Suggestion: secure delete

[franc]

Possible to add the possibility to delete files securely?
Maybe like sdelete on windows from Sysinternals.

It is amazing that there are so few apps doing this.
If I lost my phone I wouldn't like somebody to undelete my files.
Frank

[Hacker]

How would such a thing work on flash memory? Is there a way? Except filling all empty space.

Roman

[franc]

How would such a thing work on flash memory?...

This is a good question. I searched a bit about it and now I know that there is "Wear Leveling", see (german):

http://www.heise.de/security/meldung/Viele-SSDs-und-USB-Sticks-lassen-sich-nicht-sicher-loeschen-1195973.html

With Wear Leveling the controller of the sd-card decides self, where to write next data, surely not exactly over the just before erased data.

So I would need to overwrite each time all the empty space of the card, if I understood well. Surely this is not an every day job just after deleting a single file.

And still there is space which only the controller himself can access, not me or any app, so 100% security is not given anyway.


So my suggestion is not very senseful, I think now

frank

PS.: some people discussed secure delete of flash memory already there:

http://www.computerbase.de/forum/showthread.php?p=12981721

[ghisler(Author)]

Because of wear leveling, overwring a file with zeroes before deleting will probably not help - the zeroes just go to a different location in the flash memory.

The only solution would be to delete all the files you want to wipe, and then overwrite the entire free space with zeroes. This way the flash doesn't have any spare cells to which it can write. You can use the following program from the play store:
https://play.google.com/store/apps/details?id=com.kovit.p.forevergone