Ways to destroy information stored on HDD
Briefly about the physical basics of information recovery. In today’s HDDs, only the recording heads write information to the magnetic disk. When subjected to the magnetic field of the head, an increase in the number and size of magnetic domains oriented in the direction of this field occurs. The magnetic surface beneath the read head produces an informative residual magnetisation and this is detected during the read operation. The level of the head’s magnetic field is less than the magnetic saturation level, leaving relatively small volumes of magnetic domains aligned with the direction of the previous magnetic interaction. The magnetic field of these domains is weak and will not affect the reading response of the host controller. However, these domains can be detected by more sensitive special heads (sensors) or detected by detailed analysis of the fine structure of the magnetic field generated by a section of the working surface of the drive.
Data destruction algorithms.
U.S. Department of Defense (NISPO) DoD 5220.22-M, 1995 Number of recording cycles 3 Cycle 1 random code recording Cycle 2 random code recording Cycle 3 random code recording Note: NISPO prohibits using this algorithm to destroy data marked “DETECT.SECRET” Alternative methods (according to NISPO): demagnetization; physical destruction.
Standard VISR, 1999. (Germany) Number of recording cycles 3 Cycle 1 recording zeros Cycle 2 recording ones Cycle 3 recording code with alternating zeros and ones.
GOST P50739-95 (Russia) (Russia) For data protection classes 1 ..3 number of write cycles 2 Cycle 1 write zeros Cycle 2 write random codes For data protection classes 4..6 One cycle write zeros.
Bruce Schneier Algorithm Number of recording cycles 7 Cycle 1 recording units Cycle 2 recording zeros Cycles 3..7 recording random codes.
Peter Gutman Algorithm Number of cycles 35 Cycles 1 ..4 arbitrary code writing Cycles 5 ..6 write codes 55h, AAh Cycles 7 ..9 write codes 92h, 49h, 24h Cycles 10..25 sequential code writing from 00, 11h, 22h, etc. to FFh Cycles 26..28 similar to cycles 7..9 Cycles 29..31 code writing 6Dh, B6h Cycles 32..35 similar to cycles 1.4
In my opinion, the best program that has all of the above algorithms is Acronis Privacy Expert. www.acronis.com
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