Patent Application
20110213987
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2010-043384, filed Feb. 26, 2010, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a controller for a data storage device, a data storage device, and a control method thereof.
There are data storage devices that encrypt data before storing it to prevent information leakage when stolen or is disposed of. For example, Japanese Patent Application Publication (KOKAI) No. 2004-341768 discloses a magnetic disk device, i.e., hard disk drive (HDD), with encryption that encrypts plaintext data from a host and writes the encrypted data to the magnetic disk after the user is authenticated. The HDD decrypts the encrypted data on the magnetic disk to transfer the plaintext to the host after the user is authenticated. That is, when used by an authorized user, similar to a conventional HDD without using encryption, the HDD with encryption exchanges plaintext data with a host via an interface.
In a conventional technology, upon updating a data key used to encrypt or decrypt data to be stored in the magnetic disk, data is loaded from the magnetic disk into the buffer random access memory (RAM). The data is decrypted by the encryption/decryption circuit using an old data key and is once again stored in the buffer RAM. The data stored in the buffer RAM is then encrypted by the encryption/decryption circuit using a new data key, and is written back to the magnetic disk via the buffer RAM.
Even an HDD with encryption function sends plaintext data to a host if a backup HDD does not support encryption function. Accordingly, the plaintext data is stored in the backup HDD (for example, HDD of the host). Therefore, if the backup HDD is stolen or is disposed of, all information may leak therefrom, which is a security worry. To cope with this, if the host encrypts the data again using a backup key, the host is required to manage the backup key. Moreover, the host is necessitated to perform the processes except data backup always with data encryption, which increases load on the host.
As in the conventional technology, if data stored in the magnetic disk is decrypted using an old data key and once stored in the buffer RAM, and is then encrypted using a new data key and written back to the magnetic disk via the buffer RAM upon updating a data key, when the buffer RAM is located outside the integrated circuit (IC) chip provided with the encryption/decryption circuit, the decrypted data is once stored outside the one-chip IC chip, which may result in the leakage of information indicating the old and new data keys and the plaintext data to the third party.
A general architecture that implements the various features of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention.
Various embodiments will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment, a controller configured to control a data storage device provided with a storage module that stores data encrypted with a first key comprises an input and output module, a plurality of encryption and decryption modules, and a connector. The input and output module is configured to manage data input and output between the storage module and a host. The encryption and decryption modules are configured to be switched to function as an encryptor or a decryptor. The connector is configured to change connection between the encryption and decryption modules and the host. When encrypted data is backed up, one of the encryption and decryption modules on the side of the storage module is switched to function as a decryptor, while one of the encryption and decryption modules on the side of the host is switched to function as an encryptor. The decryptor, the encryptor, and the host are connected in series. The encrypted data is decrypted by the decryptor with the first key and is then encrypted by the encryptor with a second key to be output from the input and output module to the host.
According to another embodiment, a data storage device comprises a storage module, an input and output module, a plurality of encryption and decryption modules, and a connector. The storage module is configured to store data encrypted with a first key. The input and output module is configured to manage data input and output between the storage module and a host. The encryption and decryption modules are configured to be switched to function as an encryptor or a decryptor. The connector is configured to change connection between the encryption and decryption modules and the host. When encrypted data is backed up, one of the encryption and decryption modules on the side of the storage module is switched to function as a decryptor, while one of the encryption and decryption modules on the side of the host is switched to function as an encryptor. The decryptor, the encryptor, and the host are connected in series. The encrypted data is decrypted by the decryptor with the first key and is then encrypted by the encryptor with a second key to be output from the input and output module to the host.
According to still another embodiment, there is provided a control method applied to a data storage device comprising a storage module configured to store data encrypted with a first key, an input and output module configured to manage data input and output between the storage module and a host, a plurality of encryption and decryption modules configured to be switched to function as an encryptor or a decryptor, and a connector configured to change connection between the encryption and decryption modules and the host. The control method comprises: when encrypted data is backed up, switching one of the encryption and decryption modules on the side of the storage module to function as a decryptor; switching one of the encryption and decryption modules on the side of the host to function as an encryptor; connecting the decryptor, the encryptor, and the host in series; decrypting the encrypted data by the decryptor with the first key to obtain decrypted data; encrypting the decrypted data by the encryptor with a second key; and outputting the encrypted data encrypted with the second key from the input and output module to the host.
