JP6247729B2 - REPRODUCTION MANAGEMENT DEVICE, REPRODUCTION MANAGEMENT METHOD, REPRODUCTION MANAGEMENT PROGRAM, CONTENT RECEIVING SYSTEM, AND CONTENT DISTRIBUTION SYSTEM - Google Patents

Description

  The present invention relates to a reproduction management apparatus, a reproduction management method, a reproduction management program, a content reception system, and a content distribution system that perform reproduction management of encrypted content.

  It is widely performed to distribute content signals from broadcast stations and reproduce them with electronic devices such as smartphones, personal computers, and televisions. In the case of pay broadcasting, the content distributor encrypts and distributes the content signal in order to ensure profits from the distribution. In this case, only a specific user who has a contract with the content distributor can decode the content signal and view the content.

  Even when the content signal is encrypted and distributed, the viewer may not be allowed to view the content for a short period of time in order to increase the number of subscribers. Such short-time playback of content is also called a preview. In order to realize the preview, it is necessary to output a key for decrypting the encrypted content signal for a predetermined preview time.

JP 2011-216951 A Japanese Patent Laid-Open No. 11-308595

  If the decryption key is inadvertently output, there is a high possibility that the decryption key will be used illegally. Further, in order to accurately manage time, it is generally necessary to provide a time source that is expensive and difficult to falsify.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a playback management apparatus, a playback management method, a playback management program, a content reception system, and a content distribution capable of realizing preview with high security and low cost Is to provide a system.

According to one aspect of the present invention, a content signal encrypted using a key updated at a predetermined update cycle, and information indicating the reproduction time of the key and the encrypted content signal are encrypted. A reproduction management device used in a receiver for receiving the obtained first control information, an interface for receiving the first control information from the receiver, decrypting the first control information, and the key and Based on the first decryption unit for restoring the playable time of the encrypted content signal, the playable time of the encrypted content signal, and the key update period, the key is sent to the receiver. And a control unit that outputs the restored key to the receiver when the output is determined to be output.
The reproducible time here may be a time during which the encrypted content signal can be reproduced without a contract for reproducing the encrypted content signal, that is, a preview time.

  Specifically, the control unit may output the key by the number of times corresponding to a value obtained by dividing the reproducible time by the update period.

  It is desirable that the reproduction management device has higher security than the receiver.

  As an example, the update cycle is a predetermined fixed value, and a storage unit that stores the update cycle may be provided.

  As another example, the receiver receives second control information obtained by encrypting information indicating the update period, and the interface receives the second control information from the receiver, and performs the reproduction management. The apparatus may include a second decoding unit that decodes the second control information and restores the update period.

  As another example, information indicating an update period of the key may be included in the first control information.

  As yet another example, the first control information includes time information together with the key, and the first decryption unit decrypts the first control information and includes the one key. The key update cycle may be acquired based on the time information and the time information included together with the updated key.

  Preferably, the reproduction management device is an IC chip or an IC card inserted into the receiver.

  According to another aspect of the present invention, a receiver that receives the encrypted content signal and the first control information, and the playback management device according to any one of claims 1 to 9 And the receiver transfers the first control information to the reproduction management device and receives the encrypted content signal when the key output from the reproduction management device is received. There is provided a content distribution system for decrypting using.

  According to another aspect of the present invention, the content signal encrypted using a key updated at a predetermined update cycle, and information indicating the key and the reproducible time of the encrypted content signal are stored. A reproduction management device used in a receiver that receives the first control information obtained by encryption, receives the first control information from the receiver, decrypts the first control information, the key and the key Information indicating the reproducible time of the encrypted content signal is restored, and the key is output to the receiver based on the reproducible time of the encrypted content signal and the key update period. A reproduction management method is provided for outputting the restored key to the receiver when it is determined whether or not to output.

  According to another aspect of the present invention, the content signal encrypted using a key updated at a predetermined update cycle, and information indicating the key and the reproducible time of the encrypted content signal are stored. A reproduction management device used in a receiver that receives the first control information obtained by encryption, means for receiving the first control information from the receiver, decrypting the first control information, and the key and Based on the means for restoring information indicating the reproducible time of the encrypted content signal, the reproducible time of the encrypted content signal, and the key update period, the key is transmitted to the receiver. Means for determining whether or not to output, and a reproduction management program for causing the restored key to function as means for outputting to the receiver when it is determined to output are provided.

