The hardware assisted authentication using the security token or smart card is possible for USB to SPI. Encryption can be carried out or supported by the hardware (such as TPM or hard drives with special firmware). Metaphorically speaking, encryption is like the door of a house.
The door may, for example, be made of wood or steel. Transferred to the mobile hard drives that would mean that a simple XOR operation or encryption according to AES (Advanced Encryption Standard) can be used with different key lengths and block modes.
The choice of an appropriate encryption decides on the best way to achieve a high level of data security. For the highest standards of data security, the Federal Office for Security in Information Technology recommends encryption in XTS-AES mode. Attackers who want to spy on an encrypted hard drive, usually attempt to gain the password in various ways.