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key disk

Posted on 1999-01-12
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Do you know a cheap method to phisically distroy a small part of a floppy disk? It should be used as a key disk for an application. Or do you know a source of cheap perforated (or in other way phisically marked) floppy disks?  
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Question by:neamtu
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by:neamtu
ID: 1133237
The method should work for a large amount of floppies...
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jhance earned 130 total points
ID: 1133238
There are two commonly used ways of doing this, software and hardware.

1) Software - This is most often done with a special "FORMAT" program that overwrites the disk format on a certain part of the disk.

2) Hardware - Here some physical method is used to ruin part of the disk surface.  Some use a laser to burn a small hole in the disk.  Others use a small hole punch to punch a small hole.

With software, you can control the exact track/sector on the disk to destroy.  With hardware, you can really only get a region, several tracks and no telling which sector(s).

BTW, this is a really LAME copy protection scheme.  Most disk copy tools on the market today will copy bad sectors as bad sectors over to the copy.
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Expert Comment

by:vikiing
ID: 1133239
The cheapest way is to puncture some tiny holes (with a hot needle) on disk surface, just in any place (and several places, while rotating disk into folder).

Once you've done that, you have to get "a map" of destroyed portions; a stupid program which tries to read (or format) all sectors of all tracks and reports those places where it's unable to access.

It's true that many copy programs can copy everything, but a physical damage, created in a random scheme, CAN NOT be EXACTLY duplicated. With that, you can distinguish between your "genuine" destroyed disk from a copied one.


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Author Comment

by:neamtu
ID: 1133240
Did you try the solution with the hot needle? I do not intend to destroy the user's floppy drive head. If you tried it, how small the needle was and how did you manage the deformation of the floppy surface when you made the holes?
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by:vikiing
ID: 1133241
I've tried the hot needle approx. 6 years ago, when 5 1/4 floppies were the rule. Although I didn't work with 3 1/2, I see no differences.

A common broderie needle suits OK; put it directly on a gas flame (not a candle, because it gives you "dirty" fire), and when it is well red, it's simply to touch disk surface and remove it quickly.

Needle must be hot enough in order to not need to make pressure, precisely to avoid disk deformation. If making so, the sole fact of touching disk makes the hole without leaving rests of plastic debris. Anyway, if you see the hole has a thicker border, one of the points of a razor blade will complete the job. You don't need to pass the needle all the way long; just the point is enough to destroy a one or two tracks.

I remember someone developed a special drive, with a tiny laser beam into it, to burn tracks with absolute precision. Of course, that was a headache for pirates and hackers, who saw an unsolvable problem to pass over. They went to justice and, arguing laser left some tiny particles of carbon debris, which (they said) damaged the head, they finally won the battle, and laser drives were prohibited.

I've used that method during a couple of years (making about 100 diskettes) with no problem. And as hole has no debris to free into drive, floppy head will not suffer.

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