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New Tech In Data Retrieval
Johnath writes: "Story over at Science News about magnetoresistive microscopy, which allows very high-res inspection of magnetic media. The article is touting it primarily as a forensic tool, and gets me thinking -- how many passes of write-over-with-random-data are now required to securely delete a file?"
...which just proves that the only REAL way to destroy your confidential data is with a BIIIIIIIIG hammer.
{shhhhh... the froggies are asleep.}
spam-proofing?
.................................................
Could we now recover the erased portion of the watergate tapes? Sure it is analog, but that would only make the task more difficult, not impossible.
Unless you've got a magnetoresistive microscope to test your "erased" tape or disk with , you can't really say. Of course, if the data is sufficiently encrypted in the first place, it really doesn't matter if it can be retrieved from tape scraps etc.
Still, the equipment necessary to recover a 7 times read/write-over pass is probably out of the price range of all but the most well-funded groups; I wouldn't worry too much about it, especially if you use an encrypted file system and encrypted swap files.
Free music from Jack Merlot.
Similar technologies have been around for a few years that could reconstruct the data stored on a disk from magnetic "shadows". This technology just gives them a much higher resolution method to do the same thing.
At any rate, the one true way to prevent anyone from seeing what's on your disk is to encrypt it- even if they recover the data, there's not much that can be done with it!
... but if they've overwritten that area they show with the NIST logo once, that's some rather serious degradation from just one pass- and therefore, 5 or so passes ought to do the job.
But that's just my seriously uninformed guess.
--Perianwyr Stormcrow
What we call folk wisdom is often no more than a kind of expedient stupidity.-Edward Abbey
If you're up against the kind of resources that can and will do this sort of thing to get your data, then you'll have to resort to more drastic means, like sticking the hard drive in a really hot furnace. That should do the trick.
Regular tape erasing lends itself to recovery by tools like this because the erase process applies an almost "uniform" transform to the tape being erased.
Technology like this may provoke new erase technologies that erase and attempt to obscure the original information. One way to obscure something is to write "similar" information over it so it becomes difficult to tell what is part of what.
A demonstration of this technique is the write something in pen on paper. You cannot erase this easily and if you try to darken the words with more ink, a careful eye can still find the pattern of the letters. To really "erase" the words without destroying the paper, write other letters/numbers over the original letters/numbers. If you do enough of these it becomes impossible to read the original words.
The same technique would work for digital and analog recordings. Until now however, such steps would have seemed pointless.
Interestingly enough, there's an article on ABCNews.com here that talks about just that. It seems that even at 7 passes there's enough data left to get a good picture of what was there. The government aparently thinks that 7 times is enough to make it difficult but not impossible for matters of national security (i.e. when some random nuclear greasemonkey decides to copy the plans for the latest blow-up-the-solar-system goodies to his home PC and has second thoughts afterwards, Big Brother(tm) can still find out about it.)
Just my 0x2a yen.
Briefly, the main problems are the "ghost" of the old data, track misalignment leaving part of the old data on the side of a track, and bad sectors which are marked off by the drive electronics. There are also issues with drives that promise to write the data to the store immeditately, but in fact just cache it.
The only thing you can do is overwrite with random data several times in the hope that this will be enough.
Paul.
You are lost in a twisty maze of little standards, all different.
Has anyone put a disk in a paper shredder? A good quality one will do disks, cds, mouse pads etc. I suggest that as a fun and fool proof way to get rid of data. Of course it isn't fool proof if you accidently put your hand in it.
Kate
_________________________ Visit me at http://pornforcomputers.com
Your disk will get full in a couple of minutes or hours (depends on your /dev/urandom), and data in /your/secret/file will be most likely overwritten only once.
Burn all media!
