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Edit: this is not about how to securely erase, but how to check whether the erase was secure enough.

I have over written my SSD with very large video files, in order to overwrite any sensitive data I may have had, before selling the SSD.

I use the Mac program Disk Drill to try and recover deleted files, but it didn't find any file to recover.

Does that mean my SSD is safe to sell?

What if I use another similar program, will it be able to find something, or do they all look for data the same way?

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    Possible duplicate of How can I reliably erase all information on a hard drive? – Polynomial Jan 9 '17 at 14:17
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    Oh man - SSD's are easy to recover from.. you just need the right tools :D Hahahah. The problem is wiping the chips - Because of self managed wear levelling the same sector you think you are overwriting may be a completely different sector the next time you write to it.. leaving your old data unwipped in the old section of the chip. The only secure way to wipe HDD's - even SSD is to invoke the BIOS standard full format. The specification says that each HDD must have this function to fully erase all sectors, mapped or umnapped - From BIOS to comply with DOD standards.Not all bios's support this – Piotr Kula Jan 9 '17 at 14:59
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    Send it to a data recovery service and ask them to restore the data. Will cost ~700 €. When they found nothing you can sell the SSD: – Thomas Weller Jan 9 '17 at 14:59
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    @ppumkin The standard you're referring to is called ATA Secure Erase, and it has nothing to do with the DoD specifically. It's not a BIOS feature; it's an ATA command supported by the hard disk controller, which causes it to destroy and change the master key used to encrypt all previously written data. – Polynomial Jan 9 '17 at 15:14
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    @ppumkin Yeah, it's considered sufficiently secure by most data security standards. Just be careful not to refer to it as a DoD standard, because it isn't at all. – Polynomial Jan 9 '17 at 15:17
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Some drives conform to higher ATA standards than others. An ATA secure wipe (if available) will tell the controller to "release the charge in the NAND chips", effectively making it appear that there is no data on the drive. This can brick drives, as some overwrite firmware as well.

More importantly, a study done by the University of California San Diego showed that an ATA secure erase command may not sufficiently destroy data: http://nvsl.ucsd.edu/index.php?path=projects/sanitize

Some older consumer SSDs (and some newer ones) are SEDs, or Self Encrypting Drives. Each write to drive is first passed though the drive's controller which encrypts data before it is written. The advantages of these types of drives is that by changing the key used for encryption, one can have some level of confidence that the data is not recoverable. Data is unrecoverable by consumers.

As others have pointed out, with SSDs, there are other "reserve" blocks of memory which do not tend to be overwritten when preforming a disk wipe (especially generic disk wipes). This again should not be of significant worry for consumers as consumer level disk recovery software would be unable to recover from those special blocks.

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SSDs are rather odd when it comes to secure erasing them because their behavior is not deterministic. With their mapping table and spare space etc you can't ever really be sure that data is actually being overwritten, in fact it usually isn't. On the other hand as soon as a Trim command is processed by the drive the data should be completely unrecoverable by trying to read the drive normally. Once the drive no longer knows where the information is trying to read the blocks will only return 0's and can't return your data. It may still be on the drive in some piece of flash somewhere but once it is trimmed the drive won't read it again.

Assuming you aren't being targeted by some three letter state agency a simple trim of all the space on the drive is all that is needed to make all the data on the SSD unrecoverable from un-delete type programs.

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This doesn't answer the question as asked, but I believe it addresses the spirit of the question.

The fact is that you really can't ever be totally sure. Even if a drive advertises itself to support ATA Secure Erase, even if it claims to wipe the master key as a Self-Encrypting Drive, you can't know for certain.

If you think the value of the contents of the drive is enough that someone would be willing to spend the time and money to recover its contents, the best options you have are: use OS-level full-disk encryption from the start, or destroy the drive when you're done using it.

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Try using a application called BCwipe, it does a military secure level wipe writing 1's and 0's over entire drive 7 times

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    This is terrible advice for modern hard disks, particularly for SSDs. – Polynomial Jan 9 '17 at 14:54
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    SSDs have over-provision space to limit the effects of flash wear, which cannot be properly erased by direct writes to the disk. Any data wipe approach lessens the lifespan of SSDs, whereas there is a standard called ATA Secure Erase which properly erases the contents of an SSD by discarding the master key used for transparent full-disk encryption performed automatically by all modern SSDs. – Polynomial Jan 9 '17 at 15:02
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    Additionally, DoD specification wipe passes (as well as others such as Guttmann passes) are based upon old theorised attacks such as magnetic force microscopy (MFM) recovery, which have not been possible since magnetic hard disks grew beyond the tens of gigabytes in capacity, due to the effects of increased platter density. A single random pass is sufficient for wiping modern magnetic hard disks. The only reason that DoD data erasure specifications are still used in government work is for compliance with old standards which were written before more modern research was completed. – Polynomial Jan 9 '17 at 15:05
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    @ppumkin Tools are available from most SSD manufacturers to issue a Secure Erase command. Alternatively you can use hdparm on Linux to do it. Additionally, most modern operating systems support TRIM, which blanks sectors to zero on the fly when they are not in use by the filesystem, which is actually done for performance reasons but doubles up as a nice security benefit too. – Polynomial Jan 9 '17 at 15:51
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    This no longer answers the question after edits. – schroeder Jan 19 '17 at 7:36

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