According to another aspect of the present invention, a broadcasting device, a receiver, and an I inserted into the receiver.
A content distribution system comprising a C card and a playback device that does not have a tuner for processing broadcast waves from the broadcast device, wherein the broadcast device updates the content signal at a predetermined update period (Tud). The first encryption unit (11) that generates an encrypted content signal by encrypting using the first key (Ks), the first key (Ks), and the reproducible time of the first key (Ks) (Tpre) is encrypted using the second key (Kw), and the second encryption unit (12) for generating the first control information (ECM) and the second key (Kw) are A third encryption unit (14) that encrypts using a third key (Km) unique to the IC card and generates second control information (EMM), and the encrypted content signal, the first The control signal (ECM) and the second control signal (EMM) are The receiver transmits the broadcast wave to the receiver, and the receiver receives a tuner (21) for processing the encrypted content signal and the first control signal (ECM), and the first key (Ks) from the IC card. A first decryption unit (22) that decrypts the encrypted content signal and restores the content signal when output, and the restored content signal is reproduced by the reproduction device; The IC card has higher security than the receiver, receives the second control information (EMM) via the receiver, and uses the third key (Km) of the IC card to perform the second control. A second decryption unit (32) for decrypting information (EMM) and restoring the second key (Kw); and receiving the first control information (ECM) via the receiver and restoring the restored Second key (K ) Is used to decrypt the first control information (ECM) to restore the first key (Ks) and the reproducible time (Tpre) of the first key (Ks); And a control unit (35) for outputting the first key (Ks) by the number of times corresponding to a value obtained by dividing the playable time (Tpre) by the update period (Tud). A system is provided.

  Since it is determined whether or not the key is output in the reproduction management apparatus, the preview can be realized with high security and low cost.

The block diagram which shows schematic structure of the content delivery system which concerns on one Embodiment. FIG. 3 is a block diagram illustrating an example of an internal configuration of the broadcasting device 1. The block diagram which shows an example of the internal structure of the receiver 2. FIG. FIG. 3 is a block diagram showing an example of an internal configuration of the IC card 3. The figure explaining the output of the key Ks by the control part 35 of IC card 3. FIG. The sequence diagram which shows an example of the processing operation of a content delivery system.

  Embodiments according to the present invention will be specifically described below with reference to the drawings.

  FIG. 1 is a block diagram illustrating a schematic configuration of a content distribution system according to an embodiment. The content distribution system includes a broadcasting device 1, a receiver 2, an IC card (playback management device) 3, and a playback device 4. In the figure, one set of the receiver 2, the IC card 3, and the playback device 4 are depicted, but there are usually a plurality of these sets. Moreover, there may be a plurality of broadcasting apparatuses 1. The receiver 2 and the IC card 3 constitute a content receiving system.

The broadcasting device 1 is provided in a broadcasting station, for example, and broadcasts an encrypted content signal (hereinafter simply referred to as an encrypted content signal) and control information ECM (Entitlement Control Message) and EMM (Entitlement Management Message) described later. Send by wave.
The receiver 2 is used by the user, receives the content signal and the control information ECM and EMM, and transfers the control information ECM and EMM to the IC card 3.
The IC card 3 is inserted into the receiver 2 and transmits a key Ks (scramble key) for decrypting the encrypted content signal to the receiver 2 only when a predetermined condition is satisfied. Upon receiving the key Ks, the receiver 2 can decrypt the encrypted content signal using the key Ks. The decrypted content signal is reproduced by the reproduction device 4.

  As an example, the receiver 2 is a dongle, and the playback device 4 is a smartphone that can be connected to the dongle. With such a configuration, even if the smartphone does not have a tuner and cannot process broadcast waves, the user can enjoy content using the smartphone. As another example, the receiver 2 may be a set-top box, and the playback device 4 may be a display that can be connected to the set-top box with an HDMI (registered trademark) cable or the like. Alternatively, the receiver 2 may be built in the playback device 4. Further, a reproduction management device corresponding to the IC card 3 may be incorporated in the receiver 2 as an IC chip.

