JP2012038183A - Theft preventing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect undoing of connection to electronic equipment of the other party to the connection by utilizing a digital interfacing function, notify the connection trouble and make the electronic equipment inoperable, even if the electronic equipment is stolen, without connection to a prescribed electronic equipment item so as to discourage any prospective thief from stealing, and thereby to prevent theft.SOLUTION: Key selection vector (ksv) extractors/comparators 102 and 202, every time HDCP authentication is effected by connection to HDMI receiving side equipment of the other party to the connection, compare key vectors extracted from signals transmitted from the HDMI equipment of the other party with authentic key vectors Bksv and Aksv stored in nonvolatile memories 106 and 206; if the HDMI equipment of the other party has been replaced with another HDMI equipment different from that at the time of setting, the ksv extractors/comparators 102 and 202 output comparison results of inconsistency, and controls output permission switches 103 and 105 and input permission switches 203 and 205 to stop outputting or inputting of video signals.

Description

  The present invention relates to an anti-theft device, and more particularly, to an anti-theft device for preventing theft of electronic equipment having a digital interface standard such as HDMI (High-Definition Multimedia Interface).

  In general, AV devices, which are electronic devices such as television receivers and video playback devices, installed in public places are conventionally relatively low in value compared to money and precious metals. There are few measures taken, and the risk of suffering theft is high. Fortunately, however, AV equipment installed in public places is a heavy cathode-ray tube TV, which is difficult to carry away in the case of a television receiver, and a video deck as a video playback device is also inexpensive. Because there were many things and public places where AV equipment was installed were relatively limited places such as government offices and hospital waiting rooms, the damage was minor.

  However, in recent years, television receivers have become thinner and lighter and larger in screen size, and video playback devices have become more sophisticated, such as network players and Blu-ray recorders, compared to conventional CRT televisions and video decks. Since it became quite expensive, the risk of suffering has increased dramatically. Furthermore, these latest AV devices are also placed in educational facilities such as schools, and the risk of encountering damages is higher. For this reason, anti-theft technology for AV equipment has attracted attention.

  FIG. 6 is an explanatory diagram of each example of a conventional anti-theft device. The anti-theft device shown in FIG. 6A is a case 2 for storing an anti-theft AV device 1 and a case 2 so that the cover of the case 2 is not opened. 1 is composed of a mechanical key 3 for preventing a third party from taking out 1 illegally.

  The anti-theft device shown in FIG. 6B fixes the wire 5 having one end fixed to the anti-theft AV device 1 placed on the desk 4 and the other end of the wire 5 and fixed to the desk 4 The fixed part 6 is made up of. This anti-theft device fixes the AV device 1 on the desk 4 with a wire 5 having a hard structure that is difficult to cut, and prevents the AV device 1 from being taken away from the desk 4 by a third party.

  Another known anti-theft device is an anti-theft device that issues an alarm when, for example, the disconnection of a wire connected to an anti-theft AV device is detected electrically. Yes (see, for example, Patent Document 1). This anti-theft device mechanically and electrically connects an object mounting unit to which an anti-theft AV device is to be mounted, an alarm unit to be fixed at a predetermined position, and the object mounting unit and the alarm unit. A detection means for outputting a detection signal when detecting that the wire and the object mounting unit or the alarm unit are removed, or electrically detecting that the wire is cut; And a sounding device for sounding.

Japanese Patent Laid-Open No. 10-105841

  However, the anti-theft device shown in FIGS. 6A and 6B has a relatively simple configuration and is not sufficient for anti-theft. In addition, the anti-theft device described in Patent Document 1 requires a separate object mounting unit to be attached to an anti-theft AV device, which is not convenient.

  In addition, as for the prevention of theft of the installed AV device, there is no definite crime prevention measure, although it can be considered focusing on the time when people enter and exit. However, if the anti-theft device is used with an anti-theft device that is more expensive than an anti-theft AV device, it will be a fall.

