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Kilroy
Premium,MVM
join:2002-11-21
Saint Paul, MN
reply to antdude

Re: Securedly erase memory cards?

If you're concerned destroy them.

Due to the way that they write there isn't a good way to wipe them.


antdude
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said by Kilroy:

If you're concerned destroy them.

Due to the way that they write there isn't a good way to wipe them.

Really? Don't they use the same method as Flash memory?


StuartMW
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Galt's Gulch
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1 edit

1 recommendation

said by antdude:

Don't they use the same method as Flash memory?

They are flash memory. All USB/SD/etc cards use flash memory. Not sure why Kilroy See Profile thinks they can't be wiped.

If you only have SD (vs CompactFlash, USB sticks etc) cards you can use the official SD Card Formatter with the overwrite option.

»www.sdcard.org/downloads/formatter_3/
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Kilroy
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join:2002-11-21
Saint Paul, MN

1 recommendation

If the card supports wear leveling you can't be sure that it is wiped.
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StuartMW
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Well the SD Card Formatter actually performs a bulk erase before formatting assuming the card supports it and you ask it to.

quote:
FULL (Erase):
This option initializes the file system parameter in the card, and initializes all the user data areas (Initialize it by executing erase processing (data deletion) of the card to all the user data areas). This option has the possibility that it takes the format time long according to the capacity of card. There is something that doesn't support to the erase processing according to the SD interface
device. The erase processing is skipped when "FULL (erase)" format type is selected in the unsupported environment. In this case it is same as selected QUICK option.

Some USB sticks can also be bulk erased/formatted with a utility provided by the manufacturer. I've used such in the past. That said you usually have to know the OEM to find the tool (if it exists).

That said you're correct that simply writing zeroes to the device using something like DBAN may not erase everything.
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antdude
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1 edit
reply to StuartMW
said by StuartMW:

said by antdude:

Don't they use the same method as Flash memory?

They are flash memory. All USB/SD/etc cards use flash memory. Not sure why Kilroy See Profile thinks they can't be wiped.

If you only have SD (vs CompactFlash, USB sticks etc) cards you can use the official SD Card Formatter with the overwrite option.

»www.sdcard.org/downloads/formatter_3/

I will try it out later. No Linux port, eh? I hope full erase and full overwrites are enough.
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Ant @ AQFL.net and AntFarm.ma.cx. Please do not IM/e-mail me for technical support. Use this forum or better, »community.norton.com ! Disclaimer: The views expressed in this posting are mine, and do not necessarily reflect the views of my employer.


StuartMW
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1 recommendation

said by antdude:

No Linux port, eh?

Geez, you're a fussy ant
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antdude
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said by StuartMW:

said by antdude:

No Linux port, eh?

Geez, you're a fussy ant

Ya, but it looks like I am limited to Windows and Mac ports so I will have to use that one then.
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Ant @ AQFL.net and AntFarm.ma.cx. Please do not IM/e-mail me for technical support. Use this forum or better, »community.norton.com ! Disclaimer: The views expressed in this posting are mine, and do not necessarily reflect the views of my employer.


Sr Tech
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join:2003-01-19
New Britain, CT
kudos:1

2 recommendations

One way to check would be install Recuva and see if you can recover the data after wiping, if not you should be ok. Also Recuva can tell you the state of the file well as can perform overwriting as well.


antdude
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reply to StuartMW
said by StuartMW:

said by antdude:

Don't they use the same method as Flash memory?

They are flash memory. All USB/SD/etc cards use flash memory. Not sure why Kilroy See Profile thinks they can't be wiped.

If you only have SD (vs CompactFlash, USB sticks etc) cards you can use the official SD Card Formatter with the overwrite option.

»www.sdcard.org/downloads/formatter_3/

I finally tried it. Full Erase failed: »i.imgur.com/NWEnF.gif but Full Overwrite worked. Recuva couldn't recover any files so I hope that' secured enough.
--
Ant @ AQFL.net and AntFarm.ma.cx. Please do not IM/e-mail me for technical support. Use this forum or better, »community.norton.com ! Disclaimer: The views expressed in this posting are mine, and do not necessarily reflect the views of my employer.


Blackbird
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Fort Wayne, IN
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1 recommendation

said by antdude:

... I finally tried it. Full Erase failed: »i.imgur.com/NWEnF.gif but Full Overwrite worked. Recuva couldn't recover any files so I hope that' secured enough.

A full overwrite should work for normal purposes. The problem that Kilroy See Profile was referring to is that in a flash device with wear leveling, there is a built-in mechanism that assures that all cells in the device get written-to roughly the same number of times, to prevent wear-out from literally writing/erasing/writing too often to the same cells. In such a case, any kind of partial rewrite to the device may skip over a previously-used (but marked as "erased") cell in favor of a cell that's been written-to fewer times. A forensic access of such a device can conceivably look into those previously-used cells and read what voltage states are still actually left in them. By fully writing to the device, all cells are over-written with the voltage states corresponding to the new signals.

That still leaves the question of whether an extremely sensitive, scientific lab analysis might still be able to see a slight variance from nominal in a cell's present voltage state, left from the data that was there prior to a single re-write... but the likelihood for success of that kind of forensics is very questionable, even among experts - unless the over-write signal is all ones or all zeroes. In that case, the faint 'echo' of the cell's stored voltage state that was there before may conceivably be slightly easier to detect and "read".
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