Method and apparatus for securing data stored in semiconductor memory cells

• US 5,644,636 A
• Filed: 12/30/1994
• Issued: 07/01/1997
• Est. Priority Date: 12/30/1994
• Status: Expired due to Term

• Current Assignee: XTec, Incorporated
• Original Assignee: XTec, Incorporated
• Inventors: Fernandez, Alberto J.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US08/367,084
• Time in Patent Office: 914 Days
• Field of Search: 380/3, 380/4, 380/9, 380/23, 380/25, 380/49, 380/50, 380/59, 395/1, 395/3, 340/825.31, 340/825.34
• US Class Current: 711/163
• CPC Class Codes: G11C 16/22 Safety or protection circuits preventing unauthorised or accidental access to memory cells

Abstract

A method and apparatus for securing data stored in semiconductor memory cells of a semiconductor device is described. A reference fingerprint corresponding to numerical representations of a measurement of the levels of charges trapped in the memory cells is generated and stored. The measurement is performed immediately after programming data to the memory cells. The reference fingerprint is then compared to a measurement of numerical representations of the levels of charges trapped in the memory cells of a memory device that has been presented to a reader. If a match occurs, then the data stored in the memory device is authenticated. An intentional offset error voltage may be applied when writing data to the memory cells to enhance the security of the data. The reference fingerprint may also be encrypted prior to storage for added security. Lastly, fuzzy logic techniques may be used to compensate for environmental and hardware related fluctuations in the levels of trapped charges of the programmed memory cells.

Claims

1. A method for securing data in a semiconductor memory cell of a semiconductor memory device, comprising the steps of:

programming data in the memory cell by applying a voltage which causes charges to be trapped in the memory cell;

making a measurement of the level of trapped charges in the memory cell after the memory cell is programmed;

generating a numerical representation of the level of trapped charges as a reference fingerprint of the memory cell; and

storing the numerical representation.

2. The method of claim 1, wherein the numerical representation is written onto the semiconductor memory device.

3. The method of claim 1, wherein the numerical representation is written to an external device.

4. The method of claim 3, wherein the external device is a database.

5. The method of claim 1, wherein the step of generating the numerical representation further comprises:

encrypting the numerical representation.

6. A method for authenticating data stored in a plurality of semiconductor memory cells in a semiconductor memory device, comprising the steps of:

programming data to the plurality of memory cells by applying a plurality of voltages such that charges are trapped in each of the memory cells;

measuring the levels of the trapped charges in the plurality of memory cells after the memory cells are programmed;

generating numerical representations of the measured levels of trapped charges as a reference fingerprint;

storing the reference fingerprint; and

,

comparing the reference fingerprint to numerical representations of a subsequent measurement of the levels of trapped charges in the memory cells defining an authentication fingerprint, in order to determine whether the data stored in the memory cells is authentic.

7. The method of claim 6, wherein fuzzy logic techniques are utilized to generate the reference fingerprint and the authentication fingerprint to compensate for variations in the numerical representations of the measured levels of trapped charges in the memory cells which are caused by environmental and hardware related factors.

8. The method of claim 6, wherein the reference fingerprint is written onto the semiconductor memory device.

9. The method of claim 6, wherein the reference fingerprint is written to an external device.

10. The method of claims 9, wherein the external device is a database.

11. The method of claim 6, wherein the step of generating the reference fingerprint further comprises:

encrypting the reference fingerprint.

12. The method of claim 6, wherein the step of programming the memory cells further comprises:

introducing intentional random offsets to each of the applied plurality of voltages.

13. A secure semiconductor memory cell apparatus comprising:

first and second semiconductor cells;

a data out line selectively connected to the first and second semiconductor memory cells upon which voltages are applied for programming data to the first and second semiconductor memory cells, causing charges to be trapped in the first and second memory cells; and

an analog out line selectively connected to the first and second semiconductor memory cells for selective connection to a measurement apparatus for making an analog measurement of the levels of trapped charges in the first and second memory cells, wherein said second memory cells are utilized for storing a reference fingerprint generated from numerical representations of the levels of trapped charges measured in the first memory cells, such that a comparison of the stored reference fingerprint to numerical representations of a subsequent measurement of the levels of trapped charges in the first memory cells provides for authenticating the data stored in the first memory cells.

