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?

In WW2, Berlin-based company Heimsoeth & Rinke not only produced the Enigma, but also a cipher cylinder, about which as good as nothing is known. Can my readers help to research the history of this device?

In 1875, a man living in Vienna received an encrypted postcard from a family member. Can you break this cryptogram?

British comedian Chris Sievey, also known as Frank Sidebottom, left behind a number of encrypted messages. British Codebreakers deciphered them and will publish the solutions in a few days. Can a reader break these cryptograms beforehand?

In the 19th century, a sailor working on the Great Lakes kept an encrypted diary. Can a reader decipher it?

In a Kansas library an unknown person has written an encrypted message into a book. Can a reader solve this “book cipher”, which is probably not a book cipher?

In 1909, an unmarried woman in Santa Monica received a postcard encrypted in an unusual cipher. Can a reader break this encryption?

My readers have shown that a Playfair cryptogram consisting of only 40 letters can be broken. Here’s a Playfair challenge with only 30 letters. Can you break it, too?

In 1978, a Kansas TV station placed a subliminal message in a TV program in order to catch a serial killer.

German poet and translator Stefan George (1868-1933) created his own secret language. It has never been deciphered – probably because only two lines written in it have survived.