Re: Secure way to delete data in hard disc
Noah Pugsley wrote: Can I interest you in a pair of steganograpanties? Or for cooler weather, steganograpantaloons? are you suggesting there are messages hidden in pictures of beck's ass? the russians will be very upset. you should have taken thermite to those disks... Marco Peereboom wrote: They'll use it as torture material during the next krieg. On Wed, Oct 28, 2009 at 04:48:28PM -0600, Bob Beck wrote: What, you have pictures of my ass too? Obviously I must make something to write a random pattern over my entire ass so that It won't be recognized if some germans steal it.
Re: Secure way to delete data in hard disc
On 29 October 2009 c. 15:34:42 Jacob Yocom-Piatt wrote: Noah Pugsley wrote: Can I interest you in a pair of steganograpanties? Or for cooler weather, steganograpantaloons? are you suggesting there are messages hidden in pictures of beck's ass? the russians will be very upset. you should have taken thermite to those disks... Yes, we're very, very upset! Personally I 'm going to my two handy bears now, to drink vodka Putinka and think about using SA-20 as hard disc destroyer device... -- Best wishes, Vadim Zhukov A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?
Re: Secure way to delete data in hard disc
2009/10/28 Noah Pugsley noa...@bendtel.com: Can I interest you in a pair of steganograpanties? Or for cooler weather, steganograpantaloons? The problem with steganograpanties is that residual images of my ass are present *underneath* the panties - therfore if the offending Germans were to use high technology panty-removing chemicals (like ethanol) they could actually view the residual data present underneath the panties! As assuredly every german who is after my ass will possess this technology it behooves me to take adequate precatuions to obscure the data... I'm thinking kind of along the lines of the full-ass Kat-Von-D stenographic ass-stealthing tattoo...
Re: Secure way to delete data in hard disc
On Oct 27 16:12:54, Jordi Espasa Clofent wrote: $ dd if=/dev/urandom of=disk_to_delete $ dd if=/deb/zero of=disk_to_delete ?Do you think is it safe enough? I mean ?is it enough against the common recovery low-level data tools? Could we please stop this thread now and never bring it back? Thank you. (1) Your data is not that interesteing to anyone. Nobody cares about the data on your wiped disks and nobody will ever spend any resources trying to read it. (2) If you think you work with data that is so sensitive (which it isn't), then you surely have the money needed to buy a new disk. Just destroy the old disk and be done with it. (You can even have fun doing it.) (3) If you simultaneously (a) work with sensitive data that cryptoaliens might be interested in (b) don't have the money to buy a new disk then just dd if=/dev/zero of=/dev/sd0c which _is_ enough; nobody ever recovered jack shit from this, and never will, period. (4) If you come accross a slashdot article that says that with a million dollars and loads of time to spend you _can_ recover a byte here and there, don't mail it to nobody.
Re: Secure way to delete data in hard disc
Put the sensitive files in a pseudo-device vnd and then delete it. 2009/10/28 Jan Stary h...@stare.cz: On Oct 27 16:12:54, Jordi Espasa Clofent wrote: $ dd if=/dev/urandom of=disk_to_delete $ dd if=/deb/zero of=disk_to_delete ?Do you think is it safe enough? I mean ?is it enough against the common recovery low-level data tools? Could we please stop this thread now and never bring it back? Thank you. (1) Your data is not that interesteing to anyone. Nobody cares about the data on your wiped disks and nobody will ever spend any resources trying to read it. (2) If you think you work with data that is so sensitive (which it isn't), then you surely have the money needed to buy a new disk. Just destroy the old disk and be done with it. (You can even have fun doing it.) (3) If you simultaneously (a) work with sensitive data that cryptoaliens might be interested in (b) don't have the money to buy a new disk then just dd if=/dev/zero of=/dev/sd0c which _is_ enough; nobody ever recovered jack shit from this, and never will, period. (4) If you come accross a slashdot article that says that with a million dollars and loads of time to spend you _can_ recover a byte here and there, don't mail it to nobody.
