Félix-Marie Delastelle (2 January 1840 – 2 April 1902) was a French cryptographer, best known for inventing the
bifid cipher, first presented in the ''Revue du Génie civil'' in 1895 under the name of "cryptographie nouvelle". This cipher combines
fractionation
Fractionation is a separation process in which a certain quantity of a mixture (of gasses, solids, liquids, enzymes, or isotopes, or a suspension) is divided during a phase transition, into a number of smaller quantities (fractions) in which t ...
with
transposition, and was an early cipher to implement the principles of
confusion and diffusion
In cryptography, confusion and diffusion are two properties of a secure cipher identified by Claude Elwood Shannon, Claude Shannon in his 1945 classified report ''A Mathematical Theory of Cryptography''. These properties, when present, work toge ...
. David Kahn described it as a "system of considerable importance in cryptology."
Delastelle's other
polygraphic substitution ciphers included the
trifid
Trifid is Latin for "split into three parts" or "threefold" and may refer to:
* ''Trifid'' (journal), a Czech-language periodical
*Trifid Nebula in the constellation Sagittarius
* Trifid cipher, a fractionated cipher
Distinguish from
*Triffid, a ...
and
four-square cipher
The four-square cipher is a manual symmetric encryption technique. It was invented by the French cryptographer Felix Delastelle.
The technique encrypts pairs of letters (''digraphs''), and falls into a category of ciphers known as polygraphic ...
s.
[Delastelle, p. 77.] The last of these is a variant on the earlier
Playfair cipher: Delastelle may have been unaware of Playfair, but he had certainly read of the fractionating cipher described by
Pliny Chase in 1859.
There are few biographical details. Félix-Marie's father, a master mariner, was lost at sea in 1843. Félix attended the College of Saint-Malo until 1860. After leaving school, he worked in the local port, as a bonded warehouseman, for forty years, and pursued his interest in amateur cryptography as a hobby.
Following his retirement in 1900, he rented a single room in a holiday hotel where he wrote a 160 page book ''Traité Élémentaire de Cryptographie'' which he completed in May 1901. On hearing news of his brother's sudden death, he collapsed and died in April 1902. His book appeared three months later, published by Gauthier-Villars of Paris.
Delastelle is unusual for being an amateur cryptographer at a time when significant contributions to the subject were made by professional soldiers, diplomats and academics.
Notes
References
*
*
External links
*
{{DEFAULTSORT:Delastelle, Felix
19th-century cryptographers
French cryptographers
1840 births
1902 deaths