Enclosure tamper detection and protection

• US 20080042834A1
• Filed: 04/20/2007
• Published: 02/21/2008
• Est. Priority Date: 04/20/2006
• Status: Active Grant

• Current Assignee: NVE Corporation
• Original Assignee: NVE Corporation
• Inventors: Daughton, James, Deak, James
• Granted Patent: US 7,468,664 B2
• Time in Patent Office: Days
• US Class Current: 340/551
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: G11C 11/1695 Protection circuits or methods

Abstract

A tamper detecting enclosure arrangement for enclosures containing an interior space in which a protected item is positioned having a magnetoresistive sensing memory storage cell positioned in or near the protected item in the enclosure having a two state offset magnetoresistance versus externally applied magnetic field. A magnet is positioned at a selected separation distance from the magnetoresistive sensing memory storage cell to thereby provide a magnetic field about the magnetoresistive sensing memory storage cell if said enclosure has not been opened in such a manner as to result in substantially increasing said separation distance.

Claims

1. A tamper detecting enclosure arrangement for enclosures containing an interior space in which a protected item is positioned to which access is to be denied absent providing a subsequent indication that such an access has occurred, said arrangement comprising:

a magnetoresistive sensing memory storage cell positioned in or near said protected item in said enclosure having a magnetoresistance versus externally applied magnetic field characteristic with two states of differing resistive values each reached from that other by an externally applied magnetic field having a magnitude change exceeding a corresponding one of a pair of relatively small transition field value intervals each having externally applied magnetic field values occurring therein of a common field direction but with those externally applied magnetic field values occurring therein differing in magnitudes from those in that other transition field value interval, and

a magnet positioned at a selected separation distance from said magnetoresistive sensing memory storage cell to thereby provide a magnetic field about said magnetoresistive sensing memory storage cell if said enclosure has not been opened so as to result in substantially increasing said separation distance.

2. The arrangement of claim 1 wherein said enclosure has a receptacle with at least part of said interior space therein and a cover which can be positioned so as to render said interior space surrounded by said enclosure, said magnet being positioned in said cover.

3. The arrangement of claim 1 wherein said magnetoresistive sensing memory storage cell is formed in a monolithic integrated circuit positioned in said interior space.

4. The arrangement of claim 1 further comprising a portion of a layer of magnetically permeable material positioned adjacent said magnetoresistive sensing memory storage cell.

5. The arrangement of claim 1 further comprising another magnetoresistive sensing memory storage cell positioned in or near said protected item in said enclosure having a magnetoresistance versus externally applied magnetic field characteristic with two states of differing resistive values each reached from that other by an externally applied magnetic field having a magnitude change exceeding a corresponding one of a pair of relatively small transition field value intervals each having externally applied magnetic field values occurring therein of a common field direction but with those externally applied magnetic field values occurring therein differing in magnitudes from those in that other transition field value interval.

6. The arrangement of claim 1 wherein said magnetoresistive sensing memory storage cell has a length along a selected direction and a width substantially perpendicular thereto that is smaller in extent than said length and together have a shaped end portion extending over a portion of said length in which said width gradually reduces to zero at that end thereof.