JP2014126935A - Ic card, data duplication control method, and data duplication control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an IC card, a data duplication control method and a data duplication control program capable of preventing data from being duplicated illegally and externally even when external attacks are repeated at plural times.SOLUTION: Response data stored in a prescribed address of a memory is duplicated in a communication buffer according to a prescribed size, and it is determined whether the address of the duplication source is proper according to the duplication. When it is determined that the address of the duplication source is not proper, the duplication of the response data is stopped.

Description

  The present invention comprises a controller that executes a predetermined process corresponding to a command received from an external terminal, and a memory that stores response data to be output to the external terminal based on a result of the process, the response data The present invention relates to a technology of an IC card that copies the response data copied from the memory to the communication buffer and then outputs the response data copied to the communication buffer to the external terminal.

  An IC card that places importance on security must be provided with a means for preventing unauthorized operation due to an attack from the outside. The attack from the outside is a means for causing a malfunction in an IC chip mounted on an IC card called failure analysis, and a typical example is DFA (Differential Fault Analysis).

  The IC card uses a contact I / F or a non-contact I / F for communication with an external terminal. The command transmitted from the external terminal is received by those I / Fs, interpreted and executed, and then response data is returned. This response data is a value held in the IC card or a value obtained by calculation in the card. When returning these data from the IC card to the external terminal, the IC card Is copied (copied) to the communication buffer, and then returned as response data to the external terminal. At this time, if an attack is received from the outside when copying to the communication buffer, the data at the wrong address will be copied to the communication buffer, and data that should not be output will be output. There is a risk.

  Patent Document 1 discloses a technique for preventing response of internal confidential data or the like to the outside when an unauthorized attack is performed from the outside. In the technique of Patent Document 1, before transferring data to a transmission buffer from a memory having a response data area for storing response data for response to the outside in the IC card, the transfer source of the data responds to the response of the memory. If the data transfer source is the response data area of the memory, the data transfer to the transmission buffer is permitted, otherwise the data transfer to the transmission buffer is confirmed. Is supposed to stop.

Japanese Patent No. 4713878

  However, when an attack from the outside is repeatedly performed a plurality of times, in the technique of Patent Document 1, after confirming that the data transfer source is the response data area of the memory, data transfer to the transmission buffer is permitted, and then external There is a possibility that data will be copied illegally.

  Therefore, the present invention provides an IC card, a data duplication control method, and data duplication that can prevent illegal duplication of data even when an external attack is repeated a plurality of times. An object is to provide a control program.

  In order to solve the above problem, an invention according to claim 1 is a controller for executing a predetermined process corresponding to a command received from an external terminal, and outputting to the external terminal based on a result of the process. A memory for storing response data, and after replicating the response data from the memory to the communication buffer, an IC card that outputs the response data copied to the communication buffer to the external terminal. Data replication means for replicating the response data stored at a predetermined address to the communication buffer for each predetermined size; and determination means for determining whether the address of the replication source is valid for each replication of the predetermined size; If the determination means determines that the address of the copy source is not valid, the response data Replication interrupting control means of, characterized in that it comprises a.

  According to a second aspect of the present invention, there is provided a controller that executes a predetermined process corresponding to a command received from an external terminal, and a memory that stores response data to be output to the external terminal based on a result of the process. An IC card that outputs the response data copied to the communication buffer to the external terminal after the response data is copied from the memory to the communication buffer, and stored in a predetermined address of the memory A data duplicating unit for duplicating response data to the communication buffer for each predetermined size; a determining unit for determining whether the address of the duplication source is valid for each duplication of the predetermined size; and the response by the data duplicating unit When data replication is complete, the response data copied to the communication buffer Control means for outputting the response data to the external terminal, and when the determination means determines that the address of the copy source is not valid, the control means copies the response data for each predetermined size. And the output of the response data copied to the communication buffer to the external terminal is disabled.

  According to a third aspect of the present invention, in the IC card according to the first or second aspect, the IC card further includes an address duplicating unit that duplicates a value indicating the address in the memory before starting the duplication of the response data. Determines whether the value indicating the address from which the response data is copied matches the value indicating the address copied to the memory, and if not, determines that the address is not valid It is characterized by.

