' letter of 30 May 1552 to Edward VI in French and in cipher. Since it seems unlikely that Charles shared a cipher with the English king, the letter may be enclosed in a letter to the ambassador in England to be deciphered before being presented to Edward. Inspection of the manuscript is desired.
(A duplicate of a letter of Imperial ambassadors in England to Mary I of 24 July 1553, right after her succession to the throne, is also in French and in cipher (CSP). This letter was enclosed in a letter to the Emperor of the same date.)
Simon Renard was ambassador in England. Having supported the Catholic Mary, he had a strong influence on the Queen. He even succeeded to arrange a match between the Queen and Prince Philip, eleven years her junior. The Emperor had been forced to retreat into the Netherlands in 1552 by the protestant princes backed up by an alliance with France and he saw a chance to obtain an alliance with England in the death of the protestant boy king Edward VI.
Mary was willing to the idea but she made clear that she would never allow the groom to encroach in the government of England. In October 1553, Mary gave her word to marry Philip. However, the necessary power from Philip arrived in England only on 18 January 1554. Moreover, while the Prince's letters conferred upon Renard full power to promise whatever was necessary for the marriage, they were in cipher and Renard was at a loss how he could use them (CSP). Notwithstanding, the marriage treaty was concluded without much fuss and Philip came over to England and the wedding took place in July 1554.
As with his predecessors, Renard paid efforts to obtain cipher keys of the French ambassador. But when in January 1554 the French ambassador's letter fell in the hands of the English government and was deciphered by the Chancellor (Stephen Gardiner), he was yet to obtain the key to that cipher. (The French ambassador actually expected the bearer of his letter might be searched for letters and gave him one which may be handed over but his precaution did not prevent the seizure.) (CSP)
However, having a letter deciphered by an ally's hand had disadvantages. Renard noticed a peer's name mentioned at the beginning of the letter was left blank in the decipher he received, though he could guess it would be Edward Courtenay, Earl of Devon. Renard managed to persuade the Queen to hand over the original cipher letter, which he made out and found that Courtenay's name had been left out on purpose, "for it was there whole and without the introduction of meaningless letters."
Renard warned the Queen, pointing out that the Chancellor and other members of her Council had always favoured Courtenay and he suspected that they approved of recent insurrection of Thomas Wyatt. Actually, Courtenay, who was a great-grandson of Edward IV through the latter's daughter Catherine of York, had reportedly been encouraged by Gardiner to consider himself as a likely suitor for Mary (Wikipedia) before the choice fell on Philip. In reply to the ambassador's warning, the Queen reassured him that she would never take any other husband than Philip. According to Renard, when the Chancellor was shown the correct decipherment and saw Courtenay's name on it, "he changed colour so obviously that it was easy to read his mind." (CSP)
Because of the detection of the plot, the conspirators were forced to take up arms before they had intended and the premature insurrection was suppressed.
When Courtenay's implication was examined, he was accused by several other prisoners of having had a share in the plot; he had a cipher, carved on a guitar, to be used with Peter Carew, one of the chief rebel leaders. (CSP)
When further packets of the French ambassadors were seized, according to what Renard heard, the Chancellor deciphered them but kept them to himself. Renard thought they might contain something against Courtenay. (CSP) In the end, Courtenay was exiled.
The French ambassador was aware that his letters were seized and deciphered. In protest, he insisted that his letters ought to be given back to him, saying that they could not possibly be deciphered. He had heard that Renard had made a try, but contended that no trust was to be put in his decipherment, for there was no chance whatever of his making out the characters. (CSP)
As it turned out, it was not only Renard who conducted espionage against a rival ambassador. In 1555, it was discovered that Renard's secretary had been for years selling Renard's ciphers and papers to the French (CSP). Eventually, he was dismissed by Philip.
Charles V's cipher was not impenetrable. In 1526, the Papal legate in Venice relied on Giovanni Soro (Wikipedia), a Venetian cryptanalist, to decipher letters written by the ambassador of Charles V at Rome. In a little more than a month, Soro had deciphered three long letters written by the Imperialists (CSP).