  Note that the IC card 3 is a high security module, and it is desirable that the security is at least higher than that of the receiver 2 and high resistance to unauthorized access from the outside. In order to ensure such high security, the IC card 3 has a high tamper resistance, or a reproduction management device equivalent to the IC card 3 is mounted in a tamper resistance area provided in a part of the general-purpose processor. That's fine.

Hereinafter, each device will be described in detail. It should be noted that although a predetermined contract is required to reproduce the encrypted content signal, a preview when the contract is not made will be mainly described.
FIG. 2 is a block diagram illustrating an example of the internal configuration of the broadcasting device 1. The broadcast device 1 includes a scrambler 11 (encryption unit), an encryption unit 12, a storage unit 13, and an encryption unit 14.

  The scrambler 11 scrambles (encrypts) the content signal using the key Ks. The content signal is, for example, a video signal or an audio signal. The encrypted content signal that is not reproduced without the key Ks is generated by the encryption. The key Ks is a key possessed by the broadcasting device 1 and may not be different for each receiver 2 of the transmission destination, and may not be different for each content. The key Ks is updated at a predetermined update period Tud. The update period Tud may be arbitrarily set by the broadcasting apparatus 1 or may be a fixed value determined in advance.

  The encryption unit 12 encrypts information indicating the key Ks and the preview time Tpre using the key Kw (work key), and generates control information ECM. The preview time Tpre is a time that can be reproduced without a contract for reproducing the content signal, and is determined in advance according to the content signal. That is, the control information ECM can be said to be information accompanying each content signal.

  The storage unit 13 stores a key Km (master key) corresponding to each IC card 3. That is, each IC card 3 has a unique key Km, and the storage unit 13 stores which IC card 3 has which key Km. The storage unit 13 also stores contract information for each user of the IC card 3. The contract information is information indicating whether or not a contract for reproducing the encrypted content signal is made.

  The encryption unit 14 refers to the storage unit 13, encrypts the key Kw and the contract information using the key Km held by the IC card 3 to be transmitted, and generates control information EMM for the specific IC card 3 To do.

The above encrypted content signal and control information ECM, EMM are transmitted from the broadcast apparatus 1 to the receiver 2 by broadcast waves. Note that the encrypted content signal and the control information ECM are transmitted in pairs, but the control information EMM is transmitted at an arbitrary timing, for example, when the contract information is changed. Further, since the control information EMM is used by the receiver 2 in which the specific IC card 3 is inserted, the control information EMM may be transmitted by communication, thereby saving the transmission band of the broadcast wave.

  FIG. 3 is a block diagram illustrating an example of the internal configuration of the receiver 2. The receiver 2 includes a tuner 21, an interface (IF) 22 with the IC card 3, and a descrambler 23 (decoding unit).

  The tuner 21 receives the encrypted content signal and the control information ECM and EMM from the broadcast wave, and selects a channel according to a user setting if necessary. The encrypted content signal is supplied to the descrambler 23, and the control information ECM and EMM are supplied to the interface 22.

  The interface 22 transfers the control information ECM and ECM received from the broadcasting device 1 to the IC card 3. Further, when the key Ks is output from the IC card 3, the interface 22 receives the key Ks and passes it to the descrambler 23.

  The descrambler 23 descrambles (decrypts) the encrypted content signal using the key Ks. That is, the descrambler 23 can decrypt the encrypted content signal when the key Ks is output from the IC card 3, but cannot descramble the encrypted content when the key Ks is not output. The descrambled content signal is converted into a video signal and / or an audio signal and output to the playback device 4.

  Note that if the control information EMM is transmitted by broadcast waves, the receiver 2 does not need a communication function.

  FIG. 4 is a block diagram showing an example of the internal configuration of the IC card 3. The IC card 3 includes an interface (IF) 31 with the receiver 2, a decryption unit 32, a storage unit 33, a decryption unit 34, and a control unit 35. For example, the IC card 3 is inserted into the receiver 2 and operates by receiving power supply from the receiver 2.

  The interface 31 receives control information ECM and EMM from the receiver 2. Further, in a predetermined case, the interface 31 pays out the key Ks to the receiver 2.

  The decryption unit 32 decrypts the control information EMM using the unique key Km possessed by the IC card 3, and restores the key Kw and the contract information. The key Kw and the contract information are stored in the storage unit 33. Since the key Km is unique to the IC card 3, the decrypting unit 32 can decrypt the control information EMM addressed to itself, but cannot decrypt the control information EMM addressed to other IC cards 3.