  The present invention has been made in view of the above points, and detects that the connection with the electronic device of the connection partner has been disconnected by using the digital interface function to notify the connection abnormality, and is temporarily stolen. Another object of the present invention is to provide an anti-theft device which prevents theft by preventing the device from operating without being connected to a predetermined electronic device.

  In order to achieve the above object, the present invention provides an antitheft device mounted on an electronic device having at least one of a video signal processing function and an audio signal processing function and having a digital interface. An authentication means for receiving regular key information transmitted from another electronic device connected by a digital interface and performing HDCP authentication as needed, and a security setting selection for selecting whether or not a security setting is set. Means, storage control means for storing the received regular key information in the non-volatile storage unit, and when the security setting selection means is selected by the security setting selection means, for each authentication by the authentication means, in the non-volatile storage unit It is determined whether or not the same key information as the stored normal key information is received, and a determination result indicating that the same key information as the normal key information is received. When it is not obtained, characterized by having an operation limit means for limiting at least part of the processing function.

  In order to achieve the above object, the present invention provides monitoring means for monitoring whether or not a predetermined signal is interrupted for a predetermined period or more among signals transmitted and received with other electronic devices according to the digital interface standard. And a notifying means for notifying information indicating an abnormality when the monitoring means detects that a predetermined signal has been interrupted for a predetermined time or more.

  Here, the predetermined signal may be an HPD signal or a signal having a predetermined voltage value supplied from another electronic device.

  According to the present invention, the disconnection of the connection with the electronic device of the connection partner is detected using the digital interface function to notify the connection abnormality, and even if the device is stolen, It is possible to reduce the will of theft by not operating without connection.

It is a block diagram of one embodiment of the antitheft device of the present invention. It is a connection diagram of an example of various AV devices provided with the HDMI (or DVI) standard. FIG. 2 is a diagram illustrating a general internal structure of a signal transmitted through an HDMI cable that connects between two HDMI (HDCP authentication) processing units in FIG. 1. It is a flowchart explaining the 1st step of HDCP authentication. 5 is a flowchart for explaining recognition, setting, and operation restriction of a counterpart device according to an embodiment of the anti-theft device of the present invention, and an anti-crime operation flowchart of an embodiment of the anti-theft device of the present invention. It is explanatory drawing of each example of the conventional antitheft device.

  Next, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a block diagram of an embodiment of an antitheft device according to the present invention. In the figure, an anti-theft device 100 and an anti-theft device 200 are connected via an HDMI (High-Definition Multimedia Interface) cable 300 and an analog cable 310 in parallel.

  The anti-theft device 100 is an anti-theft device on the transmission side, an HDMI (HDCP) authentication processing unit 101 that performs a well-known HDCP authentication process, a voltage detection unit 104 that detects an HPD (Hot Plug Detect) signal, and an output permission for an analog video signal , An output permission switch 105 for performing security, a non-volatile memory 106 for storing a device-specific vector (ksv: key selection vector) uniquely determined according to a secret key, a security setting control / display unit 107 for performing security settings, an alarm sound (alarm display) The generator 108 is configured. The security setting control / display unit 107 includes a physical switch and button for security setting, or a GUI (Graphical User Interface) button displayed on the screen and a display unit. Further, the HDMI (HDCP) authentication processing unit 101 includes a ksv extraction / comparison unit 102 and an output permission switch 103 that permits output of a digital video signal. Note that ksv assigned to the anti-theft device 100 is expressed as Aksv in the following description for distinction.

  On the other hand, the anti-theft device 200 is an anti-theft device on the receiving side, an HDMI (HDCP) authentication processing unit 201 that performs a well-known HDCP authentication process, a voltage detection unit 204 that detects + 5V transmitted in the HDMI standard, and an analog video signal An input permission switch 205 that performs input permission, a nonvolatile memory 206 that stores a device-specific vector (ksv: key selection vector) that is uniquely determined according to a secret key, and security settings are configured in the same manner as the security setting control / display unit 107. It includes a security setting control / display unit 207 and an alarm sound (alarm display) generation unit 208. Further, the HDMI (HDCP) authentication processing unit 201 includes a ksv extraction / comparison unit 202 and an input permission switch 203 that permits input of a digital video signal. Note that ksv assigned to the anti-theft device 200 is expressed as Bksv in the following description for distinction.

