I'm wracking my brain for reliable ways for an electronic device to detect when/if the parcel it is sealed inside is opened.

The device will be sealed inside the package and activated via Bluetooth by the sender and then queried again by the receiver to confirm there was no tampering before taking delivery.

At this stage the enclosing parcel could be a box, envelope, or wrapping paper - the only restriction that it completely encloses the contents along with the sensor and possibly packaging material - but that may include further restrictions if I can't come up with an infallible detection method.

My first thought was a simple ambient light sensor - but the tamperer would just need to open the package in a darkroom. Another thought is to actively pulse an illumination source and then average the amount reflected back from the inside of volume from multiple directions (to account for the device shifting inside the package).

Any strategies come to mind? I'm hoping this may already be a solved problem somewhere.

  • \$\begingroup\$ What's the point of it being opened in the dark room? If the person doing the tampering can't see anything they can't do anything? You can get light sensors that cover infra-red to ultra-violet, so even fancy lightly and cameras could be countered. \$\endgroup\$ – Puffafish Jan 15 '19 at 15:27
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    \$\begingroup\$ the package could be opened in the darkroom, sensor left there while the contents is taken out of the room and then the tamperer is free to do whatever. \$\endgroup\$ – norlesh Jan 15 '19 at 15:31
  • \$\begingroup\$ how do you separate the sensor and the contents when you can't see either and they could be stuck together in some fashion? \$\endgroup\$ – Puffafish Jan 15 '19 at 15:32
  • \$\begingroup\$ How does a blind person read brail? It seems incomprehensible to me but they have zero trouble navigating by touch alone. \$\endgroup\$ – norlesh Jan 15 '19 at 15:34
  • \$\begingroup\$ So the person tampering the package knows what to expect in there? They know what the device will be and how to remove it from rest of the package without setting it off? \$\endgroup\$ – Puffafish Jan 15 '19 at 15:40

Wrap a small 40 gague wire all around the package with a microprocessor on the inside and a way for the microprocessor to detect continuity of the wire. The microprocessor could log the time that the continuity was broken and you would know that the package has been opened. With a small wire one could also hide it between layers of packaging tape so no one would see it if they were opening the package.

One could also place the microprocessor on the inside of the package with contacts to the outside to make for easy installation. You cal also get microprocessors with encrypted firmware so it would be difficult to modify the time stamp.

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