In the United States, information about cryptanalysis of the cipher remained classified until a few years ago. Double Transposition consists of two applications of columnar transposition to a message.

The German police made the mistake in late 1941 of switching from the rather strong Double Transposition cipher to the more accessible Double Playfair, and for over a year Bletchley Park was able ...

The need for secret communications arose very early in civilization. It progressed due to the “intellectual arms race” ...