Re: Secure way to delete data in hard disc
On Wed, Oct 28, 2009 at 08:52:20AM -0300, Gonzalo Lionel Rodriguez wrote: 2009/10/28 Jan Stary h...@stare.cz: On Oct 27 16:12:54, Jordi Espasa Clofent wrote: Could we please stop this thread now and never bring it back? Thank you. (1) Your data is not that interesteing to anyone. (...) (2) If you think you work with data that is so sensitive (which it isn't), then you surely have the money needed to buy a new disk. (...) (3) [Otherwise,] just dd if=/dev/zero of=/dev/sd0c (...) (4) [Ignore Slashdot articles on this subject] Put the sensitive files in a pseudo-device vnd and then delete it. I think you mean put the sensitive files in a pseudo-device vnd[1] and then delete _the key_. This, in fact, is the proper way to secure data. If your data is important enough that it needs to be deleted this thoroughly, you can't risk someone jacking your laptop/a disk out of your computer, either. Joachim [1] Or softraid crypto partition.
Re: Secure way to delete data in hard disc
Jordi Espasa Clofent wrote: Hi all, The subject is auto-descriptive ;) After reading a while about wiping [1] I think there's not a unique way to do it. Finally I've chosen a simple double-step method: First, $ dd if=/dev/urandom of=disk_to_delete and next $ dd if=/deb/zero of=disk_to_delete ?Do you think is it safe enough? I mean ?is it enough against the common recovery low-level data tools? [1] http://en.wikipedia.org/wiki/Data_erasure#Standards Slightly tangential to your scripting but have you considered pre-made tools? Overkill perhaps, but in Linux world there is secure-delete. srm (the command) +options will provide 38 wipes with randomised numbers as well as recursivity and a number of even more detailed capabilities. I haven't checked, but perhaps this tool exists in OBSD world as well?
Re: Secure way to delete data in hard disc
2009/10/28 Joachim Schipper joac...@joachimschipper.nl: On Wed, Oct 28, 2009 at 08:52:20AM -0300, Gonzalo Lionel Rodriguez wrote: 2009/10/28 Jan Stary h...@stare.cz: On Oct 27 16:12:54, Jordi Espasa Clofent wrote: Could we please stop this thread now and never bring it back? Thank you. (1) Your data is not that interesteing to anyone. (...) (2) If you think you work with data that is so sensitive (which it isn't), then you surely have the money needed to buy a new disk. (...) (3) [Otherwise,] just dd if=/dev/zero of=/dev/sd0c (...) (4) [Ignore Slashdot articles on this subject] Put the sensitive files in a pseudo-device vnd and then delete it. I think you mean put the sensitive files in a pseudo-device vnd[1] and then delete _the key_. Yes. This, in fact, is the proper way to secure data. If your data is important enough that it needs to be deleted this thoroughly, you can't risk someone jacking your laptop/a disk out of your computer, either. Joachim [1] Or softraid crypto partition.
Re: Secure way to delete data in hard disc
or you should realize that you and your data really aren't that important.
Re: Secure way to delete data in hard disc
On Wed, Oct 28, 2009 at 2:27 PM, Marco Peereboom sl...@peereboom.us wrote: or you should realize that you and your data really aren't that important. It's an issue about privacy, not self-importance. Pawn shops are full of stolen computers with other people's data. That's the *only* reason I overwrite and/or encrypt data. I would rather my family photos and tax documents not be sold to the highest bid. Brad
Re: Secure way to delete data in hard disc
I would rather my family photos Yeah, but I hike with bastards who take pictures of my ass and put it up on the internet for all to see.. So how can I delete the data from his web server? Is there some kind of remote bioctl --de-assify I could run?
