SECURITY DEVICE FOR SMART CARD

摘要

PURPOSE: A security device for a smart card is provided to protect a password more safely from the external hacking by the power analysis and a decapsulation state of the smart card. CONSTITUTION: The external voltage applied to a smart card chip(6) is supplied to an internal voltage node(11) through a switch. The internal voltage node is connected to the ground voltage through a diode and a resistor. A variable capacitor is connected between the internal voltage node and the ground voltage. A variable control unit(10) comprises a comparator connecting a non-inverted input terminal with the internal voltage node and the reference voltage, an up/down counter generating the digital counting output by responding to a comparison signal output from the comparator, a DAC(Digital Analog Converter) converting the counting output into a variable control signal of an analog value.