JP3965197B2 - Playback device for playing content - Google Patents

Description

  The present invention relates to a broadcast receiving system (hereinafter referred to as a “restricted reception system”) in which only a playback device of a user who is permitted to view content in digital broadcasting can appropriately play back the content. In particular, the present invention relates to a technique for updating a master key necessary for content reproduction.

  In MPEG2 SYSTEMS (ISO / IEC13818-1), which is a standard conditional access system, the transmission side scrambles content such as video and audio with a scramble key Ks and transmits the content. Further, the receiving side reproduces the content by unscrambling with the scramble key Ks. At this time, the transmission side and the reception side must have the same scramble key Ks.

  For this reason, the transmission side stores the scramble key Ks in information called ECM (Entitlement Control Messages) and encrypts the ECM with the work key Kw before transmission. Further, the transmission side stores the work key Kw in information called EMM (Entitlement Management Messages), and transmits the EMM after encrypting it with a unique master key Km for each playback device.

The receiving side decrypts the EMM with its own master key Km to obtain the work key Kw, and decrypts the ECM with the work key Kw to obtain the scramble key Ks. Thereby, the transmission side and the reception side can hold the same scramble key Ks.
FIG. 1 is a diagram showing an outline of a conditional access system.
The broadcasting device 101 multiplexes various information such as scrambled content, ECM, EMM, and transmits the multiplexed information to the reproducing device 102 by broadcasting. The playback apparatus 102 decodes various types of information and displays them on the video receiver 103. Here, the playback device 102 uses the ID and master key Km held inside to scramble. The ID is assigned as necessary, such as for each playback device or for each manufacturer. Also, the master key Km is assigned as necessary for each playback device or manufacturer, and corresponds to the ID on a one-to-one basis.

FIG. 2 is a diagram illustrating a configuration of a playback device in the conditional access system.
The playback apparatus 201 receives various types of information such as content scrambled by the reception unit 202, ECM, and EMM, and the type determination unit 203 determines the type of various types of information. The type determination unit 203 transfers the scrambled information to the content decryption unit 211, the ECM to the ECM decryption unit 208, and the EMM to the EMM decryption unit 205.

  The ID / Km holding unit 204 holds an ID unique to the playback apparatus 201 and a master key Km. Further, the EMM decryption unit 205 decrypts the EMM using the master key Km, and inputs the work key Kw, which is a part of the decrypted EMM, to the Kw update unit 206. The Kw update unit 206 acquires the work key Kw from the EMM decryption unit 205 and updates the conventional work key. The Kw holding unit 207 holds the work key Kw updated by the Kw update unit 206.

There is also an example in which a new work key is acquired using bidirectional communication in order to update the work key Kw (see, for example, Patent Document 1).
The ECM decryption unit 208 decrypts the ECM using the work key Kw, and inputs the scramble key Ks that is a part of the decrypted ECM to the Ks update unit 209. The Ks update unit 209 acquires the scramble key Ks from the ECM decryption unit 208 and updates the conventional scramble key.

Note that the update of the work key and the update of the scramble key are usually rewriting by overwriting, but may be added.
The Ks holding unit 210 holds the scramble key Ks updated by the Ks update unit 209. The content decryption unit 211 decrypts the scrambled content using the scramble key Ks, and inputs the decrypted content to the content output unit 212. The content output unit 212 transmits the content to the video receiver.

FIG. 3 is a diagram illustrating the operation of the playback device in the conditional access system.
The playback device receives the EMM from the broadcast device (S301). The EMM includes the ID of the playback apparatus that should receive the EMM and the encrypted work key E (Kw, Km) obtained by encrypting the work key Kw with the master key Km corresponding to the ID. (Here, E (X, Y) means the information X encrypted with the key Y. The same shall apply hereinafter.)
If the ID included in the EMM matches the ID held by the playback device, the playback device decrypts E (Kw, Km) using the held Km. As a result, the playback apparatus can acquire the work key Kw (S302).

Further, the playback device receives the ECM from the broadcast device (S303). The ECM includes an encrypted scramble key E (Ks, Kw) obtained by encrypting the scramble key Ks with the work key Kw.
The playback device decrypts E (Ks, Kw) using the held work key Kw. As a result, the playback device can acquire the scramble key Ks (S304).

Further, the playback device receives the scrambled content E (Content, Ks) from the broadcasting device (S305).
The playback device decrypts E (Content, Ks) using the held scramble key Ks. As a result, the playback apparatus can acquire content (S306). Thereby, the user can view the content.

