Lesson 6

Wiping Algorithms

How does wiping perform

A some quotation from the introduction:

"Deletion is not secure. When you delete a file the first letter of the filename in a directory entry is changed to a special character (hexadecimal code E5h). This is a special tag that tells the system “this file has been deleted and the space is free”. In fact the file’s data remains on the disk. It may remain on the hard drive until it is overwritten or remain till you sell your hard drive. Whatever the case your sensitive files can be recovered. So that is the answer to why we have to use a good file shredder utility". 

About algorithms

All the secure deletion algorithms performs the overwriting of your sensitive file. 

There are several algorithms to secure deletion: 

Single Pass – data area is overwritten once with “1” or “0”. 

DoD Method – the data area is overwritten with 0’s, then 1’s and then once with pseudorandom data. 

Guttman Method – the data area is overwritten 35 times. This method overwrites the drive taking into account the different encoding algorithms used by various hard drive manufacturers. 

NSA erasure algorithm – data is overwritten seven times with “0” pattern then with “1” and so on. It is the best method for quick and secure deletion (QuickWiper can do it).

What algorithm does QuickWiper use?

QuickWiper can work in two modes - single pass erasure algorithm (when the NSA option is checked off) and the NSA erasure algorithm.

To apply the NSA erasure algorithm while wiping you should check "Use NSA erasure algorithm" in "Wipe" menu.

Note: you can skip any lesson and begin reading the following by clicking "Next->" link. Each lesson describes a separate idea so you will not lose anything. This lesson course contains eight lessons (8) so you will spend just a 10 minutes reading but after reading all the eight lesson you will know how to wipe files, wipe free disk space, clear IE history, temporary files and cache. Lessons also have information about wiping algorithms, such as NSA erasure and common tips and tricks for using QuickWiper.

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