On Thu, 23 Nov 2017 23:10:52 +0600, Yousuf Khan
wrote:

On 20/11/2017 2:00 PM, Ed Light wrote:
My Kingston SSD's software has a wipe the disk option.

Seems like if you filled up the capacity of the disk with random stuff
it would get everything. I don't know, though.

Wiping just one file is another thing.

But, no matter where it's really storing it, if it's no longer available
in the virtual hard disk representation of the SSD, such that recovery
software can't find it, then it should be as good as gone, unless some
expert takes it apart or hacks it somehow. I don't know.

That's my feeling too. But the Trim command should wipe all deleted data
too!
I don't think the TRIM command is supposed to erase any data. It is
only to tell the device that the data in the sectors is not needed
anymore. Thus the device is free to not copy the data to a new sector
when performing various operations, including the invisible to the
user wear leveling.

As to the original question, even if you write random data to fill the
entire user visible space on the device enough times to account for
the extra capacity that the device keeps for working space and spare
blocks, you still cannot be sure that there is not some user data that
is no longer visible to the user that still stored on the device.

Using the devices own encryption should ensure that no clear text
user data ever gets on the device, but it is probably depends on the
device as to if the data could be recovered from the device with
factory/laboratory access. (For example, someone having the
decryption key for the user data might be able to decrypt the data
if the original user LBA was known or if all possible user LBAs for
the sector were known and the billions of possibilities were tried.)