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Gutmann method

35 pass overwrite data

Basic "delete" operations only remove bits of information from files, so they just appear deleted, and even overwritten data can be recovered using sophisticated tools, like magnetic force microscopes.

The only way to protect your company and yourself from data or identity theft is to shred sensitive documents and files with a high security tool that is capable of rewriting the files with random series of binary data multiple times.

The Gutmann method is an algorithm for securely erasing the contents of documents and files. It destroys the magnetic memory by writing a series of 35 patterns over the entire region to be erased. This method provides highly effective security against the recovery of data.

 

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Overwrite patterns chart

Gutmann method
(
35 pass overwrite data )
Pass

 

Data written Encoding scheme targeted

 

Binary notation Hexadecimal notation
1 Random Random      
2 Random Random      
3 Random Random      
4 Random Random      
5 01010101 01010101 01010101 55 55 55 (1,7) RLL   MFM
6 10101010 10101010 10101010 AA AA AA (1,7) RLL   MFM
7 10010010 01001001 00100100 92 49 24   (2,7) RLL MFM
8 01001001 00100100 10010010 49 24 92   (2,7) RLL MFM
9 00100100 10010010 01001001 24 92 49   (2,7) RLL MFM
10 00000000 00000000 00000000 00 00 00 (1,7) RLL (2,7) RLL  
11 00010001 00010001 00010001 11 11 11 (1,7) RLL    
12 00100010 00100010 00100010 22 22 22 (1,7) RLL    
13 00110011 00110011 00110011 33 33 33 (1,7) RLL (2,7) RLL  
14 01000100 01000100 01000100 44 44 44 (1,7) RLL    
15 01010101 01010101 01010101 55 55 55 (1,7) RLL   MFM
16 01100110 01100110 01100110 66 66 66 (1,7) RLL (2,7) RLL  
17 01110111 01110111 01110111 77 77 77 (1,7) RLL    
18 10001000 10001000 10001000 88 88 88 (1,7) RLL    
19 10011001 10011001 10011001 99 99 99 (1,7) RLL (2,7) RLL  
20 10101010 10101010 10101010 AA AA AA (1,7) RLL   MFM
21 10111011 10111011 10111011 BB BB BB (1,7) RLL    
22 11001100 11001100 11001100 CC CC CC (1,7) RLL (2,7) RLL  
23 11011101 11011101 11011101 DD DD DD (1,7) RLL    
24 11101110 11101110 11101110 EE EE EE (1,7) RLL    
25 11111111 11111111 11111111 FF FF FF (1,7) RLL (2,7) RLL  
26 10010010 01001001 00100100 92 49 24   (2,7) RLL MFM
27 01001001 00100100 10010010 49 24 92   (2,7) RLL MFM
28 00100100 10010010 01001001 24 92 49   (2,7) RLL MFM
29 01101101 10110110 11011011 6D B6 DB   (2,7) RLL  
30 10110110 11011011 01101101 B6 DB 6D   (2,7) RLL  
31 11011011 01101101 10110110 DB 6D B6   (2,7) RLL  
32 Random Random      
33 Random Random      
34 Random Random      
35 Random Random      

RLL :  Run Length Limited
MFM : Modified Frequency Modulation

 

See also:

Peter Gutmann  http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html

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