Today I’m presenting a 26 letter message that has been encrypted with a Playfair cipher. To my knowledge, such a short Playfair cryptogram has never been solved before.

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.

The straddle checkerboard was an important part of many Cold War ciphers. Can a reader decipher three ciphertexts I created with this encryption method?

The American Cryptogram Association (ACA) recently celebrated its 90th anniversary. One of the birthday presents was a cake bearing an encrypted inscription. Can you decipher it?

Singer and rapper Ghostemane has published a crypto challenge in a US music magazine. Can a reader solve it?

A recent book mentions a cipher used by a German spy during the Second World War. Can you break a message I encrypted with this method?

A few years ago, German late-night show host Stefan Raab presented a number puzzle in his show “TV total”. It involves cryptography and should be easy to solve for readers of this blog.

The eighth Alan Turing Cryptography Competition for school children has been announced by the University of Manchester. The competition will start in January 2019. The challenges of the past issues are available online.

Two days ago, on Thanksgiving, the NSA sent encrypted greetings to “every NSA employee across the globe”. Can you break this encryption?