  The ksv extraction / comparison unit 102, the output permission switches 103 and 105, and the ksv extraction / comparison unit 202 and the input permission switches 203 and 205 obtain the reception determination result of the regular key information, as will be described later. When there is not, it constitutes an operation restricting means for restricting at least a part of the video signal processing function and the audio signal processing function of the mounted electronic device. In the following description, the anti-theft device according to the present invention is described as an example mounted on an electronic device having both a video signal processing function and an audio signal processing function. However, an electronic device having only one of the functions is described. It may be mounted on equipment.

  The non-volatile memories 106 and 206 constitute a non-volatile storage unit in which regular key information received by the storage control unit of the present invention is stored. The above-described crime prevention setting control / display units 107 and 207 constitute crime prevention setting selection means of the present invention for selecting presence / absence of crime prevention setting. Also, the alarm sound (alarm display) generation units 108 and 208 constitute the notification means of the present invention for notifying information indicating abnormality.

  The anti-theft device according to the present invention is an electronic device having a processing function of at least one of a video signal processing function and an audio signal processing function, and a digital interface such as HDMI or DVI (Digital Visual Interface) It is a device used for an AV device that is an (HDMI device), and may have either configuration of the anti-theft devices 100 and 200. In FIG. 1, it is assumed that the anti-theft device 100 is mounted on the AV device on the transmission side, and the anti-theft device 200 is mounted on the AV device on the reception side.

  FIG. 2 shows a connection diagram of an example of various AV devices having the HDMI (or DVI) standard. In the figure, source devices 11 and 12 are AV devices having the HDMI (or DVI) standard that serve as video and audio signal sources, for example, DVHS (registered trademark) standard digital video decks, DVD players, and video disk recorders. (VDR), tuner, Blu-ray recorder, etc. The repeater device 13 is an AV device having an HDMI (or DVI) standard that performs connection switching and the like, and has both reception and transmission functions, such as an AV amplifier and an AV selector. The sink devices 14 and 15 are AV devices having an HDMI (or DVI) standard for performing video display, audio reproduction, and the like, such as a plasma display, a liquid crystal television, and an ILA (Image Light Amplifier) projector.

  In FIG. 2, the repeater device 13 switches the video / audio signal transmitted from one or both of the source devices 11 and 12, and transmits it to the sink device 14 or 15. Therefore, the source devices 11 and 12 can be equipped with the transmission-side antitheft device 100, and the sink devices 14 and 15 can be equipped with the receiving-side antitheft device 200. In addition, the repeater device 13 can be equipped with a reception-side anti-theft device 200 in the receiving unit that receives the video / audio signals transmitted from the source devices 11, 12. It is possible to mount the antitheft device 100 on the transmission side in the transmission unit that transmits the data.

  An HDMI (HDCP authentication) processing unit 101 illustrated in FIG. 1 is a processing unit in an HDMI transmission-side device (a transmission unit of the source devices 11 and 12 and the repeater device 13) that is a transmission-side AV device having the HDMI standard. On the other hand, the HDMI (HDCP authentication) processing unit 201 shown in FIG. 1 performs processing in an HDMI receiving device (sink device 14, 15 or receiving device of the repeater device 13) that is a receiving AV device having the HDMI standard. Part. The HDMI (HDCP authentication) processing unit 101 and the HDMI (HDCP authentication) processing unit 201 are connected by an HDMI cable 300, and constitute an authentication unit that performs authentication by HDCP of the present invention as needed.

  FIG. 3 is a diagram illustrating a general internal structure of a signal transmitted through the HDMI cable 300 that connects between the HDMI (HDCP authentication) processing unit 101 and the HDMI (HDCP authentication) processing unit 201. In the figure, an EDID EEPROM (Electrically Erasable and Programmable Read Only Memory) 210 is a memory that stores EDID, which is information such as the video format, audio format, color space, and speaker position of the receiving AV device. (HDCP authentication) is provided in the processing unit 201.

