Felix Delastelle
Encyclopedia
Félix Marie Delastelle was a Frenchman
most famous for his invention of several systems of polygraphic substitution ciphers including the bifid
, trifid
, and the four-square cipher
s.
David Kahn wrote that "Delastelle invented a fractionating system of considerable importance in cryptology." This was the bifid cipher
, which combined fractionation
with transposition
as opposed to substitution, as was done by Pliny Chase
in 1859. The first presentation of the bifid appeared in the French Revue du Génie civil in 1895 under the name of cryptographie nouvelle.
Delastelle's work on the four-square cipher
was published in a book in 1902, and was a variant on the earlier Playfair cipher
. Delastelle may have been unaware of Playfair, but he had 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 150 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.
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
most famous for his invention of several systems of polygraphic substitution ciphers including the bifid
Bifid cipher
In classical cryptography, the bifid cipher is a cipher which combines the Polybius square with transposition, and uses fractionation to achieve diffusion...
, trifid
Trifid cipher
In classical cryptography, the trifid cipher is a cipher invented around 1901 by Felix Delastelle, which extends the concept of the bifid cipher to a third dimension, allowing each symbol to be fractionated into 3 elements instead of two...
, and the four-square cipher
Four-square cipher
The four-square cipher is a manual symmetric encryption technique. It was invented by famous French cryptographer Felix Delastelle.The technique encrypts pairs of letters , and thus falls into a category of ciphers known as polygraphic substitution ciphers...
s.
David Kahn wrote that "Delastelle invented a fractionating system of considerable importance in cryptology." This was the bifid cipher
Bifid cipher
In classical cryptography, the bifid cipher is a cipher which combines the Polybius square with transposition, and uses fractionation to achieve diffusion...
, which combined fractionation
Fractionation
See also: Fractionated spacecraftFractionation is a separation process in which a certain quantity of a mixture is divided up in a number of smaller quantities in which the composition changes according to a gradient. Fractions are collected based on differences in a specific property of the...
with transposition
Transposition
Transposition may refer to:Mathematics* Transposition , a permutation which exchanges two elements and keeps all others fixed* Transposition, producing the transpose of a matrix AT, which is computed by swapping columns for rows in the matrix AGames* Transposition , different moves or a different...
as opposed to substitution, as was done by Pliny Chase
Pliny Chase
Pliny Earle Chase was an American scientist, mathematician, and educator who contributed to the fields of astronomy, electromagnetism, and cryptography, among others. For many years he was Professor of Philosophy and Logic at Haverford College....
in 1859. The first presentation of the bifid appeared in the French Revue du Génie civil in 1895 under the name of cryptographie nouvelle.
Delastelle's work on the four-square cipher
Four-square cipher
The four-square cipher is a manual symmetric encryption technique. It was invented by famous French cryptographer Felix Delastelle.The technique encrypts pairs of letters , and thus falls into a category of ciphers known as polygraphic substitution ciphers...
was published in a book in 1902, and was a variant on the earlier Playfair cipher
Playfair cipher
The Playfair cipher or Playfair square is a manual symmetric encryption technique and was the first literal digraph substitution cipher. The scheme was invented in 1854 by Charles Wheatstone, but bears the name of Lord Playfair who promoted the use of the cipher.The technique encrypts pairs of...
. Delastelle may have been unaware of Playfair, but he had read of the fractionating cipher described by Pliny Chase
Pliny Chase
Pliny Earle Chase was an American scientist, mathematician, and educator who contributed to the fields of astronomy, electromagnetism, and cryptography, among others. For many years he was Professor of Philosophy and Logic at Haverford College....
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 150 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.