From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans Reiser Subject: Re: securely deleting files Date: Tue, 06 May 2003 14:37:26 +0400 Message-ID: <3EB79066.3000205@namesys.com> References: Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com In-Reply-To: List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Jason Holt Cc: reiserfs-list@namesys.com, Edward Shishkin Jason Holt wrote: >shred is a tool which is supposed to overwrite files so that they're >unrecoverable, even with fairly involved recovery techniques. > >But it isn't guaranteed to work - sensitive blocks may get moved around on the >physical disk, stored in journals, etc. > >So here's how I get around it: > >$ cat >sensitive >there's something sensitive in this file... > >$ rm sensitive >$ cat /dev/zero >foo ; sync ; rm foo # Fill up the disk, then delete. >$ cat /dev/urandom >foo ; sync ; rm foo # For the *truly* paranoid > >Now, a good friend of mine pointed out that part of the space on a filesystem >is kept aside just for root, so you may want to fill the disk up as root. >(Is this actually a concern? Can blocks which used to hold user data end up >being reserved?) > Yes. Edward, please put this in the faq, credit Jason, add a note that this will not protect against media scans using special equipment because writes and overwrites are not always equally aligned. > > >Also, if your sensitive file was in memory recently it might have been swapped >out, in which case it may still be in the swap partition. I have a program >which fills up all available *memory* as well, and I could post the source >here if everyone's interested. > > -J > > > > > -- Hans