Systems and methods for preventing data remanence in memory systems

1. A circuit comprising:

a static random access memory (SRAM);

a second memory; and

processing circuitry operable to:

periodically invert data within the SRAM and concurrently invert data within the second memory;

perform a logical exclusive-OR operation between a data output signal of the SRAM and a data output signal of the second memory; and

selection circuitry for using a first signal to select between a second signal and a complemented data output signal of the SRAM as a selection circuit output signal.

2. The circuit of claim 1 , wherein the processing circuitry is further operable to:

write data to the SRAM, and

reset the second memory.

3. The circuit of claim 1 , wherein at least a part of a combination of the second memory and the processing circuitry is located within the SRAM.

4. The circuit of claim 1 , wherein the second memory and the processing circuitry are located outside the SRAM.

5. The circuit of claim 1 , wherein a rate at which the processing circuitry is operable to periodically invert data within the SRAM concurrently with data within the second memory is configurable.

6. The circuit of claim 1 , wherein:

the SRAM comprises a plurality of memory cells each containing only one data bit, and

the second memory comprises a register containing only one data bit.

7. The circuit of claim 1 , wherein the SRAM is operable to store a cryptographic key.

8. A field-programmable gate array (FPGA) containing the circuit as defined in claim 1 , wherein the SRAM is operable to store a cryptographic key, and wherein the cryptographic key is used by the FPGA to store and communicate data.

9. A circuit comprising:

a first memory;

a second memory;

exclusive-OR circuitry for providing an exclusive-OR circuit output signal, wherein the exclusive-OR circuit output signal is a logical exclusive-OR function of a data output signal of the first memory and a data output signal of the second memory;

selection circuitry for using a first signal to select a second signal or a complemented data output signal of the first memory as a selection circuit output signal; and

interconnection circuitry configurable to:

couple a complemented data output signal of the second memory to a data input signal of the second memory;

couple the first signal to a reset signal of the second memory, and

couple the selection circuit output signal to a data input signal of the first memory.

10. The circuit of claim 9 , further comprising clock circuitry and additional interconnection circuitry configured to:

couple a clock circuitry output signal to a clock input signal of the first memory, and

couple the clock circuitry output signal to a clock input signal of the second memory.

11. The circuit of claim 9 , wherein:

the first memory comprises a plurality of memory cells each containing one data bit, and

the second memory comprises a register containing one data bit.

12. The circuit of claim 9 , wherein the first memory comprises static random access memory (SRAM).

13. The circuit of claim 9 , wherein the selection circuitry comprises a multiplexer.

14. The circuit of claim 9 , further comprising:

first level shifter circuitry, wherein the interconnection circuitry is further configurable to:

couple a first level shifter circuitry output signal to the second signal; and

second level shifter circuitry, wherein the interconnection circuitry is further configurable to:

couple a second level shifter circuitry input signal to a load signal, and

couple a second level shifter circuitry output signal to the first signal.

15. The circuit of claim 9 , wherein the first memory is used for storing a cryptographic key.

16. A field-programmable gate array (FPGA) containing the circuit as in claim 9 .

17. The FPGA of claim 16 , wherein:

the first memory stores a cryptographic key, and

the cryptographic key is used by the FPGA to store and communicate data.