  In FIG. 3, a line 301 is a “+5 V” transmission line output from the transmission-side HDMI (HDCP authentication) processing unit 101. When the line 301 becomes “+5 V”, the receiving-side HDMI (HDCP authentication) processing unit 201 detects that the transmitting-side HDMI (HDCP authentication) processing unit 101 is connected. Also, “+ 5V” indicates the power when the transmission-side HDMI device reads the information EDID stored in the EDID EEPROM 210 when the reception-side HDMI device is powered off, or the transmission-side HDMI (HDCP authentication) processing It becomes the power source of the HPD signal returned to the unit 101.

  In FIG. 3, a line 302 is an HPD signal transmission line. The transmitting-side HDMI (HDCP authentication) processing unit 101 detects that the receiving-side HDMI (HDCP authentication) processing unit 201 is connected when the HPD signal is at a high level. The HPD signal also serves as a read permission signal for information EDID stored in the EDID EEPROM 210.

  A line 303 is a DDC line that transmits an SCL signal and an SDA signal, and is used for information communication such as HDCP authentication and information acquisition of a receiving device. A line 304 is a TMDS0 to TMDS2 line for transmitting a digital video signal. A line 305 is a CEC line for transmitting / receiving a control signal of the counterpart device.

  Next, a first known HDMI CP authentication performed between the HDMI (HDCP authentication) processing unit 101 and the HDMI (HDCP authentication) processing unit 201 based on a signal transmitted through such a known HDMI cable 300. The steps will be described. FIG. 4 is a flowchart for explaining the first stage of this HDCP authentication. HDCP authentication is performed based on a signal transmitted through the DDC line 303.

  First, the HDMI (HDCP authentication) processing unit 101 stores a key vector Aksv unique to the HDMI transmission-side device in which the HDMI (HDCP authentication) processing unit 101 is mounted in a storage unit (not shown) in the HDMI (HDCP authentication) processing unit 101. Or from the non-volatile memory 106. Further, a pseudo random number An is generated (step S1). Subsequently, the HDMI (HDCP authentication) processing unit 101 transmits the pseudo random number An and the key vector Aksv that is 40-bit digital data to the HDMI (HDCP authentication) processing unit 201 via the DDC line 303 (step S2). .

  On the other hand, the HDMI (HDCP authentication) processing unit 201 stores a key vector Bksv unique to the HDMI receiving device on which the HDMI (HDCP authentication) processing unit 201 is mounted in a storage unit (not shown) in the HDMI (HDCP authentication) processing unit 201. Or from the non-volatile memory 206. (Step S3). Subsequently, the HDMI (HDCP authentication) processing unit 201 transmits the generated key vector Bksv, which is 40-bit digital data, to the HDMI (HDCP authentication) processing unit 101 via the DDC line 303 (step S4).

  The HDMI (HDCP authentication) processing unit 101 receives the key vector Bksv and generates a calculation result R0 based on the received key vector Bksv and the pseudorandom number An based on a predetermined calculation formula (step S5). On the other hand, the HDMI (HDCP authentication) processing unit 201 receives the key vector Aksv and generates a calculation result R0 ′ based on the received key vector Aksv and the pseudorandom number An based on a predetermined calculation formula (step S1). S6).

  Subsequently, the HDMI (HDCP authentication) processing unit 201 transmits the generated calculation result R0 ′ to the HDMI (HDCP authentication) processing unit 101 via the DDC line 303 (step S7). Then, the HDMI (HDCP authentication) processing unit 101 collates the generated calculation result R0 with the received calculation result R0 '(step S8). When the collation matches, it is determined that the authentication is successful, and then the process proceeds to a known second stage of HDCP authentication.

  The device-specific key vectors Aksv and Bksv used in the HDCP authentication are used only for authentication and then disappear. In the present invention, the device-specific key vectors Aksv and Bksv are stored in the non-volatile memories 106 and 206 in order to use them as the unique identifier of the partner connection device, and this memory is stored each time HDCP authentication is performed by connection of the device. Compared with the key vector, it is confirmed that the preset devices are connected to each other, and it is limited so that it operates only when the preset device is connected. Details will be described with reference to the flowcharts of FIGS.

