Trithemius Cipher

Background

Johannes Trithemius (* 1462 in Trinttenheim; † 1516 Würzburg) joined the monastery ”Sponheim“ at the age of 20 and was appointed the abbot of the monastery two years later. His research led him to the conclusions that there are four different kinds of witches and that the world was created in the year 5206 B.C. He also claimed that he knew how to control angels to send messages to other people.¹
Even his contemporaries considered some of his opinions to be very strange and so he was forced to leave the monastery. He joined another monastery and started writing books about cryptology.

Principle

The Trithemius cipher is a precursor to the Vigenère cipher. In principle, it can be viewed as Vigenère cipher with the constant key: ”ABCDEFGHIJKLMNOPQRSTUVWXYZ“.

Security

Because of the changing Caesar ciphers, the security is comparatively high. But as the key is always ”ABCDEFGHIJKLMNOPQRSTUVWXYZ“, the cipher is useless once this key is known.

References

¹ Kippenhan, Rudolf: ”Verschlüsselte Botschaften“, Nikol, 2006, P. 138f