Re: Secure way to delete data in hard disc
On Wed, Oct 28, 2009 at 01:44:00PM -0600, Bob Beck wrote: I would rather my family photos Yeah, but I hike with bastards who take pictures of my ass and put it up on the internet for all to see.. So how can I delete the data from his web server? Is there some kind of remote bioctl --de-assify I could run? It's awfully hard to unbreak an egg. Perhaps bobctl --ass-in-pants is what's needed? -- Darrin Chandler| Phoenix BSD User Group | MetaBUG dwchand...@stilyagin.com | http://phxbug.org/ | http://metabug.org/ http://www.stilyagin.com/ | Daemons in the Desert | Global BUG Federation
Re: Secure way to delete data in hard disc
On Wed, Oct 28, 2009 at 3:44 PM, Bob Beck b...@openbsd.org wrote: Is there some kind of remote bioctl --de-assify I could run? I'm not sure you can be de-assified.
Re: Secure way to delete data in hard disc
What in the world do stolen disks have to do with over writing the content on it? On Wed, Oct 28, 2009 at 03:34:07PM -0400, Brad Tilley wrote: On Wed, Oct 28, 2009 at 2:27 PM, Marco Peereboom sl...@peereboom.us wrote: or you should realize that you and your data really aren't that important. It's an issue about privacy, not self-importance. Pawn shops are full of stolen computers with other people's data. That's the *only* reason I overwrite and/or encrypt data. I would rather my family photos and tax documents not be sold to the highest bid. Brad
Re: Secure way to delete data in hard disc
On Wed, Oct 28, 2009 at 4:22 PM, Marco Peereboom sl...@peereboom.us wrote: What in the world do stolen disks have to do with over writing the content on it? The thread suggested svnd, softraid and cfs as a counter measure. An encrypted disk with no key is effectively an over written disk. How is that point lost on you? What is the difference between data patterns in an AES encrypted file and a file created with /dev/arandom as input? Brad
Re: Secure way to delete data in hard disc
Then the question asked should be How do I keep my data safe if it's stolen?, not How do I overwrote data on my not-stolen hard drive? But if somebody would actually be able to sell your family photos to the highest bidder, I'm extremely jealous. My family is not nearly so interesting. On Wed, Oct 28, 2009 at 4:38 PM, Brad Tilley b...@16systems.com wrote: On Wed, Oct 28, 2009 at 4:22 PM, Marco Peereboom sl...@peereboom.us wrote: What in the world do stolen disks have to do with over writing the content on it? The thread suggested svnd, softraid and cfs as a counter measure. An encrypted disk with no key is effectively an over written disk. How is that point lost on you? What is the difference between data patterns in an AES encrypted file and a file created with /dev/arandom as input? Brad
Re: Secure way to delete data in hard disc
* Bob Beck b...@openbsd.org [2009-10-28 20:57]: I would rather my family photos Yeah, but I hike with bastards who take pictures of my ass and put it up on the internet for all to see.. So how can I delete the data from his web server? Is there some kind of remote bioctl --de-assify I could run? yes: echo delete this pic of my ass: http:///; | mail -s asspic henning -- Henning Brauer, h...@bsws.de, henn...@openbsd.org BS Web Services, http://bsws.de Full-Service ISP - Secure Hosting, Mail and DNS Services Dedicated Servers, Rootservers, Application Hosting
Re: Secure way to delete data in hard disc
What, you have pictures of my ass too? Obviously I must make something to write a random pattern over my entire ass so that It won't be recognized if some germans steal it.
Re: Secure way to delete data in hard disc
2009/10/28 Henning Brauer lists-open...@bsws.de: * Bob Beck b...@openbsd.org [2009-10-28 20:57]: I would rather my family photos Yeah, but I hike with bastards who take pictures of my ass and put it up on the internet for all to see.. So how can I delete the data from his web server? Is there some kind of remote bioctl --de-assify I could run? yes: echo delete this pic of my ass: http:///; | mail -s asspic henning What, you have pictures of my ass too? :)
Re: Secure way to delete data in hard disc
They'll use it as torture material during the next krieg. On Wed, Oct 28, 2009 at 04:48:28PM -0600, Bob Beck wrote: What, you have pictures of my ass too? Obviously I must make something to write a random pattern over my entire ass so that It won't be recognized if some germans steal it.
