JP2005010908A - Abnormality detector and information device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abnormality detector and an information device having an information protection function for preventing confidential information from being leaked, not only by detecting an illicit act itself but also by detecting a trace of the executed illicit act. <P>SOLUTION: This abnormality detector/information device is provided with an acoustic wave generation part 10 for generating a prescribed sound wave, an acoustic wave reception part 20 for receiving the sound wave to be converted into an electric signal and for outputting it as a reception characteristic signal, an initial characteristic storage part 30 for storing an initial characteristic signal of an initial characteristic signal in initial setting, and an abnormality detecting part 40 for comparing the initial characteristic signal with the reception characteristic signal to generate an abnormality signal when detecting a difference larger than a predicted difference. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an abnormality detection device that detects an abnormality such as destruction or falsification of the device, and more particularly to an information device that includes an abnormality detection device and stores confidential information that should be protected from theft and leakage.
[0002]
[Prior art]
In recent years, information devices in which confidential information such as personal information is stored therein have become widespread. Examples of such information devices include mobile phone devices and personal computers that store information such as personal phone numbers and email addresses, biometric information and passwords related to fingerprint patterns and iris patterns, etc. for personal authentication And an authentication device that stores the authentication information. However, along with the widespread use of such information devices, fraudulent acts such as third parties destroying information devices or acquiring confidential information by removing a memory storing information from the devices are increasing.
[0003]
In developing information devices, how to prevent these illegal acts has become a major issue, and various techniques have been proposed to solve this issue. For example, by forming a fine conductive pattern inside the housing of an information device and constantly monitoring the current-carrying state of the conductive pattern, security that detects changes in the current-carrying state due to processing or deformation of the housing and detects fraud A technique has been proposed (see, for example, Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-150685
[Problems to be solved by the invention]
All of these security technologies attempt to detect fraudulent acts such as opening, destruction, disassembly, and theft of the chassis. Of course, it is desirable that fraudulent acts can be prevented by these security technologies, or that confidential information can be securely deleted when there are fraudulent acts. However, if the internal structure of the information device is known to a third party in advance, the above-described security technique may be avoided, for example, by switching to a maintenance mode. In this case, for example, if an illegal act such as attaching an eavesdropping device is performed inside the information device, and the user continues to use the information device without noticing that, there is a possibility that confidential information will continue to be stolen, The magnitude of the damage at that time is immeasurable. In addition, with recent advances in encryption technology, confidential information is usually encrypted, so it is often impossible to decrypt even if the data on the memory in the information device is simply stolen. Therefore, fraudulent acts such as eavesdropping on data in an actual operating state, instead of stealing data on the memory as it is, are increasing.
[0006]
As described above, in the conventional security technology, even if unauthorized tampering is made, it is not noticed, and there is a possibility that confidential information continues to be stolen and causes great damage.
[0007]
The present invention provides an anomaly detection device and an information device having an information protection function not only for detecting fraud itself but also for detecting traces of fraud and preventing leakage of confidential information. The purpose is to do.
[0008]
[Means for Solving the Problems]
The abnormality detection device of the present invention includes a sound wave generator that generates sound waves, a sound wave receiver that receives sound waves and converts them into electrical signals and outputs reception characteristic signals, and an initial characteristic signal that is a reception characteristic signal at the time of initial setting. The apparatus includes a stored initial characteristic storage unit, and an abnormality detection unit that generates an abnormal signal when a difference between the initial characteristic signal and the reception characteristic signal is larger than a predetermined value. With this configuration, it is possible not only to detect fraudulent acts themselves, but also to detect necessary traces of fraudulent acts and to perform necessary processing such as stopping operations, issuing alarms, and deleting confidential information. , Confidential information can be protected.
[0009]
In addition, by using electro-acoustic conversion of the sweep waveform signal as a sound wave, it is possible to investigate in detail the acoustic transmission characteristics between the sound wave generation unit and the sound wave reception unit. It can be detected reliably.
[0010]
Alternatively, the time required for detecting an abnormality per time can be shortened by using a rectangular wave signal obtained by electro-acoustic conversion as a sound wave.
