The Lorenz SZ40/42 was a German teleprinter cipher machine that XORed each 5-bit Baudot character with a pseudo-random stream from twelve wheels, while Typex was the British rotor machine derived from commercial Enigma.
Example
HELLO9WORLD4Q4LKMNKV/O
Characters: 11
Wheel patterns: built-in demo patternsWhat is the Lorenz / Typex Decoder?
Lorenz — codenamed Tunny at Bletchley Park — worked on 5-bit Baudot teleprinter code rather than letters on a keyboard. Twelve wheels generated a key stream that was XORed with the plaintext bits, and because XOR is self-inverse, the same machine and settings decoded it. It carried strategic traffic between the German high command, one level above Enigma's tactical role.
Breaking Tunny drove the construction of Colossus, the first programmable electronic digital computer, after a German operator retransmitted a message with the same key and gave the codebreakers a depth. Typex, meanwhile, was Britain's own rotor machine — an Enigma derivative with five rotors and no reciprocal-plugboard weakness, and it was never broken.
How to use the Lorenz / Typex Decoder
- Choose the machine and enter the wheel or rotor settings you are working from.
- Paste the ciphertext in Baudot/ITA2 or letter form.
- Read the decoded output and adjust the wheel start positions as needed.
When to use it
- Historical research into Second World War signals intelligence.
- Teaching how stream ciphers and XOR key streams actually work.
- Reconstructing Tunny traffic for a museum or educational project.
Lorenz / Typex Decoder at a glance
| Lorenz SZ40/42 | 12 wheels, XOR over 5-bit Baudot code |
| Bletchley name | Tunny — attacked with Colossus |
| Typex | British 5-rotor Enigma derivative, unbroken |
| Alphabet | ITA2 / Baudot, 5 bits per character |
Frequently asked questions
How was Lorenz different from Enigma?
Enigma was a hand-operated letter machine for tactical traffic. Lorenz was an automated teleprinter attachment that XORed a wheel-generated key stream onto 5-bit Baudot code, and carried strategic high-command messages.
What was Colossus?
The first programmable electronic digital computer, built at Bletchley Park specifically to speed up the statistical attack on Lorenz wheel settings.
Was Typex ever broken?
No. Typex used five rotors and avoided several Enigma weaknesses, and there is no evidence German cryptanalysts read its traffic.
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