When shit hits the fan get some of these https://youtu.be/pY-GncsZ-UE
Well if you read the article you could have read they can take data from a tape that is damaged. i think a hammer is not a problem for this kind of data reconstruction. Which lead me to the best solution: Hcl (? Is this muriatic acid in englisch = zoutzuur in het nederlands ?). Back to the question how many overwrites? An important part of the trick is to know the data density of the disk. Since they are using a head of a recent MR hard disk, it is supposed is to come close to the data density of the best hard disks that exists now. Overwriting would leave nothing in the resolution that it could scan today. SO the number of times you overwrite is according the number of years you want to hide the data. -watergate audio tape is not save at all. -your 20 MB (80286) hard disk could easly be reconstructed if overwriten once. -your 80 GB disk should be save for 5 to 10 years or it should contain very valuable data. This is like encrypting data. It is save, but only for a limited time. So the suggestion of somebody to encrypt the data is just a as (un)save. It only takes time to recover the data.
*Link to GPL'd Source Code Below*!
l .html
The DOD standard you and others mention specifies a specific set of patterns to be used for each pass, in order to maximize the chances of making the data unrecoverable. It's specified in DOD 5220.22-M and generally referred to as "DOD standard 7-pass extended character rotation wiping," which is quite a mouthful.
Sami Tolvanen has done some excellent research into the area, however, and at
http://www.tolvanen.com/eraser/
he goes into specifics, including scientific papers and providing links to the actual text of the DOD standard. He also provides a Windows binary for download and *GPL'd SOURCE CODE*, for a program he wrote called Eraser which is probably the best file shredding util out there. He concludes, based in part on a scientific paper at
http://www.cs.auckland.ac.nz/~pgut001/secure_de
that the DOD standard is outdated, and that the best answer is to use 35-pass "Gutmann shredding" using passes of specific characters as suggested by Dr. Gutmann in his paper linked above.
Maybe some people should start porting Eraser to Linux, nudge-nudge wink-wink hint-hint.
"The more corrupt the state, the more numerous the laws."--Tacitus, *The Annals*
The article was specific - it said it was using a magneto resistive head on audio/flight data tape. The MR head is so much smaller/sensistive than the audio head. Mordern hard drives have this MR head in them, so the effect is not going to be pronounced enough to be useful. If you have an older hard drive though, watch out. I bet it takes a long time to do this. Forensically it may not be possible to recover *properly erased* data with this particular technique, but I'm sure this will inspire others to try other stuff.
So if you hit your hard drive with a hammer, your just destroying the drive mechanism, not the data on the disks, and the FBI will still get you. If you smash the plates into small pieces, they'll reconstruct them (If your worth the chase). I believe that the standard for passing a erase head over data to erase it beyond recoverability is 12 times. That's what the FBI says. I wouldn't be surprised if they can still recover stuff after this though and you just don't know it. So I suggest 20 times if you have the patience. BTW, a nice wind0ze utility that does this very thing is "file shredder" included with McAfee's nuts and bolts utilities. What's the Linux equivalent?
It might be a good idea to do something like this to your financial/personal data on your old computer before you sell it. It's amazing what people leave on their hard drives when they dump their old computers. I'm wondering why we haven't heard more horror stories.
I'm pretty sure that places like the MOD do a miniumum of 7 random write passes on Hard disks that contain or have contained secure information, they then remove the platters, sand blast them and then set them on fire!!
I think that would just about do it!
Boxic
Why not use something like ramfs or a ramdisk to store data? Sure it means if your system gets shut off.. you loose your data... But that COULD be an advantage... "Ohh shoot.. the (name group your hiding from) is here... pull the power quick!"
Luke
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krystal_blade
It will be easy to motivate our fellow man; there is hardly anything people treasure more than not being annihilated.
You don't know shit boy. OSM and trollaxor are nothing. Donkpunch is the god of /. He's rounding up all the jaded and syphillitic karma whores and forming them into a well ordered militia. Once we get Signal 11 on our side, we will cleanse the universe.
--Shoeboy
I had a friend that was in the Air Force, working in computer systems. He said that at the facility he was at, there were 2 secure doors with armed guards before getting to the computer room, which was physically isolated.
