VirtualColossus

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Virtual Fialka M-125 : Wheel transport mechanism. It's complex already & I've only just begun! 3 of 10 rotors in place, you can see how the clever interlaced arrangement of fingers move with each alternate rotor pulled a different direction. @cryptomuseum.bsky.social @tnmoc.bsky.social

I've been looking at the Fialka M-125's movement mechanism. A complex interlocked set of fingers are pulled apart. Each finger tracks the pins on the rotor 2 up from itself which allows a tooth to engage (or not) to turn a step. Even & odd rotors turn in opposing directions!

After a well earned rest, I'm starting to (probably foolishly) feel the urge to begin modelling another cipher machine. Any guesses which machine this rotor might be from? @tnmoc.bsky.social @cryptomuseum.bsky.social

Update for Virtual SG-41: the numeric-only SG-41z now available at sg41.virtualcolossus.co.uk Used for sending weather reports where the details were encoded as a set of numbers. It's very similar to the SG-41 but with a few interesting omissions which I'll be documenting soon.

Work is progressing on the numeric only SG-41Z model of Virtual Schlüsselgerät 41 used for sending weather information. The print wheels were tricky but are done. Another difference is the SG-41Z only has 5 of the sensing arms (6 on SG-41) and 15 bars on the cage (25 on SG-41) so that needs work.

On 4 May 1944, Bletchley Park codebreakers saw the German Abwehr testing a cipher machine they had not seen before. This turned out to be the SG-41, and today is a great day to try out the interactive 3D simulation of that machine: sg41.virtualcolossus.co.uk. Thanks @virtualcolossus.bsky.social !

I'm working on an update to Virtual SG-41. I want to also simulate the SG-41Z which was a numeric only version of the full one used for sending encoded weather reports. It uses a lot of the same mechanics, it'll be interesting to find out the differences. sg41.virtualcolossus.co.uk

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The Nazis’ Most Notoriously Complex Cryptographic Machine Is Now Available Online gizmodo.com/the-nazis-mo...

Virtual SG-41 project brings Nazi cipher machine to life in the browser www.theregister.com/2026/04/08/v...

10 Years of Virtual Colossus: 2026 And we're up to date and therefore, today is the release of my latest project: Virtual Schlüsselgerät 41 After a year of work try it out for yourself using just your web browser. Hope you like my new website design too! sg41.virtualcolossus.co.uk

Released today: Virtual Schlüsselgerät 41 This cipher machine, based on Hagelin C-38 but WAY more complex was set to replace Enigma. Over a year of work & research & it's ready for you to try for yourself. sg41.virtualcolossus.co.uk @tnmoc.bsky.social @cryptomuseum.bsky.social

10 Years of Virtual Colossus: 2025 Did you know that Turing designed a valve computer using mercury delay lines as memory after the war? The pilot machine ran 75 years ago and was recreated as Virtual Pilot ACE this year. And we're up to date .. excited for release of Virtual SG-41 tomorrow!

10 Years of Virtual Colossus: 2024 The next sim I worked on was the M-209, an American version of the Hagelin C-38. A new resource, the CT scans of the machines at @DeutschesMuseum, meant I could very accurately model each part giving amazing detail! m209.virtualcolossus.co.uk

10 Years of Virtual Colossus: 2023 We have already completed Colossus and Lorenz SZ-42 but we only had Enigma working. It was time to learn about the Turing-Welchman Bombe and to begin building it into a fully working simulation. Find it at bombe.virtualcolossus.co.uk

10 Years of Virtual Colossus: 2022 The next machine to get 3D treatment was one I really enjoyed learning about, the Lorenz SZ-42. I completed a 2D version in 2017, but wondered if I could do this technological marvel justice. It ended up as one of my favourite sims I've ever done.

10 Years of Virtual Colossus: 2021 Now, with new 3D skills, it was time to attempt a machine that I'd always felt already had many great sims. And so, I created my most visited sim yet: Virtual Enigma both model I and M4, complete with radio & Morse key. enigma.virtualcolossus.co.uk

Two new sims were completed this yr and little did I realise that Virtual Typex would be the last in 2D. I started playing with a library called three.js and ended up recreating Virtual Colossus in full 3D! This was how it continue to today ...

10 Years of Virtual Colossus: 2019 In this year, I created a sim of E.R.N.I.E to celebrate the new 5th version. A hardware random number generator built in 1956 to find winners for the UK Premium Bonds. Designed by Harry Fensom who worked at the GPO Research Station, Dollis Hill

10 Years of Virtual Colossus: 2018 In 2018, I started looking at a BP cipher breaking machine from the American Signal Security Agency. This was Dragon, a relay machine built to drag a crib through a partially decrypted message from Colossus. A fascinating machine to learn about!

10 Years of Virtual Colossus: 2017 Having completed my Colossus sim, I became interested in how the machine that it was built to crack worked: the Lorenz SZ-42. There wasn't a working machine I knew of to see working and no videos online, so I began researching to build my own.

Can you believe that the Virtual Colossus project is now 10 years old! Today, I'm starting the countdown to the release of my latest simulation the incredible Schlüsselgerät 41. Each day, I'll show what I was working on from 2016 until we catch up to today!

