Hello, On Wed, 01 Oct 2008, Vaidhyanathan Mayilrangam Gopalan wrote: > Kapil Hari Paranjape wrote: >> For such systems one approach is to create an encrypted block device >> which uses this device as the base block device. You don't even need >> to remember the passphrase! >> >> After creating the encrypted device. say /dev/mapper/encrypt you >> can run >> >> dd if=/dev/zero of=/dev/mapper/encrypt >> >> Like shred, you can run this command multiple number of times to >> ensure that all magnetic memory is also erased. >> > > In US, for some kinds of "shred"ing, you are supposed to overwrite it > with random bit patterns before overwriting with delete. I do not know > the exact physics of it.. but it looks like data forensics is getting a > lot advanced and simple overwriting by zeros is just not enough for all.
Which is why I suggested using an encryption layer on top of the block device. Then "writing zeroes" would become "writing random data"! Of course, "shred" also fills with specific patterns which are supposed to make the disk lose its magnetic memory. I can't see any way to do this for RAID disks except to write to each disk separately. Kapil. --
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