Fraudulent smart card usage detection appts. e.g. in public telephone - detects cards connected to external electronic circuits by measurement of coupling capacitance

摘要

The appts. comprises an electronic circuit connected to the terminals of the smart card (20) when it is placed in the slot (10). The circuit comprises a source of high frequency alternating current (24) connected to the terminals (K) during the test phase. One wall of the slot (10), made of conducting material, is connected to one line of the a.c. generator. A leakage current detection circuit (26,28,30) measures the capacitance between the card and the slot wall, detecting whether external wires (22) are connected to the card. ADVANTAGE - Automatic detection of use of external connections to smart cards in attempts at fraudulent use.