Nearing the go-live date for Virtual Schlüsselgerät 41 .. or at least until I find there's yet another part that I didn't quite understand on this complex 1940s cipher machine. Here's the result & now back to final testing. Check out my new transparent case mode too!

Are you fed up with your old, slow labour-intensive Enigma machine? There is a better way .. and it's coming very soon to a browser near you! "jetzt muß die Enigma sterben" .. Now the Enigma must die. Schlüsselgerät 41 : sg41.virtualcolossus.co.uk @tnmoc.bsky.social @cryptomuseum.bsky.social

Good work @shayden1337.bsky.social for spotting a bug in my Lorenz SZ42c code! If you're not keeping up with your WW2 German cipher tech (tut), the SZ42c was to replace the SZ42a/b & wasn't ever completed. The info for how it ran comes from sparse TICOM reports. lorenz.virtualcolossus.co.uk

Make one of your New Year's Resolutions to visit The National Museum of Computing in 2026 :-)

Previously unknown instructions & settings sheets for the SG-41 have been discovered in Czech archives! Thanks to Eugen Antal, Carola Dahlke & Robert Jahn who published them in Cryptologia. I've been working to bring these into Virtual SG-41 @tnmoc.bsky.social @cryptomuseum.bsky.social

Sad news today, another veteran has been taken from us. Ruth Bourne, WWII Bletchley Park Bombe operator has died aged 98. She started working at BP aged just 18. Thank you for your service Ruth, we will remember you. news.sky.com/story/wwii-b...

The long slog to getting everything ready to release Virtual Schlüsselgerät 41 is well underway. Lots now completed on setup, tutorials and a few more bugs ticked off. No definite release date just yet as I keep adding to my to-do list, but it's very soon!

I've completed the last model for Virtual SG-41! It's ALL there & working, a 1940s technical marvel lives again! It's taken nearly a year; 378 models drawn by hand on CT scans from Deutsches Museum then animated with @threejs.org The end is in sight! @tnmoc.bsky.social @cryptomuseum.bsky.social

This week, I've started working on the paper tape reels which are held in the base of the SG-41. Two tapes can be fitted; one for the cipher text and one for the plain text to be printed. @tnmoc.bsky.social @threejs.org

Postbox in Newton Longville. We will remember them. #Rememberance #LestWeForget

We are getting so close now! This week sees the completion of the final part of the actual SG-41 mechanism; the ink cartridge & upper paper feed rollers. So is that it ... all done? Not quite, there's one important part missing. @tnmoc.bsky.social @cryptomuseum.bsky.social @threejs.org

New Rememberance Day postbox topper has been installed outside Bletchley Park / @tnmoc.bsky.social if you're visiting either. You can even press the drum to hear the noise!! I love this, remembering all the WRNS who served running the Bombe machines. Superb work Clare Reeves & Amanda Vines

The end is in sight for Virtual SG41! I've started into the paper feed block which I've been saving until last. This is the final big section to do and includes the mounting for the upper rollers, the ink cartridge, release button, paper tape reels and of course the paper itself.

JePu Machines have released a video in English & German on cracking an Enigma message using my Virtual Bombe and Enigma! It goes into huge amount of detail from encrypted message to solution. Nice work! Enigma Codebreaking with the Turing-Welchman Bombe! youtu.be/eHzsAoKXmZM?...

Virtual Schlüsselgerät 41 (SG-41). Another week and yet another mess of levers in the CT scans that do something .. but what? One of those cases where I'm just going to have to model & animate them in @blender.org & @threejs.org to find out. @tnmoc.bsky.social @cryptomuseum.bsky.social

hackaday.com/2025/10/24/t...

@microsiervos.bsky.social have posted a brief review of my Virtual Enigma. So glad they found it interesting. They did say "using the mouse and pressing buttons and switches isn't very intuitive". Any thoughts on how to make it easier or clearer what you need to do?

It's time to fill out some of the metalwork that holds everything together. It's no wonder the SG-41 weighed in at around 13kg especially as Germany were running out of lighter metals by the end of the war. @cryptomuseum.bsky.social @threejs.org @tnmoc.bsky.social

One of the final external controls completed, the F/L knob. This switches the SG-41 between Funktion (Operate) and Löschen (Clear). Clear mode releases the mechanism from the cipher wheels so they can be moved to a new position or reset. @tnmoc.bsky.social @threejs.org @cryptomuseum.bsky.social

Last month, I was thrilled to be invited to GCHQ in Cheltenham to see their rare SG-41 cipher machine for real! It has answered many questions about this amazing WW2 machine. I can now move on & complete my latest sim which will be released (hopefully later this yr) on my site virtualcolossus.co.uk

That is SO cute! Look, it's a little knitted Colossus I WANT ONE!

I've been continuing work on the paper feed mechanism after a very exciting visit which has helped a huge amount (more on that soon). The paper feed lever allows you to extract your printed cipher/plain text from the SG-41. @tnmoc.bsky.social @cryptomuseum.bsky.social