[khm]

Ako se ide u neko proučavanje ovoga po netu onda se vidi da što je veća osjetljivost sadržaj na disku to metoda uništavanja podataka mora biti brutalnija i besmislenija, a to naravno nema nikakve veze s pameću nego takve propise nameću razne sigurnosne agencije - koje naravno moraju biti paranoične.

Dovoljno je proučit pojam 'secure erase' da se vidi da nikakvo fizičko uništenje diska nije potrebno.
Svaki disk proizveden poslije 2001. može izvršiti tu naredbu.

http://cmrr.ucsd.edu/people/Hughes/SecureErase.shtml

Q: What is secure erase?

A: The ANSI T-13 committee which oversees the ATA (also known as IDE) interface specification and the ANSI T-10 committee which governs the SCSI interface specification have incorporated into their standards a command feature known as Secure Erase (SE). Secure erase is a positive easy-to-use data destroy command, amounting to “electronic data shredding.” It completely erases all possible user data areas by overwriting, including the so-called g-lists that contain data in reallocated disk sectors (sectors that the drive no longer uses because they have hard errors in them). SE is a simple addition to the existing “format drive” command present in computer operating systems and storage system software and adds no cost to hard disk drives. Since the Secure Erase command is carried out within a hard disk drive it doesn’t require any additional software to implement.

Q: Is secure erase approved for government security?

A: Secure erase has been approved by the U.S. National Institute for Standards and Technology (NIST), Computer Security Center[1]. In general data erasure techniques when used alone are approved by NIST for lower security sanitization (less than secret) since the data can be recovered at least in theory. It should be noted though that a secure erased drive that is then physically destroyed would be extremely difficult if not impossible to recover data from. According to the NIST document Secure Erase as well as certain software utilities running in protected execution environments (e.g. running inside file system hardware like RAID arrays or inside secure computers) could be verified secure.

Q: Is any data left after a secure erase?

A: Investigations at CMRR at UCSD have shown that a single pass secure erase at lower frequencies results in no remaining data signals and a second erase reduces this signal only slightly more. The resulting data signal to noise ratio (SNR) at the magnetic drive head is below that required to recover data using a disk drive channel[2]. The only recorded signal left in these experiments is a small amount of highly distorted track edge recording which is extremely difficult to recover data from even if the disk is removed from the drive and tested on a spin-stand.

[1] NIST Computer Security Resource Center, Special Publication 800-88: Guidelines for Media Sanitization, August 2006

[2] Secure Erase of Disk Drive Data, Gordon Hughes and Tom Coughlin, IDEMA Insight 2002, http://www.tomcoughlin.com/techpapers.htm

http://cmrr.ucsd.edu/people/Hughes/d...212008_000.doc


Sve piše, samo u nekoj divljoj teoriji je moguće povratiti podatke nakon brisanja diska.

Logično da će se za dokumente sa pridjevom 'secret', a pogotovo 'top secret' diskovi uništavat, ali to više ima veze sa paranojom, pa kažu da čak nije dovoljno samo uništiti disk nego ga razbiti na što više malih komadića, čak je propisana i veličina tih komadića.
Eto dokle sežu propisi kad je američka vlada u pitanju.

Q: Does physical destruction of hard disk drives make the data unrecoverable?

A: The disks from disk drives can be removed from the disk drives, broken up and even ground to very fine pieces to prevent the data from being recovered. However, even such physical destruction is not absolute if any remaining disk pieces are larger than a single record block in size, about 1/125” in today’s drives (Note that as the linear and track density of magnetic recording increases the resulting recoverable pieces of disk must become ever smaller if all chances of data recovery after physical destruction alone are to be thwarted). Pieces of this size are found in bags of destroyed disk pieces studied at CMRR2. Physical destruction nevertheless offers the highest level of data elimination (although it is more effective if the data is first overwritten since then there is almost no potential signal to recover) because recovering any actual user data requires overcoming almost a dozen independent recording technology hurdles.

A treba malo i pročitati o gutmanovoj metodi:

http://en.wikipedia.org/wiki/Gutmann_method

The National Bureau of Economic Research criticized Gutmann's claim that intelligence agencies are likely to be able to read overwritten data.[3] Published Government security procedures clearly consider an overwritten disk to still be sensitive.[4]

Companies specializing in recovery of damaged media (e.g., media damaged by fire, water or otherwise) cannot recover completely overwritten files. No private data recovery company currently claims that it can reconstruct completely overwritten data.

To je ono najbitnije.
Daj nek jedan čovjek i jedan laboratoriji uspiju vratit izbrisan disk.

Evo još i ovo od Microsofta, nema vraćanja podataka nakon korištenja ovoga >> http://technet.microsoft.com/en-us/s...rnals/bb897443