-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 At 01:44 PM 7/4/00 -0400, Tim May wrote: > > >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 The data layer is indeed under the clear coating. There was a Popular Science article several years ago, (read, late 80's, or early 90's), on the technology behind all three, and it's been that long since I read the thing, so bear with me. Since the data layer is under the clear surface, marring the surface won't cut it. I work at Hasting's, and WE sell materials for removing scratches. (A co-worker who used the stuff describes it as like car wax, so I have to assume it's more of a filler with the same index of refraction as the coating.) A message here, sometime between 6 months and a year ago, described the new FBI lab in New York having a lab for reconstructing broken disks, so simply breaking it up can probably be considered about as effective as shredding a document. With time it can probably be pieced together and read. Thus snapping it in two (or three, or four,) pieces probably isn't enough either. Reformatting a CD-RW, a couple-three times, and writing an image filled with output from the RND of the computer might be okay. This would probably take too long, however. A program could probably be written to do this, while your out, but for expedience, probably shattering the disk, then dropping into a metal container with a few feet of loose paper and a match would probably be the only way. Or, if you're in a shop, one disk data side up, one angle grinder, and a little tape, could probably reduce a disk fast enough that the complete resources of the FBI, from forensics to data-recovery (whatever they're called), could put it back together again, since, unless they collected a fairly large percentage of the pieces for any given track, they would probably be unable to be sure of the contents of more than one word of data. Of course, you could just keep all information on the disk encrypted, which will be the next probable comment, considering the pattern of this list. Next question. Under stress conditions, such as those involved in a suprise raid, how fast can the average individual reduce 1 CD-ROM to 16 pieces, (likely the smallest that can be handled without something for extra leverage, like pliers), using only a door jamb or mostly closed desk drawer, and then place on an open flame stove, or in a microwave? How fast can a food-processor reduce the same disk, (or two halves through the feed chute) into mulch, and then how fast to transfer that to a hotplate or toilet? Can either process be done in the length of time that it takes to wind up for one knock with a battering ram? And can a common residentual door be expected to last for more than one? Good luck, Sean -----BEGIN PGP SIGNATURE----- Version: PGPfreeware 6.5.1 for non-commercial use <http://www.pgp.com> iQA/AwUBOWJnCZHDoiHtqFDZEQL/OQCfd4VBeQV2xm2sLCsh5VSzomywRD4Anj4y eQ98WUmuED8wrMcWqA66H6EA =HzvZ -----END PGP SIGNATURE-----
