Two years ago a detectorist found an encrypted note hidden in a WW2 bullet in central Italy. Despite many tries this cryptogram is still unsolved.


Here’s my latest publication: a free brochure about cryptography and codebreaking especially for school children. Thanks to a great graphic artist it looks very professional.


During World War II a woman from Loiret, France, sent an encrypted message to a recipient in Nantes, France. Can a reader break this cryptogram?


The longest key ever publicly broken by exhaustive key search has 64 bits. A challenge I created a few years ago aims to improve this world record by one bit.


ADFGVX is an encryption method used by the Germans in WW1. Some 20 ADFGVX radio messages from 1918 are still unsolved.


In 1970 the corpse of a woman was found near Bergen, Norway. In her car police found encrypted notes. These notes were deciphered, but the identity and the cause of death of this woman have remained a mystery until today. Thanks to blog reader Bjarne, I can now present a few new facts about this…


In 1944 a Nazi spy located in New York sent encrypted messages via Paris to Germany. These cryptograms have never been deciphered.


The list of most-frequently used passwords has changed little over the past few years. In 2016, “123456” once again was the most popular one.


In 1999 cryptographer Ron Rivest published an encrypted text that was designed to take 35 years to break. 18 years later it is still unbroken.


Substituting letter pairs (bigrams) is an encryption method that was already known in the 16th century. Is it still secure today?