  According to a fourth aspect of the present invention, the IC card according to the first or second aspect further includes an address duplicating unit that duplicates an inverted value of the value indicating the address into the memory before starting the duplication of the response data. The determination unit confirms whether the value indicating the source address of the response data is consistent with the inverted value copied to the memory. If the consistency is not satisfied, the address is valid. It is characterized by determining that it is not.

  According to a fifth aspect of the present invention, in the IC card according to any one of the first to fourth aspects, when the control unit determines that the address of the copy source is not valid by the determination unit, Dummy data different from the response data is output to the external terminal.

  The invention described in claim 6 includes a controller that executes a predetermined process corresponding to a command received from an external terminal, and a memory that stores response data to be output to the external terminal based on the result of the process. A data replication control method performed by the controller of the IC card that outputs the response data copied to the communication buffer to the external terminal after replicating the response data from the memory to the communication buffer. Replicating the response data stored at a predetermined address in the memory to the communication buffer for each predetermined size, and determining whether the address of the replication source is valid for each replication of the predetermined size If the address of the copy source is determined to be invalid, the response data Characterized in that it comprises duplicated and the discontinuing of the.

  The invention of the data duplication control program according to claim 7 is a controller for executing a predetermined process corresponding to a command received from an external terminal, and response data for outputting to the external terminal based on a result of the process. The controller in an IC card that outputs the response data copied to the communication buffer to the external terminal after replicating the response data from the memory to the communication buffer. Data duplicating means for duplicating the response data stored at a predetermined address to the communication buffer for each predetermined size, determining means for judging whether the address of the duplication source is valid for each duplication of the predetermined size, and When the determination means determines that the address of the copy source is not valid Characterized in that to function as interrupting control means replication of the response data.

  The invention according to claim 8 includes a controller that executes a predetermined process corresponding to a command received from an external terminal, and a memory that stores response data to be output to the external terminal based on a result of the process. A data replication control method performed by the controller of the IC card that outputs the response data copied to the communication buffer to the external terminal after replicating the response data from the memory to the communication buffer. Replicating the response data stored at a predetermined address in the memory to the communication buffer for each predetermined size, and determining whether the address of the replication source is valid for each replication of the predetermined size And when the response data is copied, it is copied to the communication buffer. Outputting the response data to the external terminal, wherein the data replication control method replicates the response data for each predetermined size even when it is determined that the address of the replication source is not valid. And the output of the response data copied to the communication buffer to the external terminal is disabled.

  The invention of the data replication control program according to claim 9 is a controller for executing a predetermined process corresponding to a command received from an external terminal, and response data for outputting to the external terminal based on a result of the process. The controller in an IC card that outputs the response data copied to the communication buffer to the external terminal after replicating the response data from the memory to the communication buffer. Data duplicating means for duplicating the response data stored at a predetermined address to the communication buffer for each predetermined size, determining means for judging whether the address of the duplication source is valid for each duplication of the predetermined size, and When the response data replication is completed by the data replication means, The control unit functions as a control unit that outputs the response data copied to the communication buffer to the external terminal, and the control unit also includes the determination unit that determines that the address of the copy source is not valid. The replication of the response data for each predetermined size is continued, and output of the response data copied to the communication buffer to the external terminal is disabled.

  According to the present invention, the response data stored at a predetermined address in the memory is copied to the communication buffer for each predetermined size, and the copy source address is determined by determining whether the copy source address is valid for each copy. If it is determined that the response data is not valid, the response data replication is interrupted, or the response data is continuously replicated for each predetermined size, and the response data copied to the communication buffer is disabled from being output to the external terminal. Since it comprised in this way, even if it is a case where the attack from the outside is repeatedly performed several times, it can prevent that data are illegally copied outside.

1 is a diagram illustrating a schematic configuration example of an IC card 1. FIG. It is a conceptual diagram which shows a mode that the duplication address src is duplicated as the duplication address src_dual. (A) is a flowchart which shows the process in the data replication control method 1, (B) is a figure which shows an example of the pseudo code corresponding to the process shown to (A). (A) is a flowchart which shows the process in the data replication control method 2, (B) is a figure for demonstrating the effect by the process shown to (A).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, an IC card according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a schematic configuration example of the IC card 1. The IC card 1 is used as a cash card, a credit card, an employee card, or the like. Alternatively, the IC card 1 is incorporated into a smartphone, a mobile phone, or the like.