Like reference numerals refer to like parts throughout the several views of the drawings.
With reference to
As illustrated in
The magnetic disk 11 is rotated by the spindle motor 12. The head slider 13 is provided with the magnetic head including a write head and a read head (none of them illustrated in
With reference to
In
A magnetic head 22 includes a write head and a read head. Using the write head and the read head, the magnetic head 22 writes data to and reads data from the magnetic disk 11. As described above, the magnetic head 22 is located at an end of the actuator arm 15 and is moved in the radial direction of the magnetic disk 11 by the VCM 16 driven by the motor driver 21. When the magnetic disk 11 is not rotating, the magnetic head 22 is retracted on a ramp 23.
A head amplifier 24 amplifies a signal read by the magnetic head 22 from the magnetic disk 11 and outputs it to a read write channel (RDC) 25. The head amplifier 24 also amplifies a signal received from the RDC 25 to write data to the magnetic disk 11 and feeds it to the magnetic head 22.
The RDC 25 code-modulates data to be written to the magnetic disk 11 received from a central processing unit (CPU) 26, which will be described later, and feeds it to the head amplifier 24. The RDC 25 also code-modulates a signal read from the magnetic disk 11 and received from the head amplifier 24 and outputs it as digital data.
The CPU 26 is connected to a static random access memory (SRAM) 27 as a working memory, a flash read only memory (ROM) 28 as a nonvolatile memory, and a buffer RAM 29 as a temporary storage. The CPU 26 controls the overall operation of the magnetic disk device 1 according to firmware stored in advance in the flash ROM 28.
A hard disk controller (HDC) 30 controls data communication (including data encryption and decryption) with a host computer 40 via an interface (I/F) bus, controls the buffer RAM 29, and corrects an error in recorded data. The buffer RAM 29 is used to cache data communicated with the host computer 40 and to temporarily store data read from or to be written to the magnetic disk 11, and the like. The magnetic disk device 1 is built in or externally connected to the host computer 40. While the RDC 25, the CPU 26, the SRAM 27, and the HDC 30 constitute a controller 31 that controls the magnetic disk device 1 in the embodiment, it is not so limited. Besides, the controller 31 of the embodiment is configured as a system-on-a-chip (SoC). If the controller 31 is configured differently, among the constituent elements, at least the HDC 30 is formed of one chip. Accordingly, the salient feature of the HDC 30 described below is implemented by one-chip hardware.
A description will be given of the characteristic function and configuration of the HDC 30.
The encryption/decryption circuit of the HDC in a general HDD with encryption is implemented by a plurality of encryption/decryption circuits that realize parallel processing to ensure the data transfer capability of the interface to the host computer. For example, to achieve 3 gigabit per second (Gbps) throughput in a serial advanced technology attachment (SATA) interface using an AES-CBC encryptor supporting a 256-bit key length without parallel processing, a clock frequency of 3000*0.8/(128/17)≈319 MHz or more is required. However, by having two encryption/decryption circuits mounted in parallel, a required clock frequency is reduced to about 159 MHz, i.e., a half of that when no parallel processing is involved.
In the magnetic disk device 1 of the embodiment, the HDC 30 connects a plurality of encryption/decryption circuits (as decryptors) in parallel upon ordinary data read/write operation. On the other hand, the HDC 30 connects the encryption/decryption circuits in series upon backing up data to cause the encryption/decryption circuit at the output stage to function as an encryptor. Thus, data can be securely backed up. The backup data can be restored by applying the encryption/decryption in a reverse manner to the case of data backup with a reverse data flow.
In the following, a specific configuration of the HDC 30 will be described with reference to
As illustrated in
For example, 128-bit data from the FIFO memory 301c are sequentially decrypted by the encryption/decryption circuits (AES1 and AES0) 301f and 301g. The decrypted data are output through a switch circuit SW2301h, a transport layer 301i, a link layer 301j, and a PHY layer 301k. The transport layer 301i, the link layer 301j, and the PHY layer 301k are compliant with the SATA specification. The transport layer 301i is an element to issue a command to control the entire protocol. The link layer 301j is an element to control the PHY layer 301k and perform data encoding. The PHY layer 301k is an element to control a SATA signal, and transfers data from the link layer 301j as serial data as well as transferring received data to the link layer 301j in a form that can be analyzed by the link layer 301j.