Re: Secure way to delete data in hard disc
Can I interest you in a pair of steganograpanties? Or for cooler weather, steganograpantaloons? Marco Peereboom wrote: They'll use it as torture material during the next krieg. On Wed, Oct 28, 2009 at 04:48:28PM -0600, Bob Beck wrote: What, you have pictures of my ass too? Obviously I must make something to write a random pattern over my entire ass so that It won't be recognized if some germans steal it.
Re: Secure way to delete data in hard disc
2009/10/28 Marco Peereboom sl...@peereboom.us: They'll use it as torture material during the next krieg. I never thought that an OBSD dev ass could be so destructive!
Secure way to delete data in hard disc
Hi all, The subject is auto-descriptive ;) After reading a while about wiping [1] I think there's not a unique way to do it. Finally I've chosen a simple double-step method: First, $ dd if=/dev/urandom of=disk_to_delete and next $ dd if=/deb/zero of=disk_to_delete ?Do you think is it safe enough? I mean ?is it enough against the common recovery low-level data tools? [1] http://en.wikipedia.org/wiki/Data_erasure#Standards -- I must not fear. Fear is the mind-killer. Fear is the little-death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the fear has gone there will be nothing. Only I will remain. Bene Gesserit Litany Against Fear.
Re: Secure way to delete data in hard disc
Jordi Espasa Clofent wrote: Hi all, The subject is auto-descriptive ;) After reading a while about wiping [1] I think there's not a unique way to do it. Finally I've chosen a simple double-step method: First, $ dd if=/dev/urandom of=disk_to_delete and next $ dd if=/deb/zero of=disk_to_delete ?Do you think is it safe enough? I mean ?is it enough against the common recovery low-level data tools? [1] http://en.wikipedia.org/wiki/Data_erasure#Standards I have typically used rm -P against mount points and that has worked well for me. In one situation, someone at a customer site tried to read data from the erased directories using various commercial tools he had access to and failed. -- Vijay Sankar, M.Eng., P.Eng. ForeTell Technologies Limited 59 Flamingo Avenue, Winnipeg, MB, Canada R3J 0X6 Phone: (204) 885-9535, E-Mail: vsan...@foretell.ca
Re: Secure way to delete data in hard disc
On Tue, Oct 27, 2009 at 04:12:54PM +0100, Jordi Espasa Clofent wrote: Hi all, The subject is auto-descriptive ;) After reading a while about wiping [1] I think there's not a unique way to do it. Finally I've chosen a simple double-step method: First, $ dd if=/dev/urandom of=disk_to_delete and next $ dd if=/deb/zero of=disk_to_delete ?Do you think is it safe enough? I mean ?is it enough against the common recovery low-level data tools? Last year, I talked with a employee of a data recovery company about this. My question to him was: Is it enough to overwrite a partition or harddisk only once, or must i do this many times. His answer was: On all modern harddisk its enough to do it once (modern means all harddrives newer than 10 years!). Only one dd if=/dev/zero of=disk_to_delete is enough, but the real problem is a other: All harddrives have replacement blocks (to compensate failures). Old data can be in blocks that dd can't reach because they are marked as corrupt. The use of alternative blocks in a harddrive is manged by the drive itself. The OS can't reach these blocks. Simple forensic tools can't reach these blocks, too, but if you need really high security you must destroy your harddrive in a secure way (for example with a degausser). Regards Reni -- Reni Maroufi i...@maroufi.net
Re: Secure way to delete data in hard disc
It may not erase all data if the device can do block relocation and you don't have direct access to phisical blocks. But if data remains on hidden or discarted blocks it is still hard to someone else recover it. Jordi Espasa Clofent wrote: Hi all, The subject is auto-descriptive ;) After reading a while about wiping [1] I think there's not a unique way to do it. Finally I've chosen a simple double-step method: First, $ dd if=/dev/urandom of=disk_to_delete and next $ dd if=/deb/zero of=disk_to_delete ?Do you think is it safe enough? I mean ?is it enough against the common recovery low-level data tools? [1] http://en.wikipedia.org/wiki/Data_erasure#Standards
