Some external HDDs (notably, WD Essentials) are known to be encrypted by the USB-SATA bridge present in their case:

Essentials drives are hardware encrypted. The USB-SATA bridge board is required to decrypt the data.

This is confirmed by users who are unable to access any data once the HDD is extracted from its external case and attached directly to SATA.

I don't quite understand what purpose this kind of encryption serves. If the drive is lost or stolen, so is (most probably) the external case, so data security is unaffected. If anything, this makes legitimate data recovery more difficult, if the said bridge board is damaged. Am I missing something?

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    Can you use the drive if you create a new partition table on it? (e.g. format it)? If so, it could just be WD saving money by using standard parts (unencrypted hard drives), with a custom encryption board for those devices that implement hardware encryption
    – Matthew
    Mar 7, 2016 at 15:49
  • It looks like the drive can be used without the case when repartitioned. I have asked the SO user to check whether the HDD itself is self-encrypting or not. Mar 7, 2016 at 16:26

1 Answer 1


Having the drive pre-encrypted with the key stored on the drive or controller makes it faster if they want to later properly encrypt it - you just encrypt the key with the password, rather than having to encrypt the whole drive.

This means it's a ten-second process rather than several hours.

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