JPH04370891A - Ic card data writing/reading device - Google Patents

Abstract

PURPOSE:To obtain a data writing/reading device to an IC card which can prevent the interception of the data signals transmitted and received and can improve the security. CONSTITUTION:A power supply means 1 is provided to supply the power Vcc and the GND to an IC card 20 together with a clock supply means 3 which supplies a clock signal CLK, a data transmission/reception means 2 which transmits and receives the data signal synchronous with the signal CLK via a signal line I/O, a reset means 4 which supplies a reset signal RST, and a control means 5 which performs the general control of those means 1-4. The frequency of the clock signal supplied from the means 3 varies while the means 2 is transmitting and receiving the data signal. Therefore it is impossible to obtain the correct logical value when the data signal is intercepted on the line I/O.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data writing/reading device for an IC card, and more particularly to a technique for improving security during writing/reading.

0002

2. Description of the Related Art The demand for IC cards as a new information storage medium is increasing. This IC card has the advantage that it can ensure a higher level of security than magnetic cards or optical cards, since its internal data cannot be easily read out by unauthorized means. Furthermore, since this IC card does not have an internal power supply or clock generation source, it has the advantage of being much more compact than a general computer even though it has a built-in IC.

[0003] In order to access such an IC card, a data writing/reading device is required. A general data writing/reading device is provided with an insertion slot for inserting an IC card, and when the IC card is inserted here, the electrodes come into contact with the external connection terminals of the IC card inside the device, and the device is connected to the device. It is electrically connected to the IC card. The currently popular IC cards have two terminals for receiving power supply, one terminal for receiving clock signal supply, one terminal for transmitting and receiving data, and one terminal for resetting. One terminal is provided for each. A power supply voltage, a clock signal, a data signal, and a reset signal are supplied from the data writing/reading device side to the IC card side through these terminals. Note that data signals are transmitted bidirectionally via the same terminal.

0004

[Problems to be Solved by the Invention] In the future, the demand for IC cards will tend to increase more and more, and they are also being used for applications that handle information of high economic value. In such applications, ensuring security is the most important issue. especially,
An IC card may also store a PIN code that only the card issuer can know, and it is important to ensure security that such PIN codes are read by general card users or third parties. becomes a serious problem. However, as described above, information is transmitted between the data writing/reading device and the IC card by transmitting a serial signal over only one signal line. Therefore, it is possible to intercept the transmitted data signal from this signal line.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a data writing/reading device for an IC card, which can prevent data signals being sent and received from being intercepted on the way and improve security.

[0006]

[Means for Solving the Problems] The present invention provides a power supply means for supplying power to an IC card, a clock supply means for supplying a clock signal, and a data signal which is transmitted and received in synchronization with the clock signal. In a data writing/reading device comprising a data transmitting/receiving means and a reset means for supplying a reset signal, when the data transmitting/receiving means is transmitting/receiving a data signal, the frequency of the clock signal supplied by the clock supplying means is It was designed to change.

[0007]

[Operation] The present invention focuses on the feature that an IC card operates based on a clock signal supplied from a data writing/reading device rather than an internally generated clock signal. That is, the data writing/reading device according to the present invention has a function of changing the frequency of the clock signal supplied to the IC card. and,
Data signals transmitted and received with the IC card are synchronized with this clock signal whose frequency changes. Therefore, even if a data signal is intercepted from the signal line connecting the two, it will not be possible to recognize it as meaningful information because the frequency of the clock signal is not constant.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on illustrative embodiments. FIG. 1 is a block diagram showing a general connection relationship between an IC card and a writing/reading device. The writing/reading device 10 includes a power supply means 1, a data transmission/reception means 2, a clock supply means 3, a reset means 4, and a control means 5 for controlling these in an integrated manner.
A process for writing information into the IC card 20 and a process for reading information from within the IC card 20 are performed. The control means 5 is connected to a higher level host computer 30.

The power supply means 1 supplies power to the IC card 20 via two signal lines, a signal line Vcc and a signal line GND. The IC card 20 operates using this power supply. The data transmitting/receiving means 2 exchanges data with the IC card 20 via the signal line I/O. That is, when writing data to the memory in the IC card 20, the signal line I/
A data signal is transmitted to the IC card 20 via the I
When reading data from the memory in the C card 20, a data signal transmitted from the IC card 20 via the signal line I/O is received by the data transmitting/receiving means 2. In this way, bidirectional data transfer is performed by one signal line I/O, and data is transmitted bit by bit as a serial signal. This serial signal is a signal synchronized with the clock signal generated by the clock supply means 3. The clock supply means 3 supplies the generated clock signal to the data transmission/reception means 2 and also connects the signal line CLK.
The same clock signal is applied to the IC card 20 via the IC card 20. Therefore, both the data transmitting/receiving means 2 and the IC card 20 transmit and receive data signals using the same clock signal. The reset means 4 provides a reset signal to the IC card 20 via the signal line RST. The IC card 20 can be reset by the reset means 4 when starting to access the IC card 20 or at other necessary times.