After the death of Soro in 1544, one of his followers, Francesco Marin, succeeded in deciphering a very complicated Spanish cipher without keys. (ibid.)
Deciphering of intercepted letters appears to have been routine on the Imperialist side, too. The following is part of a report at the time the Imperial army under the Prince of Orange (Philibert de Chalon) was conducting a seige of Florence. The republic capitulated in August 1530.
Two letters of Hernán Cortés to his agent in the capital, which use cipher, are known (Villena (1954) p.304). A part of one from Cuernavaca (25 June 1532) is reproduced in Kahn p. 115 and a page from the other from Puerto de Santiago (20 June 1533) is reproduced as Plate 1 of Villena (1954). Narváez (2007) have images of both letters (pp.22-23, p.57). The cipher appears to be composed of non-alphabetic symbols.
Two ciphers of La Gasca, viceroy of Peru from 1547 to 1550 (Wikipedia), are also known (Villena (1954) p.306-307, Plates 2, 3). These are simple monoalphabetic substitution ciphers, assigning a non-alphabetic symbol to each letter of the alphabet.
Meister (p.218-219; also p.283-284) prints a cipher of imperial ministers in Italy from the year 1555 (called the Imperial Cipher of 1555 for convenience herein). (The only examples of use of this Imperial Cipher of 1555 known to me are in the next reign. See another article.)
The cipher alphabet assigns one to three symbols to each letter.
Syllables are represented by a vowel indicator system. Unlike other ciphers with a vowel indicator system (but like the Imperial Cipher of 1544-1554 above), most syllables are assigned two symbols.
Not only two-letter syllables, but also three-letter syllables are given symbols. This is similar to a general cipher Cg.1 (1556) of the next reign (see another article).
The nomenclature represents words and names by Arabic numerals or letter codes.
Double letters and nulls are defined.
In October 1555, Charles abdicated from his various titles. Spain, the Netherlands, and the overseas colonies went to his son Philip, while Ferdinand succeeded as the Holy Roman Emperor. One of the acts of Philip in the first year of his kingship was communicating to Ferdinand of his resolution to change the cipher used by Charles (see another article).
Calendar of State Papers (CSP), Spain (British History Online)
Juan Carlos Galende Díaz (1992), 'La correspondencia cifrada del embajador Lope de Soria', Hispania: Revista espanola de historia, 52, No. 181, pp. 493-520
Juan Carlos Galende Díaz (1995), Criptografía, Historia de la escritura Cifrada
Juan Carlos Galende Díaz (2006), 'Basic Concepts of the Cryptology: The Manuscript of the Biblioteca Nacional,' Documenta & Instrumenta, 4, pp.47-59 (PDF) (in Spanish)
María José Bertomeu Masiá (2009). La guerra secreta de Carlos V contra el Papa: La cuestion de Parma y Piacenza en la correspondencia del cardenal Granvela
Roberto Narváez (2007), 'Historia y Criptología: Reflexiones a Propósito de dos Cartas Cortesianas', EHN 36, enero-junio 2007, pp.17-62 (PDF) (in Spanish)
Guillermo Lohmann Villena (1954), 'Cifras y Claves Indianas,' Anuario de Estudios Americanos, XI, p.285 (in Spanish)
Devos, J. P. (1950), Les chiffres de Philippe II (1555-1598) et du Despacho universal durant le XVIIe siècle
Alcocer, Mariano (1934), 'Criptografía española', Boletin de la Real Academia de la Historia, vol.105, pp.337-460 (Biblioteca Virtual)
Aloys Meister (1906), Die Geheimschrift im Dienste der Papstlichen Kurie von ihren Anfangen bis zum Ende des XVI. Jahrhunderts
Le Comte Vesin de' Romanini (1857), La cryptographi devoilee (Internet Archive)
Corpus documental de Carlos V, Vol. 1 (Google)
Kamen, Henry (1997), Philip of Spain
S. Tomokiyo, Spanish Ciphers during the reign of Ferdinand and Isabella
S. Tomokiyo, Spanish Ciphers during the Reign of Philip II