<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type"> </head> <body bgcolor="#ffffff" text="#000000"> Hi, Amedee! On 21/12/2009 14:36, Amedee Van Gasse (ub) wrote: <blockquote cite="mid:f0c2dda67892be2aec1cc3395cf38a77.squirrel@amedee.be" type="cite"> <pre wrap="">On Mon, December 21, 2009 10:04, Gilles Gravier wrote: </pre> <blockquote type="cite"> <pre wrap="">The problem with these commands, is that you're not really helping... Forensics tools will read below one or more levels of re-write. You need to do this several times in a row... and, more importantly, you need to use special data patterns that will actually make reading shadows of former data harder if not impossible. There are standards for that. And they do not involve writing random data or zeros, but actual specific patterns. </pre> </blockquote> <pre wrap=""> Hi! Can you name a few of those forensics softwares? + documentation about how they actually work and what the conditions are to get usable results? Preferably something recent, not some outdated standards published by the USA government (I don't trust foreign governments on that subject, I don't even trust my own government). </pre> </blockquote> The standards are still there, like DoD 5220.22-M (3 passes)... and more also. See the list on my previous post. <blockquote cite="mid:f0c2dda67892be2aec1cc3395cf38a77.squirrel@amedee.be" type="cite"> <pre wrap="">Or are you talking about disassembling a hard disk in a dustfree room and reading the actual magnetic patterns with a scanning probe microscope to get a palimpsest image of the disk? </pre> </blockquote> That's why you want to have many overwrites... or a full gaussian demagnetization (there are machines to do that)... Of course if you want to re-use your drive... overwrites is the way to go. Or assured delete. <blockquote cite="mid:f0c2dda67892be2aec1cc3395cf38a77.squirrel@amedee.be" type="cite"> <pre wrap="">If you're afraid of a casual hacker or even most law enforcement (I have played a bit with the forensic tools cd of our Federal Computer Crime Unit), overwriting it 10 times with random data will be more than enough. </pre> </blockquote> Random data is not enough... If you're going random, you might as well do one pass. If you want to benefit from multiple passes, you should use one of the patterns created for that. <blockquote cite="mid:f0c2dda67892be2aec1cc3395cf38a77.squirrel@amedee.be" type="cite"> <pre wrap="">It's only when you're afraid of *very* large organisations (intelligence agencies, multinationals) that procedures with special RLL patterns are worth the effort. But then again, if your data is really *that* important, you should physically destroy the disk. Throw it in the blash furnace of a steel mill. But that's just my humble opinion... </pre> </blockquote> True. <blockquote cite="mid:f0c2dda67892be2aec1cc3395cf38a77.squirrel@amedee.be" type="cite"> <pre wrap="">Another argument, if you have 10 KB of sensitive data on a 500 GB drive, the chances that it will be found are close to zero. The data density is just too high. And then there is the case of perpendicular recording. </pre> </blockquote> Unless there is clear text in that block that allows a sector search to find it... <blockquote cite="mid:f0c2dda67892be2aec1cc3395cf38a77.squirrel@amedee.be" type="cite"> <pre wrap="">What about flash memory? To shred data on a NAND memory device you will need something that is covered by patent WO/2009/009052</pre> </blockquote> Or you use assured delete... Gilles. <div class="moz-signature">-- <meta content="text/html; charset=ISO-8859-1" http-equiv="content-type"> <title>Signature Home Chastity</title> <meta content="Gilles Gravier" name="author"> <div style="text-align: left;"> <table style="text-align: left; background-color: rgb(102, 102, 102); width: 500px; height: 73px;" border="1" cellpadding="3" cellspacing="3"> <tbody> <tr> <td style="text-align: center; vertical-align: middle; background-color: rgb(204, 204, 204); white-space: nowrap;"> <div style="text-align: center; background-color: rgb(204, 204, 204);"><tt>Gilles Gravier = <a href="mailto:Gilles@Gravier.org">Gilles@Gravier.org</a></tt> </div> <div style="text-align: center; background-color: rgb(204, 204, 204);"><tt>ICQ : <a href="http://www.icq.com/whitepages/about_me.php?Uin=77488526">77488526</a></tt> <tt> || </tt><tt>MSN Messenger : <a href="http://members.msn.com/Gilles@Gravier.org">Gilles@Gravier.org</a></tt><tt> </tt>Skype<tt> : <a href="callto://ggravier">ggravier</a></tt><tt> || </tt><tt>Y! : <a href="http://profiles.yahoo.com/ggravier">ggravier</a></tt><tt style="font-weight: bold;"> || </tt><tt>AOL : <a href="aim:goim?screenname=gillesgravier">gillesgravier</a> </tt><tt>Aka-Aki : <a href="http://www.aka-aki.com/profiles/view/ggravier">ggravier</a></tt><tt> </tt><tt style="font-weight: bold;">|| </tt><tt>PGP Key ID : <a href="http://pgp.mit.edu:11371/pks/lookup?search=0x8DE6D026&op=index">0x8DE6D026</a> "Living on Earth is expensive, but it does include a free trip around the sun." </tt> </div> </td> </tr> </tbody> </table> </div> </div> </body> </html>