From:	Rocco Loscalzo <rocco AT lawless-games DOT com>
Newsgroups:	comp.games.development.programming.misc,comp.os.msdos.djgpp
Subject:	Re: Disk Serial Numbers
Date:	Thu, 28 Oct 1999 23:35:02 +0100
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Ben Davis wrote:
> 
> This may be slightly off topic, but please bear with me...
> 
> I have noticed that some floppy disks have serial numbers; the serial number
> appears when I type 'dir/w'. Can someone confirm that the serial number of a
> floppy disk cannot be changed through software (if at all), and explain how
> to write a program which reads it? (After all, 'dir' does it, so it must be
> possible.)
> If there is a DJGPP function to do this, I would like to know. Otherwise I
> will use whatever low-level DOS Interrupts or whatever are necessary.
> 
> Ben Davis

Copy protection via the serial number, or anything else written to the
boot sector for that matter, is not of any real use. If you want to do
something that will 'foil' your moderate hacker, one strategy is to
format one or more tracks of the disk in a different, even non-standard
way, and then write some known information to this different area. When
it's written, it will need to be 'told' how it should be read. You can
then use this technique to ensure that the disk has not been duplicated
in a normal way. That said though, there will be much better hackers
around for which there is probably no escape.

One of the other posts mentioned Ralf Brown's interrupt list. This is
truly excellent albeit rather old stuff now. Plus, any good book on
MS-DOS should cover what you need to do.

-- 
Cheers,
Roc (CyberFrog) 8:)
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