Intrusion detection apparatus and method

Abstract

An apparatus and method to detect intrusion into a protected enclosure without requiring electrical power. The invention consists of an array of at least two magnetic memory elements, each of which has two electronically-readable stable states in the presence of a bias magnetic field, and a means for providing the required bias magnetic field. The magnetic memory elements and the means for providing the bias magnetic field are both located within a protected electronics enclosure and disposed such that any attempt to disassemble the enclosure will cause a change in the bias magnetic field and resultant permanent change to the content stored in the magnetic memory. Intrusion-detection functionality is initialized by electronically writing a binary code into the magnetic memory after the protected volume is completely assembled. Subsequent intrusion will automatically cause the initialization code to erase. The reaction to the detected intrusion may be an alarm or alert, or a reaction (such as erasing data or software) causing the protected equipment to lose functionality.

1 . An apparatus for detecting attempted intrusion into a protected enclosure, comprising: 
 a magnetic memory array comprising at least two magnetic memory elements, each adapted to store a binary value only in the presence of a bias magnetic field having a magnetic field strength and direction within predetermined limits; and    means for providing said bias magnetic field.    
   
   
       2 . The apparatus of  claim 1 , wherein said magnetic memory array and said means for providing said bias magnetic field are disposed such that any attempt to intrude into said enclosure alters said bias magnetic field sufficiently to change at least one of the binary values stored in said memory array.  
   
   
       3 . The apparatus of  claim 1 , wherein said magnetic memory elements comprise spin-valve devices.  
   
   
       4 . The apparatus of  claim 1 , wherein said magnetic memory elements comprise spin-tunneling devices.  
   
   
       5 . The apparatus of  claim 1 , wherein said means for providing said bias magnetic field comprises at least one permanent magnet.  
   
   
       6 . The apparatus of  claim 5 , wherein said means for providing said bias magnetic field comprises a plurality of permanent magnets.  
   
   
       7 . The apparatus of  claim 5 , wherein said magnetic memory array and said at least one permanent magnet are disposed such that any attempt to intrude into said enclosure causes relative motion between said magnetic memory array and at least one permanent magnet.  
   
   
       8 . The apparatus of  claim 1 , wherein said means for providing said bias magnetic field comprises at least one magnetic shielding element.  
   
   
       9 . The apparatus of  claim 9 , wherein said magnetic memory array and said at least one magnetic shielding element are disposed such that any attempt to intrude into said enclosure causes relative motion between said magnetic memory and at least one magnetic shielding element.  
   
   
       10 . The apparatus of  claim 1 , further comprising: 
 means for storing a code in said magnetic memory array; and    means for reading said stored code.    
   
   
       11 . The apparatus of  claim 10 , further comprising: 
 means to use said code as an encryption key.    
   
   
       12 . A method for detecting attempted intrusion into a protected enclosure, comprising: 
 providing a magnetic memory array disposed within said protected enclosure, said magnetic memory array operable to store a binary number of at least two bits in the presence of a bias magnetic field having magnetic field strength and direction within predetermined limits; and    providing said bias magnetic field at said magnetic memory array;    wherein said magnetic memory array is disposed within said enclosure such that any attempt to intrude into said enclosure alters the magnetic field at said memory array sufficiently to change the state of at least one bit of said binary number.    
   
   
       13 . The method of  claim 12 , further comprising: 
 storing a predetermined binary number into said magnetic memory array after said enclosure is assembled; and    comparing the binary number stored in said array with said predetermined binary number to determine if attempted intrusion has occurred.    
   
   
       14 . The method of  claim 12 , further comprising: 
 storing a binary number into said magnetic memory array after said enclosure is assembled;    periodically reading the binary number stored in said magnetic memory array; and    using the binary number read from said magnetic memory array as an encryption/decryption key.    
   
   
       15 . The method of  claim 14 , wherein the step of reading the binary number stored in said magnetic memory array is performed every time the encryption/decryption key is used.