A Data Storage Device (DSD) includes a Non-Volatile Memory (NVM) including a private partition with a write-once partition only internally accessed by a controller of the DSD. Data stored in at least one memory of the controller and in the private partition is encrypted. According to one aspect, the NVM includes a firmware partition, and at least one key associated with the DSD stored in the write-once partition is descrambled or decrypted using a scrambler key or decryption key stored in the firmware partition. According to another aspect, a method for establishing a root of trust includes generating a scrambler key or a decryption key, and generating at least one key associated with the DSD. The scrambler key or the decryption key is stored in a firmware partition of an NVM of the DSD, and the at least one key associated with the DSD is stored in a write-once partition.