Charles Dellschau (1830-1923) was a US outsider artist, who left behind fascinating paintings. Some of these contain encrypted texts.

Tengri 137 is the name of a mystery game, in the center of which is an encrypted book. The last seven pages of this book still wait to be deciphered.

Within a few hours, blog reader Norbert Bierman solved the Reihenschieber challenge I introduced last Monday. His work shows that I used this device in a wrong way.

For the second time in a few months, an encrypted bottle post has been found in the river Alster in Hamburg. Can a reader decipher these mysterious messages? Can we find out who is behind these bottle posts?

The Reihenschieber was a simple encryption device used by the Germans in the Cold War. I built a model of it with Lego bricks. Can you solve an encrypted text I produced with it?

The greatest European crypto history event ever will take place in May 2017. So, save the date, consider handing in a paper, and come to Bratislava!

Blog reader Tony Gaffney has provided me a strange drawing from a British archive. Does it code a text? Is it a cipher tool? Any help from my readers is welcome.

Last week I introduced a cryptogram made with a Fleissner grille. Blog reader Armin Krauß found the solution, although I had made a serious mistake in the encryption process.

A gamer has offered a reward for solving two ciphers appearing in a video game. This gives you the chance to make money on your codebreaking skills.

The Schlüsselkasten (key box) was a small and simple encryption machine developed by the Germans in World War II. According to an NSA report, it could have changed the course of the war if it had been introduced a little earlier.