Am Mon, 3 Apr 2017 16:15:24 -0400 schrieb Rich Freeman <ri...@gentoo.org>:
> On Mon, Apr 3, 2017 at 2:34 PM, Kai Krakow <hurikha...@gmail.com> > wrote: > > > > Just dd /dev/zero to the complete device. That purges everything you > > need: partition tables, boot sectors, contents: > > > > # dd if=/dev/zero of=/dev/sdX > > > > If it contains data you'd prefer not be recoverable you might want to > use shred or ATA secure erase. I wonder if shredding adds any value with the high density of modern drives... Each bit is down to a "few" (*) atoms. It should be pretty difficult, if not impossible, to infer the previous data from it. I think most of the ability to infer the previous data comes from magnetic leakage from the written bit to the neighbor bits. And this is why clever mathematicians created series of alternating bit patterns to distribute this leakage evenly, which is the different algorithms the shredder programs use. Do you have any insights on that matter? Just curious. > Shred overwrites the drive with random data using a few passes to make > recovery more difficult. Some debate whether it actually adds value. For a mere mortal it is already impossible to recover data after writing zeros to it. Shredding is very time consuming and probably not worth the effort if you just want a blank drive and have no critical or security relevant data on it, i.e. you used it for testing. But while you are at it: Shredding tools should usually do a read check to compare that the data that ought to have been written actually was written, otherwise the whole procedure is pretty pointless. As a side effect, this exposes sector defects. If you want to do this to pretend data has never been written to the drive, you're probably out of luck anyways: If you'd be able to recover data after a single write of zeros, it should be easily possible to see that the data was shredded with different bit patterns. The S.M.A.R.T counters will add the rest and tell you the power-on hours, maybe even amount of data written, head moves etc. (*): On an atomic scale, that's still 1 million atoms... -- Regards, Kai Replies to list-only preferred.