[0011]
The information device of the present invention erases information in the information storage unit when the abnormality detection device of the present invention, an information storage unit storing erasable information, and an abnormality detection unit of the abnormality detection device generates an abnormal signal And a control unit. With this configuration, since the confidential information is erased when an illegal act or its trace is detected, it is possible to provide an information apparatus having a reliable information protection function without leaking the confidential information.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an information device according to an embodiment of the present invention will be described with reference to the drawings.
[0013]
(First embodiment)
FIG. 1 is a block diagram showing a configuration of an information device according to an embodiment of the present invention. The information device 1 of the present invention is an information device including an abnormality detection device, and includes a sound wave generation unit 10 including a signal generation circuit 12 that generates a specific transmission sound signal and a speaker 14 that converts the transmission sound signal into a sound wave, A sound wave receiving unit 20 including a microphone 22 that receives sound waves and converts them into electric signals, and an audio signal processing circuit 24 that performs necessary signal processing on the electric signals output from the microphones 22 and outputs reception characteristic signals. An initial characteristic storage unit 30 that stores an initial characteristic signal that is a reception characteristic signal at the time of initial setting such as shipping, and an abnormality that compares the reception characteristic signal with the initial characteristic signal and generates an abnormal signal when the difference is equal to or greater than a certain value A detection unit 40, a control unit 50 that controls the entire information device 1, and an information storage unit 60 that stores erasable confidential information are provided.
[0014]
Next, the operation of the information device 1 in the present embodiment will be described. In response to a command from the control unit 50, the signal generation circuit 12 generates a transmission sound signal having a sweep waveform whose frequency changes continuously, and the speaker 14 radiates the sound as a sound wave inside the housing. Sound waves radiated to the internal space of the case by the speaker 14 are transmitted through a complicated space formed by the case, a printed circuit board inside the case, various electronic components, wiring, or the like, or directly transmitted through the case, the printed circuit board, and the like. It is converted into an electric signal by the microphone 22. In this way, an acoustic path having a very complicated acoustic transmission characteristic unique to each information device is formed between the speaker 14 and the microphone 22, and the characteristics of the speaker 14 and the microphone 22 are formed from the microphone 22. In addition to this, an electrical signal affected by the above-described acoustic transfer characteristics is output. The audio signal processing circuit 24 extracts the characteristic of the acoustic transfer characteristic as a frequency characteristic based on the electric signal output from the microphone 22 and outputs it as a reception characteristic signal.
[0015]
The abnormality detection unit 40 compares the initial characteristic signal stored in advance at the time of factory shipment initialization for each information device 1 with the reception characteristic signal newly output from the audio signal processing circuit 24. Thereby, it is possible to compare the sound transfer characteristic at the initial setting with the current sound transfer characteristic. At this time, if the same sound transfer characteristic as the sound transfer characteristic at the time of initial setting is reproduced, it is determined that fraud has not been performed. However, if there is a difference in the sound transfer characteristics, such as when a specific frequency is emphasized, attenuated, or phase changed, there was some change in the case or inside the case, such as drilling or adding extra circuitry. It is determined that there is an illegal act and an abnormal signal is generated. When the control unit 50 receives an abnormality signal from the abnormality detection unit 40, the control unit 50 transmits a signal to the information storage unit 60 to delete important information such as personal information stored in the information storage unit 60. In response to this signal, the information storage unit 60 erases predetermined important information or all stored information.
[0016]
The series of operations described above are executed according to a command from the control unit 50 before the confidential information is read when the information device 1 in the present embodiment attempts to read the confidential information. Therefore, when the abnormality detection unit 40 determines that there is an illegal act, in addition to the process of deleting the confidential information itself through the control unit 50, the operation is stopped, a warning is given to the administrator, etc. Necessary processing can be performed to prevent leakage of confidential information.
[0017]
Next, the housing and internal structure of the information device 1 will be described.
[0018]
FIG. 2 is a perspective view of the information device 1 according to the embodiment of the present invention with the lid removed. FIG. 2 schematically shows an example of the arrangement of the circuit components of the information device 1 and the speakers and microphones in the present embodiment. A printed circuit board 110 on which main circuit blocks and a power supply block of the information device 1 are mounted is fixed inside the housing 100, and a speaker 14 is mounted on the upper left end of the printed circuit board 110. A sound wave reflector 130 is formed and fixed on the printed circuit board 110 so as to cover the information storage unit 60 and the digital circuit block in which the confidential information is stored and to form an acoustic path together with the printed circuit board. A microphone 22 as an audio receiving unit is installed near the exit of the acoustic path. Here, as the speaker 14, for example, a small piezoelectric speaker may be used, and as the microphone 22, for example, a small electret condenser microphone may be used.
