The Crypto Books page operated by Nils Kopal and Tobias Schrödel is the leading information source for books about historical cryptology. Currently, it has 541 entries.

A museum director from Switzerland is asking for help. Can a reader decipher the inscription on an executioner’s sword?

A German news magazine has published an encrypted message from a German 1970s terrorist. The solution is known, but some of the details remain unclear.

Crypto collector Ralph Simpson is compiling a list of all Kryha machines that are known to exist. Can my readers support him?

A German egyptologist claims to have deciphered the Voynich Manuscript. Does this solution make more sense than the dozens that have been published before.

In 1648, English king Charles I wrote four encrypted letters while in captivity on the Isle of Wight. Can a reader break these cryptograms?

Here’s a French letter from the 17th century, encrypted probably in a homophonic system or a nomenclator. Can a reader decipher it?

A hundred years ago, German textile engineer Rudolf Zschweigert invented a remarkable encryption machine. A paper I recently published gives an introduction to this device.

For ten years, adventurers and puzzle fans have been hunting for a treasure hidden by US millionaire Forrest Fenn. As it seems, a person who wants to stay anonymous has now found it.

Gravestones bearing an encrypted or hidden message are one of my favorite blog topics. Here’s a speciment I recently discovered on Reddit.