At 12:09 PM -0400 7/4/00, dmolnar wrote:
>Why wouldn't you just shred, melt, and scatter the CD if you want to wipe
>the info on it? Trying to nondestructively wipe a hard drive makes some
>sense, because you'd like to re-use the space...but CD-Rs are down to
>something like $5/CD and you can't re-use the used space anyway.
>What do you have in mind by "wipe" ?
>
>On Tue, 4 Jul 2000, David Honig wrote:
>
>>
>> Has anyone ever studied how hard it is to wipe a rewritable CD?
>> I'd imagine the STM tricks you can play with a magdisk also work,
> > with the right tip..
David H. was talking about a CD-RW, which is indeed rewritable. In a
drive which handles CD-RW disks, as my audio HHB 850 does, and as
many drives shipped with newer computer systems support. CD-RWs may
be rewritten millions of times.
And as for prices, CD-RWs are now under a dollar, and CD-Rs are about
40-50 cents.
BTW, I wouldn't expect the STMs to work well with CDs or CD-Rs or
CD-RWs. I know that the active layer of a CD is under a transparent
plastic layer. Not sure about CD-Rs and CD-RWs.
The STM probably can't see anything below the surface layer. On
magnetic disk drives, the magnetic domains are at the surface. In
chips, surface layers are usually stripped off.
Stripping off the surface layers of a CD-R or CD-RW should be
possible, with the right solvents.
(In at least some of them the writing process involves a thermal
shift, but not necessary a "burning" or ablation of the active layer.
This could be done under a protective coating layer. I'm sure many
folks here know how the writing is really done, and the Web should
have plenty of details.)
But of course I agree that there is no motivation to worry about
completely wiping a CD-RW, not when they are essentially disposable.
Easy enough to just break them into a bunch of pieces. (Whack 'em a
few times with a ball peen hammer...)
Snapping them in half may not be enough (reports that machines exist
to read fragments, and then the data fragments are stitched
together). The microwave trick ought to make even these machines
useless.
Or a solvent bath.
Probably the easiest is just to throw them into a fire.
--Tim May
--
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Timothy C. May | Crypto Anarchy: encryption, digital money,
ComSec 3DES: 831-728-0152 | anonymous networks, digital pseudonyms, zero
W.A.S.T.E.: Corralitos, CA | knowledge, reputations, information markets,
"Cyphernomicon" | black markets, collapse of governments.
