Blog readers Richard Bean, Frode Weierud and George Lasry have broken most of the ciphertexts from the Biafran War I recently introduced.

It’s probably not a Christmas card, but at least an encrypted card that was sent on the occasion of a celebration. Can a reader decipher this cryptogram?

Here’s one of the oldest encrypted postcards I have ever seen. Can a reader decipher it?

Konstantin Hamidullin from Latvia has solved my Playfair challenge from November 2019. With only 26 letters, this is the shortest Playfair cryptogram ever broken.

Last week, I introduced a 750-letter ciphertext created with a bigram substitution. Jarl Van Eycke and Louie Helm have now solved this challenge. As far as I know, this is the shortest bigram cipher challenge ever broken.

According to a TV documentary, a German WW2 soldier created encrypted notes describing the location of a hidden tunnel system in Czechia while in captivity. There are rumours about a treasure hidden in this facility.

Christopher Columbus frequently used a signature that included seven letters not belonging to his name. Do they represent an abbreviation?

Jarl Van Eycke and Louie Helm recently solved a bigram substitution ciphertext consisting of 1000 letters – the shortest one ever broken. Now I have created a 750-letter challenge of the same kind.

Bavarian artist Martin Dorn has provided me a seven-pages encrypted manuscript. Can a reader decipher it?

A video documentary presents new facts about the history of the Enigma in the 1930s and its deciphering in the Second World War.