Security Basics mailing list archives
RE: Hard drives v. CF/Smart media/etc.
From: Alexander Klimov <alserkli () inbox ru>
Date: Wed, 19 Oct 2005 23:06:04 +0200 (IST)
On Tue, 18 Oct 2005, Herman Frederick Ebeling, Jr. wrote:
: Yes since they are for the most part using FAT or FAT32 as the file : system. So deleting a file still only marks the space as overwritable : not actually removing the data. What if someone is using the NTFS file system? How many time would one have to overwrite the data before it became unrecoverable? Would say PGPs wipe function be more effective on flash media then on an actual HD/floppy disk?
Since it is impossible to overwrite a single sector of flash without erasing (and writing back) the whole erase unit, and also due to the need of wear leveling the FTL (Flash Translation Layer) is used in most of the flash ``disks''. That is when you overwrite some sector on your `block' device what really happens is that the flash driver allocates a new place for the new sector and leaves the previous version unchanged. So, wiping data by overwriting ``sectors'' which belong to file is mostly pointless (IIRC this is exactly what pgpwipe does). OTOH, if you fill the whole flash with random data, it is likely that the driver will have to overwrite the old data as well (note that to continue normal operation flash has to have some reserve of free space even when it is full, so you can not be really sure that the data you want to destroy is really gone). So, either write random data until the flash is full several times, or, better, never write unencrypted data. -- Regards, ASK
Current thread:
- Re: Hard drives v. CF/Smart media/etc., (continued)
- Re: Hard drives v. CF/Smart media/etc. Alloishus BeauMains (Oct 18)
- RE: Hard drives v. CF/Smart media/etc. Herman Frederick Ebeling, Jr. (Oct 18)
- Re: Hard drives v. CF/Smart media/etc. Alloishus BeauMains (Oct 18)
- Message not available
- Re: Hard drives v. CF/Smart media/etc. Alloishus BeauMains (Oct 21)
- RE: Hard drives v. CF/Smart media/etc. Herman Frederick Ebeling, Jr. (Oct 21)
- Re: Hard drives v. CF/Smart media/etc. Raoul Armfield (Oct 18)
- RE: Hard drives v. CF/Smart media/etc. Herman Frederick Ebeling, Jr. (Oct 18)
- Re: Hard drives v. CF/Smart media/etc. Raoul Armfield (Oct 21)
- Re: Hard drives v. CF/Smart media/etc. Micheal Espinola Jr (Oct 21)
- Re: Hard drives v. CF/Smart media/etc. FocusHacks (Oct 24)
- RE: Hard drives v. CF/Smart media/etc. Alexander Klimov (Oct 21)
- Re: Hard drives v. CF/Smart media/etc. crazy frog crazy frog (Oct 21)
- Re: Hard drives v. CF/Smart media/etc. Alloishus BeauMains (Oct 24)
- Re: Hard drives v. CF/Smart media/etc. Micheal Espinola Jr (Oct 18)
- Re: Hard drives v. CF/Smart media/etc. Steven Meyer (Oct 18)
- RE: Wireless Security Herman Frederick Ebeling, Jr. (Oct 13)
- RE: Wireless Security Herman Frederick Ebeling, Jr. (Oct 14)