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Unread 13 Jan 2003, 19:45   #1
Ragnarak
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Secure erasing of data

I'm selling an old hard drive to someone but i've used it before to store files that've contained credit card info aswell as a number of passwords to sites that have my CC info stored.

Even tho i've deleted the files how likely is it that they could be recovered?

I don't really want to have to completely format it as it has a load of games/programs and stuff that he wants leaving on, but if there's no way to securely delete everything i'll have to just reformat it all which'll be a big hassle
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Unread 13 Jan 2003, 20:03   #2
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I'm not sure how NTFS works, but when you delete something on a FAT partition all it does is remove the entry in the FAT (File Allocation Table, the database of files on the harddrive) and leaves the file intact (in fact it doesn't even fully erase it from the FAT). All anyone wanting to recover your files need to is scan the drive with a recovery tool and everything recently deleted will probably come up ('deleted' files get destroyed over time by having others written on top of them).

If you have Norton Utitlites you can use Wipeinfo to securely erase the "blank" parts of your harddrive (and files if you want) up to military spec.
I believe Evidence Eliminator offers the same kind of service, as do several other programs.

This should be sufficient to remove the chance of anyone recovering the files.
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Unread 13 Jan 2003, 20:05   #3
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Quote:
Originally posted by meglamaniac
This should be sufficient to remove the chance of anyone recovering the files.
With any normal technology anyway. There's a reason the MoD burns them after use
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Unread 13 Jan 2003, 21:59   #4
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there was evidence that if you go over the data on a disk 9 times, it could still be recovered...
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Unread 13 Jan 2003, 22:41   #5
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magnets are your friends.

(im not sure if they work with hard drives)
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Unread 15 Jan 2003, 22:10   #6
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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

PGP is supposed to be able to wipe data. Don't know how well, though.
-----BEGIN PGP SIGNATURE-----
Version: PGP for Tactical Alien Invasion Planning 5.5.2

iQA/AwUBPiXAS3hSe91I1T1mEQIjOwCeL+4xcBLEResDxaQvb7uDE/K4ofMAn1ri
2fUP9wO5obEsRqjrSOTZ1O9H
=ZN6j
-----END PGP SIGNATURE-----
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Unread 15 Jan 2003, 22:25   #7
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How about filling up the ENTIRE disk with big files, then removing them again. Preferably do a defrag before them to make sure no gaps are being missed.

Anyway, I don't think it's likely someone is going to search through your disk for deleted files.
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Unread 16 Jan 2003, 14:31   #8
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write a small program the creates a file full of random **** the size of your free space or summit
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Unread 18 Jan 2003, 04:37   #9
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I think you can wipe most of it with Norton Utilities, but i'm not sure. But to be honest i think could sell the drive to some friends that know ain't able to recover your data, or just keep the drive yourself. After all you'll never know when you might need an extra drive.

Play it safe and paranoid and just keep the drive for yourself is what i think is the best thing to do if there's really important information on it.
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Unread 18 Jan 2003, 12:38   #10
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Eraser is an advanced security tool, which allows you to completely remove sensitive data from your hard disk by overwriting it several times with carefully selected patterns.

You can drag and drop files and folders to the on-demand eraser, use the convenient Explorer shell extension or use the integrated scheduler to program overwriting of unused disk space or, for example, browser cache files to happen regularly, at night, during your lunch break, at weekends or whenever you like.

The patterns used for overwriting are based on Peter Gutmann's paper "Secure Deletion of Data from Magnetic and Solid-State Memory" and they are selected to effectively remove the magnetic remnants from the hard disk making it impossible to recover the data.

Other methods include the one defined in the National Industrial Security Program Operating Manual of the US Department of Defense and overwriting with pseudorandom data.


How does it Erase Data i hear you cry...well heres some more crap from the help file incase your wondering....


This method is based on Peter Gutmann’s paper “Secure Deletion of Data from Magnetic and Solid-State Memory”. In chapter “Erasure of Data from Magnetic Media” he represents 27 deterministic passes that should overwrite the data despite drive encoding.