14. The apparatus of claim 13, wherein the memory cells are included in an integrated circuit.

15. The apparatus of claim 13, further comprising:

an analog to digital converter comprising an input and an output,

wherein the analog out line connects the input to the memory cells, and wherein the analog to digital converter converts any analog signals detected on the analog out line to digitized numerical representations and provides said numerical representations at the output.

16. The apparatus of claim 15, wherein the microcontroller and the analog to digital converter are fabricated on an integrated circuit.

17. The apparatus of claim 15, further comprising:

a microcontroller for providing applied voltages on the data out line for programming the first memory cells and the second memory cells,

wherein the microcontroller further comprises a processor and a memory,

wherein the processor stores in the memory the numerical representations of the measured levels of trapped charges of the first memory cells, and

wherein the processor generates the reference fingerprint from the stored numerical representations obtained from the measurements involving the first memory cells and regenerates the reference fingerprint from measurements of the second memory cell, if the reference fingerprint is stored in the second memory cells.

18. The apparatus of claim 17, wherein the processor provides voltage signals on the data out line for writing the reference fingerprint to the second memory cells.

19. The apparatus of claim 17, wherein the processor provides voltage signals at an input and output port of the microcontroller for purposes of storing the reference fingerprint on an external device.

20. The apparatus of claim 19, wherein the external device is a database.

21. The apparatus of claim 17, wherein the processor compares the reference fingerprint to numerical representations of a subsequent measurement of the trapped charge levels in the first memory cells to determine the authenticity of the data stored in the first memory cells.

22. The apparatus of claim 17, wherein the processor introduces an intentional random offset to the respective voltages applied for programming the first memory cells.

23. The apparatus of claim 17, wherein the processor encrypts and stores the reference fingerprint.

24. The apparatus of claim 23, wherein the processor provides voltage signals on the data out line for writing the reference fingerprint to the second memory cells.

25. The apparatus of claim 23, wherein the processor provides voltage signals at an input and output port of the microcontroller for storage of the reference fingerprint on an external device.

26. The apparatus of claim 17, wherein the microcontroller, the analog to digital converter and the memory cells are fabricated on an integrated circuit.

27. A method for authenticating data stored in a plurality of first semiconductor memory cells in a first semiconductor memory device to prevent counterfeiting comprising the steps of:

programming the data to the plurality of first memory cells by applying a plurality of voltages, respectively, which cause charges to be trapped in the plurality of the first memory cells;

measuring the levels of the trapped charges in the plurality of first memory cells after programming the first memory cells;

generating numerical representations of the measured levels of trapped charges as a reference fingerprint;

measuring the levels of the trapped charges in a plurality of second memory cells in a second semiconductor memory device which is presented to a semiconductor memory device reader;

generating numerical representations of the measured levels of trapped charges in the second memory cells as an authentication fingerprint;

retrieving the stored reference fingerprint; and

comparing the reference fingerprint to the authentication fingerprint to determine whether the data stored in the second memory cells are authentic.

28. The method of claim 27 wherein the reference fingerprint is written onto the first semiconductor memory device.

29. The method of claim 27, wherein the reference fingerprint is written onto an external device.

30. The method of claim 29, wherein the external device is a database.

31. The method of claim 27, wherein the step of storing the reference fingerprint further comprises:

encrypting the reference fingerprint.

32. The method of claim 27, wherein the step of programming the first memory cells further comprises:

introducing an intentional random offset to each of the applied plurality of voltages.

33. A method for securing data in a semiconductor memory cell of a semiconductor memory device, comprising the steps of:

programming data in the memory cell by applying a voltage which causes charges to be trapped in the memory cell, said step of programming data in the memory cell further comprising introducing an intentional random offset to the applied voltage;

measuring the level of trapped charges in the memory cell after the memory cell is programmed;

generating a numerical representation of the level of trapped charges measured; and

storing the numerical representation.

34. A method for securing data in a semiconductor memory cell of a semiconductor memory device, comprising the steps of:

programming data in the memory cell by applying a voltage which causes charges to be trapped in the memory cell;

measuring the level of trapped charges in the memory cell after the memory cell is programmed;

generating a numerical representation of the level of trapped charges measured;

storing the numerical representation;

comparing the stored numerical representation to a numerical representation of a subsequent measurement of the level of trapped charges in the memory cell; and

authenticating the data stored in the memory cell if the stored numerical representation matches the second numerical representation.