An encrypted postcard I recently discovered looked familiar to me. As it turned out, I had already blogged about a card from the same sender.

In the early 20th century, a young man sent encrypted postcards to his spouse. Can a reader decipher these?

I need the help of my readers to correctly decipher two encrypted newspaper ads from 1882.

The inscription on the Goldenes Dachl ( Golden Roof) in Innsbruck, Austria, is one of the oldest unsolved crypto mysteries known to exist. According to press reports, the cipher has now been broken.

Crypto history expert Frode Weierud has provided me a number of unsolved German cipher messages from the Second World War. Can a reader break them?

Jim Sanborn, the creator of the famous Kryptos sculpture, said his third clue would be the last one. But now he has published another word that appears in the plaintext: EAST.

The Cylob Cryptogram is a little-known, but fascinating crypto mystery. Here are a few new thoughts on it.

An anonymous note published on Reddit contains a number of digits and a reference to a Beatles album. Is there a message hidden in this text?

In a 1984 video clip by British Heavy Metal band Iron Maiden, several messages consisting of strange symbols can be seen. Can they be decrypted?

A museum in Polotsk, Belarus, is struggling with an encrypted postcard. Can a reader help?