from Cambridge, MA
Delastelle's work on the four-square cipher was published in a book in 1902, and was a variant on the earlier Playfair cipher.
CryptographerArea of science:
…"The solution", writes historian David Kahn, "was Rejewski's own stunning achievement, one that elevates him to the pantheon of the greatest cryptanalysts of all time." Rejewski used a mathematical theoremthat two permutations are conjugate if and only if they have the same cycle structu...