Fringe-Effect Capacitive Proximity Sensors for Tamper Proof Enclosures

Capacitive sensors can be constructed for tamper resistant enclosures to prevent unauthorized intrusions. The use printed circuit can provide serpentine geometric patterns of conductors. Any penetration of this envelope interferes with the conductive serpentine, producing a detectable warning of intrusion. Capacitive sensors discussed in this paper are suitable for implementing in the area of physical security cryptographic modules. These sensors conform to Levels 3 and 4 of the Federal Information Processing Standard (FIPS) 140-2