In 1905 a certain Miss Rhodes from Colchester, UK, received an encrypted postcard signed with “C.Y.K.”. Can you decipher it?

Here’s another encrypted text from an advertisement. It comes from Canada.

Already 30 years ago, US historian Albert C. Leighton collected historical cryptograms and tried to coordinate the study of these. He even thought of an equivalent of today’s crypto history conference, HistoCrypt. To my regret, nobody seems to know what happend to his collection after his death.  

In 1931 US shoe manufacturer Hood published a series of advertisements containing encrypted messages in a boy scout magazine. Can you solve them?

Two years ago, I blogged about an encrypted notebook from the Soviet Union. Within a few days, a reader solved this crypto mystery. It is high time that I introduce this solution in a blog post.

In the 1920s, a textiles expert developed a code for transmitting information about clothing by telegram. He even received a patent for this invention.

Fritz Menzer was one of the brightest German cryptologists of the Second World War. A number of important points in his biography are still unclear. Can my readers solve these mysteries?

A Reddit user has posted a postcard from Sweden written in 1910. Can a reader decipher it?

An advertisement poster that is currently shown in London underground trains contains an encrypted message. It is not very hard to solve.

In World War II German secret agents used a little known cipher device named Schlüsselrad (Cipher Wheel). An old document blog reader Ralph Erskine made me aware of contains the first photographs I have ever seen of this device, as well as some additional information.