;-)
In case of imminent security breach, the room featured axes, as well as special magnesium based devices at the tops of the computer racks. The magnesium, once ignited, was supposed to burn through the computers in the racks.
That was at least 5 years ago. Sounds like the old methods are still best
Yeah. Try this instead:
/my/secret/file|awk '{print $5}'` count=1;done
while true; do dd if=/dev/urandom of=/my/secret/file bs=`ls -l
That should do it. Be careful, though, 'cause it could take a while to go through each repetition. Fiddle with your mouse and hit some random keys to help it along. It also might chew up a fair amount of CPU or I/O on slower machines.
Data destruction in four easy steps:
1) Cook data container (floppy disk, cd-rom, hd, etc) in microwave/oven for 20 minutes @ 400 degrees.
2) Take container and pour into vat of hydrochloric acid (good enough for government work!). Let sit for 24 hours.
3) Pour the new solution into 10 different beakers.
4) Take beakers to 10 different landfills and fling 1 per location into rubble.
Of course, this is a bit of overkill, but how else are you going to keep your forensic data recovery specialist girlfriend from finding your jpegs of Natalie Portman?
love,
br4dh4x0r
Colin Plumb's shred(1) is part of GNU fileutils 4.0, standard install on Red Hat 6.2. From the info page:
"This uses many overwrite passes, with the data patterns chosen to maximize the damage they do to the old data. While this will work on floppies, the patterns are designed for best effect on hard drives. For more details, see the source code and Peter Gutmann's paper `Secure Deletion of Data from Magnetic and Solid-State Memory', from the
proceedings of the Sixth USENIX Security Symposium (San Jose, California, 22-25 July, 1996)."
Ask a silly person, get a silly answer.
1) -Triggering of a super strong electro-magnet, followed by,
2) -An instantaneous release of acid that would eat away at the surface of the disk.
These ideas may seem stupid to most, but you must realize that by opening a harddrive, you are ruining it anyway. I got this idea from the Guinness Tall Boy cans which have a Nitrogen Booster that gets released as soon as you open the can. The drives would have to be manufactured in such a way that these mechanisms could not be interjected before opening the case. This kind of hardware would not be targeted to the average consumer, but to those who may feel a little paranoid about the MAN getting a hold of their data.
http://www.nist.gov/public_ affairs/releases/g00-108.htm
I don't think this press release is referenced at the Science News article.
I hear that's how they do it at TransMeta so it's gotta be a Good Thing (tm)... : )
You need:
- Media to dispose of
- A GNU-Herd (tm)
- A fast vehicle
Do this:- Put the media in the way of a migrating GNU-herd (tm).
- Wait till the GNU-Herd (tm) passes.
- Pick up stomped media
- Use fast vehicle to transport media infront of GNU-Herd (tm)
- Repeat
Thank you.--
"No se rinde el gallo rojo, sólo cuando ya está muerto."
$HOME is where the
-- silver_p
Answer: Assume that security via obliteration will be ineffective. Instead, use non-random data. Use something so nasty, atrocious, and baiting that those that pry go for the lure rather than the information beneath the palimpsest.
Security through what-they-want-ifiscation.
Mojotoad
> I'm not a data recovery expert, but wouldn't a random sequence of bits written between
> each step of writing the specified sequential pattern of bits make it harder to
> establish physical patterns during data recovery?
The point of using specified patterns when wiping is so that those patterns will have the combined effect of completely obliterating the magnetic signature of any stored data. That's why certain patterns are mathematically thought to have a much more useful effect in the secure deletion of files than just using random data.
