Félix Delastelle

Félix-Marie Delastelle (1840 to 1902) was a French cryptographer, best known for inventing the bifid cipher, which he first presented in the Revue du Génie civil in 1895 under the name cryptographie nouvelle. The cipher combines fractionation with transposition and was an early cipher to apply the principles of confusion and diffusion. His other polygraphic substitution ciphers include the trifid cipher and the four-square cipher, a variant of the earlier Playfair cipher. He was unusual as an amateur: his father, a master mariner, was lost at sea in 1843, he left the College of Saint-Malo in 1860, and he worked about forty years as a bonded warehouseman in the local port while pursuing cryptography as a hobby. After retiring in 1900 he wrote a 160-page book on elementary cryptography, completed in May 1901 and published in Paris after his death in April 1902.