Recently I had an SSD fail and am attempting to do a data recovery. The data recovery company tells us that it is complicated because the build-in drive controller uses encryption. I presume this to mean that when it writes data to the memory chips it stores it in an encrypted format on the chips. If this is true, why on earth would they do that?
Answer
Always-on encryption allows you to secure your data by setting a password without having to wipe or separately encrypt the data. It also makes it fast and easy to "erase" the entire drive.
The SSD does this by storing the encryption key in plaintext. When you set an ATA disk password (Samsung calls this Class 0 security), the SSD uses it to encrypt the key itself, so you'll need to enter the password to unlock the drive. This secures the data on the drive without having to erase the entire contents of the drive or overwrite all data on the drive with an encrypted version.
Having all the data encrypted on the drive also brings another perk: the ability to effectively erase it instantly. By simply changing or deleting the encryption key, all data on the drive will be rendered unreadable, without having to overwrite the entire drive. Some newer Seagate hard drives (including several newer consumer drives) implement this feature as Instant Secure Erase.1
Because modern hardware encryption engines are so fast and efficient, there is no real performance advantage to disabling it. As such, many newer SSDs (and some hard drives) have always-on encryption. In fact, most newer WD external hard drives have always-on hardware encryption.
1In response to some comments: This may not be entirely secure considering that governments may be able to decrypt AES within the near future. It is, however, generally sufficient for most consumers and for businesses who are trying to reuse old drives.
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