Trithemius and the Steganographia: Angels, Ciphers and Secret Writing

Johannes Heidenberg, born in 1462 in Trittenheim on the Moselle, has gone down in history under the Latin name of his village: Trithemius. A Benedictine monk, at only twenty-one he became abbot of Sponheim in the Rhineland and assembled there a library of about two thousand volumes, famous throughout Germany. He was a historian, bibliographer and theologian, but his most lasting fame came from a book almost no one in his time was able to read: the Steganographia.

A Scandal Born from a Letter

Around 1499 Trithemius announced the project in a letter to the Carmelite Arnold Bostius of Ghent. In it he promised a work that would teach how to send messages over distances, secretly and safely, with the help of spirits. Bostius had died before the letter arrived, and the text passed into other hands, arousing amazement and suspicion. From then on the abbot was surrounded by a reputation as a necromancer.

In 1503 the French philosopher Charles de Bovelles visited Sponheim and was able to leaf through the unfinished manuscript. Some years later, in a letter that became famous, he described it as a work of demonic magic, full of barbarous names of spirits. His verdict made the book even more feared, and Trithemius never published it.

Angels or Alphabets

The Steganographia was printed only in 1606, in Frankfurt, almost a century after its author's death in 1516. A few years later it was placed on the Index of Prohibited Books. The first two books contain a long series of invocations addressed to spirits with strange names, each linked to an hour or a direction. The third, unfinished book seems to speak of planetary influences and numerical tables.

As early as the seventeenth century some readers suspected that the invocations were a disguise. They were right. The first two books conceal methods of encryption in which the meaningful letters are arranged according to precise rules within apparently magical texts. In the 1990s cryptography scholars also deciphered the tables of the third book, showing that they contain enciphered messages in Latin.

The Polygraphia and the Birth of Modern Cryptography

Trithemius also wrote an openly cryptographic work, the Polygraphia, completed in 1508 and printed in 1518, dedicated to Emperor Maximilian I. Among other things it sets out a system in which each letter of the message is replaced by a word, so that the ciphertext looks like a Latin prayer. It also contains the tabula recta, a table of shifted alphabets that underlies many ciphers of later centuries.

For this reason Trithemius is remembered today among the founders of Western cryptography. The very term steganography, meaning “hidden writing”, comes from the title of his book and still denotes the art of concealing the existence of a message within another. The word has entered the technical vocabulary of computing, where it refers to techniques that hide data inside images or sound files, a sign of how modern the abbot's insight was.

The case of the Steganographia shows clearly the ambiguity of secret knowledge in the Renaissance. What contemporaries read as magic was largely the engineering of language, and the angelic frame also served to protect secrets from the curious. It was this master, both erudite and restless, who welcomed the young Cornelius Agrippa at Würzburg and encouraged him to write the Occult Philosophy.