JP4162166B2 - IC card with variable response time - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an IC card in which the transmission timing of a response from an IC card in response to a command input from the terminal device is made variable in communication between the IC card and the terminal device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a preventive measure against illegal use of an IC card, one that pays attention to the response time of the IC card in response to an external command is known. For example, Japanese Patent Laid-Open No. Sho 62-251963 dares to make the response time for collating Personal Identification Number (hereinafter PIN) constant, which is determined when determining whether the PIN is correct or incorrect. When the logic changes, the response time changes, so that it is possible to analogize the logic. Therefore, by deliberately making the response time constant, it is devised to prevent logic analogy from a malicious person.
[0003]
In Japanese Patent Laid-Open No. 10-69222, in the case where encryption processing and decryption processing are performed in an IC card, the key used for encryption and the response time have a correlation, and the property of the key is determined from the response time. Since there is a possibility of understanding, the analogy of the key is prevented by randomly delaying the response time.
[0004]
[Problems to be solved by the invention]
The timing of the response from the IC card to the command for accessing the information recording unit or the access control unit of the IC card differs depending on the result of verification or authentication correctness and the information generation procedure included in the response, but the same processing procedure In this case, the time required for processing tends to be almost constant. For example, in a medium having a high security function such as an IC card, the time required for outputting the collation result for a random PIN input by an unauthorized user is the same as that of a legitimate user. An attack may reveal the PIN.
[0005]
An object of the present invention is to solve the above-described problems, and it is an object of the present invention to make it impossible to analogize a PIN or an authentication encryption key from a brute force attack and improve security.
[0006]
[Means for Solving the Problems]
The present invention has an information storage means and an information processing control means. The information processing control means interprets an externally input command, accesses the information storage means to perform a certain process, and An IC card that returns a response after verifying the authentication code every time there is an input, and if the input authentication code is not authentic as a result of verifying the authentication code, delay the timing when returning the response And a counter that increments when the verification code is not authentic, and the delay means increases the delay time stepwise each time the count value of the counter reaches a predetermined value. To do.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 is a conceptual diagram of a system according to the present invention. When an IC card 2 is set in a terminal device 1, a command (command) is transmitted from the terminal device 1 to the IC card 2, and the IC card that has received this command. 2 interprets a command, executes processing such as writing, reading, and reading, and returns a processing result to the terminal device 1 as a response.
[0008]
FIG. 2 is a conceptual diagram showing the configuration of the IC card of the present invention. The IC card has a CPU 20, an information storage unit 21, an unauthorized PIN counter 22, a delay circuit 23, and a transmission / reception circuit 24. The information storage unit 21 has a program storage area, a work area, and a rewritable nonvolatile memory area. When receiving a command transmitted from the terminal device 1, the CPU 20 reads data transmitted together with the command, accesses the information storage unit 21, performs necessary processing, and outputs the result as a response from the transmission / reception circuit 24. Furthermore, the present invention has an illegal PIN counter 22 and a delay circuit 23. The illegal PIN counter 22 counts the number of input times when the PIN input is made continuously, and the delay circuit 23 is for delaying the response time. The delay means may be realized by software in the delay circuit.
[0009]
FIG. 3 shows the signal flow of the IC card. As shown in the figure, when a PIN input is made through the transmission / reception circuit 24, the CPU 20 performs collation to determine whether or not the input PIN is authentic. Is transmitted as a response through the transmission / reception circuit 24. The illegal PIN counter 22 counts the number of illegal PIN inputs that are continuously input. For example, as shown in FIG. 4, when the number of illegal PIN inputs reaches a predetermined value, a predetermined delay time is set in the delay circuit 23. To do. It is set so that the delay time increases stepwise with respect to the number of illegal PIN inputs. For this reason, if a PIN input is attempted by a brute force attack, the response time is drastically increased according to the number of inputs, and therefore it is impossible to steal genuine PIN information after all.
[0010]
FIG. 5 is a diagram showing a processing flow for delaying a response.
When a PIN input is received and received (S1), collation is performed to determine whether the input PIN is authentic (S2). If the result of the collation is authentic, the process proceeds to the next process. If it is determined that the result is not authentic, the illegal PIN counter is incremented (S3, S4). Next, it is determined whether or not the value of the illegal PIN counter is equal to or greater than a predetermined value K (S5). If it is less than the predetermined value K, it is output as a response that the PIN is incorrect at a normal timing (S7). If it is greater than or equal to K, the response time is delayed (S6) and output.
[0011]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent a brute force attack by a random PIN input by significantly delaying the time until the response is transmitted from the IC card with respect to continuously input illegal PIN inputs. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a system of the present invention.
FIG. 2 is a diagram showing a configuration of an IC card according to the present invention.
FIG. 3 is a diagram showing a signal flow of an IC card.
FIG. 4 is a diagram illustrating a relationship of a delay time with respect to the number of illegal PIN inputs.
FIG. 5 is a diagram showing a processing flow for delaying a response.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Terminal device, 2 ... IC card, 20 ... CPU, 21 ... Information storage part, 22 ... Incorrect PIN counter, 23 ... Delay circuit, 24 ... Transmission / reception circuit

Claims (1)

An information storage means and an information processing control means, the information processing control means interprets an externally input command, accesses the information storage means to perform a certain process, and each time an authentication code is input And a delay means for delaying the timing when returning the response when the authentication code input is not authentic as a result of the verification of the verification code. And a counter that increments when the verification result authentication code is not authentic, and the delay means increases the delay time stepwise every time the count value of the counter reaches a predetermined value. Variable IC card.

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