  FIG. 5A is a flowchart for explaining recognition, setting, and operation restriction of a counterpart device connected to the anti-theft device of the present embodiment, and FIG. 5B is a crime prevention of the anti-theft device of the present embodiment. The flowchart for operation | movement description is shown. Since the antitheft devices 100 and 200 of the present embodiment perform the same operation, the operation of the antitheft device 100 will be mainly described below as a representative.

  First, as shown in the flowchart of FIG. 5 (A), the anti-theft devices 100 and 200 are both powered on, and the HDCP authentication process is performed according to the flowchart shown in FIG. It is assumed that the authentication is successful (step S11).

  Next, the HDMI (HDCP authentication) processing unit 101 of the anti-theft device 100 determines whether a security setting has been selected by the user from the setting screen based on a signal from the security setting control / display unit 107 (step S12). When the HDMI (HDCP authentication) processing unit 101 determines that the security setting has been selected, it determines whether a password has already been set (step S13). The password is set using the security setting control / display unit 107 so that the security setting is not easily canceled.

  When the HDMI (HDCP authentication) processing unit 101 determines that the crime prevention setting is not selected, the HDMI setting processing unit 101 opens a password setting screen and allows the user to set a password (step S16). On the other hand, if it is determined in step S13 that the security setting is selected, an input screen is opened on the display unit of the security setting control / display unit 107, and a password set in advance by the user is requested (step S14).

  Subsequently, the HDMI (HDCP authentication) processing unit 101, when a correct password is input based on the request in step S14, or after setting the password in step S16, (1) “Turn on crime prevention setting (ON) ) / OFF (OFF) ”, (2)“ Update connection permission information ”, and (3)“ Return ”menu screen is displayed on the display unit (step S15).

  Of the above three items, when the item “ON / OFF of crime prevention setting” is selected by the crime prevention setting control / display unit 107, the HDMI (HDCP authentication) processing unit 101 determines whether the crime prevention setting is ON. Is determined (step S17). When it is determined that the crime prevention setting is set to OFF (step S17: OFF), the menu screen is continuously displayed. If the item “Return” is selected by the security setting control / display unit 107, the screen returns to the normal setting screen unrelated to the security setting (step S18). On the other hand, when the HDMI (HDCP authentication) processing unit 101 determines that “security setting ON” is selected by the security setting control / display unit 107 (ON in step S17), or “update connection permission information” item. Is determined to have been selected, an inquiry message “Is it possible to set it to operate only when connected to the currently connected device?” Is displayed on the display unit of the crime prevention setting control / display unit 107. (Step S19).

  When “No” is selected by the security setting control / display unit 107 according to the inquiry message (“No” in Step S20), the HDMI (HDCP authentication) processing unit 101 displays the menu on the display unit. The screen is displayed (step S15). On the other hand, if “Yes” is selected by the security setting control / display unit 107 according to the above inquiry message (“Yes” in step S20), the HDMI (HDCP authentication) processing unit 101 displays the connection partner's HDMI receiving side. The Bksv value of the device's normal key vector is stored in the non-volatile memory 106. After that, in the state where the authentication with the connection-destination HDMI receiving device is not successful, the content of video and audio content excluding the setting screen is saved. The output is stopped (step S21).

  In step S21, the non-volatile memory 106 in the anti-theft device 100 stores the key vector Bksv from the connected HDMI receiving device. On the other hand, the non-volatile memory 206 in the anti-theft device 200 stores a key vector Aksv from the HDMI transmission side device of the connection partner on which the anti-theft device 100 is mounted. In addition, the output stop of the content in step S 21 includes a digital video signal output disapproval by the output permission switch 103 and an analog video signal output disapproval by the output permission switch 105.