Pass Pattern (binary, hex)
1 01010101 01010101 01010101, 0x55
2 10101010 10101010 10101010, 0xAA
3 10010010 01001001 00100100, 0x92 0x49 0x24
4 01001001 00100100 10010010, 0x49 0x24 0x92
5 00100100 10010010 01001001, 0x24 0x92 0x49
6 00000000 00000000 00000000, 0x00
7 00010001 00010001 00010001, 0x11
8 00100010 00100010 00100010, 0x22
9 00110011 00110011 00110011, 0x33
10 01000100 01000100 01000100, 0x44
11 01010101 01010101 01010101, 0x55
12 01100110 01100110 01100110, 0x66
13 01110111 01110111 01110111, 0x77
14 10001000 10001000 10001000, 0x88
15 10011001 10011001 10011001, 0x99
16 10101010 10101010 10101010, 0xAA
17 10111011 10111011 10111011, 0xBB
18 11001100 11001100 11001100, 0xCC
19 11011101 11011101 11011101, 0xDD
20 11101110 11101110 11101110, 0xEE
21 11111111 11111111 11111111, 0xFF
22 10010010 01001001 00100100, 0x92 0x49 0x24
23 01001001 00100100 10010010, 0x49 0x24 0x92
24 00100100 10010010 01001001, 0x24 0x92 0x49
25 01101101 10110110 11011011, 0x6D 0xB6 0xDB
26 10110110 11011011 01101101, 0xB6 0xDB 0x6D
27 11011011 01101101 10110110, 0xDB 0x6D 0xB6
These deterministic passes should be committed in random order to make it more difficult for an opponent to recover the data. Permutation should be done with cryptographically strong random number generator.

Eraser shuffles the pass array using its own cryptographically strong random number generator based on the one described in Dr. Gutmann’s paper “Software Generation of Practically Strong Random Numbers”. Tiger hash function by Ross Anderson and Eli Biham is used for mixing the entropy pool.

It is also stated that the overwriting sequence can be slightly improved by performing random passes before and after the deterministic passes above.

Eraser writes four passes containing random data before and after writing the deterministic passes in random order, therefore ending up with total 35 passes. The data used in the random passes is created using the ISAAC pseudorandom number generator.


--------------

These two methods are based on “National Industrial Security Program Operating Manual”, NISPOM (also known as US DoD 5220.22-M), of United States Department of Defense from January 1995 (chapter 8, section 3, 8-306. Maintenance).


The first alternative consists of parts E (which is D without verifying), C and E (once more) of the clearing and sanitization matrix.

Pass Matrix Pattern
1 E [1] Random character X
2 E [2] Bit-wise complement of X
3 E [3] Random data
4 C Random character Y
5 E [1] Random character Z
6 E [2] Bit-wise complement of Z
7 E [3] Random data
X, Y, Z = [0,255]
The latter version includes only part E of the matrix, and the first two passes consist of constants instead of random characters.


Pass Matrix Pattern
1 E [1] 00000000, 0x00
2 E [2] 11111111, 0xFF
3 E [3] Random data
All random data is created with the ISAAC pseudorandom number generator.

Even though these overwriting methods are faster than the Gutmann method, they are less secure, especially when there is a chance that someone will try to use hardware recovery methods in attempt to restore the previous data.

-------------------------


Cryptographically strong pseudorandom data used for overwriting is created using the ISAAC (Indirection, Shift, Accumulate, Add and Count) algorithm by Bob Jenkins. The ISAAC generator is reseeded before each task using Eraser’s own multi-source polling random number generator.

The random data generated using ISAAC is guaranteed to have a period length of 2^40 numbers, and the average cycle is 2^8295 32-bit (4-byte) numbers. Therefore, the average amount of data provided by the generator before the sequence starts from the beginning is 4.12e2488 gigabytes (and is at least 4096 gigabytes), which is more than enough for overwriting even the largest hard drives.

The number of overwriting passes for this method is user selectable, the maximum being ((2^16) - 1) = 65535 passes.

For more information, see the source code.






http://www.tolvanen.com/eraser/

is its webby.

dont know if thats what you want but its what ive been using after i ran an 'undelete' program and saw mountains of stuff i tohught was gone
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Unread 18 Jan 2003, 16:04   #11
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That eraser thingy looks good.
I was going to test it erasing my free disk space on the docs drive (13gb or so), but when the estimate hit the best part of 24 hours I decided to give it a miss.
That was using the strongest method though.

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