Years ago, Otto Leiberich, the former president of the West German cipher authority, told me about a little known encryption system developed by his team. Can you break a challenge cryptogram I have created with this system?

Blog reader Matthias Axinger has drawn my attention to an encrypted message that played a role in the TV series “Operation Mozart”. Can you solve a cryptogram that was created with the same method?

The encrypted inscription on the Kryptos sculpture located in front of the CIA building in Langley, Virginia, is the world’s most famous crypto puzzle. In March, a Kryptos gathering organized by Elonka Dunin will take place.

Blog reader Nils Kopal has purchased a copy of a famous 16th century crypto book. Inside he found more than he had expected. Can a reader tell him what these additional texts and illustrations mean?

Blog reader Magnus Ekhall has created a software that simulates an Enigma breaking device. He has also published a few challenges, one of which is still unsolved.

In the early 19th century, an unknown person sent an encrypted postcard from Munich to Berlin. It is not hard to decipher.

When it comes to cryptography, the world is not enough. Nevertheless, the story of cryptography in space has never been told in the crypto history literature. Can you help the HeinzNixdorf MuseumsForum to change this?

Louis XIV of France, also known as the Sun King, is one of the most important figures in European history. An encrypted letter he wrote in 1693 has never been deciphered.

According to a recent BBC article, a British student has broken a “religious code” from the 18th century. What is behind it?

In 2017 I blogged about a Pigpen ciphertext that had been discovered in the London suburb of Croydon. This cryptogram is still unsolved.