Think about it this way; the following parallel isn't accurate as to the exact process, but should illustrate the same methodology: You have a few lines of text written on a sheet of paper, and you wish to render them unreadable even to very close examination. (Obviously you'd burn the paper, but for the sake of example assume we have to keep the paper.) Now, what would be most effective in destroying your writing, randomly scribbling over each character, or carefully writing successive patterns of other letters over the existing ones in order to methodically obliterate them? A simplistic analogy, but that's the easiest way to grok it. I doubt 100 passes of random data could be as effective as 35-pass Guttmann wiping.
"The more corrupt the state, the more numerous the laws."--Tacitus, *The Annals*
Thanks for the info. I've been wanting to switch over to Linux for over a year now, but two things have kept me back: ease of use (I like GUIliciousness, and can't stand too many command lines), and the lack of easily available and easy to use security programmes which can replace all the functionality of those I use in Windoz. Thankfully, both issues seem to be being addressed increasingly well, and maybe next year I can take the final plunge. :-)
"The more corrupt the state, the more numerous the laws."--Tacitus, *The Annals*
If you need security then encrypting the data is your best bet.
Chapte r 10 - Encrypting files and drives in Linux, BSD, and other Unices
and
Chapte r 9 - Encrypting files and drives in Windows 95, 98, NT and 2000.
As well I have 2+ gigs of OpenSource cryptographic software at CryptoArchive
I'd add that DoD standard is seven times overwritten with zeros, not "random data", and that anyone who uses random data as an overwrite is probably going to get what they deserve sooner or later (particularly if their "random" data isn't as random as they thought it was).
-- the most controversial site on the Web
Same for magnetic media - as we know how each pass alters state of the media, knowing all the patterns we could try to invert the operation.
Obviously signal to noice ratio would decrease with each pass, but introducing some randomness (artificial noise) into patterns will make this process more controllable and faster.
I think the best solution is a special random patterns: one should have a [mathematical] set of optimal patterns and choose one of them at random every time.
Every secretary using MSWord wastes enough resources
- da Lawn
't used to be LawnMOWER, really...
As the sample moves back and forth, the head detects the strength and direction of the magnetic field at millions of points. A computer then can make a topographic image from the data or interpret the data directly-into sound, for instance.
Imagine the possibilities: you could record sound onto a piece of magnetic material - a loop of tape coated with powdered iron oxide, for example - and this advanced computer technology would allow you to play back that sound at will! The gramophone will be a thing of the past! I predict that in ten years' time room-sized devices based on this technology will be available, making it possible to listen to music anywhere there is access to a 24 kW power supply (required to run the computer). Now if only we could find a smaller, less power-hungry replacement for vacuum tubes...
$ cat < /dev/mouse
If you have secrets, there is no good alternative to destroying the media. Disks are cheap; presumably your secrets are worth more. -- Stolen from Applied Cryptography
sid=steelcage
Are you man enough?
--Shoeboy
Anyways, this should destroy just about anything.. work as an emergency device for the paranoid.
...42...
Didn't you know that O'Brien has been doing this for ages? He always manages to find some fragments of the file which he can use to reconstruct the original. I always thought it was a little far-fetched. Guess I was wrong.
> primarily as a forensic tool, and gets me
> thinking -- how many passes of write-over-with
> random-data are now required to securely delete
> a file?"
the more interesting aspect is that if you've got such a great method of recovering partially deleted data, you can easily pack more data onto the medium by just writing more data over it.
Retrieval will be *really* slow but this might change in the future.
Da Warez D00d
Point being, 99% of the time, if you want to get rid of all of the data on a hard drive... you'd probably like to be able to use that drive again in the future. The security of my data is not worth the $200 that I payed for my drive (I have nothing important), however if I can protect myself by writing over the data x times, in pattern y, then I am interested.
--
Restating the obvious since nineteen aught five.
If you can't count on your data being dead even after you performed a multi-pass wipe of the hard drive and then burned it, then where do you seek protection?
Obviously, encryption.
Big brother is watching, if you want to keep anything secret you better use something that will at least be hard for "them" to penetrate. Encryption is the only known last defense.
