On the SSD, USB Flash memory devices and SD cards for secure deletion
Secure Deletion on Solid-state Disks (SSDs), USB Flash Drives, and SD Cards
And article excerpts translated from SSD.EFF.org
Straight to the point, unfortunately - because of the way SSD, USB Flash memory devices and SD cards, local security erase hard to do . Unless you piece of equipment (each file and free space) all erased.
Thus, on these devices, you can be the best way to protect data is to enable encryption . Based encryption, even if the file still exists on the hard disk, the file appears to other people found some data is meaningless, and can not force you to decrypt the file.
All in all, for the present, and there is no universal method of trust can clearly be safely removed solid data on your hard disk. If you want to know why, read on:
As we mentioned above, the solid-state hard drives and USB flash devices use what is called a balanced-wear technology ( Wear leveling technology). We will describe below roughly how it works.
For mechanical hard disk space on which is divided into a number of blocks ( Blocks ), just like many pages on the chapter of a book. When a file is written to the hard disk, it will be assigned to (block sequence) of a block or group of blocks. If you want to overwrite the file, you have to do things just hard to tell override these blocks.
But for solid-state drives and USB flash devices, because each block can only be "erased - and then write" a limited number of times, the block will exceed this limit will not work (as in a number of writing and erasing paper after difficult to use). Frequently erased and re-written in the same block is difficult to do.
To solve this problem, a solid-state hard drives and USB flash memory devices, each will be a block - number "Erase and then write" as equal as possible, so that your device has a longer life.
As a side effect, sometimes, to erase block or writing files is not as literal as instantly store, but do not touch the block itself, only mark it as invalid and modified files stored in other blocks in. This is like the page to be modified to place but no matter what you want to write modified on other pages, modify and update the table of contents page of the book points out.
Everything on the very bottom of the hard disk electronic level occur, so that the operating system will not even notice they have occurred. This performance is when you want to overwrite a file, in fact, the computer does not guarantee the actual override it, which explains why security is so difficult to erase data on solid-state storage device.
This article Translator: yakuback
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