  The storage unit 33 stores a key Ks update period Tud in addition to the key Kw and the contract information. When the update cycle Tud is a fixed value, the update cycle Tud is embedded and stored in the storage unit 33 in advance.

  The decrypting unit 34 decrypts the control information ECM using the key Kw, and restores the key Ks and the preview time Tpre.

The control unit 35 determines whether or not to output the key Ks to the receiver 2 based on the contract information, the preview time Tpre, and the key Ks update period Tud. When the contract information indicates that a contract for reproducing the encrypted content signal is made, the control unit 35 determines to output the key Ks. When the contract information indicates that the contract is not made, the control unit 35 performs a preview process based on the preview time Tpre and the update cycle Tud. Specifically, the control unit 35 determines to output the key Ks by the number of times obtained by dividing the preview time Tpre by the update period Tud. When it is determined to output, the control unit 35 outputs the key Ks to the receiver 2 via the interface 31. Hereinafter, the determination by the control unit 35 in the preview process will be described in detail.

  FIG. 5 is a diagram for explaining the output of the key Ks by the control unit 35 of the IC card 3. In the following description, delays due to decoding and data transmission / reception are ignored unless otherwise specified. In the figure, it is assumed that the preview time Tpre is 90 seconds and the update period Tud of the key Ks is 30 seconds. Under this assumption, the key Ks is updated 3 (= Tpre / Tud) times during the preview time Tpre. Hereinafter, the updated keys Ks are sequentially referred to as keys Ks1, Ks2, and Ks3.

  In FIG. 5, it is assumed that the receiver 2 receives the encrypted content signal and the control information ECM at time t1. At the time of reception, the number of times the key Ks has been output is zero.

  Therefore, at time t1, the control unit 35 outputs the key Ks1 at this time (first output). Thereby, the descrambler 23 of the receiver 2 can decrypt the encrypted content using the key Ks1 for 30 seconds from the time t1 to the time t2 when the update period Tud elapses. Since the key Ks has been updated after time t2, the descrambler 23 cannot decrypt the encrypted content with the key Ks1.

  At time t2, the control unit 35 receives control information ECM obtained by encrypting the updated new key Ks2. At this point, the number of times the key Ks has been output is still one. Therefore, the control unit 35 outputs the key Ks to the receiver 2 (second output). Thus, the descrambler 23 of the receiver 2 can decrypt the encrypted content using the key Ks2 for 30 seconds from the time t2 to the time t3 when the update period Tud elapses. Since the key Ks is updated after the time t3, the descrambler 23 cannot decrypt the encrypted content with the key Ks2.

  At time t3, the control unit 35 receives the control information ECM obtained by encrypting the updated new key Ks3. At this point, the number of times the key Ks has been output is still two. Therefore, the control unit 35 outputs the key Ks to the receiver 2 (third output). Thereby, the descrambler 23 of the receiver 2 can decrypt the encrypted content using the key Ks3 for 30 seconds from the time t3 to the time t4 when the update period Tud elapses. Since the key Ks has been updated after time t4, the descrambler 23 cannot decrypt the encrypted content with the key Ks3.

  At time t4, the control unit 35 receives control information obtained by encrypting the updated new key Ks. However, at this point, the control unit 35 has already output the key Ks three times. Therefore, thereafter, the control unit 35 does not transmit the key Ks to the receiver 2. Therefore, the descrambler 23 cannot decrypt the encrypted content after time t4.

  In this way, the encrypted content signal is decrypted and reproduced just for 90 seconds of the preview time Tpre.

  FIG. 6 is a sequence diagram illustrating an example of a processing operation of the content distribution system. It is assumed that the control information EMM has already been transmitted to the receiver 2 and the key Kw is stored in the storage unit 33 thereof. It is also assumed that no contract for reproducing the encrypted content signal has been made.

The broadcast device 1 transmits the encrypted content signal and the control information ECM to the receiver 2 using a broadcast wave (step S1). The control information ECM includes information indicating the encrypted key Ks and the preview time Tpre.
The receiver 2 receives the encrypted content and the control information ECM (step S11), and transfers the control information ECM to the IC card 3 (step S12).