FIG. 4 is a diagram showing an outline of a conditional access system in a plurality of playback devices.
The playback device 1 and the playback device 2 receive various information transmitted from the broadcast device 101. Note that the video receiver is omitted. ID1 and ID2 are assigned to each playback device and are different from each other. Since the ID and the master key Km have a one-to-one correspondence, Km1 and Km2 are also different from each other. Here, the ID is assigned to each playback device, but may be assigned to each specific group such as each manufacturer, each playback device model, each production lot, and the like. In this case, a plurality of playback devices in the group hold the same ID and master key Km, but the ID and master key Km held by playback devices in different groups are different.

FIG. 5 is a diagram illustrating operations of a plurality of playback devices in the conditional access system.
The playback device 1 selectively receives EMM1 from the broadcasting device (S501). The EMM1 includes ID1 and an encrypted work key E (Kw, Km1) obtained by encrypting the work key Kw with a master key Km1 corresponding to ID1. Therefore, the playback device 1 can recognize that this EMM is an EMM addressed to itself by the ID 1 of the EMM 1.

The playback device 1 decodes E (Kw, Km1) using the stored Km1. Thereby, the reproducing | regenerating apparatus 1 can acquire the work key Kw (S502).
The playback device 2 selectively receives EMM2 from the broadcasting device (S503). The EMM2 includes ID2 and an encrypted work key E (Kw, Km2) obtained by encrypting the work key Kw with a master key Km2 corresponding to ID2. Therefore, the playback device 2 can recognize that this EMM is an EMM addressed to itself by the ID2 of the EMM2.

The playback device 2 decodes E (Kw, Km2) using the stored Km2. Thereby, the reproducing | regenerating apparatus 2 can acquire the work key Kw (S504).
Thus, each of the playback device 1 and the playback device 2 acquires the work key Kw. Subsequent procedures are the same as those in FIG.
Next, a method for preventing reproduction of content by an unauthorized reproduction device when an unauthorized reproduction device exists will be described.

FIG. 6 is a diagram showing an outline of a conditional access system when there is an unauthorized playback device.
The unauthorized playback device is a playback device that impersonates the playback device 2 by illegally acquiring ID2 and the master key Km2. In such a state, by the same procedure as the operation shown in FIG. 5, the unauthorized playback device can behave as if it were the playback device 2 and can play back the content.

Therefore, when the presence of an unauthorized playback device is detected, a method in which the broadcast device does not transmit an EMM including ID2 is conceivable in order to prevent unauthorized playback of content.
FIG. 7 is a diagram illustrating the operation of each playback device when unauthorized playback of content by the unauthorized playback device is prevented.
The difference from FIG. 5 is that the broadcast device transmits only EMM1 for the playback device 1 (S501) and does not transmit EMM2 for the playback device 2. Thereby, the unauthorized reproduction device cannot acquire the work key Kw. Therefore, the unauthorized reproduction device cannot acquire the scramble key Ks (S701) and cannot receive the content (S702).
JP 2002-16901 A

However, according to the method in which the broadcast device does not transmit the EMM including ID2, there arises a problem that even the proper reproduction device 2 cannot reproduce the content.
Accordingly, an object of the present invention is to provide a technology that can prevent content reproduction by an unauthorized reproduction device and that only a valid reproduction device can properly reproduce the content.

In order to achieve the above object, a playback apparatus according to the present invention is a playback apparatus that is used in a digital broadcast conditional access system and that decrypts various encrypted information transmitted by broadcasting and displays the information on a video receiver. Each reproducing device, each production lot, each model or each manufacturer, a holding unit that holds a unique secret key and ID, and obtains encrypted encryption key information, and uses the secret key to Key information decrypting means for decrypting the encryption key information to obtain key information, and whether the key information is key update information used for updating based on leakage of the secret key or a decryption key for decrypting the content key Determining means based on an identifier added to the key information, and when the determining means determines that the key information is key update information, a unique hack for each manufacturer incorporated in the playback device. A generating means for generating a new secret key based on the key function and the key update information, and when the determination means determines that the key information is the decryption key, obtains an encrypted content key, and Content reproducing means for decrypting the encrypted content key using a decryption key to obtain a content key, obtaining scrambled content, and descrambling using the content key to reproduce the content; The holding means holds a latest secret key and a secret key in an initial state, the key update information includes a generation number of a new secret key, and the generation means stores at least the generation number and the ID in the hash Input to the function to generate the new secret key.

The best mode for carrying out the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
[Outline of conditional access system]
FIG. 8 is a diagram showing an outline of the conditional access system in the present embodiment.
The conditional access system in this embodiment includes a key management device 801, a manufacturing device 802, a playback device 803, and a broadcasting device 804.