[0019]
FIG. 3A is a conceptual diagram illustrating a transmission audio signal generated by the signal generation circuit 12 in the information device 1 according to the first embodiment. As described above, the transmission audio signal has a sweep waveform whose frequency continuously changes from a low frequency to a high frequency. The wavelength on the low frequency side is set to the length of the casing 100, and the wavelength on the high frequency side is set to the order of millimeters in order to detect a thin wire. In the present embodiment, a sweep waveform whose frequency changes from 2 kHz to 100 kHz is used.
[0020]
FIG. 3B is a conceptual diagram showing a reception characteristic signal measured at the time of initial setting in the information device 1 according to the first embodiment, that is, a spectrum characteristic of the initial characteristic signal. In addition to the acoustic transmission characteristics determined from the shape, material, and arrangement of the casing 100 and parts of the information device 1, this characteristic includes a total transmission characteristic including the speaker 14 and the microphone 22 and the electric-acoustic conversion system. You may think that it reflects.
[0021]
FIG. 3 (c) shows an illegal act such as making a hole in the casing 100 in the information device 1 of the first embodiment or adding an extra circuit component such as a small transmitter on the printed circuit board 110. It is a conceptual diagram which shows the spectrum characteristic of the reception characteristic signal measured in the state. FIG. 3C shows an example in which the resonance frequency of the housing 100 is shifted to the high frequency side by Δω and the spectrum on the high frequency side is reduced due to the fraud. As described above, since the acoustic transfer characteristics change due to fraudulent acts such as processing and deformation of the casing 100, falsification of electronic circuits, and addition of circuits, the reception characteristic signals and the reception characteristic signals measured at the time of initial setting, that is, initial characteristics It is possible to detect fraud by comparing the signal.
[0022]
Since the acoustic transfer characteristics change in response to changes in the environment such as temperature and atmospheric pressure, when the abnormality detection unit 40 compares the analysis result of the reception characteristic signal with the analysis result of the initial characteristic signal, these environments Any configuration may be used as long as it is determined that there has been a fraudulent activity when a difference greater than the expected fluctuation can be detected from the change.
[0023]
(Second Embodiment)
Since the components of the information device 1 in the second embodiment are the same as those in the first embodiment, the same reference numerals as those in FIG. 1 and FIG.
[0024]
The second embodiment is greatly different from the first embodiment in that the transmission voice signal according to the command of the control unit 50 is a pulse waveform, and both signals are compared when the reception characteristic signal and the initial characteristic signal are compared. This is a point where the waveforms along the time axis are directly compared without converting into frequency characteristics.
[0025]
FIG. 4A is a conceptual diagram illustrating a transmission audio signal in the information device 1 according to the second embodiment. As described above, the transmission voice signal is a pulse waveform including many frequency components.
[0026]
FIG. 4B is a conceptual diagram illustrating a reception characteristic signal measured at the time of initial setting in the information device 1 according to the second embodiment, that is, a waveform of the initial characteristic signal. In the same way as in the first embodiment, this characteristic also includes an electrical-acoustic conversion system such as the speaker 14 and the microphone 22 in addition to the acoustic transmission characteristic determined by the shape, material, and arrangement of the casing 100 and parts of the information device 1. It may be considered that it reflects the overall transfer characteristics including the above.
[0027]
FIG. 4 (c) is measured in a state in which fraud has been performed, such as by making a hole in the housing 100 in the information device 1 of the second embodiment, or by adding extra circuit components such as a small transmitter. It is a conceptual diagram which shows the waveform of the received characteristic signal. Unlike the first embodiment, in the present embodiment, the reception characteristic signal is not spectrally decomposed into frequency characteristics, and thus directly indicates changes in transfer characteristics such as changes in the resonance frequency of the casing 100. is not. However, by detecting changes in the waveform itself, it is possible to detect fraudulent acts such as processing and deformation of the casing 100, falsification of electronic circuits, and addition of circuits.
[0028]
Since the acoustic transfer characteristics change in response to environmental changes such as temperature and atmospheric pressure, the reception characteristics measured by the abnormality detection unit 40 at the time of initial setting of the reception characteristics signal also in the second embodiment. When comparing with a signal, any configuration may be used as long as a fraudulent act is determined when a difference greater than the expected change from these environmental changes can be detected.
