From Fish to Colossus How the German Lorenz Cipher was Broken at Bletchley Park

by Harvey G. Cragon

"From Fish to Colossus" tells the little-known story of the German Lorenz cipher machine and how its messages were broken at Bletchley Park during World War II. The Lorenz machine enciphered five bit Baudot coded teleprinter messages prior to transmission via radio or landlines. The radio messages were first intercepted by the British in 1941. A method of deciphering was devised at BP that depended only upon the statistics of a single message; this method led to the necessity for fast digital processing machines. The most sophisticated of these was Colossus, which required 2,500 vacuum tubes. By the end of WW II thirteen Colossi were in operation. The development of the deciphering algorithm is described as well as the design of the Colossus and its predecessors. Most of the research material used in this book was either declassified in 1996 by the National Security Agency or was released in 2000 to the Public Records Office (UK).

Paperback

Published July 1, 2003