Steganos Shredder - Introduction
Why wipe files?
Deleting a file on most computers does not really remove or overwrite the file. MS-DOS and Windows 3.1 only replace the first character of the filename is by a E5h character - doing this the computer knows it can overwrite this file when the space is needed - not before.
When using Windows 95/98/NT data security is even worse: When you delete a file using the Explorer the file is simply moved to a hidden directory named "Recycled", better known as the "Recycle Bin". Even if you empty the bin the files aren't really deleted. They can be recovered using certain file recovery programs.
How does Steganos Shredder wipe files?
Data destruction in Steganos and the Steganos Shredder conform to the U.S. Department of Defense norm DoD 5220.22-M/NISPOM 8-306 and goes above and beyond this norm. First the file's content is being overwritten, once with all bits '1', then with all bits '0', and finally with random data. Since unused space behind the end of a file ("slack") could contain data, this area is also overwritten by the Steganos Shredder. Then the file will be renamed so one cannot draw conclusions from the original filename. The file's attributes are being removed, the file size is being set to zero, and file date and size are being reset. Then the file entry which has become useless is being deleted. Finally it is checked whether the deletion was successful.
Overwriting information with random data makes drive compression drivers really write the data. Normally these drivers don't do multiple writing of the same data for performance reasons. In addition to that random data makes it more difficult to restore data using electron tunnelling microscopes.
Steganos and the Steganos Shredder use the same functions to wipe files.
Note: Since modern operating systems (such as Windows 95/98/NT) swap data to the hard disk, the risk that sensitive data remains somewhere on the system cannot be completely eliminated. Don't forget that it is impossible to completely erase data off magnetic media. Electron tunneling microscopes even restore data being overwritten several times. So if you really have to keep a secret it could be cheaper to physically destroy the magnetic medium (after wiping a file) than loosing the secret.
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