Portable memory device and method of securing the integrity of stored data therein utilizing a starting address and a stored memory cycle number

• US 5,493,665 A
• Filed: 12/21/1992
• Issued: 02/20/1996
• Est. Priority Date: 12/21/1992
• Status: Expired due to Fees

• Current Assignee: BAE Systems Plc
• Original Assignee: BAE Systems Plc
• Inventors: Eisenberg, Alan J.
• Primary Examiner(s): Gossage, Glenn
• Application Number:
  US07/994,382
• Time in Patent Office: 1,156 Days
• Field of Search: 395/425, 395/2, 395/442, 395/479, 395/490, 364/406, 364/478, 235/380, 235/492, 365/236, 365/195
• US Class Current: 711/115
• CPC Class Codes: G06F 12/1441 for a range
• CPC Class Codes: G07C 9/28 the pass enabling tracking or indicating presence

Abstract

A portable memory device and method of securing the integrity of data stored therein. The integrity of the stored data is secured by writing input data into the device in a preselected range of storage locations between a first address and a last address, storing a starting address corresponding to a memory address between the first address and the last address, sequentially addressing the memory from the starting address and writing input data into each of the sequentially addressed storage locations. The writing of input data sequentially from the first address to the last address constitutes a memory cycle and the number of the current memory cycle is stored in the device. The stored output data is transmitted outside of the device along with the number of the current memory cycle, so that each storage location in the range of storage locations has a memory cycle number associated with the data stored therein to indicate if an overwrite and therefore a loss in the integrity of the data has occurred. The writing of input data into the portable memory device may be prevented by producing a write halt signal when the starting address is greater than the last address. A new memory cycle may also be started in response to a restart signal.

Claims

1. A method of securing the integrity of data stored in a portable memory device, comprising the steps of:

providing a memory in the portable memory device having a plurality of storage locations which are sequentially addressable and into which input data is writable and from which output data is readable;

preselecting a range of storage locations with a set of addresses extending from a first address to a last address;

storing a starting address in the memory corresponding to a memory address between the first address and the last address;

writing input data into the memory only within the preselected range of storage locations by sequentially addressing the memory from the starting address, a new memory cycle being started each time the starting address is the first address;

storing a current memory cycle number in the memory;

incrementing the stored memory cycle number for each new memory cycle; and

outputting the stored memory cycle number with the output data read from the preselected range of storage locations, whereby each location in the preselected range of storage locations has a memory cycle number associated with the data stored therein to indicate if an overwrite and therefore a loss in the integrity of the data has occurred.

2. The method according to claim 1, wherein the step of storing the starting address comprises storing the starting address in a portion of the memory outside of the preselected range of storage locations.

3. The method according to claim 1, wherein the step of storing the memory cycle number comprises storing the memory cycle number in a portion of the memory outside of the preselected range of storage locations.

4. The method according to claim 1, wherein the memory is a random access memory and said method further comprises output data from the preselected range of storage locations by selectively accessing addresses therein.

5. The method according to claim 1, further comprising the step of receiving the input data via modulated electromagnetic waves.

6. The method according to claim 1, further comprising providing a read-only memory in the portable memory device having a unique signature code stored therein and wherein the signature code is provided with the output data and the stored memory cycle number.

7. The method according to claim 1, wherein the stored starting address is incremented by one for each storage location into which input data is written to indicate a next available address to be written into.

8. The method according to claim 1, further comprising preventing writing of input data into the memory at an end of a memory cycle.

9. The method according to claim 8, wherein the step of preventing comprises producing a write halt signal when the starting address is greater than the last address.

10. The method according to claim 9, further comprising starting a new memory cycle and incrementing the stored memory cycle number in response to a restart signal.

11. A portable memory device, comprising:

a memory having a plurality of storage locations which are sequentially addressable and into which input data is writable and from which output data is readable, the plurality of storage locations including a preselected range of storage locations with a set of addresses extending from a first address to a last address; and

a processor for storing a starting address in the memory corresponding to a memory address between the first address and the last address and for writing input data into the memory only within the preselected range of storage locations by sequentially addressing the memory from the starting address in a memory cycle, wherein a new memory cycle is started each time the starting address is the first address, and wherein the processor stores a current memory cycle number in the memory and increments the stored memory cycle number for each new memory cycle; and

wherein the processor outputs the stored memory cycle number with the output data read from the preselected range of storage locations, whereby each location in the preselected range of storage locations has a memory cycle number associated with the data stored therein to indicate if an overwrite and therefore a loss in the integrity of the data has occurred.

12. The device according to claim 11, wherein the processor stores the starting address in a portion of the memory outside of the preselected range of storage locations.

13. The device according to claim 11, wherein the processor stores the memory cycle number in a portion of the memory outside of the preselected range of storage locations.

14. The device according to claim 11, wherein the memory is a random access memory and wherein the processor reads output data from the preselected range of storage locations by selectively accessing addresses therein.

15. The device according to claim 11, further comprising a receiver for receiving input data via modulated electromagnetic waves.

16. The device according to claim 11, further comprising a read-only memory having a unique signature code stored therein and wherein the processor outputs the signature code with the output data and the stored memory cycle number.

17. The device according to claim 11, wherein the processor increments the stored starting address by one for each storage location into which input data is written.

18. The device according to claim 11, wherein the processor further comprises means for preventing writing of input data into the memory at an end of a memory cycle.

19. The device according to claim 18, wherein the means for preventing comprises a write halt signal produced by the processor when the starting address is greater than the last address.

20. The device according to claim 19, wherein the processor increments the stored memory cycle number in response to receiving a restart signal.

21. A control process comprising the steps of:

moving a portable memory device from one station to at least one other station;

transmitting input data from a station to the portable memory device for storage therein;

receiving output data from the portable memory device at a station; and

securing the integrity of data stored in the portable memory device by

providing a memory in the portable memory device having a plurality of storage locations which are sequentially addressable and into which input data is writable and from which output data is readable;

preselecting a range of storage locations with a set of addresses extending from a first address to a last address;

storing a starting address in the memory corresponding to a memory address between the first address and the last address;

writing the input data into the memory only within the preselected range of storage locations by sequentially addressing the memory from the starting address, a new memory cycle being started each time the starting address is the first address;

storing a current memory cycle number in the memory;

incrementing the stored memory cycle number for each new memory cycle; and

outputting the stored memory cycle number with the output data read from the preselected range of storage locations, whereby each location in the preselected range of storage locations has a memory cycle number associated with the data stored therein to indicate if an overwrite and therefore a loss in the integrity of the data has occurred.

22. The process according to claim 21, further comprising preventing writing of input data into the memory at an end of a memory cycle.

23. The process according to claim 22, wherein the step of preventing comprises producing a write halt signal and transmitting the write halt signal to a station when the starting address is greater than the last address.

24. The process according to claim 23, further comprising incrementing the stored memory cycle number in response to a restart signal from a station.