Designing a secure and convenient encryption algorithm that doesn’t require a computer program or a machine is quite a challenge. The Handycipher is an interesting method of this kind.

Crypto history expert Frode Weierud has found a number of encrypted messages in an archive. Can we help him to decipher these cryptograms?

Tissie and Jabber as well as Harry and Caroline were two amorous couples, who exchanged encrypted messages via newspaper ads more than a century ago. Their encryption codes are unsolved to date.

Last week I presented the mystery of an encrypted note found in an antique silk dress. Has the codebook used now been found?

A young man, who had disappeared from his home in California, sent an encrypted message from Israel to his parents. This cryptogram has been unsolved for over four decades. Can a reader decipher it?

A letter sent by some Oscar P. Schaub in the 1920s looks like it has been written in Hebrew or a similar script. However, even Hebrew experts can’t read it. Is it encrypted in a clever cipher?

Yesterday and today about 25 European cipher history experts have met at Smolenice Castle in Slovakia. It was a great event.

There are hundreds of places in the world that are worth seeing for people interested in cryptology. This is why I have created a list of cryptographic sights. I hope, my readers can help me to extend it.

A postcard from 1910 is encrypted in three different ciphers. Can a reader solve this unusual cryptogram?

In 2014 Maryland-based costume collector Sara Rivers-Cofield discovered an encrypted note in an antique silk dress. This cryptogram is unsolved to date.