  As shown in FIG. 1, an IC chip 1 a is mounted on the IC card 1. The IC chip 1a includes a CPU (Central Processing Unit) 11, a RAM (Random Access Memory) 12, a flash memory 13, and an I / O circuit 14. Note that an EEPROM (Electrically Erasable Programmable Read-Only Memory) may be used instead of the flash memory.

  The CPU 11 is a controller that executes various programs, executes predetermined command processing corresponding to the command received from the external terminal 2 according to the data replication control program of the present invention, and reads / writes data from / to the RAM 12 and the flash memory 13 I do. The external terminal 2 includes a reader / writer for performing communication with or without contact with the IC card 1. Examples of the external terminal 2 include an ATM, a ticket gate, and an authentication gate. Alternatively, when the IC card 1 is mounted on a mobile terminal, the external terminal 2 corresponds to a control unit responsible for the function of the mobile terminal. In some cases, an external terminal of an attacker from the outside is a communication partner of the IC card 1, and the IC card 1 also in this case is data to be kept confidential (data of an address that should not be output originally). Is configured not to be output.

  The RAM 12 is a volatile memory that temporarily stores data. A predetermined storage area of the RAM 12 is used as a communication buffer. The data stored in the communication buffer is output to the external terminal 2 via the I / O circuit 14.

  The flash memory 13 is a nonvolatile memory for storing programs (including the data replication control program of the present invention) and data. The flash memory 13 stores response data to be output to the external terminal 2 based on the result of command processing by the CPU 11. This response data is, for example, a value (eg, key data) held in the IC chip 1a or a value obtained as a result of calculation in the IC chip 1a.

  The I / O circuit 14 serves as an interface with the external terminal 2. The I / O circuit 14 is provided with eight terminals C1 to C8 defined by, for example, ISO / IEC7816. For example, the C1 terminal is a power supply terminal, the C2 terminal is a reset terminal, the C3 terminal is a clock terminal, the C5 terminal is a ground terminal, and the C7 terminal is a terminal that performs data communication with the external terminal 2.

  In the command processing, the CPU 11 functions as data duplicating means in the present invention, thereby outputting response data stored at a predetermined address in the flash memory 13 (that is, for outputting to the external terminal 2 based on the result of the command processing). The response data) is copied (copied) to the communication buffer for each predetermined size. For example, the response data is repeatedly copied to the communication buffer a plurality of times for each fixed-length byte from the top of the response data.

  Further, the CPU 11 functions as a determination unit in the present invention to perform a determination process for determining whether or not the copy source address (address of the flash memory 13) is valid for each copy of the response data having a predetermined size. . In other words, the copy source address is checked each time the copy is performed for each predetermined size. As this check method, there are a method of verifying by duplication (or more than triple) of an address (value indicating an address) and a method of verifying by an error detection code of an address (value indicating an address).

  In the method of verifying by duplication of addresses, duplication source addresses are duplicated and held before the start of duplication of a predetermined size of response data. In other words, the CPU 11 functions as the address duplicating means in the present invention, and retains the duplication source address by duplicating it in the memory (for example, the stack provided in the RAM 12 or the flash memory 13) before the response data duplication starts. To do. The values held at this time are “replication source address” and “same value as the replication source address”.

  FIG. 2 is a conceptual diagram showing how the source address src is duplicated as a duplicated address src_dual. Then, the duplicated addresses are compared when the response data is copied at a predetermined size (src and src_dual are compared), and when the addresses match each other, it is determined that the duplication source address is valid. . On the other hand, if the addresses do not match, it is determined that the addresses are not valid. Alternatively, the values held at this time may be “replication source address” and “replication value of the replication source address”. In this case, the consistency between the "replication source address" and the "inverted value of the replication source address" is confirmed at the time of duplication of the response data of the specified size. The original address is determined to be valid. On the other hand, if consistency is not achieved, it is determined that the address is not valid. For example, in FIG. 2, when the source address is stored in src and the inverted value of the source address is stored in Src_dual, if the inverted value of src and src_dual match, the source address is valid. Determined. By holding the inversion value in this way, security can be improved. As a characteristic, the memory may be “easy to change to a specific value when attacked”. In this case, if the original value is kept doubled as it is, if both are attacked, both will change to the same value. However, in the case where the inverted value is held, it is possible to detect the attack even if both are attacked and become the same value.