  Therefore, according to the anti-theft device 100 of the present embodiment, when it is set so as to operate only with the currently connected counterpart device, the ksv extraction / comparison unit 102 thereafter sets the counterpart HDMI. Each time HDCP authentication is performed by connection with the receiving device, the key vector extracted from the signal transmitted from the HDMI receiving device of the connection partner and the normal key vector Bksv stored in the nonvolatile memory 106 If the comparison result is the same, transmission / reception with the HDMI receiving device of the connection partner is normally performed. On the other hand, when the HDMI receiving side device of the connection partner is changed to another HDMI receiving side device different from the setting time, the ksv extraction / comparison unit 102 outputs the comparison result of mismatch, and the output permission switches 103 and 105 are set. The control stops the output of the digital video signal and the output of the analog video signal.

  For this reason, when the HDMI transmitting device on which the antitheft device 100 is mounted is taken away and the HDMI transmitting device is connected to another HDMI receiving device different from the HDMI receiving device to which the HDMI transmitting device was originally connected, ksv Since the mismatch / comparison result is output from the extraction / comparison unit 102 and the output of the digital video signal and the analog video signal is prohibited, the use of the HDMI transmission side device equipped with the anti-theft device 100 can be disabled. .

  In other words, the HDMI transmitting device on which the antitheft device 100 is mounted can be used only with the HDMI receiving device that was originally connected, and the HDMI transmitting device on which the antitheft device 100 is mounted is stolen to generate another HDMI. Since it cannot be used even if the receiving device is connected, the thief's willingness to steal can be reduced, and as a result, theft can be prevented.

  The same applies to the case where the HDMI receiving device equipped with the anti-theft device 200 is taken away. However, in the case of the anti-theft device 200, since the mismatched comparison result is output from the ksv extraction / comparison unit 202 and the input of the digital video signal and the analog video signal is prohibited by the input permission switches 203 and 205, the anti-theft It is possible to disable the use of the HDMI receiving device on which the device 200 is mounted.

  As described above, according to the present embodiment, the non-volatile memories 106 and 206 are used in order to use the device-specific key vector ksv used in HDCP authentication and normally deleted after authentication as the unique identifier of the partner device. This makes it possible to prevent theft by an extremely simple configuration in which the stored key vector is compared with the received key vector of the counterpart device every time HDCP authentication is performed by connecting the device. it can.

  The key vector ksv used at the time of HDCP authentication is made public by putting a key vector of a device that has been fraudulent by a predetermined organization on a list called SRM (System Renewability Message) when a certain device has been fraudulent. ing. Therefore, the ksv extraction / comparison units 102 and 202 confirm that the key vectors Bksv and Aksv extracted from the signal received at the time of HDCP authentication are regular key vectors not listed in the SRM, and then nonvolatile It is desirable to have a function of storing in the volatile memories 106 and 206.

  Next, the crime prevention operation of the antitheft devices 100 and 200 will be described with reference to the flowchart of FIG.

  Now, it is assumed that both the antitheft device 100 on the transmission side and the antitheft device 200 on the reception side are turned on and the crime prevention setting is valid (step S31). The fact that the crime prevention setting in step S31 is valid means that the setting in step S21 has been made.

  Subsequently, not only in the operation state but also in the maintenance state, the HPD signal of the counterpart device is monitored if it is a transmission side, and the HDMI 5V is monitored if it is a reception side (step S32). That is, in step S32, the transmission-side antitheft device 100 determines whether the HPD signal transmitted from the reception-side HDMI (HDCP) processing unit 201 through the HPD signal transmission line 302 has a predetermined potential. To monitor. On the other hand, the reception-side antitheft device 200 monitors the voltage detection unit 204 for +5 V transmitted from the transmission-side HDMI (HDCP) processing unit 101 via the line 301 in step S32.

  Subsequently, the anti-theft device 100 determines whether the HPD signal has been stopped for 5 seconds or more, and the anti-theft device 200 determines whether +5 V has been stopped for 5 seconds or more (step S33). The anti-theft device 100 determines that the connection with the counterpart device is disconnected when the HPD signal is stopped for 5 seconds or more, and the anti-theft device 200 is not input +5 V for 5 seconds or more. In addition to this, a warning is displayed on the display unit of the mounted device (step S34).

