Self-encrypting flash drive

A method comprises receiving a plaintext message (m), encrypting the plaintext message and generating a cipher text (c) and authentication data (t), storing the cipher text in a user data portion of a data storage device, and storing the authentication data in a meta data portion of the data storage device.

FIELD

Secure hard drives are a class of disk drives that implement various security features to protect stored user data. Self-Encrypting Drives (SED) are a particular class of secure disk drives that automatically encrypt data as they are being written, and conditionally decrypt data as they are being read from the drive.

The contents of an SED is always encrypted and the encryption keys are themselves encrypted and protected in hardware. Because disk encryption is handled in the drive itself, the overall system performance is not affected or subject to attacks targeting other components of the system.

Due to heightened threat to data privacy and security, SEDs are viewed as an increasingly vital tool in combating data loss and theft. Designing SEDs poses technical challenges on how the encryption and decryption process can be performed.

SUMMARY

A method comprises receiving a plaintext message (m), encrypting the plaintext message and generating a cipher text (c) and authentication data (t), storing the cipher text in a user data portion of a data storage device, and storing the authentication data in a meta data portion of the data storage device.

A method comprises receiving an initialization vector (IV), receiving a key (k), reading cipher text (c) from a user data portion of a flash storage device, reading authentication data (t) from a meta data portion of the flash storage device, and decrypting the cipher text using the initialization vector, the key, and the authentication data, and generating plaintext (m).

A flash storage device comprises a memory space configured for storing user data, a memory space configured for storing meta data, an encryption module adapted to receive plaintext (m), a key (k), an authentication tag (t), and an initialization vector (IV) to encrypt the plaintext to generate a cipher text (c), and the flash memory device configured to store the cipher text in the user data portion of the flash storage device, and store the authentication tag in the meta data portion of the flash storage device.

DETAILED DESCRIPTION

There are a number of data encryption algorithms in use today, for instance AES (Advanced Encryption Standard), TLS (Transport Layer Security), and other algorithms such as authenticated encryption where an encryption algorithm is combined with a Message Authentication Code (MAC) to provide data confidentiality (privacy) as well as protection from message tampering to additionally provide data integrity (authenticity).

Flash storage devices have been recognized as an attractive data storage option for mobile computers and smartphone devices because of their small size, light-weight, shock resistance, fast access speed, and low power consumption. It is anticipated that with further advances in flash memory technology, its popularity may rival or even outpace hard disks. The flash memory device can be adapted to perform as a self-encrypting drive according to the present disclosure.

FIG. 1is a simplified diagram illustrating a preferred embodiment of the encryption process10for a flash storage device according to the present disclosure. A data fetch control block12receives the user's plaintext message (m)14to be stored in the flash storage device, and generates a sector allocation16, and a user key (k)18along with the plaintext. The encryption key generally remains constant and it can be used to identify the user. The encryption key can be encrypted. Auxiliary data20such as the sector address combined with some function of an attribute of the flash block like its “age,” for example, can be provided to a flash translation layer22to generate an initialization vector (IV). Other attributes such as utilization information and erase count may be used with or instead of age data. The primary function of the flash translation layer22is to perform a translation or mapping function in order to interface the linear flash memory with a file-based or sector-based system. The flash translation layer22is tasked with mapping between the logical block address (LBA) used by the host central processing unit (CPU) and the physical address locations in the flash storage device.

The following is a functional model of an authenticated encryption (AE) algorithm according to the present disclosure.
E(k, IV, m)→(t, c)

Where E is the encrypting machine, k is a user key, IV is a unique (random or pseudorandom) initial value (Initialization Vector) per message, m is the plaintext message to be encrypted, t is an authentication tag, and c is the resultant cipher text.

As shown inFIG. 1, the flash translation layer22is adapted to further generate an initialization vector (IV). The initialization vector is variable and dependent on the auxiliary data20so that the encryption is secure. Therefore, the auxiliary data is used to generate a unique initialization vector each time a sector is written. The flash translation layer22also generates meta data, which are stored in separate portions of the flash storage device. The meta data is used for flash maintenance functions per sector. The user plaintext14, user key18, initialization vector and meta data24are provided to an encryption machine26. The encryption machine26is adapted to encrypt the user plaintext14using the user key18, and initialization vector, to generate an output consisting of the cipher text32, an authentication tag, t, and the meta data (unchanged)34. The output from the encryption machine26is stored in the user data portion of the flash device28via a NAND flash device controller30.

In flash storage device there is some amount of meta data that is available for flash maintenance functions per sector. A portion of the area used to store meta data can be set aside to store the authentication data or “tag” that is output from the encryption process. This authentication tag is used during decryption to detect and protect from third party tampering of user data.

Additionally, the meta data passes through the same encryption machine and is optionally not encrypted, and it may still be accounted for in the authentication tag. Thus, the meta data, whether encrypted or not, may be protected from tampering because any tampering will be detected by the decryption engine due to a mismatched authentication tag. A different embodiment may have the meta data hashed and optionally encrypted using a completely different key (k) and initialization vector, giving it a mutually exclusive level of confidentiality and integrity with respect to the user data.

The decryption machine inverts this process as follows:
D(k, IV, c, t)→m OR NULL

Where D is the decrypting machine, IV is the same unique number used during encryption, c is the cipher text, t is the authentication tag, and m is the plaintext message. If the cipher text has been tampered with the decryption will output a “bottom” or “NULL” which implies that the decryption was not successful.

FIG. 2is a simplified diagram illustrating a preferred embodiment of a decryption process40for a flash storage device according to the present disclosure. A user read request42is received by the data fetch control block12, which is adapted to generate the user key18and a sector reference44to the data. The flash translation layer22receives the auxiliary data or sector table information20as well as the sector reference44, and generates an initialization vector46based on those data. The decryption machine48uses the user key18, initialization vector46, along with the authentication tag and meta data34stored in the flash device28to decipher the encrypted data or cipher text32. As stated above, the authentication tag is primarily used to detect data tampering. If there is a mismatch of the authentication tag, the decryption machine outputs null or error that indicates unsuccessful deciphering.

The features of the present invention which are believed to be novel are set forth below with particularity in the appended claims. However, modifications, variations, and changes to the exemplary embodiments described above will be apparent to those skilled in the art, and the self-encrypting flash drive described herein thus encompasses such modifications, variations, and changes and are not limited to the specific embodiments described herein.