Re: Secure way to delete data in hard disc
On Tue, 27 Oct 2009 17:14:52 +0100, Rene Maroufi wrote Last year, I talked with a employee of a data recovery company about this. My question to him was: Is it enough to overwrite a partition or harddisk only once, or must i do this many times. His answer was: On all modern harddisk its enough to do it once (modern means all harddrives newer than 10 years!). Only one dd if=/dev/zero of=disk_to_delete is enough, but the real problem is a other: All harddrives have replacement blocks (to compensate failures). Old data can be in blocks that dd can't reach because they are marked as corrupt. The use of alternative blocks in a harddrive is manged by the drive itself. The OS can't reach these blocks. Simple forensic tools can't reach these blocks, too, but if you need really high security you must destroy your harddrive in a secure way (for example with a degausser). According to the Center for Magnetic Recording Research, 'Secure erase does a single on-track erasure of the data on the disk drive. The U.S. National Security Agency published an Information Assurance Approval of single pass overwrite, after technical testing at CMRR showed that multiple on-track overwrite passes gave no additional erasure.' http://en.wikipedia.org/wiki/Data_erasure See the secerase master command of atactl(8), to force ATA hardware that is -capable- of it to overwrite sectors that have previously been reallocated. Note: FREEZE LOCK is used by sys/dev/ata/wd.c at boot, so either a custom kernel or a power cycle of the drive will be needed to enable the capability. I don't know if SCSI devices have similar secerase capability.
Re: Secure way to delete data in hard disc
On Tue, Oct 27, 2009 at 04:12:54PM +0100, Jordi Espasa Clofent wrote: to do it. Finally I've chosen a simple double-step method: First, $ dd if=/dev/urandom of=disk_to_delete and next $ dd if=/deb/zero of=disk_to_delete I overwrite the disk 7 times with arandom, using the following command for x in `jot -s ' ' 7`; do dd if=/dev/arandom of=/dev/rDEVc bs=BLOCKSb ; done where DEV is the abbreviated disk name (for example, sd2), and where BLOCKS is the number of blocks to buffer. The speed of the operation is highly dependent on a proper choice of BLOCKS. I have used 128 with a 160GB external hard drive, and it takes approximately 16 hours to complete all 7 overwrites. You'll have to experiment to see what choice of BLOCKS is fastest on your hardware. I use arandom instead of urandom because it's slightly faster.
Re: Secure way to delete data in hard disc
On Tue, Oct 27, 2009 at 11:12 AM, Jordi Espasa Clofent jordi.esp...@opengea.org wrote: $ dd if=/deb/zero of=disk_to_delete ?Do you think is it safe enough? I mean ?is it enough against the common recovery low-level data tools? There is no evidence of over-written data *ever* being recovered. There is some theory in research papers that suggests it may be possible. There may be aliens and bigfoot and the NSA may be able to recover over-written data if you are of interest to them. OK, back to reality... the only suggestion I would make is to use arandom rather than urandom. You can cron that same command except output to a file rather than to the device to periodically overwrite the unallocated sectors. I do that. It kills a lot of the forensics tools that have the ability to recover deleted files, etc. Something like this on each partition: file=$$.random dd if=/dev/arandom of=$file sync rm -f $file sync Brad
Re: Secure way to delete data in hard disc
On Tue, Oct 27, 2009 at 11:12 AM, Jordi Espasa Clofent jordi.esp...@opengea.org wrote: After reading a while about wiping [1] I think there's not a unique way to do it. Finally I've chosen a simple double-step method: You take the hard drive out, you melt it, then you put a new one in. If your data isn't worth a $100 hard drive replacement, it isn't worth wiping, let alone recovering.