Hmmm, let's see if I can get Echelon to take notice of this post. Nuclear weapons grade plutonium uranium kryptonite terrorism attack make the infidels pay bomb blood killing death www.terrorists.org DEATH TO THE UNBELIEVERS! allah'u akbar muhammad purple monkey dishwasher.
I remember reading that big HDDs were starting to be sold where the _real_ capacity was quite a bit larger than the stated capacity and the drive automatically looked for sectors about to go bad and started using the 'spare' parts of the drive. Hence giving a more reliable drive than you might otherwise get. If this is the case then you might be writing your obscuring data over the parts of the platters that the HDD is using _now_ but not what it was using when you first got it and started using it to store your por^H^H^H sensitive data.
Anyone know any more about this?
Don't Destroy The Archives is an interesting page which suggests things that could be done to restore old audio tape recordings. I like the idea about correcting wow and flutter using the bias signal. I wonder if this technology comes close to making this sort of restoration possible?
Molly.
Will cut through case and spinning drive.
Friends don't help friends install M$ junk.
sort of like holography? more data in the same space?
I'm sure you all recall the technique used to erase hard drives in the event of imminent seizure in "Cryptonomicon" - winding wire around the inside of a doorframe and electrifying it so that a large amount of magnetic flux goes through that door, null-and-voiding any hard drive carried through that portal. Would anyone with a little more practical knowledge than myself care to share whether or not that would be effective?
My dad was working for Controll Data Corporation back in the '70s, which was then a big comptuer company. (Cray designed their systems before starting his own company).
They had drum drives. Like a normal harddrive, but instead of a platter it was a drum (like a big tin can). The department of defense bought on of these units, which turned out to be defective. After a few days of operation it broke, and deformed the drum. There was now no machine that could read it. They DOD sent it back to the factory for replacement - with two armed gaurds. Those gaurds were with the machine at all times until technitions opened the case. Then they took rags, rubed the magnetic coating off the drum, and burned the rags.
Believe it or not, that may not be enough. Guttmann's paper goes into some detail as to how much magnetic field is required to fully reset the media. As an example of an "adequate" field, he mentions a DOD device which produced a field so strong it actually bent the drive platter.
The military actually uses these things. One of the neater James Bond devices I've seen is what appears (at first glance) to be two thick hanging file folders. One at the front of the drawer, one at the back. Then you notice the wires attached to them. They're shaped explosive charges, designed to completely destroy the contents of a file cabinate or safe quicky. For use in the event of "imminent compromise" of security by enemy forces.
dragonhawk@iname.microsoft.com
I do not like Microsoft. Remove them from my email address.
Anyone know any more about this?
Yes, most any hard drive made past 1990 or so will have "spare sectors", which are used to replace sectors the drive detects are going bad. This is considered a problem for the DoD, which is why you are required to either (1) use drives certified not to do that or (2) physically destroy the drive before you can call it "clean".
dragonhawk@iname.microsoft.com
I do not like Microsoft. Remove them from my email address.
Since this incident we have gone back to the traditional method of: 1) Place drive on bare concrete floor 2) Hit repeatedly with a 50# sledge (this is a BIG mofo) 3) Put your new extreme slimline drive in the trash.
Note that physical deformation may still leave recoverable magnetic signatures on the recording medium. There are companies who specialize in this sort of data recovery. I know of at least one case where a laptop (with hard drive) was run over by a truck, completely crushing it. The company was able to recover all most all of the data.
dragonhawk@iname.microsoft.com
I do not like Microsoft. Remove them from my email address.
I wrote a Tempest certified disk formatter in the 80s and was required to do 10 passes with specific patterns to qualify. To prove their point they had me write a text file onto a disk and then run the formatter. With earlier/fewer passes they were able to print the file out and give it to me (I chose the text) This was in the 80s, so I'm sure it's better now. They used to grind up bad disk drives so that all that came out was sand, that was the preferred method to "sanitize" them
Take your hard drive to the nearest foundry, throw it into the crucible... voila-- it is now a molten puddle that is intermingled with the rest of the metal in that crucible.. and I welcome any FBI,CIA,NSA geek to read that data. I have destroyed several older hard drives that way, (The nickel and Aluminum are useful alloys in some metal batches, while everything else floats to the top as slag.
