Magnus Ekhall from Sweden has solved my Playfair challenge from September 2019. With only 28 letters, this ciphertext is the shortest of its kind ever broken.

My users ure usually very successful when it comes to breaking encrypted postcards. Anyway, the one I’m going to introduce today might be a tough challenge.

After the First World War, Italian engineer Luigi Nicoletti invented a transposition cipher tool. Can you break a ciphertext I created with this device?

Two online games for crypto enthusiasts have been launched – one in Germany, one in Poland.

Blog reader Karsten Hansky has provided me a nice encrypted postcard from 1954. Can a reader decipher it?

George Lasry has found an interesting collection of challenge ciphers, probably used to train codebreakers during the early Cold War. Today, I’m going to present one of these challenges.

CrypTool is the world’s leading crypto e-learning software. Currently, the 20th anniversary of this outstanding tool is celebrated in Munich. Among the guests are some renowned codebreakers.

Outsider artist James Hampton’s writing in an unknown script is one of the world’s most puzzling crypto mysteries. Today, I’m going to introduce an unencrypted text that can be read on Hampton’s only artwork. As far as I know, this note has never been published before.

A few weeks ago, I introduced a 1000-letter ciphertext created with a bigram substitution. Jarl Van Eycke and Louie Helm have now solved this challenge and set a new world record.

At the NSA Symposium on Cryptologic History, I gave a presentation about brute-force attacks. After a subsequent discussion with Whitfield Diffie, I realized that we need a new DES challenge. Here it is.