First, a procedure in which the key management device 801 and the playback device 803 have the same ID and master key Km is shown.
The key management device 801 allocates a unique ID and a master key Km as necessary, such as for each playback device, each production lot, each model, each manufacturer, and provides them to the manufacturing device 802.

The manufacturing apparatus 802 that manufactures the playback apparatus 803 provides the user with the playback apparatus 803 after incorporating the ID assigned by the key management apparatus 801 and the master key Km into the playback apparatus 803.
In this way, the key management device 801 and the playback device 803 can have the same ID and master key Km.

Next, a procedure when the user views desired content will be described. As a specific example, it is assumed that the user playback device 803 stores an ID “00000001” and a master key Km “2783529”.
The user applies to the broadcast device 804 that broadcasts the desired content for viewing the content. At this time, the broadcast apparatus 804 is notified of the ID “00000001” stored in its playback apparatus 803.

In response to the application from the user, the broadcasting device 804 stores the ID “00000001” of the playback device 803 and the work key Kw in the EMM and transmits them to the key management device 801.
Here, the work key Kw is a key that can be obtained only by the playback device of the user who is permitted to view.
The key management device 801 receives the EMM from the broadcasting device 804 and extracts the ID “00000001” stored in the EMM. Then, the master key Km “27832529” corresponding to the ID is specified, and the EMM is encrypted with the master key Km “27832529” and transmitted to the broadcasting device 804.

The broadcast device 804 broadcasts the encrypted EMM.
The playback device 803 receives the EMM and determines whether or not the EMM is broadcast to itself based on the ID stored in the EMM. In this case, since the ID stored in the EMM is “00000001”, it is determined that it is addressed to itself. Then, the playback device 803 decrypts the EMM with the master key Km “2783529” and acquires the work key Kw.

In this way, the broadcast device 804 and the playback device 803 can have the same work key Kw.
The broadcasting device 804 broadcasts not only EMM but also ECM including the scramble key Ks, contents scrambled by the scramble key Ks, and the like. The user playback device 803 can acquire the scramble key Ks by decrypting the ECM with the work key Kw, and can acquire the content by decrypting the content scrambled with the scramble key Ks.

Next, updating of the master key Km, which is a feature of the present embodiment, will be described.
In principle, the master key Km need not be updated. However, for example, when the ID “00000001” and the master key Km “27832529” of the playback device 803 are leaked to other users, the other users copy the ID and the master key Km to their playback devices and register them. By doing so, it is possible to illegally view the content that the user of the playback device 803 is permitted to view. In such a case, it is necessary to update the master key Km.

In such a case, the broadcast device 804 broadcasts the ID of the playback device to be updated and the seed information that is the source of the new master key in the EMM. Then, the playback device to be updated generates a new master key based on the seed information.
Here, an algorithm for generating a new master key from the seed information is determined when the playback device is manufactured, and is incorporated in the playback device in a state where security is ensured. The same algorithm is also incorporated in the key management device in a state where security is ensured. In other words, since only the key management device and the right user's playback device have the same algorithm, only the key management device and the right user's playback device have the same new master key. Can do.

Therefore, the conditional access system according to the present embodiment can eliminate unauthorized viewing of content by other users after updating the master key.
A reproducing apparatus and a key management apparatus that realize such a conditional access system will be described in detail below.
[Configuration of playback device]
FIG. 9 is a diagram illustrating a configuration of a playback device in the conditional access system.

The playback device 901 includes a receiving unit 902, a type determining unit 903, an ID / Km holding unit 904, an EMM decoding unit 905, an update information determining unit 906, a Kw updating unit 907, a Kw holding unit 908, an ECM decoding unit 909, and a Ks updating unit. 910, a Ks holding unit 911, a content decrypting unit 912, a content output unit 913, and a Km updating unit 914.
The receiving unit 902 receives various information such as scrambled content, ECM, and EMM from the broadcasting device.

The type determination unit 903 determines the type of various information and transfers it to each decoding unit. As a result, the scrambled content is transferred to the content decryption unit 912, the ECM is transferred to the ECM decryption unit 909, and the EMM is transferred to the EMM decryption unit 905.
The ID / Km holding unit 904 holds an ID unique to the playback device 901 and a master key Km, and inputs the master key Km to the EMM decryption unit 905 as necessary. Note that the master key Km is set as an initial value by the manufacturer and is updated by the Km updating unit 914 as necessary.

The EMM decryption unit 905 decrypts the EMM using the master key Km and inputs it to the update information determination unit 906.
The update information determination unit 906 determines whether the EMM includes seed information for updating the master key Km or a new work key Kw for updating the work key Kw based on the identifier included in the EMM. The identifier will be described later.

