How was the Colossus computer used against the Lorenz cipher?

The Colossus computer was developed by British codebreakers at Bletchley Park to assist in the cryptanalysis of high-level German Lorenz stream cipher messages during World War II. Using thermionic valves to perform Boolean and counting operations, Colossus automated the decryption process to handle intercepted radiotelegraphy traffic known as Tunny. By the end of the war, ten Colossus machines were operating, helping the Allies decode about 90 percent of selected Tunny messages and providing crucial Ultra intelligence.

What we know

• Colossus was a set of computers developed between 1943 and 1945 specifically to aid in the cryptanalysis of the Lorenz cipher. [3]
• The computers used thermionic valves, or vacuum tubes, to execute Boolean and counting operations. [3]
• By the end of World War II, ten Colossus machines were in active use, enabling the decryption of roughly 90 percent of selected Tunny messages. [3, 4]
• The deciphered Lorenz messages yielded high-level strategic intelligence that contributed significantly to the Allied victory. [2, 4]

Where to go next

• whoWho designed and engineered the Colossus computer?
• whereWhat role did Bletchley Park play in breaking World War II codes?
• compared withHow did the Enigma machine differ in design and cryptanalysis from the Lorenz cipher?
• how it workedWhat were the technical specifications and operational steps of the Lorenz SZ rotor stream cipher?
• what followedHow did decrypted intelligence from Tunny and Enigma impact the outcome of World War II?
• an unexpected connectionHow were teleprinters adapted for secret wartime military communications?The Lorenz machines were built as in-line attachments to standard teleprinters, transforming ordinary communication terminals into cryptographic generators of high-level strategic secrets.

Sources

• [1]Lorenz cipher (Wikidata Q695493) · CC0 1.0
• [2]Lorenz cipher · CC BY-SA 4.0
• [3]Colossus computer · CC BY-SA 4.0
• [4]Cryptanalysis of the Lorenz cipher · CC BY-SA 4.0
• [5]Enigma machine · CC BY-SA 4.0