JP2002222402A - Ic card - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an IC card which makes it difficult to detect data used in the IC card from outside. SOLUTION: The IC card 10 has a signal processing means 11 which executes commands from the reader writer 2 and a counting means 14 which counts how many times the commands from the reader writer 20 are executed. The signal processing means 11 varyies the response time of the commands according to the count value. This signal processing means 11 increase the response time of the commands by executing a dummy routine and the execution frequency of the dummy routine corresponds to the count value of the counting means 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an IC card.

[0002]

2. Description of the Related Art An IC card can perform sophisticated and complicated signal processing using an IC chip in the IC card.
On the other hand, it is possible to statistically detect data on the bus by measuring a current value or a change in current flowing in the bus between the central processing unit (CPU) and the memory in the IC card. There are research reports. The above analysis method (D
In the PA method), the same signal processing is repeatedly performed by an IC card, the value of a current flowing in the bus or a change in the current is measured, and detection target data appearing at a predetermined timing is detected.

[0003]

SUMMARY OF THE INVENTION From the viewpoints of the reliability and security of an IC card, the I / O method according to the above analysis method is used.
It is desired to make it difficult to detect data in the C card. SUMMARY OF THE INVENTION It is an object of the present invention to provide an IC that can make it difficult to externally detect data used inside an IC card.
To provide a C card.

[0004]

An IC card according to the present invention has signal processing means for executing a command from a reader / writer device, and counting means for counting the number of executions of the command from the reader / writer device. The signal processing means changes a response time of the command based on a count value of the counting means.

[0005] In the IC card according to the present invention, preferably,
The signal processing means increases the response time of the command by executing the dummy routine, and the number of executions of the dummy routine is a number corresponding to the count value. In the IC card according to the present invention, more preferably, the signal processing unit executes the command after executing the dummy routine.

Preferably, the IC card according to the present invention further includes a memory for storing secret data, and the counting means counts the number of executions of a specific command among the commands from the reader / writer device. The specific command is a command for causing the signal processing unit to perform a process using the secret data in the memory.

In the IC card according to the present invention, preferably,
The signal processing unit increases the response time of the specific command by executing the dummy routine, and the number of times the dummy routine is executed is a number corresponding to the count value. In the IC card according to the present invention, more preferably, the signal processing unit executes the specific command after executing the dummy routine.

The signal processing means can change the command execution timing by changing the response time of the command based on the count value of the counting means, making it difficult to detect data inside the IC card by the DPA method. can do. In addition, by increasing the response time of the command, the rate of increase in the number of command executions thereafter can be suppressed, and the time required for executing a large number of commands required for the analysis of the DPA method can be lengthened to increase the Analysis can be hindered.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an IC according to the present invention.
FIG. 2 is a schematic configuration diagram illustrating an embodiment of a card. The IC card 10 includes a signal processing unit 11, a bus 12,
It has a memory 13, a counting means 14, a control means 15, and an interface means (I / F means) 16.

The I / F unit 16 is provided with a reader / writer device 20
Is supplied to the control means 15 in a form required for processing by the control means 15. When the IC card 10 is a non-contact type IC card, the I / F means 16 may have, for example, a configuration including a coil and an amplifier circuit connected to the coil, and the IC card 10 is a contact type IC card. In this case, for example, a configuration having connection terminals may be adopted.

The control unit 15 is a controller that controls the entire operation of the IC card 10 and controls the I / F unit 16, the counting unit 14, the signal processing unit 11, the memory 13, and the like. The control means 15 is constituted by, for example, a microcomputer. The control means 15 includes a reader / writer device 20
If the command data D20 is command data for executing a specific command, the count value of the counting means 14 is updated.

The control means 15 causes the signal processing means 11 to execute a dummy routine, and causes the signal processing means 11 to execute a command indicated by the command data D20 from the reader / writer device 20. In addition, the control means 15
Data indicating a (Waiting Time Extension), data D10 indicating a processing result of the signal processing unit 11, and the like are transmitted to the reader / writer device 20 via the I / F unit 16.

The signal processing unit 11 executes a dummy routine, a command indicated by the command data D20, and the like under the control of the control unit 15. The signal processing unit 11 and the memory 13 are connected by a bus 12, and the confidential data DK recorded in the memory 13 is read from the memory 13 via the bus 12.