[0010] The control means 5 has a function of centrally controlling each of these means, and is connected to the host computer 30. Therefore, data given from the host computer 30 can be written to the IC card 20, and conversely, data read from the IC card 20 can be transferred to the host computer 30.

The above configuration is the same as that of a conventional general data writing/reading device. A feature of the present invention is that a function for changing the frequency of the clock signal generated by the clock supply means 3 is added. FIG. 2 shows an example of the configuration of the clock supply means 3 according to the present invention. In this embodiment, five clock generation circuits 31-35 are provided, and these generate clock signals CLK1-CLK5 of different frequencies, respectively. The selector 36 selects this 5
It has a function of selecting one of the two clock signals and outputting it as the clock signal CLK. Furthermore, the selected clock signal is switched one after another over time. In this way, the output clock signal CLK is transmitted to the data transmitting/receiving means 2 and the IC card 20.
, but the frequency will be switched from time to time. The selector 36 may switch the selection by any method. For example, every 20ms,
CLK1 to CLK5 may be sequentially switched and selected. Alternatively, a predetermined selection pattern may be determined in advance, and switching may be performed according to this selection pattern (for example, if CLK3 is selected for 20ms, then CLK5 is selected for 15ms, then CLK2 is selected for 30ms, etc.). ). Alternatively, a random number may be generated and switching may be performed at random based on this random number. In order to prevent data interception and improve security, it is preferable to perform switching that cannot be predicted by a third party.

When the selection is switched by the selector 36 in this way, the frequency of the clock signal changes while the data signal is being transmitted to the signal line I/O. For example, using a constant frequency clock signal CLK shown as "CLK" in FIG.
33"("00110011" in binary representation), the change in voltage level on the signal line I/O is as follows:
The waveform is shown as "I/O" in the figure. Below that, “BIT”
” corresponds to the logic value of each bit corresponding to this waveform, and “S” indicates the start bit.

However, even when transmitting exactly the same hexadecimal number "33", if the clock frequency is changed midway, the result will be as shown in FIG. 4. That is,
The clock signal CLK shown in FIG. 4 has the same frequency as the clock signal shown in FIG. 3 until a certain time t, but the frequency is switched to 1/2 at time t. Signal line I/O
The data signal transmitted to is always synchronized with the clock signal CLK, so it has a waveform as shown as "I/O" in FIG. If you look at the content shown under "BIT", you will understand that there is no error in the logical value to be transmitted.

[0014] In this way, even if the frequency of the clock signal is switched during data signal transmission, no problem occurs in data transmission and reception. This is because the clock signal used by the data transmitting/receiving means 2 and the clock signal used by the IC card 20 are both the same clock signal generated by the clock supply means 3, so even if the frequency changes midway, the clock signal used by the IC card 20 is the same. Because the frequencies of the clock signals used change simultaneously, a data signal sent from one side is always correctly received at the other side. However, for someone who intercepts the data signal on the signal line I/O, correct reception is prevented. Since the frequency of the clock signal used for transmission and reception is generally believed to be constant, eavesdroppers generally do not monitor the clock signal. Then, the data signal intercepted from the signal line I/O is shown in FIG.
If the waveform shown in the I/O is taken, this data signal will be interpreted as indicating a logical value of "001100001111". In this way, correct information can be prevented from being intercepted.

Although the present invention has been described above based on the illustrated embodiment, the present invention is not limited to this embodiment only, and can be implemented in various other forms. For example, in the clock supply means 3 shown in FIG. 2, a plurality of clock generation circuits are prepared and the frequency of the clock signal is switched by selecting one of them.
It is also possible to configure the clock supply means 3 using an oscillator whose oscillation frequency changes based on the applied voltage, and to change the clock frequency by changing the applied voltage.

[0016]

Effects of the Invention As described above, according to the data writing/reading device according to the present invention, the frequency of the clock signal is changed when transmitting and receiving data signals to and from an IC card. This will prevent signals from being intercepted and improve security.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a general connection relationship between an IC card and a writing/reading device.

FIG. 2 is a block diagram showing an example of a clock supply means used in the data writing/reading device according to the present invention.

FIG. 3 is a diagram showing a state in which a data signal is transmitted to a signal line I/O using a clock signal CLK having a constant frequency.

[Figure 4] Clock signal CLK whose frequency changes at time t
2 is a diagram illustrating a state in which a data signal is transmitted to a signal line I/O using an I/O. FIG.

[Explanation of symbols]

1...Power supply means 2...Data transmission/reception means 3...Clock supply means 4...Resetting means 5...Control means 10...Writing/reading device 20...IC card 30...Host computer 31 to 35...Clock generation circuit 36...Selector

Claims (1)

[Claims] 1. A power supply means for supplying power to an IC card, a clock supply means for supplying a clock signal, a data transmitting/receiving means for transmitting and receiving a data signal synchronized with the clock signal, and a reset signal. In the data writing/reading device, the frequency of the clock signal supplied by the clock supplying means is changed when the data transmitting/receiving means is transmitting/receiving the data signal. A data writing/reading device for an IC card, characterized by: