Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

That photo of Colossus

tnmoc.org

Post reply on HN
Print view View original

21–30 of 37 posts

Re: That photo of Colossus

#21

Post by Animats »

mirimir wrote: post #17
ngcc_hk wrote: post #10

Earlier quoted context omitted.

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.

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.

Re: That photo of Colossus

#23

Post by mirimir »

Animats wrote: post #21
mirimir wrote: post #17

Earlier quoted context omitted.

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.

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?

Re: That photo of Colossus

#25

Post by mathieuh »

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.

Re: That photo of Colossus

#26

Post by spongeb00b »

mathieuh wrote: post #25

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 im…

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.

Re: That photo of Colossus

#27

Post by Waterluvian »

mathieuh wrote: post #25

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 im…

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'".

Re: That photo of Colossus

#28

Post by arethuza »

mirimir wrote: post #17
ngcc_hk wrote: post #10

Earlier quoted context omitted.

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.

Re: That photo of Colossus

#29

Post by mathieuh »

Waterluvian wrote: post #27
mathieuh wrote: post #25

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 im…

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

Re: That photo of Colossus

#30

Post by lb1lf »

mirimir wrote: post #23
Animats wrote: post #21

Earlier quoted context omitted.

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.

Post reply on HN