FIGS. 2 and 3 show the IC card 10 of FIG.
5 is a schematic flowchart showing the operation of the first embodiment. First, in step S1, the control unit 15 controls the reader / writer device 2
Command data D20 from 0 is supplied via the I / F means 16.

In step S2, the control means 15 determines whether or not the command indicated by the command data D20 is a specific command for executing signal processing using the secret data DK in the IC card 10. The secret data DK is, for example, data of an encryption key and data of a password. If the command indicated by the command data D20 is not a specific command, the process proceeds to step S5. If the command indicated by the command data D20 is a specific command, the process proceeds to step S3.

In step S3, the control means 15 updates the count value of the counting means 14 by incrementing it by one. For example, the count value may be set to an initial value by resetting the IC card 10. In the case of a contact type IC card, the count value may be set to an initial value by discharging the IC card 10 from the reader / writer device 20. It may be.

In step S4, the control means 15 causes the signal processing means 11 to execute the dummy routine N times. N
Is an integer greater than or equal to 0, and is a value corresponding to the count value of the counting means 14. For example, the execution number N is set to 0 when the count value is less than the threshold value, and is set to 1 or more when the count value is equal to or more than the threshold value. It is desirable that the number of executions N be a value that increases according to the count value.

If the count value of the counting means 14 exceeds the threshold value, there is a possibility that the DPA method has been performed. That is, in the DPA method, the same command using the secret data to be detected is repeatedly executed, so that the number of executions of the command greatly exceeds the normal number of executions. Thus, it is possible to detect whether or not the number of times of normal command execution is significantly larger by comparing the count value with the threshold value. By delaying the signal processing by the dummy routine when the count value is equal to or more than the threshold value, the number of command executions within a certain time can be reduced and the timing of the signal processing can be changed. It can be difficult.

In step S5, the control means 15 causes the signal processing means 11 to start executing the command indicated by the command data D20.

In step S6, the control means 15 sends a setting time BWT (Block Wait) to the reader / writer device 20.
It is determined whether or not the signal processing result of the signal processing unit 11 can be responded within (ing Time). If the signal processing result can be responded within the set time BWT, the process proceeds to step S8. If the signal processing result cannot be responded within the set time BWT, the process proceeds to step S7.

In step S7, the control means 15 sends data indicating an extension request WTX (Waiting Time Extension) to the reader / writer device 20 via the I / F means 16, and returns to step S6.

In step S8, the control means 15 responds to the response data D10 indicating the signal processing result of the signal processing means 11.
Is returned to the reader / writer device 20 via the I / F means 16, and the processing of this flowchart ends.

In the above flowchart, when the count value is equal to or larger than the threshold value, the increase in the number of command executions is suppressed by the processing of the dummy routine. On the other hand, if the function of inhibiting the signal processing of the IC card 10 is provided when the count value is equal to or more than the threshold value, the signal processing is inhibited even when the analysis of the DPA method is not performed. become,
Problems occur. Therefore, in the IC card 10, the processing time is increased by executing the dummy routine, but the DPA
When a general user who does not perform analysis by a method uses it, it is possible to prevent the occurrence of trouble.

The counting means 14 may count the number of executions of a specific application, or may count the number of executions of a command in which the secret data DK in the IC card 10 flows through the bus 12. May be counted. Further, the count obtained by combining these execution counts may be used as the count value.

When a plurality of applications are registered in the IC card 10 in a plurality of directories of the control means 15, a count value is counted for each directory of the control means 15, and a threshold value and the number N of executions of the dummy routine are set. May be set.

In steps S6 and S7 in FIG. 3, for example, the following processing may be performed. ISO7816
-3 (JIS X 6304), IC card 1
If a response cannot be returned within the set time BWT (for example, when the encryption processing time exceeds the set time BWT), the 0 side sends data indicating a request for extending the set time BWT WTX.

The set time BWT is the maximum allowable time from when the reader / writer device 20 transmits the last character to when the reader / writer device 20 receives the first character from the IC card 10. Is passed, the reader / writer device 20 stops waiting for a response and shifts to an end process. The IC card 10 includes the reader / writer device 2
When the configuration is such that a clock signal is supplied from 0, the set time BWT is expressed by the following equation (1).

[0028]

BWT = 2 ^BWI × 2 × 960 × 372 / f + 11 × (current ETU) (1)

BWI (Block Waiting Time integer)
Is the initial response ATR (Answer To Rese
The upper bits b8 to b5 of TB (i) (i> 2) of t) are defined. The frequency f of the clock signal is generally 3.
57 × 10 ⁶ Hz, and may be 4.92 × 10 ⁶ Hz. BWI is a value between 0 and 9, and is typically 4.

