Earlier this year I blogged about Printer Identification Codes, which are one of the IT world’s best-kept secrets. As it seems, a US secret service has now used this technology to track down a whistleblower.


US mathematics professor Craig Bauer has published a great book about unsolved cryptograms. Most of these crypto mysteries have been covered on this blog before.


The Handycipher is an encryption algorithm that doesn’t require a computer program or a machine. But is it secure?


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.