Gawd, why do it the hard way? In a hurry you are toast anyways (Except for the primercoard idea... wrap that HDD in primercord... but then you'll spend the same amount of time in jail for disfiguring the officers there to apprehend you.
Although, back in my hacker days (friends who did the cracking, I just built the hardware) I had a degaussing coil wrapped around the hard drive (Monster 20MEGS!) one flip of the switch and it starts degaussing (If you heard of a bust you have time to sanitize, if you dont hear of the bust then you are the first
Do not look at laser with remaining good eye.
... wouldn't it be nice if opening a harddrive and by breaking the vacuum seal ...
... but you must realize that by opening a harddrive, you are ruining it anyway.
It is a common misconception that hard drives are vacuum sealed. In fact, Winchester-style disk drives use an air cushion to "float" the heads above the disk platters. They won't work in a vacuum. Furthermore, hard disk drives have filtered "breather holes" which connect the inside of the drive to the outside. They need to do this because as the spindle motor heats up, the air inside the chamber expands, and it needs a place to go.
Not true. The danger is contamination -- i.e., dust. If even a tiny dust particle gets between the read/write head and the platter while it is spinning at 3600 RPM or faster, Bad Things Happen. If you use a clean-room environment, you can open up a hard drive -- and even run it with the cover off. Data recovery companies sometimes do this sort of thing.
dragonhawk@iname.microsoft.com
I do not like Microsoft. Remove them from my email address.
To hell with the Nixon Tapes,I wanna hear about the content on the Clinton/Gore drives!
I recall they have a problem with "lost" e-mail.
I doubt he heated them,probably "accidentally"
formatted them.
*Repent!Quit Your Job!Slack Off!The World Ends Tomorrow and You May Die!
Even without the key it is possible to decrypt the data. It just takes a lot of time. But if you have the means to read the overwritten data from a disk, you surely could afford the equipment to decrypt the data.
:conspicacy mode on
:conspiracy mode off
The NSA already has tools to decrypt DES-128, that is why it is realeased for export.
Overwriting 7 times is possible to recover.
I remember something about data destruction from the cypherpunks list a few years ago. Releasing some sort of acid that will wash the platters clean, suspending the media in solution and completely destroying the data.
The acid in question was not harmful to skin, thus avoiding charges of a "terrorist device" from Thermite or some more dangerous substance. (make that avoiding reasonable accusations of)
Sounded good, if one of you real chemists can point this in the proper direction it would be appreciated.
Eve Fairbanks says I drive a hybrid!LOL
Splendid! Now everybody go and replace your rm with this :)
I work in a bookstore (computer bookstore) near the DND (Dept. of National Defence in Ottawa, Canada) and I spoke to a Senior Officer in the Security Dept. and he indicated to me there in no commerically available product which would have the ability of wiping a drive which could not be recovered. He also told me that he was not aware of any method that he knew of that could prevent his dept. from recovery data on any drive. Of course the techiques his dept. has access to I'm assuming are limite too very few groups any where in the world. So for the must of us we are safe. :-)
If you guys want more information on exactly HOW they recover this information, check out this page: this page.
hlag
Although technically interesting, I don't see this new technology as all that earth-shattering. I can easily forsee it coming into use in retrieving black box data from flight recorders (or late-model GM vehicles), as that data is extremely valuable in not only determining what went wrong, but possibly how lives could be saved later.
But let's get back to you and me. Is this really going to affect us? I somehow doubt it. Even if you were the most notorious hacker, the most villanous virus-writer, the most heinous of DoS'ers, would this technology ever be used against you? Probably not.