Re: Secure way to delete data in hard disc
Jordi Espasa Clofent wrote: ... $ dd if=/deb/zero of=disk_to_delete ?Do you think is it safe enough? I mean ?is it enough against the common recovery low-level data tools? Do just this, and no software-based recovery tool will ever see all your data again. You might get some pay-dirt if you can release the locked out bad blocks...and there are some...and y contain data that is useful in small chunks (and yes, some data is). If you think about the claims of data recovery from zeroed disks, they basically imply there is astronomical storage capacity in drives that is not tapped...and I do not believe the manufacturers have been holding out on us. It may be possible to get hints of data, but with massive error rates and gaps. If you are worried about recovering data after a single pass of writing zeros to the entire disk, you need to grind up or melt down the disk. If you are convinced there is (or will be) mysterious technology that can recover zeroed disks and your data is that interesting to these people, you don't know the abilities of it, so don't assume process X will keep your data deleted and never recovered. Nick.
Re: Secure way to delete data in hard disc
On Tuesday 27 October 2009 14:12:56 Brad Tilley wrote: On Tue, Oct 27, 2009 at 11:12 AM, Jordi Espasa Clofent jordi.esp...@opengea.org wrote: $ dd if=/deb/zero of=disk_to_delete ?Do you think is it safe enough? I mean ?is it enough against the common recovery low-level data tools? There is no evidence of over-written data *ever* being recovered. There is some theory in research papers that suggests it may be possible. There may be aliens and bigfoot and the NSA may be able to recover over-written data if you are of interest to them. OK, back to reality... the only suggestion I would make is to use arandom rather than urandom. You can cron that same command except output to a file rather than to the device to periodically overwrite the unallocated sectors. I do that. It kills a lot of the forensics tools that have the ability to recover deleted files, etc. Something like this on each partition: file=$$.random dd if=/dev/arandom of=$file sync rm -f $file sync Brad Saying that data has never been recovered is not true. I personally was involved with a disk disaster on a 10M RLL disk back in 1985 or so, and there was some--not all, but some--data recovered after being overwriten. Today's disks are far different. No, I don't think you can scoop up data en mass on a 500G disk. Wether multiple overwrites provides more security is a matter of debate. The real danger today are sectors that got mapped out which are bad, but could contain interesting or embaressing data; 512 bytes could hold a lot of stuff, like passwords. If you aren't using the disk for really sensitive data, erase it and be done with it. If its sensitive, have some fun by taking it apart (you can recycle the aluminium) and do something creative with the platters. I think Theo once took a blowtorch to some? That might provide entertainmant. --STeve Andre'
Re: Secure way to delete data in hard disc
On Tue, 27 Oct 2009 15:25:51 -0400, STeve Andre' wrote ...The real danger today are sectors that got mapped out which are bad, but could contain interesting or embaressing data; 512 bytes could hold a lot of stuff, like passwords. Perhaps what I already noted, in this thread, suggesting atactl's secerase master to overwrite those bad sectors got lost in the noise. http://marc.info/?l=openbsd-miscm=125666302218718w=2
Re: Secure way to delete data in hard disc
/dev/zero is like a bazillion times faster, and just as secure. -B p.s. Why do I have deja vu? http://archives.neohapsis.com/archives/openbsd/2008-09/1453.html http://archives.neohapsis.com/archives/openbsd/2008-09/thread.html#1215 On Tue, Oct 27, 2009 at 8:12 AM, Jordi Espasa Clofent jordi.esp...@opengea.org wrote: Hi all, The subject is auto-descriptive ;) After reading a while about wiping [1] I think there's not a unique way to do it. Finally I've chosen a simple double-step method: First, $ dd if=/dev/urandom of=disk_to_delete and next $ dd if=/deb/zero of=disk_to_delete ?Do you think is it safe enough? I mean ?is it enough against the common recovery low-level data tools? [1] http://en.wikipedia.org/wiki/Data_erasure#Standards -- I must not fear. Fear is the mind-killer. Fear is the little-death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the fear has gone there will be nothing. Only I will remain. Bene Gesserit Litany Against Fear.