If the work key Kw is stored, the update information determination unit 906 inputs the work key Kw to the Kw update unit 907. If seed information is stored, the seed information is input to the Km update unit 914.
The Kw update unit 907 acquires the work key Kw from the update information determination unit 906 and updates the work key. The update of the work key is usually rewriting by overwriting, but may be added.

The Kw holding unit 908 holds the work key Kw updated by the Kw update unit 907, and inputs the work key Kw to the ECM decryption unit 909 as necessary.
The ECM decryption unit 909 decrypts the ECM using the work key Kw, and inputs the scramble key Ks stored in the ECM to the Ks update unit 910.
The Ks update unit 910 acquires the scramble key Ks from the ECM decryption unit 909 and updates the scramble key. The update of the scramble key is usually rewriting by overwriting, but may be added.

The Ks holding unit 911 holds the scramble key Ks updated by the Ks update unit 910, and inputs the scramble key Ks to the content decryption unit 912 as necessary.
The content decryption unit 912 decrypts the scrambled content using the scramble key Ks, and inputs the decrypted content to the content output unit 913.
The content output unit 913 transmits the content to the video receiver.

  The Km update unit 914 acquires seed information from the update information determination unit 906 and updates the master key Km using the seed information. The update of the master key is usually rewriting by overwriting, but may be added. As a result, the ID / Km holding unit 904 holds the master key before the update in addition to the latest master key, so when the latest master key cannot be used due to some trouble, any of the pre-update master keys A master key can be used. Further, the ID / Km holding unit 904 may hold only the master key in the initial state in addition to the latest master key.

Further, the ID may be updated together with the master key update, or a combination of the ID and the master key may be updated for generation using a part of the ID as a generation number. At this time, the update of the ID may be rewritten by overwriting or may be added.
FIG. 10 is a diagram showing a detailed configuration of the Km update unit in the first embodiment.

The Km update unit 914 includes a seed information acquisition unit 1001, a Km generation unit 1002, and a Km storage unit 1003.
The seed information acquisition unit 1001 acquires seed information from the update information determination unit, and inputs the seed information as an argument of the master key generation algorithm of the Km generation unit 1002.
The Km generation unit 1002 generates a new master key Km ′ using an incorporated algorithm. Note that this algorithm differs for each playback device, each production lot, each model, or each manufacturer, and the same algorithm is held in the key management device.

The Km storage unit 1003 stores the master key Km in a form that the ID / Km storage unit 904 can store.
In this way, the playback device 901 can update the master key Km using the EMM broadcast from the broadcast device.
The Km update unit can be divided into the following two methods depending on the timing of generation of a new master key, either of which may be adopted.

The first method is a method for generating a new master key as soon as seed information is acquired.
The second method is a method in which seed information is held as it is after obtaining seed information, and a new master key generation process is performed as necessary. In this case, for example, when an EMM is input to the EMM decryption unit, a new master key generation process may be started after receiving a signal from the EMM decryption unit.

Next, the data structure of EMM will be described.
FIG. 11 is a diagram illustrating a data structure of a normal EMM.
The EMM consists of an ID part and a data part. The ID section stores the ID of the playback apparatus that should receive this EMM. Thereby, the reproducing | regenerating apparatus can selectively decode only the EMM in which self ID was stored among the EMMs broadcast from a broadcasting apparatus.

The data part stores an identifier and key information. The identifier is information for identifying whether the key information included in the data part is a work key or seed information. For example, when “0x01”, the work key Kw is included, and “0x02” ", It is assumed that seed information is included.
In addition, an information length, a protocol number, an expiration date, and the like are also stored in the data portion, but the description thereof will be omitted.

FIG. 12 is a diagram showing a data structure of the EMM for updating the master key Km.
This EMM is composed of an ID part and a data part in the same way as a normal EMM.
The data part stores an identifier and seed information.
The seed information is information that is a source of a new master key, and for example, a generation number representing a generation of the master key Km, a random number, or a combination thereof can be considered.

FIG. 13 is a diagram illustrating an example of an algorithm in the Km generation unit.
(A) shows a method of acquiring the master key Km from the playback device ID and the generation number using the original hash function.
(B) shows a method of acquiring the master key Km by encrypting the random number generated by the key management device using the original encryption function.

The method for generating a new master key is not limited to the above-described method as long as the new master key can be safely held by the playback device and the key management device. For example, the ID, generation number, and seed information may be generated by inputting the original hash function for each manufacturer.
[Operation of playback device]
FIG. 14 is a diagram illustrating the operation of the playback device in the conditional access system.

