SMART CARD SYSTEM AND OPERATING METHOD THEREOF

• US 20090194598A1
• Filed: 01/14/2009
• Published: 08/06/2009
• Est. Priority Date: 01/31/2008
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Jong-Cheol, Kim, Eui-Seung
• Granted Patent: US 8,104,690 B2
• Time in Patent Office: Days
• US Class Current: 235/492
• CPC Class Codes: G06K 19/073 Special arrangements for circuits, e.g. for protecting identification code in memory protection against unauthorised use of computer memory G06F12/14

Abstract

A smart card system having: a smart card including a security logic circuit to detect an external attack; and a reader communicating with the smart card. The security logic circuit detects the external attack by measuring the external input capacitance through an input/output pad of the smart card and comparing the external input capacitance to the input capacitance of the reader. This improves the security of the smart card system.

Claims

1. A smart card system comprising:

a smart card including a security logic circuit to detect an external attack; and

a reader communicating with the smart card,

wherein the security logic circuit detects the external attack by measuring an external input capacitance through an input/output pad of the smart card and comparing the external input capacitance to an input capacitance of the reader.

2. The smart card system of claim 1, wherein the security logic circuit comprises:

an input/output driver providing a constant current to the input/output pad; and

a capacitance measurer controlling the input/output driver to provide the constant current to the input/output pad for a predetermined time and, after providing the constant current to the input/output pad for the predetermined time, generating a control signal to inactivate communication between the smart card and the reader if a voltage of the input/output pad is lower than a reference voltage.

3. The smart card system of claim 2, wherein the input/output driver comprises:

a current source providing the constant current to the input/output pad; and

a switching circuit providing a ground voltage to the input/output pad instead of the constant current.

4. The smart card system of claim 2, wherein the capacitance measurer comprises a counter measuring a time up to the predetermined time for providing the constant current to the input/output pad.

5. The smart card system of claim 4, wherein the capacitance measurer enables the counter in response to a capacitance measuring signal.

6. The smart card system of claim 4, wherein the capacitance measurer compares a voltage of the input/output pad with the reference voltage if a count value of the counter reaches a predetermined value and generates the control signal if the voltage of the input/output pad is lower than the reference voltage.

7. The smart card system of claim 1, wherein the smart card transfers a predetermined capacitance value to the reader and the reader adjusts the input capacitance of the reader by the predetermined capacitance value.

8. An operating method of a smart card system including a smart card and a reader, comprising:

measuring an external input capacitance through an input/output pad;

comparing the external input capacitance with an input capacitance of the reader; and

inactivating communication from the smart card to the reader if the external input capacitance is different from the input capacitance of the reader.

9. The method of claim 8, wherein the measuring is carried out by providing a constant current to the input/output pad for a predetermined time.

10. The method of claim 9, wherein the comparing is carried out by comparing a voltage of the input/output pad with a reference voltage.

11. The method of claim 10, wherein the inactivating is carried out by resetting the smart card if the voltage of the input/output pad is lower than the reference voltage.

12. The method of claim 8, which further comprises:

before the measuring, transferring a predetermined capacitance value to the reader and adjusting the input capacitance of the reader in accordance with the predetermined capacitance value.

13. An integrated circuit card comprising:

a security logic circuit providing a current to a pad, measuring a voltage of the pad and generating a control signal when the voltage of the pad reaches a predetermined level; and

an internal circuit communicating data with an external device and inactivating the communication in response to the control signal.

14. The integrated circuit card of claim 13, wherein the security logic circuit provides the constant current during a predetermined time.

15. The integrated circuit card of claim 13, wherein the security logic circuit measures a capacitance coupled to the pad by providing a constant current during a predetermined time and measuring a voltage level of the pad.

16. The integrated circuit card of claim 13, wherein the security logic circuit detects an external attack.