Lorenz and Colossus [military cryptography]

Abstract

The German Army High Command asked the Lorenz company to produce for them a high security teleprinter cipher machine to enable them to communicate by radio in complete secrecy. The Lorenz company designed a cipher machine based on the additive method for enciphering teleprinter messages invented in 1918 by Gilbert Vernam in America. The Vernam system enciphered the message text by adding to it, character by character, a set of obscuring characters thus producing the enciphered characters which were transmitted to the intended recipient. The paper discusses the Colossus computer. Colossus reduced the time to break Lorenz messages from weeks to hours and just in time for messages to be deciphered which gave vital information to Eisenhower and Montgomery prior to D Day.