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.

A Reddit user has posted a strange cryptogram engraved on a metal plate. Can a reader make sense of it?

The encrypted diary of prisoner of war Donald Hill is unique. Hill not only encrypted his entries but also disguised them as a collection of mathematical tables. In a self-experiment, I tried to encrypt and hide a text like he did.

My friend Stefan Beck, owner of a typewriter museum, has purchased a rare Hagelin encryption machine. Does a reader know, why it looks different from other devices of the same model?

A Polish publishing house has launched a new Voynich manuscript facsimile. Another Voynich replica – much smaller in size – is available as a doll house accessory.

This year’s HistoCrypt conference will involve a unique line-up of world-renowned speakers and panelists – including Bill Clinton, Giovanni Infantino, and Bill Cosby.