Secure deletion method
Cryptographically Strong Random Data
This method overwrites the contents of a file with random data from the Windows cryptographic random number generator, as many times as you choose. It is the fastest secure method in Advanced File Shredder and the right choice for most everyday shredding.
How it works
Each pass writes fresh random bytes over the whole file. The bytes come from the Windows cryptographic random number generator, the same source Windows uses to create encryption keys, so the data written has no pattern that could be predicted or reversed. After the last pass, Advanced File Shredder reads the data back from the disk, bypassing the Windows cache, and checks that it matches what was written.
Why cryptographically strong?
- Unpredictable: an ordinary pseudo-random generator repeats a predictable sequence; cryptographic random data cannot be reproduced to separate it from what was underneath.
- Not compressible: random data cannot be compressed. On NTFS-compressed files and compressed drives, a pattern such as all zeros shrinks to a few bytes and may leave most of the original clusters untouched; random data fills the full space the file occupies.
- Fast: a few passes give strong protection in a fraction of the time of the 35-pass Gutmann method.
How many passes?
A single pass of random data already defeats data recovery software. Selecting 5–7 passes adds a wide safety margin. Choose more passes only if your security policy requires it; each pass adds the time needed to write the whole file again.
Whatever the number of passes, Advanced File Shredder also overwrites the file’s cluster tail and its NTFS alternate data streams, and renames the file and resets its time stamps before deleting it.