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Old 11-22-2006, 07:41 PM   #1
youngstructural
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Lightbulb ReiserFS secure deletion question...


I have read alot of varying information about the possibility of restoring a file in a journaled (or log based) file system. I really want to cut through the fog and get an asnwer specific to my situation.

I am running a ReiserFS system and would like to do the following to securely delete some files:

1. Use rm to delete all files which we wish to have "destroyed".
2. As root (to ensure the last 5% gets done as well), fill all free space with junk files (random copies of known files).
3. With freespace down to the minimum possible, start shredding files. I have been using "shred -n5 -z FILENAME", as I am not paranoid and simply want a secure delete (after all, you can't defend against a truly determined data recovery and still keep your drive; head shifting and electron microscopes see to that).
4. Repeat for all "junk" files which we desire destroyed.
5. Do not delete any individual file until all files have been treated this way.
6. rm the junk files.

Please let me know what you think. I would appreciate explanations and/or pointers to technical papers...

Speaking of which, this is a great/informative read: Secure Deletion of Data from Magnetic and Solid-State Memory by Peter Gutmann, Department of Computer Science, University of Auckland

Thanks all,
Regards,

YS
 
Old 11-22-2006, 09:38 PM   #2
kotnik
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Don't fill free space with junk files. Do it with /dev/random. Repeatadly.
 
Old 11-22-2006, 09:57 PM   #3
youngstructural
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I just thought of something.... I don't know enough about Reiser to know the answer, but I really hope that Shred is not just writting the whole junk files over and over again into whatever little free space there may be left on the drive... Any thoughts? Anybody know if this is how Reiser would handle this request?

I guess I'm just worried that there isn't an effective solution...

YS
 
Old 11-22-2006, 09:59 PM   #4
youngstructural
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Sounds promising kotnik, but how would I go about actually doing that?

What would the commands be? I may not be a flat out noob, but I am not exactly a master of the *nix as of yet...

Working on it! *smiles*

Thanks for the reply...

YS
 
Old 11-22-2006, 10:04 PM   #5
kotnik
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Yes there is. But, question is do you wan't to get rid of that hard drive. If you do, then shred /dev/hdX until the poor thing dies. If you don't, and want to be secure, use encryption. But use a good one, encfs for example.

As a rule of thumb, sensitive files should never touch the hard drive unencrypted.
 
Old 11-22-2006, 10:08 PM   #6
kotnik
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To kill the evidences from hard drive's free space, use scrub utility.
 
Old 11-22-2006, 10:19 PM   #7
youngstructural
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I don't want to get rid of the hard drive... I don't even want to get rid of the entire partition. I simply want to get rid of (permanently) a number of files.

I'm actually quite familiar with using shred to get rid of whole partitions, and individual files on ext3; the issue is specific to Reiser...

I think I have the command for your suggestion, by the way: dd if=/dev/random of=myfile bs=SizeINeedInKB

That right?

Thanks again!

YS
 
Old 11-22-2006, 10:28 PM   #8
kotnik
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It's the same on ReiserFS as it is on EXT3. Shred the files you don't need (with -u option).

As for hard drive's free space, use scrub (and don't forget do delete a big file it makes, as happened to me more than once ).
 
Old 11-26-2006, 04:18 PM   #9
youngstructural
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Any other opinions???

My appologies all, but I really want to "bump" this and get another couple of opinions...

I don't think it's correct to say that shred will work equally on etx3 and reiser...

Any thoughts?

Thanks,

YS
 
Old 11-26-2006, 08:01 PM   #10
kotnik
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They're both journaling file systems... so, it'll work the same... At least, it should I'm not 100% sure...
 
  


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