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The cleverest floppy disc protection ever? Western Security Ltd

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Re: The cleverest floppy disc protection ever? Western Security Ltd

#11
post #5

Who recalls the provenance of this old legend about the fellow who challenged his pal to decode a certain floppy? It was a bog-standard DOS boot disk (IIRC) that he could put in his machine and boot normally. But his pal put it in his computer and... nothing doing, no boot. Analysis of the floppy availed not. The challenge went unmet. What did our hero do to make the floppy? .esrever ni nups evird eht os ytiralop eti…

The spoiler format is perfectly adapted to the content :)

Re: The cleverest floppy disc protection ever? Western Security Ltd

#13
post #5

Who recalls the provenance of this old legend about the fellow who challenged his pal to decode a certain floppy? It was a bog-standard DOS boot disk (IIRC) that he could put in his machine and boot normally. But his pal put it in his computer and... nothing doing, no boot. Analysis of the floppy availed not. The challenge went unmet. What did our hero do to make the floppy? .esrever ni nups evird eht os ytiralop eti…

Would that work for CDs too?

Re: The cleverest floppy disc protection ever? Western Security Ltd

#15
post #6

I don't think it was mentioned, but I wonder if the mains power fluctuation (voltage or hz) would affect drive sector length / rpm also? So even the same drive couldn't produce a high fidelity copy of one of these discs if the power input was different.

I'm not sure how good the power supplies were back then, but ideally you'd have no idea what the mains power was at the drive since the power supply converts everything to DC. Now of course rectification isnt perfect so there were probably some artifacts, but enough to detect on the disk? Seems unlikely.

Re: The cleverest floppy disc protection ever? Western Security Ltd

#16
IIRC, Quaid software's Copywrite on the PC was able to reliably duplicate weak bits, and had a companion called "zerodisk" which would -- in cooperation with marks left by Copywrite -- emulate laser holes.

I remember at least one copy protection system I analyzed, which get "free reign" into writing tracks, by configuring the drive to write just one huge sector per track (which ended up being longer than the track), end encoding the sector gaps "in band" which later became "out of band" because the main track header was overwritten (and an "in band" one became out-of-band).

It was interesting, but I have no nostalgia for that.

Re: The cleverest floppy disc protection ever? Western Security Ltd

#17
post #5

Who recalls the provenance of this old legend about the fellow who challenged his pal to decode a certain floppy? It was a bog-standard DOS boot disk (IIRC) that he could put in his machine and boot normally. But his pal put it in his computer and... nothing doing, no boot. Analysis of the floppy availed not. The challenge went unmet. What did our hero do to make the floppy? .esrever ni nups evird eht os ytiralop eti…

Hint: If the hero had tried a Plan 9 boot disk on his machine it would have booted into Inferno :-)

Re: The cleverest floppy disc protection ever? Western Security Ltd

#18
Slightly off-topic, but since when were floppies referred to as "disc", as opposed to "disk"? I thought it was from Diskette?

Is it a language / region thing?

Optical discs were "disc", but at least growing up in the UK in the 80s/90s with DOS/Windows, I'm pretty certain I remember them always being "disk" for floppies?

Am I misremembering?

Re: The cleverest floppy disc protection ever? Western Security Ltd

#19
post #6

I don't think it was mentioned, but I wonder if the mains power fluctuation (voltage or hz) would affect drive sector length / rpm also? So even the same drive couldn't produce a high fidelity copy of one of these discs if the power input was different.

Seems like intentionally randomizing this would be a good way to mass produce fingerprinted copies - in addition to any variants in the media.

Re: The cleverest floppy disc protection ever? Western Security Ltd

#20
My favorite copy protection was on some games I had (I want to say they were Microprose games? But I could be wrong) where they would cut the hole in the disk just slightly bigger, and then take advantage of the fact that in DOS you could talk directly to the hardware to convince the read head to go just a little too far. Then it could read the magic 41st track to load the game, but no disk copy program could copy it.
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