Abstract:
Exemplary embodiments of the present invention disclose a method for detecting a tampering event of a component. In a step, an exemplary embodiment encapsulates a fluorescent dye in one or more microcapsules. In another step, an exemplary embodiment embeds the one or more microcapsules in a translucent polymeric resin. In another step, an exemplary embodiment secures at least part of a component in the translucent polymeric resin. In another step, an exemplary embodiment detects a fluorescence of the fluorescent dye from a microcapsule in the translucent polymeric resin that is ruptured during a tampering with a light source that causes the fluorescent dye to fluoresce.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the detection of tampering with secure electronic components and more specifically to the use of microcapsules filled with a liquid that fluoresces under ultraviolet light when a capsule is ruptured during tampering. 
     BACKGROUND 
     Electronic devices whose physical security must be guaranteed, e.g., cryptographic and weapon-related devices, warrant special precautions against unauthorized physical access and undetected modification. Geographically dispersed manufacturing and assembly processes frequently result in many opportunities for unauthorized access, and after they are assembled and in operation, secure devices continue to require careful monitoring against unauthorized physical access. Physical access can result in circuit modification or an attachment of a monitoring device that can result in undetectable information leaks, a means to shut down a device&#39;s operation at will, and an opportunity to insert erroneous or misleading information into a secure information flow by an unauthorized entity. 
     Tamper evident techniques are less costly to implement than tamper prevention techniques, but both techniques are sometimes used concurrently. A tamper evident technique attempts to make a physical access to a device nearly impossible without leaving evidence of the access. Attractive tamper evident techniques provide an evidence of a tampering that is easily detectable without using expensive equipment or lengthy procedures while making the tampering impossible to accomplish without leaving such evidence. A tamper evident technique is even more attractive if a tampering entity remains oblivious to any evidence that his or her tampering creates, leaving several options open for security enforcement personnel to manage a tampering incident. 
     Some tamper evident techniques that are applied to electronic devices use mechanical enclosures and/or seals which are difficult to bypass without leaving evidence of a tampering event. However, these techniques increase weight which can be a factor in some implementations and they may require microscopic examination of an enclosure or a seal to detect a tampering. Also, they are less effective in an environment where sophisticated tools may be available to perform a tampering, subsequent to a physical interception of a device during manufacture, transportation, or storage, for example. 
     SUMMARY 
     Exemplary embodiments of the present invention disclose a method for detecting a tampering event of a component. In a step, an exemplary embodiment encapsulates a fluorescent dye in one or more microcapsules. In another step, an exemplary embodiment embeds the one or more microcapsules in a translucent polymeric resin. In another step, an exemplary embodiment secures at least part of a component in the translucent polymeric resin. In another step, an exemplary embodiment detects a fluorescence of the fluorescent dye from a microcapsule in the translucent polymeric resin that is ruptured during a tampering with a light source that causes the fluorescent dye to fluoresce. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  depicts a formation of microcapsules containing a UV dye core material in accordance with one embodiment of the present invention. 
         FIG. 2  depicts a security component that is encapsulated in a translucent polymeric resin containing microcapsules with a UV dye core material in accordance with one embodiment of the present invention. 
         FIG. 3  depicts a compression of a translucent polymeric resin encapsulating a security component causing a release of the microcapsule&#39;s UV dye core under a household light in accordance with one embodiment of the present invention. 
         FIG. 4  depicts a compression of a translucent polymeric resin encapsulating a security component causing a release of the microcapsule&#39;s UV dye core under a UV light in accordance with one embodiment of the present invention. 
         FIG. 5  depicts a compression of a translucent polymeric resin encapsulating a security component that is coated with one or more microcapsules causing a release of the microcapsule&#39;s UV dye core under a household light in accordance with one embodiment of the present invention. 
         FIG. 6  depicts a compression of a translucent polymeric resin encapsulating a security component that is coated with one or more microcapsules causing a release of the microcapsule&#39;s UV dye core under a UV light in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In an exemplary embodiment, one or more microcapsules containing an ultraviolet dye (a UV dye) are formed using an oil-in-water emulsion technique to create a polymeric shell around a UV dye core. These microcapsules are then dispersed into a translucent polymeric resin which is then used to encapsulate a security component. A security component is an electronic component whose physical security must be guarded against a tampering and/or against an undetected tampering. When sufficiently compressed or punctured, cut, gouged, scratched, scraped, or otherwise penetrated, the one or more microcapsules rupture and release a UV dye material into the translucent polymeric resin. The UV dye from a ruptured microcapsule is irregular compared to a UV dye sphere within a non-ruptured microcapsule and can be visually identified under a UV lamp or by using a UV detecting instrument to determine that the one or more microcapsules have ruptured, thus indicating a tamper event. 
     In the exemplary embodiment one or more microcapsules are formed that contain a UV dye core material in a process  100  that is depicted in  FIG. 1 . A UV dye  101  (e.g., Anthracene, etc.) in an oil phase is dispersed in a solvent that is further dispersed into an aqueous continuous phase and stirred, which starts an emulsion process. A cross-linking agent  102  is introduced and reacts with a polymeric emulsifying agent  103  to generate a capsule wall around a UV dye particle. In one embodiment, UV dye particle size is controlled by adjusting a stir speed of the reaction in stirring and size control process  104  to produce a homogeneous UV dye particle size. In one embodiment, a higher stir speed results in smaller UV dye particles. Finally, a curing process  105  completes a reaction between cross-linking agent  102  and polymeric emulsifying agent  103  to form a spherical microcapsule with a UV dye core  106  surrounded by a polymeric shell  107 . 
