TheCodeBreakers
At 47, Vigenere quit the court, turned over his annuity of
1,000 livres a year to the poor of Paris, married the much younger Marie
Vare, and devoted himself to his writing. His Traicte des Chiffres, which
was written in 1585 despite the distraction of a year-old baby daughter,
appeared, elegantly rubricated, in 1586, and was reprinted the following
year. His autokey system used the plaintext as the key. It provided a
priming key. This consisted of a single letter, known to both encipherer
and decipherer, with which the decipherer could decipher the first
cryptogram letter and so get a start on his, work. With this, he would get
the first plaintext letter, then use this as the key to decipher the second
cryptogram letter, use that plaintext as the key to decipher the third
cryptogram letter, and so on.
key DA UNO MD ELETERNE
plain au nom de léternel
cipher XI AHG UP TMLSHIXT
annaabi.ee 
