Registers – Records – Conductive
Patent
1998-06-19
2000-12-26
Lee, Michael G
Registers
Records
Conductive
235441, 235438, G06K 1906
Patent
active
061645508
DESCRIPTION:
BRIEF SUMMARY
The present invention relates generally to access control systems including an integrated circuit (IC) card, or "smart" card, for limiting access to information in signal processing application. More particularly, the present invention relates to a smart card reader operation when a fault is detected.
Systems such as pay-TV systems include access control sub-systems that limit access to certain programs or channels. Only users who are entitled (e.g., paid a fee) are permitted to view the programs.
Access control systems may include an integrated circuit (IC) card, or "smart" card, feature. A smart card is a plastic card the size of a credit card that has a signal processing IC embedded in the plastic. A smart card is inserted into a smart card reader that couples signals to and from the IC in the card. The IC in a smart card processes data such as security control information as part of an access control protocol. The IC includes a control microcomputer, such as the 6805 processor from Motorola Semiconductor, Austin, Tex., which includes ROM, EEPROM, and RAM memory. The processor performs various security control functions including entitlement management and generating a key for descrambling the scrambled data component of the signal.
Sometimes, the various contacts on the smart card may be shorted together by debris or by malfunctioning of the smart card circuitries. For example, debris can accumulate on the contacts of a smart card during manufacturing, shipment, user replacement or wiping action of the smart card. This shorting of the smart card contacts will, in turn, short the smart card power supply or present a low impedance to the power supply, causing it to go into a current limiting condition. If the signals to the card are not turned off or modified immediately, large current from the control lines could be coupled into the smart card, causing destruction. This may damage the circuitries in both the smart card and the smart card reader.
In accordance with an aspect of the present invention, a circuit is provided to detect when a variation in a power supply coupled to a smart card reader has occurred, indicating a possible fault in the smart card (e.g., shorted contacts or other malfunctions). As an example, the circuit detects this variation by comparing the voltage coupled to smart card with a reference voltage. If the circuit detects that the voltage has dropped below the reference voltage, it will modify the smart card control signals, for example, by clamping them at or near ground potential. This prevents any potential damage to either the smart card or the smart card reader.
The invention may be better understood by referring to the accompanying drawing in which:
FIG. 1A shows the physical layout of the contacts of an exemplary smart card as defined by the current ISO standard 7816.
FIG. 1B shows the contact and signal assignments of an exemplary smart card as defined by the current ISO standard 7816.
FIG. 2 shows an exemplary embodiment of the current invention as employed in a smart card reader.
FIG. 3 shows another embodiment of the present invention using Field Effective Transistors (FETs).
FIG. 4 shows another embodiment of the present invention using transmission gates to isolate the control lines to the smart card.
International Standards Organization (ISO) standard 7816 establishes specifications for a smart card interface. In particular, the ISO standard 7816-2 specifies that the electrical interface to the card will be via eight contacts positioned on the card surface as shown in FIG. 1A. Six of the eight signals at the contact points are defined as Vcc (supply voltage), RST (reset signal), CLK (clock signal), GND (ground), Vpp (programming voltage for programming memory in the card IC), and I/O (serial data input/output). Two contacts are reserved for future use. The assignment of the signals to the smart card contacts is shown in FIG. 1B.
FIG. 2 shows an exemplary embodiment of the present invention. An ISO 7816 compliant smart card 100 having eight contacts C1-C8 is shown cou
REFERENCES:
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patent: 4990760 (1991-02-01), Tomari et al.
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Patent Abstracts of Japan, vol. 12, No. 173, May 24, 1988 & JP 62-282389.
Patent Abstracts of Japan, vol. 11, No. 153, May 19, 1987 & JP 61-289480.
Patent Abstracts of Japan, vol. 14, No. 369, Sep. 9, 1990 & JP 2-135589.
Lee Diane I.
Lee Michael G
Liao Frank Y.
Shedd Robert D.
Thomson Licensing S.A.
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