     Microcapsules are then embedded within a translucent polymeric resin (e.g., polyurethane, polypropylene, or polyethylene, etc.). A quantity of microcapsules made depends on a flow property of a polymeric resin used, a microcapsule size, and a desired density of microcapsules in the polymeric resin. A density of microcapsules desired is low enough to enable an irregular shape of a ruptured microcapsule or a regular shape of a non-ruptured microcapsule to be easily identified within a translucent polymeric resin, but high enough so a tampering event will rupture one or more microcapsules. Consequently a regular shape of a florescence from a non-ruptured microcapsule can be discriminated from an irregular shape of a florescence from microcapsule that is ruptured as a result of a tampering. 
     Several methods to detect a tampering can be performed, depending on whether or not an non-ruptured microcapsule is opaque, i.e., whether a florescence of a UV dye in a non-ruptured microcapsule is visible under UV light (as in a case of a non-opaque microcapsule) or not (as in a case of an opaque microcapsule). For example, in accordance with one embodiment, a camera can capture an image of a resin incorporating microcapsules and the image may be analyzed to detect a florescence from at least one ruptured microcapsule and signal a tampering. In such an embodiment, a microcapsule is opaque which requires a microcapsule to be ruptured before a florescence can manifest in a resin and therefore any detection of florescence by the camera indicates a tampering. A less expensive sensor may be used instead of a camera when a microcapsule is opaque since any florescence indicates a tampering. In another embodiment, a microcapsule is translucent, so a camera sees only non-ruptured microcapsules with sphere shaped florescence in an absence of a tampering, and in the presence of a tampering a camera sees sphere shaped florescence from non-ruptured microcapsules and irregular shaped florescence from ruptured microcapsules. An image processing technique is capable of classifying a shape of a viewed florescence as a smooth spherical shape or an irregular shape that indicates a tampering. 
       FIG. 2  depicts a security component  201  that is given tamper evident protection. Security component  201  is encapsulated in a translucent polymeric resin  204 . A sectional volume  202  of the polymeric resin  204  contains a microcapsule  203  that contains UV dye. 
       FIG. 3  depicts a ruptured microcapsule  302  in a translucent polymeric resin  303  that encapsulates a security component  301 . A tampering force  307 , (e.g., a force that results in a compression or a puncture, cut, gouge, scratch, or scrape of translucent resin  303 ), causes a microcapsule rupture and the ruptured microcapsule  302  releases a UV dye  305  into the translucent resin  303 . Microcapsule  304  has not been ruptured by tampering force  307 . Common indoor light, household light  306 , does not fluoresce the released UV dye  305  and therefore an evidence of tampering is not apparent to a perpetrator of a tampering under common indoor lighting. 
       FIG. 4  depicts a ruptured microcapsule  402  in a translucent polymeric resin  403  that encapsulates a security component  401  under UV light  406 . A tampering force  307  has ruptured microcapsule  402  which releases a UV dye  405  into the translucent resin  403 . Microcapsule  404  has not been ruptured by tampering force  307 . A UV light  406  causes the released UV dye  405  to fluoresce in an irregular pattern which is an evidence of tampering that is readily detected. 
     In another exemplary embodiment, depicted in  FIG. 5  and  FIG. 6 , a security component is coated with one or more microcapsules and then the one or more microcapsules and the security component are encapsulated in a translucent polymeric resin (e.g., polyurethane, polypropylene, or polyethylene, etc.). 
     In the other exemplary embodiment,  FIG. 5  depicts a ruptured microcapsule  502  in a translucent polymeric resin  503  that encapsulates a security component  501 . A tampering force  507  causes a microcapsule rupture and the ruptured microcapsule  502  releases a UV dye  505  into the translucent resin  503 . Microcapsule  504  has not been ruptured by tampering force  507 . A household light  506  does not fluoresce the released UV dye  505  and therefore an evidence of tampering is not apparent to a perpetrator of a tampering. 
     In the other exemplary embodiment,  FIG. 6  depicts a ruptured microcapsule  602  in a translucent polymeric resin  603  that encapsulates a security component  601  under UV light  606 . A tampering force  507  has ruptured microcapsule  602  which releases a UV dye  605  into the translucent resin  603 . Microcapsule  604  has not been ruptured by tampering force  507 . A UV light  606  causes the released UV dye  605  to fluoresce and cause an evidence of tampering to be readily apparent. 
     The forgoing description are example embodiments only, and those skilled in the art understand that an infrared dye (e.g., Nickel(II) phthalocyanine) or other dye may be used, that a microcapsule that contains a dye may be made in many ways, and that entirely encapsulating a security component with a translucent polymeric resin is not always desired, and that a partial encapsulation or a coating of a portion of a security component may be desired. Those skilled in the art understand that microcapsules may be uniformly dispersed in a resin or concentrated in particular volumes in a resin or concentrated in particular volumes that constitute a pattern in a resin. In the forgoing descriptions, a word translucent denotes a range of transparencies that enable a microcapsule to be detected and that enable a dye from a microcapsule to be detected.