In 1907, a young woman from Orimattila, Finland received an encrypted postcard. Can a reader decipher it?

The seat covers in EasyJet airplanes bear symbols that look like pigpen letters. Blog reader Matthias Axinger has provided me an interesting analysis of these glyphs.

This might be the cryptogram discovery of the year: a manuscript containing some 7000 illustrations, many of them with encrypted (?) captions. Can a reader make sense of these unusual artworks?

A. J. Jacobs, a successful US author and journalist, has provided me scans of an encrypted journal written by a renowned psychologist. Can a reader break it?

Blog reader Mario Gerlach has provided me a picture of an encrypted graffiti he saw in Nördlingen, Germany. Can a reader solve this cryptogram?

An encrypted diary recently posted on Reddit looks easy to solve, but so far nobody has broken it.

Jim Sanborn, creator of the famous Kryptos sculpture, has published a third clue: the word NORTHEAST appears in the plaintext of the unsolved message part.

Here are two cryptograms that are easy to solve: a postcard sent from Dortmund, Germany, in September 1900 and another one sent from the same place a few weeks later.

The Zodiac Killer murdered five or more people and sent four encrypted messages to newspapers. The case and three of the cryptograms have never been solved.

Henry Debosnys (1836-1883), a convicted murderer, left behind four cryptograms, which  are unsolved to date. Breaking them could shed light on the many mysteries that surround this case.