SECURING A FLASH MEMORY BLOCK IN A SECURE DEVICE SYSTEM AND METHOD

• US 20080117679A1
• Filed: 02/26/2007
• Published: 05/22/2008
• Est. Priority Date: 11/19/2006
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Acer Cloud Technology, Inc. (Acer, Inc.)
• Inventors: Chan, Andy, Mielke, Paul, Wheeler, Rob, Srinivasan, Pramila, Princen, John
• Granted Patent: US 8,200,961 B2
• Time in Patent Office: Days
• US Class Current: 365/185.04
• CPC Class Codes: G06F 21/79 in semiconductor storage media, e.g. directly-addressable memories

Abstract

A technique for securing a flash memory block in a secure device system involves cryptographic techniques including the generation of a Message Authentication Code (MAC). The MAC may be generated each time a file is saved to one or more data blocks of a flash memory device and stored with the file'"'"'s metadata and to each of the data blocks. A technique for reading and storing versioned files may be employed when applications utilize versioning.

Claims

1. A method comprising:

encrypting data;

storing the encrypted data in a flash memory block of a flash memory device;

generating a cryptographic message authentication code (MAC) covering the data and informational variables, wherein the informational variables are generated by or accessible to the operating system software, wherein at least some of the variables are not stored on the flash device

storing the MAC in the flash memory block;

retrieving the encrypted data and the MAC from the flash memory block;

performing a validation check on the retrieved data using the MAC;

rejecting the retrieved data if the retrieved data fails the validation check;

if the retrieved data passes the validation check;

accepting the retrieved data;

decrypting the retrieved data.

2. The method of claim 1, further comprising using a DES or an AES method to encrypt and decrypt data.

3. The method of claim 1, further comprising storing the MAC in spare area of the flash memory block.

4. The method of claim 1, wherein the MAC is generated using an HMAC technique.

5. The method of claim 1, wherein storing the MAC includes storing a copy of the MAC in spare area.

6. The method of claim 1, wherein the plurality of variables accessible to the operating system software is selected from one or more of a group consisting of a value determined by software means of the operating system during run-time, a unique number that is assigned to the file and stored with file-specific meta data, a value representing a logical block index, a physical block number of the flash memory block, a variable associated with an application.

7. The method of claim 1, wherein the plurality of variables accessible to the operating system software includes an application variable, wherein the application variable includes one or more values selected from the group consisting of an application ID parameter, an input to a security kernel for use as part of the data covered by the message authentication code, a version number of the data in the flash memory block.

8. A system comprising:

a flash memory device including at least one flash memory block;

a flash memory device driver embodied in a computer-readable medium;

a security kernel embodied in a computer-readable medium;

wherein, in operation, the security kernel generates a MAC using a plurality of variables accessible to operating system software and the flash memory device driver facilitates sending the MAC to the flash memory device for storage in the flash memory block, and wherein, in operation, the flash memory device driver facilitates receiving the MAC from the flash memory block and the security kernel performs a validation check using the MAC.

9. The system of claim 8, wherein the MAC is stored in the flash memory block spare area.

10. The system of claim 8, wherein a protected key associated with the flash memory device driver is stored in secret non-volatile memory accessible through the security kernel.

11. The system of claim 8, further comprising an encryption/decryption engine, embodied in a computer-readable medium, for encrypting and decrypting data for storage in or read from the flash memory block.

12. A method comprising:

reading a file version number associated with a versionable file;

storing file data in one or more flash memory blocks of a flash memory device;

updating a copy of a global version number on the flash memory device, wherein the global version number is associated with all versioned files stored, at least in part, on the flash memory device;

updating the global version number in non-volatile memory of a secure kernel;

generating a MAC, to protect the global version number, using a plurality of variables accessible to operating system software;

storing the MAC in the one or more flash memory blocks of the flash memory device;

storing a copy of the updated global version number in the one or more flash memory blocks of the flash memory device;

storing the global version number in non-volatile memory of the security kernel.

13. The system of claim 12, further comprising saving the MAC in spare area of the one or more flash memory blocks.

14. The method of claim 12, wherein the MAC is generated using an HMAC technique.

15. The method of claim 12, wherein the plurality of variables accessible to the operating system software includes one or more variables selected from the group consisting of a value that is determined by software means of the operating system during run-time, a unique number that is assigned to the file and stored with the file-specific meta data, a number representing a logical block index, a physical block number of the flash memory block, an owner ID of a computer system associated with the security kernel, a variable associated with an application.

16. The method of claim 15, wherein the variable associated with an application includes a value selected from the group consisting of, an application ID parameter, an ID parameter tagged by the application and written to the flash memory device, the version number of the data in the flash memory block.

17. The method of claim 12, wherein storing the MAC includes storing the MAC in spare area of the flash memory block.

18. The method of claim 12, wherein storing the MAC includes storing a copy of the MAC.

19. The method of claim 18, wherein storing a copy of the MAC includes storing the MAC in spare area of the flash memory block.

20. The method of claim 12, further comprising signing a block including the global version number, using at least some parameters not stored on the device.

21. The method of claim 20, including a file specific version number associated with each versioned file in the block.

22. The method of claim 21, further comprising using the file specific version number as a variable in calculating the MAC that protects data blocks of the versioned file.

23. A method comprising,

reading a first global version number stored in non-volatile memory of a security kernel;

reading a second global version number stored in a header of a flash memory device, wherein the flash memory device includes a plurality of flash memory blocks;

verifying the first global version number against the second global version number;

reading a first MAC stored in the header of the flash memory device;

generating a second MAC;

verifying the second MAC with the first MAC;

reading a file version number of a versioned file having data stored in a flash memory block of the plurality of flash memory blocks from the header of the flash memory;

reading a third MAC stored in the flash memory block;

generating a fourth MAC using a key stored in non-volatile memory of the security kernel and the file version number as parameters;

verifying the fourth MAC with the third MAC;

receiving data associated with the versioned file.