In addition 128 bit AES encryption provides data protection and in particular can be used to rapidly erase the encryptionkey so the drive can be repurposed without concern about the old data being accessible.
Since your bits may travel through an upstairs apartment or the house next door, HomePlug uses a networkwide password as an encryptionkey to keep your data invisible to neighbors' prying eyes.
Many factors are at play here dealing with individual or third-party data retention policies sometimes beyond your control as well as continued usage of the same private encryptionkey and password.
PUFs are an innovative way of safeguarding individual chips from data theft by using the unique 'fingerprint' inherent in every semiconductor device to protect its encryptionkey, making it very hard to clone and thus reverse-engineer and compromise security microcontrollers.
Hitachi's version "scrambles data using a password-generated key" as the data is written, and then descrambled with the key as it is retrieved using the highly-touted Advanced Encryption Standard (AES) algorithm.
At the time, the federal government was also pushing hard to get companies to add so-called "key escrow" type technologies to their encryption products so that law enforcement could obtain access to encrypted data on demand.