Re: Secure way to delete data in hard disc
On Tuesday 27 October 2009 15:47:37 Josh Grosse wrote: On Tue, 27 Oct 2009 15:25:51 -0400, STeve Andre' wrote ...The real danger today are sectors that got mapped out which are bad, but could contain interesting or embaressing data; 512 bytes could hold a lot of stuff, like passwords. Perhaps what I already noted, in this thread, suggesting atactl's secerase master to overwrite those bad sectors got lost in the noise. http://marc.info/?l=openbsd-miscm=125666302218718w=2 But that assumes that the firmware on the disk will do just that. Someone, Toshiba I think had problems with that on travelstar type disks in the past. You can't truly trust being able to talk to an entire disk these days. Well, maybe, if you have a test jig for it, or have documentation on some hardware strap to throw to get into some interesting mode. Complexity gives rise to all sorts of tools, and possibly, mischief. --STeve Andre'
Re: Secure way to delete data in hard disc
Another route to securely erasing information is encryption. OpenBSD includes at least 3 systems for disk encryption (svnd, softraid, and cfs (ports)). I've personally used cfs and svnd, and as is usually the case on OpenBSD, both work nicely once you RTFM. (I should really write an undeadly article on how to use svnd.) If you erase/forget the keys (passphrases), then to the extent that you trust the crypto, the data is effectively erased. You can erase an encrypted disk (whether partition, filesystem, or file) this way even if the physical disk drive is broken and won't let you do 'rm -P' or other such overwriting. Moreover, if your hardware is still alive, there's probably considerable synergism between encryption and secure deletion: it seems likely that data recovery is much easier if the recovered data can be easily recognizable as such, rather than looking like random noise. Good crypto results in in the on-disk data before secure deletion looking like random noise, so it should make data-recovery harder. (To get any useful information, data-recovery would then have to be followed by somehow breaking the encryption.) ciao, -- -- Jonathan Thornburg [remove -animal to reply] jth...@astro.indiana-zebra.edu Dept of Astronomy, Indiana University, Bloomington, Indiana, USA Washing one's hands of the conflict between the powerful and the powerless means to side with the powerful, not to be neutral. -- quote by Freire / poster by Oxfam
Re: Secure way to delete data in hard disc
A paper has been published about the claim that you can recover data with an electron microscope (http://www.springerlink.com/content/408263ql11460147/). Unfortunately the paper is not available for free, but the summary is that after overwriting it 1 time you can't recover data anymore with hardware (not to mention software); only if you're very lucky you might retrieve some bytes. After 3 wipes you will only see random noise (on a magnetic level). So if you really want to be sure use either 3xdd or run dban.org. If your data is so valuable that an attacker will go the length (and has the resources) to retrieve bytes from reallocated sectors and then try to solve this puzzle, then you need way more protective measures than just encryption. See also http://en.wikipedia.org/wiki/Rubber-hose_cryptanalysis and http://en.wikipedia.org/wiki/Social_engineering_(security). regards, Robert Vijay Sankar wrote: Jordi Espasa Clofent wrote: Hi all, The subject is auto-descriptive ;) After reading a while about wiping [1] I think there's not a unique way to do it. Finally I've chosen a simple double-step method: First, $ dd if=/dev/urandom of=disk_to_delete and next $ dd if=/deb/zero of=disk_to_delete ?Do you think is it safe enough? I mean ?is it enough against the common recovery low-level data tools? [1] http://en.wikipedia.org/wiki/Data_erasure#Standards I have typically used rm -P against mount points and that has worked well for me. In one situation, someone at a customer site tried to read data from the erased directories using various commercial tools he had access to and failed.
