That photo of Colossus | Hacker News Reader

That photo of Colossus

tnmoc.org

131 pointssohkamyung33 comments

I'm not sure of the prior history, which may affect my appreciation for it, but as far as I know, what happened with Colossus was that they were aware the cipher seeds changed each day, and they obtained an Enigma machine so they could decipher Enigma codes, it was the fact there was a reliance on intercepting the day’s seeds, or having a spy/double agent leak them which meant cracking Enigma messages was usefully impossible within the timeframe in which military strategies could be formulated and altered.

So Colossus brute-forced every combination of Enigma symbols and seeds until it got something that made sense.

Colossus did this in hours, instead of the weeks waiting for code breakers with brain-power and persistence alone, and to my knowledge this was the first application of computers as we recognise them today.

I find it amazing that Turing sat and thought to himself, in the 1940s, "I bet I can make a machine that does this", and built the thing, and built it so well it deciphered the codes within the day, before the seeds changed. I'm sure a brute force on paper existed before Colossus, but Colossus is a stunning, visceral machine to watch.

Seeing Colossus operating is an absolute experience for computerphiles. There's something more soulful (in the laïc sense) in seeing a big wall of spinning disks and tape and reassuring thuds and whirs than in modern solid-state computers.

Small correction, Colossus was designed to break the Lorenz cypher (which was considerably more complex than Enigma). The machine itself was designed by Tommy Flowers (not Turing), who was a post office worker who had previously worked with vacuum tubes and thought it would be possible to build a programmable computer with them. After the war Flowers applied for funding to build a similar machine (Colossus being top secret) and was denied on account of the idea being impractical.

The machine Turing is famous for his work on was Bombe, which was designed to crack Enigma.

Can't edit my comment now that it has children (I think that's how the logic works) so upvoting you for visibility.

I’ve visited the rebuilt Colossus at TNMOC a couple times now. I think the usually turn it on at noon, I like to get there just before and stand there in silence looking up at it, and then listening to the thrum, ker-chunk and whir at it comes to life is like nothing else.

Wasn't it that they could feed in certain known possible letters to cut down on the number of options? Something like, "this encrypted segment is usually the weather so the s is probably the word 'sunny'".

I'm shamefully unsure of how it works exactly, but it's possible they had subroutines that looked for phrases like "weather", "movement", "troops" etc. to try and speed up the brute force.

https://www.youtube.com/watch?v=9HH-asvLAj4

Here's a really good video I've watched before and since forgotten the details of which explains Colossus and its context

Some enigma operators had flourishes that the code-breakers could pick up on. Starting or ending a lot of messages with "Heil Hitler" was also a factor IIRC

Yes this is correct. The resulting ciphertext from Enigma was sent by manual Morse transmission. Morse operators can identify others by thier “hand” which is the Morse equivalent of the sound of your voice in speech.

Earlier in the war the Germans typically sent their call signs in plaintext. Many of the intercept operators in the “Y stations” in the UK became familiar with the “hands” of various German operators. Later in the war the Germans started encrypting their call signs, but Bletchley was generally able to distinguish them by the intercept operator’s familiarity with the “hands” of the German Morse operators.

That's a fantastic story. At my grandfather's funeral (he was an electronic and medical researcher who developed early foetal pulse monitors as well as the respirators now used to treat sleep apnoea) it gradually became apparent that I was chatting with two of the people who'd installed one of New Zealand's first computer systems. Incredible conversation but it only lasted half an hour and then off they went. I wish I'd had a chance to record some of it.

I guess one of my favorite movies took its name from this?

https://www.imdb.com/title/tt0064177/

Damn, high-speed paper-tape! I used an early DNA sequencer controlled by paper tape, and it's touchy to keep the tape from breaking. I think that they migrated the mechanism from looms. The belt drives also remind me of the water- and steam-powered eras.

Paper tape is indeed a descendant of the Jacquard Loom.

https://en.wikipedia.org/wiki/Jacquard_loom#Mechanical_Jacqu...

First thing i think of. In fact the Ibm for quite a while can be considered as a punch paper card company (and their first antitrust is about their use of that to meter the computer use)

Paper tape was even more of a pain than cards were. Or at least, in different ways. Cards jammed, it's true. But you could easily replace damaged cards. Repairing damaged tape was iffy. On the other hand, one might drop a stack of cards. So some of us would number the cards in pencil. Carefully, and lightly.

About 1995 I remember speaking to a guy who had programmed using a hand drill...

He worked for a company that did industrial control systems and one plant (a steel mill I think) had a very old system controlling it that booted from tape. However, as it was very old the paper tape had long since worn out and had been replaced with a sturdy length of leather. He needed to make an alteration to the boot process so had to resort to the hand-drill.

Colossus had an endless loop of paper tape zipping by to present patterns for matching. It wasn't a general purpose computer. It was a key-tester, like a Bitcoin miner.

Ah. So they could have many copies of those tapes, and quickly replace ones that broke, right?

I seem to recall reading in either Kahn's or Sebag-Montefiore's book on Bletchley Park that one early failure mode of the tape was that it was run through the reader at a fast enough pace to occasionally catch fire.

Oops.

Basic problem of early computing: no good memory devices. IBM had electronic arithmetic before WWII, as an experimental tube multiplier. But nobody had a memory device that didn't require lots of parts per digit or bit. Hence cards and paper tape.

I had an old friend who worked with 60s era mainframes. You had a decent enough CPU, but no memory. And very slow storage.

So you worked out some set of instructions with total execution time comparable to storage I/O. And put that into ~firmware. Then you read data from one device, and wrote data to another device. And kept repeating that, with other instruction sets, until you were done.

That's not very different from current usage. Except that most intermediate results go into various sorts of memory. Or /tmp devices, if there's too much data for memory. And at the CPU level, instruction sets are just about as small.

But the point is that one could process ~huge amounts of data. Many GiB, as I recall. Just very slowly, with lots of thrashing tape.

And now one can use the same approach, except with clusters. And process humongous amounts of data.

Any idea what this DNA sequencer was as it must have been really early. I can't think of any sequencer even in the 1980s that used paper tape.

This was in the early 1970s. It was more or less a prototype.

A decade ahead of the industry! Was that Hood’s early work at Caltech?

Yeah, that was it.

I’ve seen the Colossus replica running at Bletchley Park. It was quite impressive to see.

Let us also not forget the Forbin Project.

I came here for exactly this comment.

Thank you.

If interested in WW2 Allied code breaking you may want to watch the BBC documentary Station X - The Code Breakers of Bletchley Park on Acorn tv

Simon Singh's "Code" also has an approachable description of the decoding process.

Both museums at Bletchley are just fantastic... can’t wait to get back there sometime again in the future!

Where’s the new photo?

It's in the Photo Gallery to the right of the main photo.

“D. Well I was quite angry as we had kept it a secret for so long. There is me now in all the books. I didn’t like that!” Cannot stop laughing. Rip Dorothy. Uk has a fighting chance with you girls working in that industry. Would have to play a visit.

Guess no one would catch me as a chinese spy to copy that ba.

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