I see this technology being used almost exclusively on audio and video tapes. Why? If you're using a hard drive and doing something bad, chances are your hard drive isn't the only one out there that has information on what you've been doing. Your ISP might have logs of what FTP sites you've been to. Your friend's computer might still contain those inflated-ego e-mails you sent him/her. Countless other web servers might have registered your IP (or your firewall's, or your ISP's, or whatever). Most likely, the authorities don't need to recover *your* hard drive (after you've shot it, trash-compacted it, and put it in your saltwater aquarium) to nail you.
However, we'll now finally be able to recover that episode of B5 that your mother recorded her Celine Dion special over....
Mr. Ska
Here's what I would do if i was afraid of someone getting at my deleted stuff.
1. Delete stuff
2. Buy new hard drive
3. Use a disk image utility that only copies existing files to image to the new disk.
4. Destroy old disk.
Hmmm... I hadn't thought about that. For a short file, it shouldn't make any difference (since the first 12(?) blocks on an ext2 FS are accessed directly through the inode, which should be the same even if open(2) is carried out with the O_TRUNC flag. I don't know wenough about the kernel's inner workings (especially how it caches these sort of operations before writing them out to physical media) to make any definite statements, but it would certainly seem like there's a race condition between the time the file's truncated and the random data is written out (unless these two operations are actually carried out atomically, which I think is unlikely). In normal use, it probably doesn't matter too much, but we're talking about normal use by extreme paranoiacs, so it's obviously not good enough.
To do thus properly, you'd have to go digging into the kernel and alter the unlinking operation to all the random overwriting before it actually unlinks the file. Bummer.
shred -n 35 -z core
Now no one will ever know that my latest program for school dumped a core.
Here are the articles:
Trashing your PC - http://archive.abc news.go.com/sections/tech/Geek/geek000706.html
Data Dump - http://archive.abc news.go.com/sections/tech/Geek/geek000622.html
The Hard (Drive) Facts - http://archive.abc news.go.com/sections/tech/Geek/geek000615.html
I could not justify my existence if I were a turkey farmer. Would I terminate myself? Undoubtably, yes.
Just wondering... how many of you have actually had the FBI come to your door looking for your hard drive? Are we being a little over-paranoid?
However, if you use cryptography, for example, the Steganographics File System, and if you implement it securely, then it doesn't matter what people can retrieve.
Of course, with cryptography, you run into some of the same issues. In particular, keeping your keys secure is, in itself, not trivial. For example, if you type in your key and the program that reads the key gets swapped out, your plaintext key will have been written to disk.
Re: ultimate hard disk wipes
I would worry that the physical media surface shape and properties are history dependent and readable (with technical effort) with a scanning tunneling atomic force microscope technology....
I think that the Curie point is a good start when 'they' are sneaking through (or busting down the door), perhaps use an 1100 watt microwave (careful about FCC emission regs here). Also thermite and magnesium may have weapons charge or possession problems in some jurisdictions.
I think that fusion (melting) or dissolution (acid or oxidizer) are safest for drop dead security. Run the microwave just a little longer, the hard drive is going to heat fast. Just how big and uninterruptable is that power supply?
Magnesium, microwave or thermite, do it in a fire protected area (concrete block). Don't let 'them' add arson to the list, much less torching your place over a little misunderstanding.
Good luck. Great business opportunities are in some really scary places with strange people who have interesting connections.
The help files that come with PGP recommend:
3 passes for personal use
10 passes for commercial use
18 passes for military use
26 passes for maximum protection
And it says that commercial data recovery companies have been able to recover data after it was overwritten 9 times.
pulled the platters our of a bad Maxtor IDE drive (drive motor went out) and put them into another drive. Spun the drive up while open and copied about 30 meg of stuff off of it for a client. I was in my fairly dirty basement. I let it run for a couple of hours on my bench and it worked fine. I pulled those really nice magents our of both drives and trashed the rest when I was done playing.