  On the other hand, in the method of verifying with the error detection code of the address, before starting the replication of the response data of a predetermined size, CRC (Cyclic Redundancy Check, CRC) is performed on the replication source address and the CRC value is held. Then, the CRC value obtained by performing CRC calculation on the original address at the time of duplicating the response data with the predetermined size is compared with the CRC value calculated and held before duplicating the predetermined size. If the values match, the address of the copy source is determined to be valid. Alternatively, in another method of verifying with an error detection code for an address, the checksum value is calculated by calculating the checksum of the copy source address before starting to copy the response data with a predetermined size. Then, the value obtained by calculating the checksum of the copy source address at the time of duplicating the response data with the predetermined size is compared with the checksum value calculated and held before duplicating the predetermined size. If the checksum values match, the copy source address is determined to be valid.

  Comparing the verification method using address duplication with the error detection code of the address, the method of verification using address duplication and the processing time is shorter than the verification method using the error detection code of the address. Can do. On the other hand, the method of verifying with the error detection code of the address can suppress the memory capacity than the method of verifying with the double address.

  Then, the CPU 11 functions as a control unit in the present invention, so that when the duplication is completed without determining that the duplication source address is not valid, the response data duplicated in the communication buffer is I / O The data is output to the external terminal 2 via the circuit 14. On the other hand, if the CPU 11 determines that the duplication source address is not valid during the duplication processing and determination processing, the CPU 11 interrupts the response data duplication processing (data duplication control method 1). Alternatively, even when it is determined that the copy source address is not valid during the copy process and the determination process, the CPU 11 continues the copy of the response data for each predetermined size and stops the subsequent process after the copy is completed. (Data replication control method 2). In the case of the data duplication control method 2, the CPU 11 disables output of the response data duplicated in the communication buffer to the external terminal 2.

  Next, the processing of the CPU 11 when receiving a command from the external terminal 2 will be described with reference to FIGS. FIG. 3A is a flowchart showing processing in the data replication control method 1, and FIG. 3B is a diagram showing an example of pseudo code corresponding to the processing shown in FIG. FIG. 4A is a flowchart showing processing in the data replication control method 2, and FIG. 4B is a diagram for explaining the effect of the processing shown in FIG. 4A. FIG. 3A and FIG. 4A are processes in the case of applying the method of verification by address duplication, and are started when, for example, a data read command is received.

  First, processing in the data replication control method 1 shown in FIG. In step S1 shown in FIG. 3A, the CPU 11 duplicates and holds the duplication source address as described above. Next, the CPU 11 starts duplication processing (step S2), and determines whether or not the duplication source address of the response data is valid (step S3). For example, the CPU 11 determines whether or not the response data replication source address matches the address stored in step S1, and if they match, the CPU 11 determines that the address is valid (step S3: YES). When it is determined that the address is valid in this way, the CPU 11 copies the predetermined length of the response data to the communication buffer (in other words, transfers it to the communication buffer) (step S4).

  Next, the CPU 11 determines whether or not the response data has been copied (step S5). If the response data has not been replicated (step S5: NO), the CPU 11 returns to step S2 and continues the replication process for each predetermined length of the response data. On the other hand, when copying of the response data is completed (step S5: YES), the CPU 11 outputs the response data copied to the communication buffer to the external terminal 2 via the I / O circuit 14 (step S6).

  On the other hand, when the response data replication source address does not match the address held in step S1 in step S3, the CPU 11 determines that the address is not valid (detects an abnormality) (step S3: NO). ) Response data replication is interrupted to stop the operation (system stop) (step S7). That is, when an abnormality is detected due to the mismatch of the addresses, it is considered that there has been an attack from the outside, and the replication process is interrupted. In step S7, the CPU 11 may respond an error to the external terminal 2. In step S7, if the CPU 11 is configured to output dummy data (fixed value or random number) different from the response data to the outside (for example, the attacker's external terminal), the CPU 11 outputs the data to the attacker. Therefore, it is possible not to narrow down whether or not the processed data is data to be kept secret.