[0029]
As described above, in the present embodiment, by using a pulse waveform as a transmission voice signal, one measurement time can be significantly shortened compared to a sweep waveform. Furthermore, since the waveform of the reception characteristic signal is directly compared with the reception characteristic signal measured at the time of initial setting, the signal processing is simplified, and as a result, the abnormality detection unit 40 or the audio signal processing circuit 24 is simplified.
[0030]
Also in the second embodiment, the abnormality detection unit 40 or the audio signal processing circuit 24 is provided with a Fourier transform function, so that a received waveform signal and an initial characteristic obtained by Fourier transform are used while using a pulse waveform as a transmission audio signal. A configuration may be adopted in which the frequency characteristic with the signal is analyzed in detail to extract the characteristic of the acoustic transfer characteristic, and the abnormality is detected based on the difference.
[0031]
In the first and second embodiments, the detection of the reception characteristic signal change is performed every time immediately before the confidential information is read. However, it may be performed periodically at a certain time interval, for example, it may be performed only once when the power is turned on.
[0032]
Furthermore, although one speaker 14 and one microphone 22 are provided, the number of speakers and installation locations, and the number of microphones and installation locations are expected depending on the size and mounting form of the electronic device and the state of the acoustic path inside the housing. You can choose to be able to detect fraudulent acts that are most sensitive.
[0033]
In addition, for example, when the information device 1 is an authentication device, the speaker 14 may be configured to be shared with a speaker for generating sound for notifying an authentication target person of an authentication result or the like.
[0034]
Furthermore, for example, a hammer may be used as the sound wave generation unit, and a pickup may be used as the sound wave reception unit, for example, to detect an illegal act by detecting a change in acoustic characteristics based on sound generated from the entire information device.
[0035]
【The invention's effect】
As described above, the abnormality detection device and the information device of the present invention not only detect the illegal act itself, but also detect the trace of the illegal act and prevent the leakage of confidential information in advance. Therefore, it is possible to reliably prevent leakage of confidential information.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an information device according to an embodiment of the present invention. FIG. 2 is a perspective view of the information device according to an embodiment of the present invention with a lid removed. The conceptual diagram (b) showing the transmission voice signal in the information device of the first embodiment is the conceptual diagram (c) showing the spectral characteristic of the initial characteristic signal in the information device of the first embodiment. FIG. 4 is a conceptual diagram showing a spectrum characteristic of a reception characteristic signal measured in a state where fraud has been performed in the information apparatus of FIG. 4A. FIG. 4A is a conceptual diagram showing a transmission voice signal in the information apparatus of the second embodiment. (B) is a conceptual diagram showing the waveform of the initial characteristic signal in the information device according to the second embodiment. (C) is a reception characteristic measured in the state where fraud is performed in the information device according to the second embodiment. Schematic diagram showing the signal waveform Akira]
DESCRIPTION OF SYMBOLS 1 Information apparatus 10 Sound wave generation part 12 Signal generation circuit 14 Speaker 20 Sound wave reception part 22 Microphone 24 Audio | voice signal processing circuit 30 Initial characteristic memory | storage part 40 Abnormality detection part 50 Control part 60 Information storage part 100 Case 110 Printed circuit board 130 Sound wave reflection board

Claims (4)

A sound wave generator for generating sound waves;
A sound wave receiving unit that receives the sound wave, converts it into an electrical signal, and outputs a reception characteristic signal;
An initial characteristic storage unit that stores an initial characteristic signal that is a reception characteristic signal at the time of initial setting; and
An abnormality detection device comprising: an abnormality detection unit that generates an abnormality signal when a difference between the initial characteristic signal and the reception characteristic signal is greater than a predetermined value. The abnormality detection apparatus according to claim 1, wherein the sound wave is an electro-acoustic conversion of a sweep waveform signal. The abnormality detection apparatus according to claim 1, wherein the sound wave is an electro-acoustic conversion of a rectangular waveform signal. The abnormality detection device according to any one of claims 1 to 3,
An information storage unit storing erasable information;
An information device comprising: a control unit that erases information in the information storage unit when the abnormality detection unit of the abnormality detection device generates the abnormality signal.

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