Johannes Trithemius (1 February 1462 - 13 December 1516) was born Johann Heidenberg. The name by which he is more commonly known is derived from his native town of Trittenheim on the Mosel in Germany.
He studied at the University of Heidelberg. Travelling from university back to his home town in 1482, he was surprised by a snowstorm and took refuge in the Benedictine abbey of Sponheim near Bad Kreuznach. He decided to stay and was elected abbot in 1483, at the age of twenty-one. He set out to transform the abbey from a poor, undisciplined and ruinous place into a centre of learning. In his time, the abbey library increased from around fifty items to more than two thousand. However, his efforts did not meet with praise, and his reputation as a magician did not further his acceptance. Increasing differences with the convent led to his resignation in 1506, when he decided to take up the offer of the Lord Bishop of Würzburg, Lorenz von Bibra (bishop from 1495 to 1519), to become abbot of the Schottenkloster ("Scottish monastery") in Würzburg. He remained there until the end of his life.
Among his pupils were Heinrich Cornelius Agrippa (1486 - 1535) and Paracelsus (1493 - 1541).
His most famous work is Steganographia (written c.1499; published Frankfurt, 1606, placed on the Index Librorum Prohibitorum in 1609). This book is in three volumes, and appears to be about black magic - specifically, about using spirits to communicate over long distances. Since the publication of the decryption key to the first two volumes in 1606, they have been known to be actually concerned with cryptography and steganography. Until recently, the third volume was widely still believed to be about magic - but recently the "magical" formulae were shown to be covertexts for yet more cryptography content. The work has lent its name to the modern field of steganography.
Other works include De septum secundeis (The Seven Secondary Intelligences, 1508), a history of the world based on astrology; Annales Hirsaugiensis (1514); and Polygraphia (1518).