A description will be given of the operation of the magnetic disk device 1 having the host I/F 301 in the HDC 30 configured as above and the host computer 40 to back up data in the magnetic disk device 1 and to restore the backup data in the magnetic disk device 1.
With reference to
As illustrated in
The HDC 30 of the controller 31 in the magnetic disk device 1 receives the data from the host computer 40 (S503). Then, as illustrated in
With this connection, the encryption/decryption circuit (AESO) 301g as a decryptor decrypts data read from the magnetic disk 11 using a data key generated and retained by the HDC 30. The encryption/decryption circuit (AES1) 301f as an encryptor encrypts the data read from the magnetic disk 11 and decrypted using the backup key received from the host computer 40 (S506). In this manner, the data read from the magnetic disk 11 of the magnetic disk device 1 is decrypted by the data key and encrypted by the backup key in the HDC 30, and transferred to the host computer 40 (S507).
The host computer 40 receives encrypted data transferred from the HDC 30 of the controller 31 (S508), and stores it in the backup HDD (S509).
With reference to
To restore data backed up by the host computer 40 into the magnetic disk device 1, as illustrates in
As illustrated in
With this connection, the backup data is transferred from the host computer 40 (S705). The host computer 40 can be notified of the data transfer timing by polling therefrom or a predetermined notification sent from the controller 31 to the host computer 40.
When the HDC 30 of the controller 31 receives the backup data from the host computer 40 (S706), the encryption/decryption circuit (AES1) 301f as a decryptor decrypts the backup data using the backup key received from the host computer 40 to restore the backup data. Meanwhile, the encryption/decryption circuit (AES0) 301g as an encryptor encrypts the data previously decrypted with the backup key using the data key generated and retained by the HDC 30 (S707). The encrypted data is stored in the magnetic disk 11 (S708). In this manner, the data transferred from the host computer 40 is decrypted with the backup key by the HDC 30 of the controller 31. The decrypted data is encrypted with the data key and is stored in the magnetic disk 11.
As described above, according to the embodiment, at the time of backup and restore, a plurality of encryption/decryption circuits (301f and 301g), which are generally connected in parallel, are connected in series. With this, data generally exchanged as plaintext with the host computer is encrypted using a backup key and is output as backup data. Thus, the data can be securely backed up. Further, the data encrypted with the backup key and backed up by the host computer is decrypted with the backup key by the HDC 30, and thereby can be restored.
In an HDD with encryption (the magnetic disk device 1, etc.), the data key may be updated to ensure data security. In such a case, an output module (in the case of
With reference to
Upon updating a data key, to achieve the above configuration as illustrated in
The encrypted data is looped back to the buffer RAM 29 via the buffer manager 301a, and thereby the data encrypted with the new data key is loaded into the buffer RAM 29. The data encrypted with the new data key is written back from the buffer RAM 29 to the magnetic disk 11 (S1006). This process is repeated for the entire user data area. Thus, the data key is updated.
As described above, according to the embodiment, using a plurality of encryption/decryption circuits for encrypting data to be stored and decrypting data to be output, data encrypted with a key (an old data key) on the buffer RAM 29 is decrypted in the HDC 30 of the controller 31. Further, the data is encrypted again with a different key (a new data key) and is written back to the buffer RAM 29. With this control, unencrypted plaintext data and a data key are not leaked out of the one-chip controller 31 such as SoC (to the buffer RAM 29, etc.). Accordingly, when a data key used to encrypt data is updated, a new data key and the data can be maintained secret.
While the embodiment is described above as being applied to the magnetic disk device, it is not so limited. The embodiment may be applied to other data storage devices such as a solid state drive (SSD). In addition, the operations illustrated in the sequence diagrams are examples for the purpose of description.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-043384 | Feb 2010 | JP | national |
