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?