JPH0271345A - Ic card - Google Patents

Abstract

PURPOSE:To inhibit the alteration of an LSI by detecting a fact that the main body case of the LSI is opened via a sensor to turn on a switching circuit with the detection output of the sensor and applying a destructive battery to the LSI. CONSTITUTION:When a main body case of an LSI 4 is opened for alteration of the memory contents of the LSI 4, a solar battery 8 is irradiated by the light and generates the electromotive force. Thus both transistors Tr1 and Tr2 of a switching circuit 10 are turned on, and the collector voltage of both transistors have low levels. Then the gate voltage levels of the MOS transistors 6a and 6b are inverted by an inverter 12 into high levels. Thus both MOS transistors are turned off. While the gate voltage of the MOS transistors 14a and 14b of the circuit 10 are set at low levels. Thus both 14a and 14b are turned on. As a result, the LSI is destroyed.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an IC card, and more particularly to a security technique against tampering with the memory contents of an LSI.

<Prior art> Currently, with IC cards, the main body case is opened and the
It is possible to analyze and tamper with the memory contents inside the SI, which poses a security problem. *) Chi, IC card, cash card, prepaid car 1
・If the payment amount is fraudulently tampered with, it will cause confusion in financial transactions and cause social harm. However, some kind of protection measure against tampering with LSI is required. 4. <Object 1 of the Invention> The present invention has been made in view of the above circumstances, and is a Objective 1-1 is to reliably prevent the alteration of the memory contents of the line l).

<Configuration of the Invention> The present invention adopts the following configuration in order to achieve the object stated in ``-''.

That is, the IC cart of the present invention (J, a sensor that detects opening of the main body case, and a switching circuit that turns on in response to the detection output of the stiffness sensor), and a switching circuit that operates to turn on in response to the detection output of the sensor that detects the opening of the main body case, and a reverse polarity It is characterized by comprising an LSI destruction battery connected to the

According to the above configuration, an attempt is made to tamper with the memory contents of the LSI by opening the main body case (this is detected by the sensor. The detection output of this sensor turns on the switching circuit, and accordingly, the SI A reverse bias is applied to [-SI from the destruction battery.

Since the saw, l-, SI is destroyed, tampering becomes impossible.

<Example> The figure is a circuit configuration diagram of the power supply circuit part inside the LSI.
, In the figure, 1 is a power supply circuit for the IC card, which is built in the main body case. 2 is a main battery, 1 is an LSI that receives power supply from this main battery 2, 6a, 61J
is an I interposed between the main battery 2 and the LSI 4.
8 is a solar cell as a sensor for detecting opening of the main body case, and 10 is a switching circuit turned on by the electromotive force of the solar cell 8.

This switching circuit IO includes two transistors Tr.
+, Tr, the base resistors 1, rz, and collector resistors R1, R4 of the valley transistors Tr+, Tr2, the inverter 12, and a pair of P-channel type MOSFETs 14a, 11b and t:, rj. +6 is an LSI destruction 11^ pond connected to the LSI 4 in L through the ζ switching circuit 10 with opposite polarity 5
,Next, we will explain the operation of the above configuration.4,5,Since the power supply circuit I is built in the main body case,,usually, the output type of the solar cell is,l,:,(l,v,5,. For,
Both transistors Tr11r of the switching circuit 10,
is in the off state (this is 1.nokoka-) - the voltage from the main battery 2 is level inverted by the inverter 12 and the MO
The gate voltages of the S transistors 6a and 6b are at the 1- level. By Nii 1, MOS)-Langistaro a, 6bfj on state and /a:'l, L S I 4
i] J: Power from main battery 2 jj; i city II, 'V
Apply cc. Therefore, in this case, the MOS of the switching circuit 10)
Since the voltage is introduced at a high level, both MOS+
-Ransistor 14a, +41+fJO: is in state.

From this state, in an attempt to modify the memory contents of the LSI 4, the main body case is opened (3), and the solar cell 8 is irradiated with light, generating an electromotive force! Both tranovs of circuit IO, rii”r, ′I゛r
, are both turned on, and their respective collector voltages become low level. Then, the gate voltages of the MOS transistors 6a and 6b are inverted in level by the inverter I2 and become high level, so that the MOS transistors 6a and 6b are turned off. On the other hand, since the gate voltage of the MOS transistors 14aS and 14b of the switching circuit IO becomes the [1- level], both the MOS transistors 14a and 14b are turned on. As a result, from 16 batteries for LSI destruction, 1.
, S14 is applied and the LSI is destroyed, making tampering impossible.

<Effects of the Invention> According to the present invention, since the LSI is destroyed when the main body case is opened, tampering with the memory contents of the LSI can be reliably prevented.

[Brief explanation of the drawing]

The drawing shows an embodiment of the present invention and is a circuit configuration diagram of a power supply circuit portion of a tIC card. I・1! Muku circuit, 4・LSI, 8・Sensor (solar cell), 10・Switching circuit, +6-LS ■Battery for destruction.

Claims (1)

[Claims] (1) A sensor that detects opening of the main body case, a switching circuit that turns on in response to the detection output of this sensor, and an LSI destruction battery that is connected to the LSI with opposite polarity via the switching circuit. An IC card characterized by comprising the following.