Solving a Mystery From the Thirty Years’War: Karel Rabenhaupt ze Such´e’s Encrypted Letter to Landgravine Amalie Elisabeth

Abstract

In 2013, an unsolved encrypted message was presented in a Czech cryptogram solving competition. This message was sent by Karel Rabenhaupt ze Such´e to Amalie Elisabeth von Hanau-M¨unzenberg, Landgravine of Hessen-Kassel at the end of the Thirty Years’ War. During the following years, many crypto enthusiasts tried to solve the cipher without success. Finally, in 2020, the authors of this paper were able to reveal the content of the encrypted message. Here we present the decryption of the encrypted message, including the historical background of the communication. We also present an analysis of the used encryption system.