Deleting deleted files


P

Paul

Mark said:
I know that no number of passes ensures actually clearing any
particular page on an SSD, but writing just a bit more than the
total space on the device does work with some devices. 3 passes
of the user view of the space works for most devices. Using
random data ensures something always gets written. Also,
since the programs that I use all eventually have all of the space
that the program thinks it is erasing allocated at the same time,
I know that at least that much space has been erased. 3 passes,
which is almost always more than 2.5 times that actual space,
so the wear leveling stuff will cause almost all of the actual
space to be cleared, but I don't count on all of the actual
cells on the device to have been erased even 1 time.
Anything that I care about is encrypted on the computer and
never gets to the device, let alone the actual flash memory,
in the clear.
See if the SSD supports Enhanced Secure Erase. It's supposed
to erase all LBAs, even spares.

I really recommend reading the info this guy provides,
since he is the person who promoted the addition of
the command to the ATA command set in the first place.

http://cmrr.ucsd.edu/people/Hughes/HDDEraseReadMe.txt

Included in there, is a description of recovering
drives that are still locked.

There is no point in having commands like that,
unless they "erase stuff" :) If the erasure doesn't
cover all the storage media, it's no better than
DBAN or equivalent.

Paul
 
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G

Gene E. Bloch

Fury? Is that the same as technical skill?
I don't know. My best guess: it's a first person shooter requiring a hot
Alien computer or similar...

And it can be played by men and women, of course, so don't accuse me of
being politically incorrect!

We're not OT yet, are we?
 
J

Jim

Did you read the details of how Secure Erase works on a
hard drive ? Maybe you've mis-interpreted the symptoms.

Secure Erase is a "posted" command. That means, if you
switch off the power on a hard drive, where Secure Erase
is currently running, the disk "remembers" it was in the
middle of a Secure Erase. This is unlike, most any other
command the drive works on. A Secure Erase might take, say,
half an hour, and you could kill the power on the computer
before it finishes.

When you turn on the power, the disk drive ignores you,
and goes back to working on the Secure Erase. It picks
up where it left off.

If you again kill the power, it will remember the new
location it got to, and pick up there the next time.

It does mean, before declaring a drive "dead", you need to
wait an hour or two with the power applied to it. Just to
make sure it isn't still working on the command internally.
Then, power off, power on, boot up, and test it again.

It should come back to life, after sufficient time has
passed, with power applied to the drive.

Paul
The drive is fubar, nothing is going to bring it back. I do have the
technical skills to try all options (and did), but as I said, I was
going to toss it, so no problem. There was no data on the drive and
this was just another experiment.

There is a clear warning from Parted Magic that there is a possibility
of a partition bug that will brick the drive permanently if a person
were to continue with the Secure Delete.

Jim
 
A

Anthony Buckland

To be explicit - I mean only cauldrons full of molten iron or steel.
Empty or cold cauldrons (cauldra?) need not apply.
This reminds me of a job +much+ earlier in my life,
as a bookkeeper. Every year my boss' boss (third
down from the president) would need to dispose of a
year's records (seven years in the past). Us junior
guys (the women were excluded from this hazardous
duty) would join the aforementioned BB in a company
truck which went to a city incinerator. On an upper
floor with a hole in the middle, below which blazed
something resembling the fires of hell, we would
shove stuff towards and down the hole. This was
judged to be secure disposal (everything was paper
back then).

The city no longer invites amateur participation.
It does not itself dispose of stuff, but sends it
out of town. And the above scenario (that was
just a hole a couple of meters across, no rails
or anything) would send legal into cardiac arrest
thinking about the liability if one of us were to
fall in now.
 
M

Mark F

I know that no number of passes ensures actually clearing any
particular page on an SSD, but writing just a bit more than the
total space on the device does work with some devices. 3 passes
of the user view of the space works for most devices. Using
random data ensures something always gets written. Also,
since the programs that I use all eventually have all of the space
that the program thinks it is erasing allocated at the same time,
I know that at least that much space has been erased. 3 passes,
which is almost always more than 2.5 times that actual space,
so the wear leveling stuff will cause almost all of the actual
space to be cleared, but I don't count on all of the actual
cells on the device to have been erased even 1 time.
Anything that I care about is encrypted on the computer and
never gets to the device, let alone the actual flash memory,
in the clear.
I thought that, although impractical, throwing the drives
into a black hole would get rid of everything, but
this article in The New York Times:
http://www.nytimes.com/2013/08/13/science/space/a-black-hole-mystery-wrapped-in-a-firewall-paradox.html?ref=science
"A Black Hole Mystery Wrapped in a Firewall Paradox"
By DENNIS OVERBYE Published: August 12, 2013
indicates that at some point in the last 50 years or so physicists
started thinking that information not only can't be destroyed by
chemical burning, but even can come out of a black hole.

Note: anyone who could get the information out of a black hole
or vaporized paper probably has access to a large quantum computer,
so I'd better start using longer keys and quantum-computer-proof
encryption also.
 
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G

Gene E. Bloch

This reminds me of a job +much+ earlier in my life,
as a bookkeeper. Every year my boss' boss (third
down from the president) would need to dispose of a
year's records (seven years in the past). Us junior
guys (the women were excluded from this hazardous
duty) would join the aforementioned BB in a company
truck which went to a city incinerator. On an upper
floor with a hole in the middle, below which blazed
something resembling the fires of hell, we would
shove stuff towards and down the hole. This was
judged to be secure disposal (everything was paper
back then).

The city no longer invites amateur participation.
It does not itself dispose of stuff, but sends it
out of town. And the above scenario (that was
just a hole a couple of meters across, no rails
or anything) would send legal into cardiac arrest
thinking about the liability if one of us were to
fall in now.
OK, it looks like I'd better suggest a cauldron with a guard rail.

It's kind of too bad that the public was disinvited and the fires
outsourced - that strikes me as a fun and cool way to be a pyromaniac
:)
 
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