The Lorenz cipher machine SZ42
Donald W. Davies · Artech House, Inc. eBooks · 1998
The German cipher traffic called tunny which was broken at Bletchley Park using the Colossus machine was produced bu an in-line “cipher-attachment” made by Lorenz, Schlussel Zusatz or SZ42. This paper is a description of the way that the SZ42 operates and its mechanism.