The Fleissner grille is one of the most popular encryption tools. In spite of its popularity, surprisingly little has been published about deciphering a Fleissner grille. I wonder if a reader can break the Fleissner challenge I am going to present today.
A German spy captured in the UK in World War II used a cipher that would hide a message in a love letter. Did this method work well in practice?
An old French magazine mentions an encrypted message that was found in the estate of a 19th century French soldier. Can a reader decipher this cryptogram?
Many color laser printers add tiny yellow dots to each page they print. These dots encode a timestamp, the printer serial number and potentially additional information. Although these dot codes have been around for at least 25 years, not much is publicly known about them.
After 20 years in the IT security business, I created a comic strip based on my experiences. Here are episodes 5 to 7.
Cicada 3301 is an internet game operated by a secret organisation since 2012. A new round always starts on January 4 of a year. Will round number six be launched tomorrow?
The new year begins with six encrypted postcards from the 19th century. They were provided to me by the National Cryptologic Museum. Can a reader decipher them?