  As described above, according to the data duplication control method 1, the CPU 11 performs duplication processing for duplicating the response data in the communication buffer for each predetermined size, and the duplication source address is valid for each duplication of the predetermined size. If it is determined that the replication source address is not valid in the middle of the replication process, the replication process is configured to be interrupted. However, it is possible to prevent internal confidential data from being output to the outside (to prevent data from being illegally copied to the outside).

  Next, processing in the data replication control method 2 shown in FIG. As a premise of processing in the data replication control method 2, an area (hereinafter referred to as “abnormality detection flag”) for recording that an abnormality has been detected is prepared. In step S11 shown in FIG. 4A, as in step S1 shown in FIG. 3A, the CPU 11 holds the duplication source address in duplicate. Next, the CPU 11 turns off (that is, resets) the abnormality detection flag (step S12). Next, the CPU 11 starts duplication processing (step S13), and determines whether or not the duplication source address of the response data is valid as in step S3 shown in FIG. 3A (step S14). If it is determined that the address is valid (step S14: YES), the CPU 11 copies the fixed length of the response data to the communication buffer, similarly to step S4 shown in FIG. 3A (step S15). ). On the other hand, when it is determined that the address is not valid (abnormality detection) (step S14: NO), the CPU 11 turns on the abnormality detection flag (for example, data “0” in an area for recording that an abnormality has been detected). Is updated to “1”) (step S16), and a predetermined length of the response data is copied to the communication buffer (step S15). That is, if an abnormality is detected during the replication process, the CPU 11 considers that there has been an external attack and turns on the abnormality detection flag, but the replication process is continued.

  Next, the CPU 11 determines whether or not the response data has been duplicated (step S17). If the response data has not been duplicated (step S17: NO), the CPU 11 returns to step S13, and the response data has a fixed length. Continue the replication process for each. On the other hand, when copying of the response data is completed (step S17: YES), the CPU 11 determines whether or not the abnormality detection flag is on (step S18). If it is determined that the abnormality detection flag is not on (step S18: NO), the CPU 11 outputs the response data copied to the communication buffer to the external terminal 2 via the I / O circuit 14 (step S19). ). On the other hand, when it is determined that the abnormality detection flag is on (step S18: YES), the operation is stopped (step S20). That is, in the data duplication control method 2, the CPU 11 checks the abnormality detection flag after all duplication processing is completed, and when it is off, continues the processing and outputs response data, and is on. Suspends the subsequent processing to disable output of the response data copied to the communication buffer to the external terminal 2. In step S20, the CPU 11 may respond an error to the external terminal 2. Further, in step S20, the CPU 11 may be configured to output dummy data (fixed value or random number) different from the response data to the outside (for example, an attacker's external terminal) as in step S7.

  As described above, according to the data duplication control method 2, the CPU 11 performs duplication processing for duplicating the response data to the communication buffer for each predetermined size, and the duplication source address is valid for each duplication of the predetermined size. If the copy source address is determined to be invalid during the replication process, the replication process is continued and the replication is completed. Since it is configured to disable output of response data to the external terminal 2, even if an attack from the outside is repeatedly performed a plurality of times, it is possible to prevent the data to be kept secret from being output to the outside. be able to. Furthermore, according to the data replication control method 2, even if it is determined that the replication source address is not valid during the replication process, the replication process is continued and the subsequent process is interrupted after the replication is completed. With this configuration, it is possible to prevent an attacker from observing (ascertaining) at which timing an abnormality has been detected. In other words, as shown in FIG. 4B, assuming that there is an attack from the first time to the fourth time, and if there is an attack at the second time, the duplication is interrupted at the attack timing. Since the operation stops after completing the fourth replication, the attacker cannot determine whether the attack timing is correct.