  The IC card 3 receives the control information ECM (step S21). Then, the decryption unit 34 in the IC card 3 decrypts the control information ECM using the key Kw (step S22), and restores the key Ks and the preview time Tpre. Further, the control unit 35 calculates the number N of outputs based on the restored preview time Tpre and the update cycle Tud stored in the storage unit 33 (step S23). More specifically, the control unit 35 sets Tpre / Tud as the output count N. Then, the control unit 35 outputs the key Ks for the first time (step S24).

  After the above processing, the control unit 35 outputs the key Ks to the receiver 2 for each update cycle Tud by the number N of outputs (steps S21 to S25). That is, if the number of times the key Ks is actually output is less than N (NO in step S25), the updated key received after the update period Tud has elapsed since the reception of a certain key Ks (for example, the key Ks1 in FIG. 5). The decryption unit 34 decrypts the control information ECM (step S21) including Ks (for example, the key Ks2 in FIG. 5) (step S22). Then, the control unit 35 outputs the restored key Ks to the receiver 2 (step S24).

  When receiving the key Ks (step S13), the descrambler 23 of the receiver 2 descrambles the encrypted content signal (step S14). Until the key Ks is updated, in other words, until the update cycle Tud elapses, the descrambler 23 can descramble the encrypted content signal (NO in step S15).

  When the update period Tud has elapsed and the key Ks has been updated (YES in step S15), if the descrambler 23 receives the updated key Ks from the IC card 3 (YES in step S13), the encrypted content signal continues. Can be descrambled (step S14). When the key Ks is updated and the updated key Ks is not transmitted from the IC card 3 (NO in step S13), the descrambler 23 cannot descramble the encrypted content signal.

  Thus, in this embodiment, since the IC card 3 knows the update cycle Tud, it can be determined whether or not to output the key Ks within the high security IC card 3. Then, only when it is determined to be output, the key Ks is output from the IC card 3 to the external receiver 2. Therefore, security is improved. In addition, the receiver 2 does not require such a high level of security, and the receiver 2 does not need to manage the preview time, so that the manufacturing cost of the receiver 2 can be reduced.

  In the present embodiment, the update cycle Tud is a fixed value and is stored in the storage unit 33 in advance. However, it is only necessary for the IC card 3 to know the update cycle Tud, and various modifications other than fixing the update cycle Tud are conceivable.

  For example, the encryption unit 14 in FIG. 2 may generate control information EMM by encrypting not only the key Kw but also information indicating the update period Tud. In this case, the update period Tud may be restored by the decoding unit 32 of FIG. 4 decoding the control information EMM and stored in the storage unit 33.

  As another example, the encryption unit 12 in FIG. 2 may generate the control information ECM by encrypting not only the information indicating the key Ks and the preview time Tpre but also the information indicating the update period Tud. In this case, the update period Tud may be restored by the decoding unit 34 of FIG. 4 decoding the control information ECM and stored in the storage unit 33.

  As another example, the encryption unit 12 of FIG. 2 may generate the control information ECM by encrypting not only the information indicating the key Ks and the preview time Tpre but also the time information. The time information indicates, for example, the time when the new key Ks is output from the broadcasting device 1. In the example of FIG. 5, the encryption unit 12 generates control information ECM1 including the key Ks1 and time information t1. Thereafter, the encryption unit 12 generates control information ECM2 including the key Ks2 and time information t2. In this case, the decoding unit 32 of FIG. 4 uses the time difference (t2−t1) between the time information t1 restored from the control information ECM1 and the time information t2 restored from the control information ECM2 as the update period Tud. It may be acquired and stored in the storage unit 33.

  At least a part of each part of the content distribution system described in the above-described embodiment may be configured by hardware or software. When configured by software, a program that realizes at least some of the functions of each unit of the content distribution system may be stored in a recording medium such as a flexible disk or a CD-ROM, and read and executed by a computer. The recording medium is not limited to a removable medium such as a magnetic disk or an optical disk, but may be a fixed recording medium such as a hard disk device or a memory.

  Further, a program that realizes at least a part of the functions of each part of the content distribution system may be distributed via a communication line (including wireless communication) such as the Internet. Further, the program may be distributed in a state where the program is encrypted, modulated or compressed, and stored in a recording medium via a wired line such as the Internet or a wireless line.

