Did Philip II Call Codebreaking "Black Magic"?

When Philip II found out that Spanish ciphers were read by the French, he complained to the Pope that it was black magic, only to become a laughing stock because the curia also had its black chamber -- this famous episode appears to be based on de Thou, contemporary French historian and a friend of the French codebreaker François Viète (e.g., Kahn p.118, 995).

However, Philip II was aware of foreign codebreaking activities (see another article) and he even had a codebreaker in the person of Luis Valle de la Cerda (see another article). It seems unlikely that Philip II thought codebreaking to be "black magic", still less delivered a complaint against it to the Pope.

Episode

Philip had learned, from his own interceptions of French letters, that Viète had broken a cipher that the Spanish - who apparently knew little about cryptanalysis - had thought unbreakable. It irritated him, and, thinking that he would cause trouble for the French at no cost to himself, told the pope that Henry could have read his ciphers only by black magic. But the tactic boomeranged. The pope, cognizant of the ability of his own cryptologist, Giovanni Batista Argenti, and perhaps even aware that papal cryptnalysts had themselves solved one of Philip's ciphers 30 years before, did nothing about the Spaniard's complaint; all Philip got for his effort was the ridicule and derision of everyone who heard about it.

The most detailed version I have seen is in Langie, Cryptography (1922, originally published in French in 1918) (Internet Archive).

[The Spaniards], angrily denounced Viète to the Holy See as a wizard and a necromancer. According to them, he could only have entered into possession of the secret by calling up the spirits of those who had known the cipher during their earthly career. But the Pope was a man of humour: he submitted the plaint to examination by a commission of Cardinals, "with urgent recommendation." The Cardinals understood the hint, and the examination is still unfinished.

De Thou

De Thou (Thuanus in Latin) (Wikipedia) published his Historia sui temporis in Latin. (The first 18 books covering 1545-1560 appeared in 1604.)

A French translation (Histoire universelle de Jacques-Auguste de Thou: depuis 1543 jusqu'en 1607 (1734) (Internet Archive)) describes Viete on p.162-165 in Book 129 in vol.14 (described in a section from p.161 describing deaths in 1603). (Its summary in English is found at MacTutor History of Mathematics, University of St Andrews, Scotland, 2007.) The paragraphs concerning cryptography is as follows (also translated in English in Davys (1737), An Essay on the Art of Decyphering):

Ce que je vais ajoûter est peu de chose au jugement même de Viete; mais je suis persuadé qu'il y a bien des gens qui n'en jugeront pas de même.
Les différentes parties dont la monarchie d'Espagne est composées sont si dispersées & si éloignées l'une de l'autre, que pour établir une communication & une espece de concert entre tous ces membres, ceux qui gouvernent ont besoin d'un secret impenétrable; comme ils ont naturellement une prudence vaste, & qui ne peche que pour porter ses vûës trop loin, pour dérober leurs lettres à la connoissance des autres nations, ils se servent de caracteres qui ne sont plus en usage, & qui sont tout-à-fait inconnus, & ils les sont fort courtes, quand ils n'écrivent qu'à une seule personne, & beaucoup plus longues lorsqu'ils les adressent à toute une Province, ou à tout un corps en général: de tems en tems même, ils s'amusent à changer l'ordre & la figure de leurs caracteres; ils les tournent & retournent en différentes manières, de peur qu'avec le tems leur secret ne se découvre; du reste il leur faut beaucoup de tems pour faire ces changemens, parce qu'ils sont obligés d'en donner avis aux Gouverneurs, qui sont dans les Indes.
Tel étoit ce chiffre composé de plus de cinq cens figures, dont ils se servoient contre nous pendant cette funeste guerre, qui a duré dix ans. On intercepta plusieurs de leurs lettres qui étoient fort longues, & qui contenoient le détail des desseins qu'ils avoient formés, & des mesures qu'ils prenoient pour les exécuter. Mais cette multitude de caracteres embarassoit tellement nos déchiffreurs, qu'ils n'y connoissoient rien.
Le Roi ordonna donc qu'on envoyât ces lettres à Viete, qui ne pensoit à rien moins, & qui auroit bien mieux aimé s'occuper à ses études ordinaires. Viete accoûtumé à méditer sur des matieres bien plus importantes, eut bien-tôt trouvé la clef, & depuis il en déchiffra sans peine beaucoup d'autres qui étoient de grande conséquence; ce qui déconcerta pendant deux ans entiers tous les projets des Espagnols.
Cependant comme ils sçurent à leur tour par nos lettres qu'ils intercepterent, que nous avions trouvé la clef de leur chiffre qu'ils croyoient inexplicable, il furent bien sachez de se voir obligez d'en chercher un autre; & comme rien ne leur coûte pour décrier leurs ennemis, & pour les rendre odieux, ils publierent à Rome, & dans toute l'Europe, que le Roi l'avoit découvert par le secours de la magie, parce qu'il n'étoit pas possible, disoient-ils, de le trouver autrement. Mais tout l'avantage qu'ils retirerent de cette calomnie, fut qu'ils s'attirerent le mépris & l'indignation de toutes les personnes raisonnables.

