François Viète

François Viète, known in Latin as Franciscus Vieta, was a French mathematician who lived from 1540 to 1603. He was born at Fontenay-le-Comte, studied law at Poitiers and worked as a lawyer, and he served as privy councillor to Henry III and Henry IV of France. His new algebra, which used letters as parameters in equations, was an important step towards modern algebraic notation. He also worked as a code-breaker for both kings: he deciphered secret letters of the Catholic League, and in 1590 he broke the key to a Spanish cipher of more than 500 characters, so that Spanish dispatches captured by the French could be read. From 1594 he was appointed to decipher enemy codes full time, and shortly before his death he wrote a last thesis on cryptography.