  Based on the above description, those skilled in the art may be able to conceive additional effects and various modifications of the present invention, but the aspects of the present invention are not limited to the individual embodiments described above. Absent. Various additions, modifications, and partial deletions can be made without departing from the concept and spirit of the present invention derived from the contents defined in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Broadcast apparatus 11 Scrambler 12 Encryption part 13 Storage part 14 Encryption part 2 Receiver 21 Tuner 22 Interface 23 Descrambler 3 IC card (reproduction management apparatus)
31 Interface 32 Decoding Unit 33 Storage Unit 34 Decoding Unit 35 Control Unit

Claims (9)

A content signal encrypted using a key updated at a fixed update period, and first control information obtained by encrypting information indicating a reproducible time of the key and the encrypted content signal; A playback management device used in a receiver for receiving
A storage unit storing the update cycle in advance;
An interface for receiving the first control information from the receiver;
A first decryption unit that decrypts the first control information and restores the key and the playable time of the encrypted content signal;
When it is determined whether to output the key to the receiver based on the reproducible time of the encrypted content signal and the update period stored in the storage unit. And a control unit that outputs the restored key to the receiver.   The playback management apparatus according to claim 1, wherein the control unit outputs the key as many times as a number corresponding to a value obtained by dividing the playable time by the update period.   The reproduction management apparatus according to claim 1, wherein the reproduction management apparatus has higher security than the receiver.   The reproduction management device according to claim 1, wherein the reproducible time is a time during which the encrypted content signal can be reproduced without a contract for reproducing the encrypted content signal.   The reproduction management device according to any one of claims 1 to 4, wherein the reproduction management device is an IC chip or an IC card inserted into the receiver. A receiver for receiving the encrypted content signal and the first control information;
A reproduction management device according to any one of claims 1 to 5,
The receiver transfers the first control information to the reproduction management apparatus, and when receiving the key output from the reproduction management apparatus, the receiver decrypts the encrypted content signal using the key. A content receiving system. A content signal encrypted using a key updated at a fixed update period, and first control information obtained by encrypting information indicating a reproducible time of the key and the encrypted content signal; The playback management device used for the receiver that receives
Receiving the first control information from the receiver;
Decrypting the first control information, restoring the key and information indicating the playable time of the encrypted content signal;
Determining whether to output the key to the receiver based on the playable time of the encrypted content signal and the update period stored in advance in the storage unit of the playback management device;
A reproduction management method of outputting the restored key to the receiver when it is determined to output. A content signal encrypted using a key updated at a fixed update period, and first control information obtained by encrypting information indicating a reproducible time of the key and the encrypted content signal; A playback management device used for a receiver that receives
Means for receiving the first control information from the receiver;
Means for decrypting the first control information and restoring information indicating the key and the reproducible time of the encrypted content signal;
Means for determining whether or not to output the key to the receiver based on the reproducible time of the encrypted content signal and the update period stored in advance in the storage unit of the reproduction management device ,and,
A reproduction management program for causing a function of the restored key to be output to the receiver when it is determined to be output. A content distribution system comprising: a broadcast device; a receiver; an IC card inserted into the receiver; and a playback device that does not have a tuner that processes broadcast waves from the broadcast device,
The broadcasting device is:
A first encryption unit that encrypts the content signal using a first key that is updated at a fixed update period and generates an encrypted content signal;
A second encryption unit that encrypts the first key and information indicating a reproducible time of the first key using a second key, and generates first control information;
A third encryption unit that encrypts the second key using a third key unique to the IC card and generates second control information;
The encrypted content signal, the first control information and the second control information are transmitted to the receiver by broadcast waves,
The receiver
A tuner for processing the encrypted content signal and the first control information;
A first decryption unit that decrypts the encrypted content signal and restores the content signal when the first key is output from the IC card;
The restored content signal is played back by the playback device,
The IC card has higher security than the receiver,
A storage unit storing the update cycle in advance;
A second decryption unit that receives the second control information via the receiver, decrypts the second control information using the third key of the IC card, and restores the second key;
Receiving the first control information via the receiver, decrypting the first control information using the restored second key, and restoring the playable time of the first key and the first key A third decoding unit,
A content distribution system comprising: a control unit that outputs the first key as many times as the number obtained by dividing the playable time by the update period stored in advance in the storage unit.

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