Philip the Second´s Cifra General



On May 24th, 1556, barely one year into power, Spanish Emperor Philip the Second wrote a letter to his uncle Ferdinand Ist (Emperor of the German Empire and King of Hungary) his decision to change his father Charles Vth´s ciphers, as they fell into obsolescence or were compromised.  Six months later, the first Cifra General (General Cipher) of Philip the Second´s kingdom was in use.


The Cifra General was used for communications between the Emperor and his main government members abroad.  We can see it as a diplomatic master cipher.  The Cifra General of 1556 was addressed to:

The Cifra General of 1556 is dated at Gent on November 8th, 1556 and, according to David Kahn, it was one of the finest encryption systems in its time.  It is made up of three parts: a monoalphabetic (with homophones) substitution vocabulary, a list of digraphs and trigraphs, and a dictionary of common terms.


The original Cifra General is stored at the Simancas Archive, Spain.  This copy comes from the book by  J.P. Devos (Les chiffres de Philippe II (1555-1598) et du Despacho Universal durant le XVIIe Siecle, 1950).



Vocabulary   Digraph/trigraph table  Dúplices/double letters)






Appendix: The Cifra General under attack


Philip the Second´s Cifra General kept secrets safe for barely three months.  In February 1557, the Papal Secretary Triphon Bencio managed to break the cipher of a letter sent to the Cardinal of Burgos, Francisco Pacecco, at Siena; Pacecco was one of the recipients of the Cifra General.  From there, the cryptanalist reconstructed part of the cipher.  Here´s the fragment he could find out.  The original was published in the book of Aloys Meister Die Geheimschrift im Dienste der Päpstlichen Kurie von ihren Anfängen bis zum Ende des XVI. Jahrhunderts (Encrypted writihg at the Papal Curia from its beginnings to the end of the XVIth Century).



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