There really isn't a standard technique that can be used to securely erase data from a solid state drive (SSD). This problem has been solved on hard disk drives (HDDs) for some time now by writing many times with different characters or by filling the space occupied by the file to be erased with zeroes. However, this technique and some other secure erase techniques really won't work on SSDs, particularly not on individual files. However, there are some techniques that will work.

There are some SSDs that will use TRIM to securely erase some files and some garbage collection to erase some things such as an old version of a file. However, since an SSD's only immediate reaction to a file that has been erased file is to forget where that file is as opposed to erasing it. This means that a file can stay on an SSD for quite a while. SSD's don't erase the file because it will cause extra wear on the SSD.

Similarly, on an SSD it is practically almost impossible to securely erase an individual file on an SSD, since the way that an SSD writes and delete files the user doesn't have any over what the SSD is doing. One of the best ways to protect an individual file is with encryption.

There are at least two reasons that the overwriting procedure that works on HDDs won't work on an SSD. Although overwriting will obscure some of the data on the SSD, it has been demonstrated that some of the data will still be readable after twenty overwrites. The reason for this is that some SSDs have additional storage space that can't be accessed by the user. There are some deletion tools that won't allow you to access this area. The only way you can get full access is to uninstall your drive by going through the BIOS. This can also occur as a result of problems with the firmware, and unless you're capable of physically confirming that this technique will work on your SSD, it simply isn't sufficiently reliable for a real secure erase.

These days, there are many SSDs that are available with secure wiping utilities that are preinstalled that are intended erase data from the cells. However, only four out of twelve drives that were tested by researchers reliably erased the data. Some SSDs have better tools for erasing data than others. For example, the drives that have Indilinx controllers have a function called sanitary erase that will restore the SSD to a new condition after deleting all of the data on the SSD.

These secure erase utilities are sufficient if all you want to do is improve the performance of your SSD. However, it isn't a great option security wise unless you can verify that your SSD is actually erasing your data.

Encrypting the contents of your SSD is the best technique to protect your data, without using the powerful tools for secure erasing that will clean tight down to the overly provisioned cracks. That way, if somebody is trying to obtain your data, the only thing that you will have to do is to ensure that the SSD has the security key. Unless somebody can crack your security code your data will be safe.

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by Martin Jennings