Flash memory device and system with randomizing for suppressing errors

• US 8,127,200 B2
• Filed: 06/13/2007
• Issued: 02/28/2012
• Est. Priority Date: 12/24/2006
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk IL Ltd. (Western Digital Corporation)
• Inventors: Sharon, Eran, Alrod, Idan
• Primary Examiner(s): Chase, Shelly A
• Application Number:
  US11/808,906
• Publication Number:
  US 20080151618A1
• Time in Patent Office: 1,721 Days
• Field of Search: 714/746, 714763-764, 714/769
• US Class Current: 714/763
• CPC Class Codes: G06F 11/1068 in sector programmable memories, e.g. flash disk G06F11/1072 takes precedence

Abstract

A device for storing data includes a nonvolatile memory and a controller and/or circuitry that randomize original data to be stored in the memory while preserving the size of the original data, that store the original data in the memory, and that, in response to a request for the original data, retrieve, derandomize and export the original data without authenticating the requesting entity. A system for storing data includes a first nonvolatile memory and a processor that similarly stores data in the first nonvolatile memory by executing driver code stored in a second nonvolatile memory. ECC encoding is applied either before or after randomizing; correspondingly, ECC decoding is applied either after or before derandomizing.

Claims

1. A device for storing data, the device comprising:

a nonvolatile memory; and

a controller, the controller operative to;

randomize original data to be stored in the non-volatile memory while preserving a size of the original data, providing randomized data;

apply error correction encoding to the randomized data, providing encoded randomized data;

store the encoded randomized data in the non-volatile memory; and

in response to a request for the original data by an entity external to the device;

retrieve the encoded randomized data from the non-volatile memory;

apply error correction decoding to the retrieved encoded randomized data, providing decoded randomized data;

derandomize the decoded randomized data, providing retrieved data that is substantially identical to the original data; and

export the retrieved data to the entity without authenticating the entity;

wherein the controller is operative to randomize the original data by summing the original data, modulo 2, with a fixed random bit sequence; and

wherein the controller is operative to derandomize the decoded randomized data by summing the decoded randomized data, modulo 2, with the fixed random bit sequence.

2. A device for storing data, the device comprising:

a nonvolatile memory; and

a controller, the controller operative to;

randomize original data to be stored in the non-volatile memory while preserving a size of the original data, providing randomized data;

apply error correction encoding to the randomized data, providing encoded randomized data;

store the encoded randomized data in the non-volatile memory; and

in response to a request for the original data by an entity external to the device;

retrieve the encoded randomized data from the non-volatile memory;

apply error correction decoding to the retrieved encoded randomized data providing decoded randomized data;

derandomize the decoded randomized data, providing retrieved data that is substantially identical to the original data; and

export the retrieved data to the entity without authenticating the entity;

wherein the controller is operative to randomize the original data by summing the original data, modulo 2, with a pseudorandom bit sequence;

wherein the controller is operative to generate the pseudorandom bit sequence using a linear feedback shift register; and

wherein the controller is operative to derandomize the decoded randomized data by summing the decoded randomized data, modulo 2, with the pseudorandom bit sequence.

3. The device of claim 2, wherein the pseudorandom bit sequence is fixed.

4. The device of claim 2, wherein a seed of the linear feedback shift register is fixed.

5. The device of claim 2, wherein the non-volatile memory is partitioned into units, each unit having a respective unit number, and wherein a seed of the linear feedback shift register is a function of a particular unit number of a particular unit wherein the encoded randomized data is stored.

6. The device of claim 5, wherein the non-volatile memory is a flash memory and wherein the units are blocks of the flash memory.

7. The device of claim 5, wherein the non-volatile memory is a flash memory and wherein the units are pages of the flash memory.

8. A device for storing data, the device comprising:

a nonvolatile memory; and

a controller, the controller operative to;

randomize original data to be stored in the non-volatile memory while preserving a size of the original data, providing randomized data;

apply error correction encoding to the randomized data, providing encoded randomized data;

store the encoded randomized data in the non-volatile memory; and

in response to a request for the original data by an entity external to the device;

retrieve the encoded randomized data from the non-volatile memory;

apply error correction decoding to the retrieved encoded randomized data, providing decoded randomized data;

derandomize the decoded randomized data, providing retrieved data that is substantially identical to the original data; and

export the retrieved data to the entity without authenticating the entity;

wherein the controller is operative to randomize the original data by scrambling the original data; and

wherein the controller is operative to derandomize the decoded randomized data by descrambling the decoded randomized data.

9. The device of claim 8, wherein the scrambling and the descrambling are effected using respective linear feedback shift registers that share a common seed.

10. The device of claim 9, wherein the common seed is fixed.

11. The device of claim 9, wherein the non-volatile memory is partitioned into units, each unit having a respective unit number, and wherein the seed is a function of particular unit number of a particular unit wherein the encoded randomized data is stored.