... re per nostras vicissim interceptas detecta necessitatem instrumenti quod inexplicabile rebantur mutandi, impositam dolebant. Itaque illi, qui ad odium et invidiam nihil non comminiscuntur, magicis artibus, nam aliter fieri non potuisse, a rege id factum, passim, et Romae praecipue, non sine risu et indignatione rectius sentientium per emissarios suos publicabant.

... by intercepting Letters of ours they discovered the Matter, and were forced to contrive a new Cypher, instead of that which they judged to be incapable of being decyphered. And to put the most odious Construction, they could, upon the Case, they industriously gave it out, especially at Rome, that the King had acted in it by magick Art; for that they were sure, the Thing could have been done by no other Means; but the Report was entertained only with Scorn and Derision by Men of Sense.

It can be seen that this does not refer to any one particular message of complaint from Philip II to the Pope. De Thou merely says Spaniards carried on propaganda especially in Rome but also in other places about Henry IV having used magic. The "scorn and derision" are attributed to "men of sense" in general.

Satire against Bishop of Senlis

I found a similar expression ("diabolique") in referring to codebreaking recorded in quotation from a satirical work much earlier than de Thou's history. The book is Satire Menippée (Wikipedia), written in 1593 and published in Tours in 1594, which criticized the Catholic League, the Duke of Mayenne, and Spain. According to Comtesse de Genlis (Wikipedia) (1815), Histoire de Henri le Grand, Vol.1 (Google), it had a great influence at the time, and the Bishop of Senlis (Wikipedia), an active member of the Catholic League, is made to call codebreaking "diabolique" (p.415, p.419).

Tout le monde connoît vos finesses, car les politiques ont des dragons dans les champs, qui prennent vos paquets, et devinent par art diabolique tous vos chiffres, aussi bien que ceux d'Espagne.

*"vos" refers to "M. le lieutenant", i.e., Mayenne.
*The "politiques" (Wikipedia) refers to those who put peace and stability of the nation before everything else in the period of religious wars. Religious toleration of Henry IV conformed to this idea.

Comtesse de Genlis says in a note that this is an allusion to the episode described by de Thou.

Reinterpretation

Although de Thou's history was not yet published at the time of Menippée, Viete's codebreaking had been made public in 1590 in a pamphlet disclosing secret correspondence by Spaniards (see another article). It is now remembered that there were many people incredulous of the feat of codebreaking at the time. (It appears that some months after Philip III acceded to the Spanish throne in 1598, the twenty-year-old King requested demonstration of codebreaking in his presence (see another article).) Thus, it may well be supposed that opponents of Henry IV attacked Viete's codebreaking with similar invectives.

At the time of the publication of Viete's codebreaking in 1590, Spanish ambassadors and agents were trying to prevent the Protestant Henry IV from being formally declared as King of France (e.g., Jensen p.200). With this context, the famous episode of complaining before the Pope may be reinterpreted as follows.

When Viete's codebreaking was made public in a pamphlet in 1590, some of the Leaguers as well as Spanish ambassadors and agents, who were campaigning against the Protestant Henry IV in Rome and elsewhere, criticized it for being "diabolique" or "black magic." But such partisan accusation was not taken seriously.

This is less dramatic than the popular version, but after all, it is little different from what is described by de Thou.