The current ETU (elementary time unit) is
There are an initial etu and a working etu, and the following equations (2A) and (2
B). The symbol D in formula (2B) is generally 1 and the symbol F is generally 372. For example, f =
For 3.57 × 10 ⁶ Hz, one initial Etu = 1.
041 × 10 ⁻⁴ seconds (0.1041 milliseconds). Note that the work etu may be set to 372 / f, so that the value may be the same as the initial etu.

[0031]

## EQU2 ## Initial etu = 372 / f (2A) Work etu = (1 / D) × (F / f) (2B)

As an example of a communication protocol using WTX, a case where WTX is transmitted twice will be described below. First, the reader / writer device 20 transmits an internal authentication command (Internal Authenticate Command) for executing the encryption process to the IC.
At the same time as sending the data to the card 10, the timer for the set time BWT is started. IC card 10 that has received the internal authentication command
Starts the encryption process in the signal processing unit 11, but the control unit 15 detects that a response cannot be returned within the set time BWT, and returns an extension request WTX.

The reader / writer device 20, which has received the extension request WTX, sends an acknowledgment ACK to the IC card 10,
The measurement of the set time BWT is restarted from the reset value. The IC card 10 that has received the acknowledgment ACK continues the encryption processing in the signal processing unit 11, but the control unit 15 detects that a response cannot be returned within the set time BWT, and returns the extension request WTX again. .

The reader / writer device 20 that has received the extension request WTX again sends an acknowledgment ACK to the IC card 10 again, and restarts counting the set time BWT from the reset value. IC card 10 that has received the acknowledgment ACK
Generates the encrypted data within the set time BWT by continuing the encryption processing in the signal processing unit 11 and returns the response data D10 having the encrypted data to the reader / writer device 20.

The number of executions N of the dummy routine may be set as follows. When the IC card 10 is actually used, it is unlikely that the command using the same confidential data DK will be continuously received 50 times or more.
In this case, for example, the first threshold value TH1 is set to 50 times, and the second threshold value TH2 is set to 100 times.

When the count value of the counting means 14 is 50 or more, the processing time T1 of the dummy routine is set to T1 = (TH1) ² × (work etu), and the number of executions N corresponds to the processing time T1. Number of times When the count value of the counting means 14 is 100 times or more, the processing time T2 of the dummy routine is set as T2 = (TH2) ³ ×
(Work etu), and the number of executions N is the number of times corresponding to the processing time T2.

The above embodiment is an exemplification of the present invention, and the present invention is not limited to the above embodiment. In the IC card 10, a signal processing unit 11, a memory 13,
The counting means 14 and the control means 15 may be integrated with one-chip microcomputer.

[0038]

As described above, according to the present invention, it is possible to provide an IC card capable of making it difficult to externally detect data used inside the IC card.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an IC card according to the present invention.

FIG. 2 is a schematic flowchart showing the operation of the IC card of FIG.

FIG. 3 is a schematic flowchart showing the operation of the IC card of FIG. 1 subsequent to FIG. 2;

[Explanation of symbols]

10: IC card, 11: signal processing means, 12: bus,
13 memory, 14 counting means, 15 control means, 16
... Interface means (I / F means), 20 ... Reader / writer device.

Claims (6)

[Claims] 1. A signal processing means for executing a command from a reader / writer device, and a counting device for counting the number of times of execution of a command from the reader / writer device; An IC card for changing a response time of the command based on a numerical value. 2. The IC card according to claim 1, wherein the signal processing means increases a response time of the command by executing a dummy routine, and the number of executions of the dummy routine is a number corresponding to the count value. 3. The I signal according to claim 2, wherein said signal processing means executes said command after executing said dummy routine.
C card. 4. A memory for storing secret data, wherein the counting means counts the number of executions of a specific command among the commands from the reader / writer device, wherein the specific command is stored in the memory. 2. The IC card according to claim 1, wherein the command is a command for causing the signal processing unit to perform the process using the secret data. 5. The IC according to claim 4, wherein the signal processing means increases the response time of the specific command by executing a dummy routine, and the number of times the dummy routine is executed is a number corresponding to the count value. card. 6. The IC card according to claim 5, wherein said signal processing means executes said specific command after executing said dummy routine.