12. The device of claim 11, wherein the non-volatile memory is a flash memory and wherein the units are blocks of the flash memory.

13. The device of claim 11, wherein the non-volatile memory is a flash memory and wherein the units are pages of the flash memory.

14. A system for storing data, the system comprising:

a first nonvolatile memory;

a second nonvolatile memory wherein is stored a driver for the first nonvolatile memory, the driver including;

code for randomizing original data to be stored in the first nonvolatile memory while preserving a size of the original data, providing randomized data;

code for applying error correction encoding to the randomized data, providing encoded randomized data;

code for storing the encoded randomized data in the first nonvolatile memory; and

code for responding to a request for the original data by;

retrieving the encoded randomized data from the first nonvolatile memory;

applying error correction decoding to the retrieved encoded randomized data, providing decoded randomized data;

derandomizing the decoded randomized data, providing retrieved data substantially identical to the original data; and

exporting the retrieved data without authenticating the request; and

a processor for executing the code of the driver.

15. The system of claim 14, wherein the code for randomizing the original data includes code for summing the original data, modulo 2, with a fixed, random bit sequence, and wherein the code for derandomizing the decoded randomized data includes code for summing the decoded randomized data, modulo 2, with the fixed random bit sequence.

16. The system of claim 14, wherein the code for randomizing the original data includes code for summing the original data, modulo 2, with a pseudorandom bit sequence, and wherein the code for derandomizing the decoded randomized data includes code for summing the decoded randomized data, modulo 2, with the pseudorandom bit sequence.

17. The system of claim 16, wherein the pseudorandom bit sequence is fixed.

18. The system of claim 16, wherein the driver further includes code for generating the pseudorandom bit sequence.

19. The system of claim 18, wherein the code for generating the pseudorandom bit sequence includes code of a linear feedback shift register.

20. The system of claim 19, wherein a seed of the linear feedback shift register is fixed.

21. The system of claim 19, wherein the first nonvolatile memory is partitioned into units, each unit having a respective unit number, and wherein a seed of the linear feedback shift register is a function of a particular unit number of a particular unit wherein the encoded randomized data is stored.

22. The system of claim 21, wherein the first nonvolatile memory is a flash memory and wherein the units are blocks of the flash memory.

23. The system of claim 21, wherein the first nonvolatile memory is a flash memory and wherein the units are pages of the flash memory.

24. The system of claim 14, wherein the code for randomizing the original data includes code for scrambling the original data, and wherein the code for derandomizing the decoded randomized data includes code for descrambling the decoded randomized data.

25. The system of claim 24, wherein the code for scrambling the original data includes first linear feedback shift code that is associated with a first seed and the code for descrambling the decoded randomized data includes second linear feedback shift code that is associated with a second seed, and wherein the first seed and the second seed are the same seed.

26. The system of claim 25, wherein each of the first seed and the second seed is fixed.

27. The system of claim 25, wherein the first nonvolatile memory is partitioned into units, each unit having a respective unit number, and wherein the seed is a function of a particular unit number of a particular unit wherein the encoded randomized data is stored.

28. The system of claim 27, wherein the first nonvolatile memory is a flash memory and wherein the units are blocks of the flash memory.

29. The system of claim 27, wherein the first nonvolatile memory is a flash memory and wherein the units are pages of the flash memory.

30. A computer-readable storage medium having computer-readable code embedded thereon, the computer-readable code being driver code for a memory device, wherein the computer-readable code, when executed by a processor, causes the processor to:

randomize original data to be stored in a memory of the memory device while preserving a size of the original data, randomizing including summing the original data, modulo 2, with a pseudorandom bit sequence generated using a linear feedback shift register, providing randomized data;

apply error code correction encoding to the randomized data, providing encoded randomized data;

store the encoded randomized data in the memory; and

respond to a request for the original data by;

retrieving the encoded randomized data from the memory;

applying error correction decoding to the retrieved encoded randomized data, providing decoded randomized data;

derandomizing the decoded randomized data, providing retrieved data substantially identical to the original data; and

exporting the decoded data without authenticating the request.

31. A computer-readable storage medium having computer-readable code embedded thereon, the computer-readable code being driver code for a memory device, wherein the computer-readable code, when executed by a processor, causes the processor to:

randomize original data to be stored in a memory of the memory device while preserving a size of the original data, including summing the original data, modulo 2, with a fixed, random bit sequence, providing randomized data;

apply error code correction encoding to the randomized data, providing encoded randomized data;

store the encoded randomized data in the memory; and

respond to a request for the original data by;

retrieving the encoded randomized data from the memory;

applying error correction decoding to the retrieved encoded randomized data, providing decoded randomized data;

derandomizing the decoded randomized data, providing retrieved data substantially identical to the original data; and

exporting the retrieved data without authenticating the request.