Data wipe algorithms
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That's what I was thinking, but that doesn't seem very realistic. Imaging if I wanted to erase a 4 GB DVD-ISO, that would mean I have to create a 4 GB byte-array before the first pass and compare each byte later.
http://johanmartensson.se - Home of MPEG4Watcher
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So if the random byte you want to write matches the existing byte, select a different random byte? Oh there's a good use for clock cycles.
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So if the random byte you want to write matches the existing byte, select a different random byte? Oh there's a good use for clock cycles.
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They must have forgotten to. What if your random bytes just happen to all match the bytes to be wiped? :-D
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They must have forgotten to. What if your random bytes just happen to all match the bytes to be wiped? :-D
PIEBALDconsult wrote:
What if your random bytes just happen to all match the bytes to be wiped?
I believe the error message would read "Woahhhh. Bummer dude."
Deja View - the feeling that you've seen this post before.
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They must have forgotten to. What if your random bytes just happen to all match the bytes to be wiped? :-D
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Read back each byte [after you write it] to be sure it's the same as what you thought you wrote? Seems fairly pointless to me; what do you do if it's not?
modified on Monday, January 07, 2008 4:05:57 PM
PIEBALDconsult wrote:
what do you do if it's not?
As always, try a couple of times, and if it continues to fail, report the failure. :)
Luc Pattyn [Forum Guidelines] [My Articles]
Happy 2008!
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PIEBALDconsult wrote:
what do you do if it's not?
As always, try a couple of times, and if it continues to fail, report the failure. :)
Luc Pattyn [Forum Guidelines] [My Articles]
Happy 2008!
Keep trying different bytes until one matches? :-D
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I have been reading up a lot on the different standard file wipe algorithms that exists and I was hoping that someone could explain one thing to me. Most of the algorithms are straightforward and shouldn't post to much difficulty to implement but I don't understand the verification part of some of them. Take the standard DoD 5220.22-M for example which states:
- US Department of Defense DoD 5220.22-M (3 passes)
DoD 5220.22-M is three pass overwriting algorithm:
first pass - with zeroes, second pass - with ones and the last pass with random bytes.
With all passes verification.or the US Army AR380-19:
- US Army AR380-19 (3 passes)
AR380-19 is data wiping scheme specified and published by the U.S. Army.
AR380-19 is three pass overwriting algorithm:
first pass - with random bytes, second and third passes with certain bytes and with its
compliment (with last pass verification).The three passes is not a problem but what am I suppose to verify?
http://johanmartensson.se - Home of MPEG4Watcher
Verify means to verify the data you wrote. Unfortunately, the way modern hard drives are designed the two algorithms are not effective at preventing physical scans of the drives as hard drives are recorded using an encoding scheme to maximize storage. Technically speaking an HDD can store less data as all 1's or all 0' than a random assortment. The easiest method is to use a degausser that is Dod approved. If you were in the states I would name drop, www.data-assassins.com, which is one of my pet projects. We just degauss them using approved degaussers.
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Happiness in intelligent people is the rarest thing I know. -- Ernest Hemingway -
Read back each byte [after you write it] to be sure it's the same as what you thought you wrote? Seems fairly pointless to me; what do you do if it's not?
modified on Monday, January 07, 2008 4:05:57 PM
Wow, this is why I like Codeproject, I go to sleep and when I wake up, theres all these suggestions to my question. However I think this is the most logical answer...
http://johanmartensson.se - Home of MPEG4Watcher
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Verify means to verify the data you wrote. Unfortunately, the way modern hard drives are designed the two algorithms are not effective at preventing physical scans of the drives as hard drives are recorded using an encoding scheme to maximize storage. Technically speaking an HDD can store less data as all 1's or all 0' than a random assortment. The easiest method is to use a degausser that is Dod approved. If you were in the states I would name drop, www.data-assassins.com, which is one of my pet projects. We just degauss them using approved degaussers.
Need a C# Consultant? I'm available.
Happiness in intelligent people is the rarest thing I know. -- Ernest HemingwayAnd I suspect it would still only verify what's in the controller's cache, not what's actually on the platter.
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And I suspect it would still only verify what's in the controller's cache, not what's actually on the platter.
Well that would be OS dependent, however, if you sent command directly to the controller I bet you could flush the cache? I bet you can even disable the cache on the HDD with a command. But again, thats why I say just degauss.
Need a C# Consultant? I'm available.
Happiness in intelligent people is the rarest thing I know. -- Ernest Hemingway