Method and device for protection of an MRAM device against tampering
View Patent ↗Data, stored in MRAM-cells should be protected against misuse or read-out by unauthorized persons. The present invention provides an array of MRAM-cells provided with a security device for destroying data stored in the MRAM-cells when they are tampered with. This is achieved by placing a permanent magnet adjacent the MRAM-array in combination with a soft-magnetic flux-closing layer. As long as the soft-magnetic layer is present, the magnetic field lines from the permanent magnet are deviated and flow through this soft-magnetic layer. When somebody is tampering with the MRAM-array, e.g. by means of reverse engineering, and the flux-closing layer is removed, the flux is no longer deviated and affects the nearby MRAM-array, thus destroying the data stored in the MRAM-cells.
1. A memory device, comprising:
a plurality of MRAM-cells; and
a security device for destroying data stored in the plurality of MRAM-cells when the memory device is subject to tampering, wherein the security device includes a magnetic source;
wherein the security device is configured such that upon tampering with the memory device, a magnetic field of the magnetic source destroys data stored in the plurality of MRAM-cells, and wherein the security device is configured to operate passively.
2. The memory device of claim 1 , wherein the security device is configured to operate without power.
3. The memory device of claim 2 , wherein the magnetic source is a permanent magnet.
4. The memory device of claim 2 , wherein the magnetic source is an electromagnet.
5. The memory device of claim 1 , wherein the security device is coupled to the plurality of MRAM-cells.
6. The memory device of claim 1 , the plurality of MRAM-cells being disposed on a substrate, wherein the security device is disposed on the same side of the substrate as the plurality of MRAM-cells.
7. The memory device of claim 1 , the plurality of MRAM-cells being disposed on a substrate, wherein the security device is disposed on the opposite side of the substrate from the plurality of MRAM-cells.
8. The memory device of claim 1 , wherein:
the security device includes a first soft magnetic flux-closing layer that is configured to deviate the magnetic field of the magnetic source such that the plurality of MRAM-cells are unaffected by the magnetic field: and
the first soft-magnetic flux-closing layer is configured to to separate from the magnetic source when the array of MRAM-cells is tampered with.
9. The memory device of claim 8 , wherein the security device comprises a magnetic field shaping device.
10. The memory device of claim 9 , wherein the magnetic field shaping device is a second soft-magnetic layer, the magnetic source and the first soft-magnetic layer being laterally displaced from the plurality of MRAM-cells at one side of the plurality of MRAM-cells, and the second soft-magnetic layer being laterally displaced from the plurality of MRAM-cells at the opposite side of the plurality of MRAM-cells.
11. The memory device of claim 1 , wherein:
the security device includes a first soft magnetic flux-closing layer; and
tampering with the memory device includes removal of at least a portion of the first magnetic flux-closing layer, which causes the magnetic field to destroy the data stored in the plurality of MRAM-cells.
12. A method for protecting from unauthorised read-out an array of MRAM-cells having data content, the method comprising:
providing a security device including a magnetic source, wherein the security device is configured to operate passively; and
automatically destroying the data content of at least some of the array of MRAM-cells by a magnetic field of the magnetic source when the array is tampered with.
13. The method of claim 12 , wherein:
the security device includes a soft-magnetic flux-closing layer; and the at least some of the array of MRAM-cells are exposed to the magnetic field by separating the soft-magnetic flux-closing layer from the magnetic source.
14. The method of claim 12 , wherein:
the security device includes a magnetic field shaping device disposed adjacent to the array of MRAM-cells; and
the magnetic field at the array of MRAM-cells is enhanced by the magnetic field shaping device.
15. A tamper-resistant memory device comprising:
a plurality of MRAM-cells; and
at least one security device coupled with said MRAM-cells, said security device including a magnetic source and a soft magnetic layer;
wherein the soft magnetic layer is configured to deviate magnetic field lines of the magnetic source, such that the plurality of MRAM-cells are unaffected by said magnetic field lines; and
further wherein the tamper-resistant memory device is configured such that tampering including at least a partial removal of said soft magnetic layer causes said magnetic field lines to destroy data stored in at least some of the plurality of MRAM-cells.
16. The tamper-resistant memory device of claim 15 , wherein the magnetic source is a permanent magnet.
17. The tamper-resistant memory device of claim 15 , wherein the soft magnetic layer is a first soft-magnetic flux-closing layer.
18. The tamper-resistant memory device of claim 15 , wherein said memory device is configured to cause said soft magnetic layer to separate from said magnetic source when the memory device is subject to tampering.
19. The tamper-resistant memory device of claim 15 further comprising a magnetic field shaping device.
20. The tamper-resistant memory device of claim 19 , wherein the magnetic field shaping device is a second soft-magnetic layer, the magnetic field source and first soft-magnetic layer being located adjacent the array of MRAM-cells at one side, and the second soft-magnetic layer being located adjacent the array of MRAM-cells at the opposite side thereof.