Camino de Santiago hiker Jens Grabarske has made me aware of an encrypted inscription in northern Spain. Can reader decipher it?

In 1913 a man sent an encrypted postcard from Jena, Germany, to his lover in the Hamburg area. Can a reader decipher this cryptogram?

The seat covers of EasyJet airplanes bear symbols that look like a pigpen cipher. Do they encode a secret message?

French crypto history expert Jean-François Bouchaudy has found something very rare: three original messages encrypted with an M-209 cipher machine. One of these is still unsolved.

An encrypted telegram sent by two Russian communists in 1918 allegedly reports the death of czar Nicholas II and his family. Can a reader decipher it?

During the Thirty Years’ War, a Swedish general wrote an encrypted letter to a German Major. Can a reader decipher this message?

Now that the LCS35 time-lock puzzle has been solved, cryptographer Ron Rivest has published a new challenge of the same kind. This time, he estimates that it’s going to take 15 years to find the solution.

Here’s an encrypted postcard from the early 20th century, which was sent to a young woman in Landreville, France. Can a reader decipher it?

A Reddit user has found two encrypted notes and a few geographic coordinates in an old travel book. Can a reader find out what these messages mean?

A statue in a northern German church bears an inscription nobody can read. What looks like Hebrew, might be encrypted. Can a reader make sense of this cryptogram?