1 IC card 1a IC chip 11 CPU
12 RAM
13 Flash memory 14 I / O circuit

Claims (9)

A controller that executes a predetermined process corresponding to a command received from an external terminal; and a memory that stores response data to be output to the external terminal based on a result of the process; After copying to the communication buffer, in the IC card that outputs the response data copied to the communication buffer to the external terminal,
Data replication means for replicating the response data stored at a predetermined address of the memory to the communication buffer for each predetermined size;
Determining means for determining whether the address of the copy source is valid for each copy of the predetermined size;
Control means for interrupting replication of the response data when the determination means determines that the address of the copy source is not valid;
An IC card comprising: A controller that executes a predetermined process corresponding to a command received from an external terminal; and a memory that stores response data to be output to the external terminal based on a result of the process; After copying to the communication buffer, in the IC card that outputs the response data copied to the communication buffer to the external terminal,
Data replication means for replicating the response data stored at a predetermined address of the memory to the communication buffer for each predetermined size;
Determining means for determining whether the address of the copy source is valid for each copy of the predetermined size;
Control means for outputting the response data copied to the communication buffer to the external terminal when the response data is copied by the data copying means;
With
The control means continues the replication of the response data for each predetermined size even when the determination means determines that the address of the copy source is not valid, and the response copied to the communication buffer. An IC card that disables output of data to the external terminal. In the IC card according to claim 1 or 2,
Further comprising address duplicating means for duplicating the value indicating the address in the memory before starting the duplication of the response data;
The determination means determines whether a value indicating the address from which the response data is copied matches a value indicating the address copied to the memory, and if not, the address is not valid. An IC card characterized by determining. In the IC card according to claim 1 or 2,
An address duplicating unit for duplicating the inverted value of the value indicating the address in the memory before starting the duplication of the response data;
The determination unit confirms whether the value indicating the source address of the response data is consistent with the inverted value copied to the memory. If the consistency is not satisfied, the address is valid. IC card characterized by not being determined. The IC card according to any one of claims 1 to 4,
The IC card, wherein the control unit outputs dummy data different from the response data to the external terminal when the determination unit determines that the address of the copy source is not valid. A controller that executes a predetermined process corresponding to a command received from an external terminal; and a memory that stores response data to be output to the external terminal based on a result of the process; A data replication control method performed by the controller of the IC card that outputs the response data replicated in the communication buffer to the external terminal after being replicated in the communication buffer,
Replicating the response data stored in a predetermined address of the memory to the communication buffer for each predetermined size;
Determining whether the address of the copy source is valid for each copy of the predetermined size;
If it is determined that the address of the replication source is not valid, the step of interrupting the replication of the response data;
A data duplication control method comprising: A controller that executes a predetermined process corresponding to a command received from an external terminal; and a memory that stores response data to be output to the external terminal based on a result of the process; After copying to the communication buffer, the controller in the IC card that outputs the response data copied to the communication buffer to the external terminal,
Data replication means for replicating the response data stored at a predetermined address of the memory to the communication buffer for each predetermined size;
A determination means for determining whether the address of the copy source is valid for each copy of the predetermined size; and
A data replication control program that functions as a control unit that interrupts replication of the response data when the determination unit determines that the address of the replication source is not valid. A controller that executes a predetermined process corresponding to a command received from an external terminal; and a memory that stores response data to be output to the external terminal based on a result of the process; A data replication control method performed by the controller of the IC card that outputs the response data replicated in the communication buffer to the external terminal after being replicated in the communication buffer,
Replicating the response data stored in a predetermined address of the memory to the communication buffer for each predetermined size;
Determining whether the address of the copy source is valid for each copy of the predetermined size;
When copying of the response data is completed, outputting the response data copied to the communication buffer to the external terminal;
Including
The data replication control method continues the replication of the response data for each predetermined size even when it is determined that the address of the replication source is not valid, and the response data copied to the communication buffer A data replication control method, wherein output to the external terminal is disabled. A controller that executes a predetermined process corresponding to a command received from an external terminal; and a memory that stores response data to be output to the external terminal based on a result of the process; After copying to the communication buffer, the controller in the IC card that outputs the response data copied to the communication buffer to the external terminal,
Data replication means for replicating the response data stored at a predetermined address of the memory to the communication buffer for each predetermined size;
A determination means for determining whether the address of the copy source is valid for each copy of the predetermined size; and
When replication of the response data is completed by the data replication unit, the response data copied to the communication buffer is made to function as a control unit that outputs to the external terminal,
The control means continues the replication of the response data for each predetermined size even when the determination means determines that the address of the copy source is not valid, and the response copied to the communication buffer. A data duplication control program that disables output of data to the external terminal.

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