Gutmann method

The Gutmann method, named after its inventor, Peter Gutmann, who first published this in 1996, is a method for complete erasure of data stored on magnetic storage media such as hard disks.

The data is a total of up to 35 times overwritten with specific values ​​for a specific pattern. This method is very time consuming, but is valid for hard drives, which use no PRML or EPRML, as the safest method of software-based residue-free data deletion. These are usually capacity disks later than the date of manufacture in 2001 or until a maximum of 15 GB. Is that accurate coding procedure of hard disk known, it is possible to restrict themselves to a part of the Gutmann method. Newer hard drives are also overwritten reliably by the method contained in the eight passes of random data, the other 27 passages are unnecessary. In fact, all it takes is a random passage in today's data densities.

Background

Background of the multiple override is that the data supplied to the hard disk for reliable storage recoded to be written on the magnetic medium. To the medium at any point in a multiple, that is to say at least two, preferably three times the magnetization reversal to achieve what the original value by means of technically complicated measurements required to prevent inferences a higher number of data patterns to the hard disk must be supplied for each possible encoding methods.

When a file is deleted normally, the memory is only marked as free. The data itself is therefore still present. Only when this free space is overwritten, no program can read the data more. However, it is possible in theory to determine these data by consuming measuring the residual magnetism. In practice, however, no data could be read even after a single overwrite.

Method

The Gutmann method uses the following passages, of which 27 targeted to certain now obsolete line codes:

Limitations

Meanwhile, IDE and SCSI hard drives have their own logic, such as bad sectors can be implicitly marked as broken and no longer used. This could perhaps be old data on this yet reconstructed.

Given the development of writing method of magnetic data carriers, it is controversial whether this method still endures, as their development is still on now no longer used coding methods such as Modified Frequency Modulation ( MFM) and Run Length Limited ( RLL) aimed. In current writing and coding process, has been going since 1996 due to the enormous data density gestiegenden assume that also significantly less overrides enough to ( with special hardware ) prevent physical processing. In addition, the data blocks affect partially each other, which complicates the evaluation to impossible.

Furthermore, using modern file systems, the so-called journaling, whereby a user may not know where their data are written so that a guaranteed overwriting the data blocks of a file (without any kernel extensions) is impossible. However, this problem only occurs when files of a mounted file system to be deleted. To delete a complete (not the mounted ) partition or hard drive, however, is quite possible.