  That is, the voltage detection unit 104 of the anti-theft device 100 determines whether or not the HPD signal at a predetermined level has been stopped for 5 seconds or more in step S33, and when it has stopped for 5 seconds or more, the HDMI with the connection partner HDMI receiving device is determined. It is determined that the connection has been disconnected due to the HDMI receiving side device being stolen, and in step S34, an alarm sound (alarm display) generation unit 108 displays an alarm sound, and an alarm display (visual threatening operation) indicating an abnormal state is performed.

  In step S33, the voltage detection unit 204 of the anti-theft device 200 determines whether + 5V has been stopped for 5 seconds or more. If the + 5V is stopped for 5 seconds or more, the HDMI connection with the HDMI transmission side device of the connection partner is HDMI transmission. In step S34, the alarm sound (alarm display) generating unit 208 displays an alarm sound and displays an alarm display (visual threatening operation) indicating an abnormal state.

  Since the HDMI connection may be temporarily disconnected (approx. 100 msec or more) in order to prompt the other device to re-authenticate, in this embodiment, sufficient time is considered to be theft and immediately after the theft. The above-mentioned 5 seconds are set as the time for which the warning can be activated. However, the present invention is not limited to this time.

  As described above, according to the antitheft devices 100 and 200 of the present embodiment, the HPD signal or +5 V transmitted from the AV device (HDMI device) having the HDMI standard of the connection partner via the HDMI cable is used. Monitoring, when it is not input for more than 5 seconds, the connection partner's HDMI device is judged to have been disconnected and stolen, and the theft is notified by a warning sound or warning display. it can.

  Note that the present invention is not limited to the above embodiment. For example, the processing when the two ksv values to be compared in step S21 do not match is the stop of the output of the digital video signal or the analog video signal. However, the present invention is not limited to this, and a method such as outputting a video signal that does not accept an operation input or cannot be normally played back may be used. In short, it may be a process that restricts at least a part of the AV operation function. .

  The present invention also includes an anti-theft program that causes a computer to execute the operations shown in the flowchart of FIG. In this case, the anti-theft program may be reproduced from the recording medium and taken into the computer, or may be distributed from the server via the network and downloaded to the computer.

100, 200 Anti-theft device 101, 201 HDMI (HDCP) authentication processing unit 102, 202 ksv extraction / comparison unit 103, 105 Output permission switch 104, 204 Voltage detection unit 106, 206 Non-volatile memory 107, 207 Security setting control / display Unit 108, 208 Alarm sound (alarm display) generator 203, 205 Input permission switch 300 HDMI cable 301 + 5V transmission line 302 HPD signal transmission line 303 DDC line 310 Analog cable

Claims (3)

An anti-theft device having a processing function of at least one of a video signal processing function and an audio signal processing function, and mounted on an electronic device equipped with a digital interface,
Authenticating means for receiving regular key information transmitted from another electronic device connected by the digital interface by the digital interface and performing authentication by HDCP as needed;
Security setting selection means for selecting presence / absence of security setting;
Storage control means for storing the received regular key information in a nonvolatile storage unit;
When the security setting selection means selects the presence of the security setting, whether to receive the same key information as the regular key information stored in the nonvolatile storage unit for each authentication by the authentication means And when the determination result indicating that the same key information as the regular key information has been received cannot be obtained, an operation limiting means for limiting at least a part of the processing function is provided. Anti-theft device. Monitoring means for monitoring whether or not a predetermined signal is interrupted for a certain period or more among signals transmitted and received according to the standard of the digital interface with the other electronic device;
The anti-theft device according to claim 1, further comprising: an informing means for informing information indicating an abnormality when the monitoring means detects that the predetermined signal has been interrupted for the predetermined time or more.   3. The antitheft device according to claim 2, wherein the predetermined signal is an HPD signal or a signal having a predetermined voltage value supplied from the other electronic device.

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