Antoine Rossignol (b. 1590, d. 1682), Bonaventure Rossignol, Antoine-Bonaventure Rossignol

The family name meant "nightingale" in French. Since the 1700s, though, "rossignol" has been the French for "skeleton key" or any tool which opens that which is locked: not because of birds, but because Antoine Rossignol was one of the great code and cipher experts, either for the making or breaking of secret communications, who created a dynasty of cryptographers and cryptanalysts in service to the crown.

In 1626, Henri II of Bourbon Prince de Condé was besieging the Huguenot city of Réalmont. A coded letter leaving the city was intercepted. Rossignol, 36 years old, was a mathematician locally known to be interested in cipher. He quickly broke the Huguenot cipher, revealing a plea for ammunition to be brought through the blockade, as the city's supplies were nearly exhausted. The next day, the cleartext of the message was presented to the commander of Réalmont, along with a demand for surrender: the Huguenots capitulated.

This brought Rossignol to the attention of the prime minister, Cardinal Richelieu, who found secure ciphers and codes to be of immense use to his diplomatic and intelligence corps. Rossignol repeated his swift decipherment of Huguenot messages at the seige of La Rochelle in 1628.

Rossignol improved the nomenclators (cipher tables) used by the French court for their own despatches. A nomenclator is a hybrid of code and cipher. Notable important words are put into code rather than spelled out, while the bulk of the message is simple cipher. Before, to make them compact, the alphabetical order of the clear words would correspond closely to the order of the code, so that the code for Artois, Bavaria, cannon, and castle, would be in that order. Rossignol insisted the correspondence be out of order, so that two tables would have to be used, one for clear to code, the other for code to clear, organized to make finding the first element easy, without reference to the order of the second.

The Abbé de Boisrobert wrote a poem in praise of Rossignol, "Epistres en Vers."

In the reign of Louis XIV (r. 1643-1715), Antoine and his son, Bonaventure, worked either at their estate at Juvisy near Paris or a room next to the King's study in Versailles. For him, they developed the Great Cipher of Louis XIV. They were the only masters of it, encoding letters, memoranda, and records. They ran for France the Cabinet Noir, the Black Chamber (founded when Louvois was Minister of War), so notable that "black chamber" became an international term for any code bureau. A generation later, when Bonaventure's son, Antoine-Bonaventure, died, the Grand Cipher fell out of use. Once the key, even the base concept, was lost, it remained uncrackable until three years of work in the latter 19th century by Etienne Bazeries. During this time, the coded diplomatic records of the time in the French archives could not be read by historians.

Antoine's title was "King's counselor." Both Bonaventure and Antoine-Bonaventure were elevated to "president of the Chamber of Accounts."

Sources: Laffin, John, Codes and Ciphers: Secret Writing Through The Ages, London, 1973

http://all.net/books/ip/Chap2-1.html

http://en.wikipedia.org/wiki/Great_Cipher

http://sunsite.utk.edu/math_archives/.http/hypermail/historia/jan99/0127.html

http://www.danjryan.com/history.html

http://www.danjryan.com/MIntl.html

http://www.smithsrisca.demon.co.uk/crypto-ancient.html

http://www.vectorsite.net/ttcode2.html

(original article by Holly Ingraham, www.hollyi.com)