Belgian scholar Michael Florent van Langren (1598-1675) proposed a naval navigation method that didn’t work. A second method he developed might be described a cryptogram that has never been solved.

On Cocos Island in the eastern Pacific, a “treasure” consisting of works created by 40 modern artists is buried. The exact location is described in an encrypted message. To my knowlege, this cryptogram has never been published.

In 1891, an unknown person published an advertisement in the Morning Post. Five words in this message are encrypted. Can a reader break this cryptogram?

Crypto expert Frode Weierud has published a collection of unsolved cryptograms from 1969. If you’re looking for a challenging codebreaking project, here you go.

In 1916, the USA bought the West Indian islands from Denmark. An encrypted telegram about this purchase, sent by the Danish ambassador, is available on a website.

Magnus Ekhall from Sweden has solved my Playfair challenge from September 2019. With only 28 letters, this ciphertext is the shortest of its kind ever broken.

My users ure usually very successful when it comes to breaking encrypted postcards. Anyway, the one I’m going to introduce today might be a tough challenge.

Blog reader Karsten Hansky has provided me a nice encrypted postcard from 1954. Can a reader decipher it?

George Lasry has found an interesting collection of challenge ciphers, probably used to train codebreakers during the early Cold War. Today, I’m going to present one of these challenges.

Outsider artist James Hampton’s writing in an unknown script is one of the world’s most puzzling crypto mysteries. Today, I’m going to introduce an unencrypted text that can be read on Hampton’s only artwork. As far as I know, this note has never been published before.