Encrypting according to The Grandmother

The investigation file Arch. No. V-2016 MV dated 1956 contains one of the prosecutions charged against the Sokol (a gymnastics organisation founded in 1862) officials who “did not agree with the unification of gymnastics in Czechoslovakia” after the 1948 communist putsch and were preparing for the restoration of the “Česká obec sokolská” (the Czech Sokol Association), which would take place after a change of regime. The State Security investigation was focused on their anti-communist resistance activities in the early 1950s.

Before an important Sokol official Evžen Köppl went in exile for fear of arrest in the autumn of 1953, he made an arrangement with his colleagues to keep a future connection with his homeland. As part of his arrangement, the password “INAR” was agreed on with Maria Petrlíková to transfer his messages to the Czech Republic through a feature called “Messages for Homeland”, then broadcast by Radio Free Europe. Marie Petrlíková received from him a well-known book by Božena Němcová entitled “Babička” (The Grandmother), which he used to teach her how to encrypt messages based on an encryption key. She also received the password and the encryption method of another colleague, Stanislav Petr. Using encrypted letters, they announced to Köppl that the password could be verified, informed about the arrests of former Sokol officials, about the course of the “Spartakiad” (a mass gymnastics event held by the communist state every five years), and distributed foreign radio reports and flyers among their friends.

In the investigation file, when asked how she actually did the encryption, Marie Petrlíková stated: “The encryption key consisted of numbers that replaced letters, and a cross marked a space between words. The encryption key was written on letter paper, about 15 x 20 cm in size, by hand and with a pencil. Shortly before my arrest, I burned it in the kitchen stove.” And she continued: “First, I wrote a message to encrypt on a piece of paper, as a normal letter, with notes in the Czech language. Then I took the encryption key and converted the individual letters from the notes according to the key into the numbers that I wrote down in the letter. The numbers in quotation marks denoted the numbers of years which individual members of the Sokol were sentenced for. An equal sign marked the end of a sentence, a hyphen marked the end of a paragraph.” Photocopies of the investigation file are published here.

In the subsequent trial, Marie Petrlíková, Karel Báša, Stanislav Petr and Metoděj Paul were sentenced for assisting to leave the republic, gathering against the republic, sedition against the republic and an administrative offence. Unconditional prison sentences were handed down: Petrlíková – 3 years, Báša – 2 years and 9 months, Petr – 1 year, and Paul – 2 years and 6 months, as well as secondary punishments (all lost their civil rights, had to pay the costs of criminal proceedings, etc.).