So that data would never be read again. People say the FBI could get data from a broken CD if they wanted to but that's only if they have %100 all the pieces and they fuse it back together. I ask because a friend of mine has bad anxiety he had a rootkit and keyloggers and he keeps thinking what if he accedwntly backed them up will backing up he's files on CDs . he said he broke all the CDs figuring they would never be placed in a PC and no PC would have a chance at getting the keylogger or rootkit again. But he says when you break a CD in half the metalic stuff data is saved on goes everywhere and some stuck to he's hands so he's all ways paranoid a piece of the memory stuff will be up he's hand and he will touch a CD making the piece stick to the CD and if he places it in a PC it will be read. I told him he's nuts but he says he can't shake the idea off
Words fail me.
So are you asking if the particles on your hand can be read or if the FBI can actually reconstruct a CD, if they tried very hard?
I believe your initial diagnosis of him being 'nuts' is correct. I don't believe particles from a damaged CD that remain on his hand could be read onto his computer via….osmosis?
But he says when you break a CD in half the metalic stuff data is saved on goes everywhere and some stuck to he's hands so he's all ways paranoid a piece of the memory stuff will be up he's hand and he will touch a CD making the piece stick to the CD and if he places it in a PC it will be read. I told him he's nuts but he says he can't shake the idea off
He's partially nuts – it's just that he doesn't know how many levels of data structure that have to fit together for it to work as he fears.
First, a CD spins sufficiently fast that it's extremely unlikely that a piece of metal from a cracked CD would stay on. So, we start with an a large improbability.
Next, if it did stick, it sticks on the CD surface. The laser that reads the CD track is not focused on the surface but on the reflective metal layer, some way into the CD. And its the difference in height between the pits and the lands that make the whole thing work – that's 100 nm, roughly. The distance between the metal layer and the surface is very roughly 0.5 - 0.6 mm – and that would be seriously out of focus in this environment. (Added That was wrong – that's DVD. On a CD it's the full 1.2 mm of the CD thickness.)
I would say it's very, very close to a technical impossibility to get any information of such a bit of stuck metal, out of the laser focus it would be interpreted as a 'hole', and any read would either fail, or if error correction was successful, restore the original content of that part.
But let's go on assume that the read, against all odds, did succeed – perhaps the laser optics does some kind of extreme autofocusing, which is capable of dealing with abrupt focus transitions. Then, the piece of track or tracks that are on that piece of metal must be aligned with the tracks it covers. If they don't align, they won't be read (entirely). Chances of that are pretty small – the metal piece can end up in just any orientation.
It can even end up upside down, which means the data would be read backwards. Let's say it's a 50-50. Not that it matters much in the overall scheme of things, as lands and pits are not 'reversible' in this sense – as far as I understand things. So 50% of another technical impossiblity.
So, assume it managed to stick on right side up. Now, the data in a CD track follows certain rules the transitions between pits and lands must follow certain rules if they are broken – and chances are very, very good they would be – that piece of track won't read correctly. (non-return-to-zero encoding)
And if it did, data is not sequential, but scattered in time (this helps error recovery) – so it's not enough that the transitions are OK, the scattered parts must also fit together. (eight-to-fourteen modulation ) It's many times more probable that any 'break' in this sequence would trigger error recovery operation, and the part of the track that is 'covered' by this stuck on metallic piece would be recovered, than the data on the metal piece would be 'spliced into' the data stream correctly.
(Added And we should have the Solomon-Reed encoding somewhere here, too.)
Sum up one technical or practical impossibility after another multiply them together and you end up with a probability that is infinitesimally small, and makes it essentially impossible that this particular scenario would work. Unless you happen to have a infinite improbability drive …
You also seem to ask about a jigsaw puzzle of these pieces being put back again … ever worked with gold leaf? you can about work a whole 5x5 cm piece if you know what you're doing, and don't have any stray draughts – don't breathe or even move too quickly! – or the whole piece will either fly away, or tear. Imagine a jigsaw of small pieces of this material that has to be put back together in exactly the right order.
Um … no. The economics of the procedure is against it a lot of people would be stuck doing just one single case. They would be far more more economically effective working normal cases instead.
(I'm fairly sure I may have messed some parts of CD architecture up – but unless I messed everything up, it won't affect the result significantly.)
Added And now I see your title says 'cracked in half' … which is something else.
Actually, extracting information out of separate halves may be doable. Idea scan each half, much like a document scanner, so that the pits and lands can be identified.
Extract data out from each half – I'd guess chances are pretty good to restore the parts that are well 'inside' each piece. It would be a bit like getting data from a file systems where 50% of the clusters have gone.
Still, it probably would require some pretty good scanning equipment, and I can't really see that such equipment would be useful in other situations. So again … don't really think it would practical.
But CD shredders do cross-cutting …
I think your mate is spot on. They are dangerous things virus'. I suggest if he has broken a CD without taking the proper precautions a wearing double gloves in a well-ventialted room (anti-static wrist band as well of course) he needs to consult his local doctor to report the virus so that it can be isolated.
On the other hand if he suspects it is actually a root kit then that is a matter to be dealt by a dentist, preferably a specialist in digital orthodentistry.
Be careful out there.
I would go further roll , re-stating, quoting myself 😯 how, once set aside the nonsense about particles sticking to fingers and being later transferred on other CD's and later being read accidentally by a common CD/DVD reader, no info is recoverable from a broken CD, even if you have all fragments of it
http//www.forensicfocus.com/Forums/viewtopic/t=9811/
http//www.forensicfocus.com/Forums/viewtopic/t=10154/
http//www.forensicfocus.com/Forums/viewtopic/p=6562618/#6562618
The answer is that - at the state of the art - (and EXCLUDED what the National Security Agencies may have in their secret labs) a single, neat or rough, cut through a CD/DVD, passing through the center hole and thus dividing the CD in two pieces is enough, even if you have both pieces, to avoid the reading of any data from it with any commercially available device.
This doesn't mean that it is "impossible", only that noone has ever documented the successful recovery of any data from such a damaged CD/DVD.
jaclaz