The playback device receives various information such as scrambled content, ECM, and EMM from the broadcasting device. Here, only the case where the EMM is received will be described.
If the playback device receives the EMM, it is determined whether the EMM includes a work key or seed information based on the identifier (S1401).
If seed information is included in the EMM (S1402, Y), the playback device acquires seed information included in the EMM (S1403).

The playback device generates a new master key based on the seed information (S1404).
The playback device holds the master key generated in step S1404, and uses the master key from the next time (S1405).
In step S1402, if the work key is included in the EMM (S1402, N), the playback device acquires the work key (S1406).

The playback apparatus holds the work key decrypted in step S1406, and uses the work key from the reception of the next ECM (S1407).
The configuration and operation of the playback apparatus that can generate a new master key based on the seed information stored in the EMM have been described above. Next, a key management apparatus that can hold the same new master key as the playback apparatus will be described.
[Configuration of key management device]
FIG. 15 is a diagram illustrating a configuration of a key management apparatus in the conditional access system.

The key management device 1501 includes an EMM receiving unit 1502, a key update determining unit 1503, a seed information generating / inserting unit 1504, a Km updating unit 1505, an ID / Km holding unit 1506, an EMM encryption unit 1507, and an encrypted EMM transmission unit 1508.
The EMM receiving unit 1502 receives the EMM transmitted from the broadcasting device and inputs it to the key update determining unit 1503.

  The key update determination unit 1503 determines whether information indicating that the master key Km should be updated is stored in the EMM. Specifically, when the identifier is “0x02”, if it is determined that “indicating that the master key should be updated”, it is sufficient to confirm whether or not the identifier is “0x02”. If the identifier is “0x02”, this is notified to the seed information generation / insertion unit 1504. The EMM is input to the EMM encryption unit 1507.

In response to the notification from the key update determination unit 1503, the seed information generation / insertion unit 1504 generates seed information and inserts it into the EMM, and inputs the seed information to the Km update unit 1505. The seed information is information that is a source of a new master key. For example, a generation number or a random number that represents the generation of the master key Km can be considered.
The Km update unit 1505 acquires seed information from the seed information generation / insertion unit 1504, and updates the master key Km using the seed information. Here, the algorithm for generating a new master key from the seed information is also held in the playback device.

The ID / Km holding unit 1506 holds a unique ID and master key Km for each playback device, each production lot, each model, each manufacturer, and the like, and the EMM encryption unit 1507 stores the master key Km as necessary. Enter. Note that the master key Km is an initial value written at the time of manufacture, and is then updated by the Km update unit 1505 as necessary.
The EMM encryption unit 1507 encrypts the EMM using the master key Km and inputs the encrypted EMM to the encrypted EMM transmission unit 1508.

The encrypted EMM transmission unit 1508 transmits the encrypted EMM to the broadcasting device.
The EMM that sends the seed information is encrypted with the old master key before update. It is from the next transmitted EMM that is encrypted with the updated new master key.
As described above, the key management device generates seed information, inserts it into the EMM, transmits the seed information to the playback device through the broadcasting device, and updates the master key Km based on the seed information. On the other hand, the playback device updates the master key Km based on the transmitted seed information. Here, since the same algorithm for generating the master key from the seed information is held in the key management device and the playback device, the same new master key is also held in the key management device and the playback device. .

FIG. 16 shows an example of management of IDs and master keys Km in the key management device.
The key management apparatus collectively manages IDs and master keys Km in the ID / Km holding unit using a management table as shown in FIG. In the management table, each generation of ID is vertically arranged and the master key Km is horizontally arranged.
When the key management apparatus allocates an ID and a master key to the manufacturing apparatus, the ID and the master key Km are added to this management table. At this time, the master key is added to the first generation column. Each time the master key is updated, new master keys are added in order, such as the second generation and the third generation.

Thus, all the past master keys are retained for the following reason.
For example, assuming that the same ID is assigned to the same model, not all playback devices have successfully updated the master key with one transmission of update information. This is because the update information encrypted using the past master key must be transmitted for the failed playback device.
[Operation of key management device]
FIG. 17 is a diagram illustrating the operation of the key management apparatus in the conditional access system.

When receiving the EMM from the broadcasting device, the key management device determines whether or not the secret key should be updated with the identifier of the EMM (S1701).
If the master key is to be updated (S1702, Y), the key management device generates seed information (S1703) and inserts the seed information into the EMM (S1704).
The key management apparatus acquires the master key held in the ID / Km holding unit (S1705), and encrypts the EMM using the master key (S1706).

Thereafter, the key management device transmits the encrypted EMM to the broadcasting device (S1707).
After transmitting the encrypted EMM to the broadcasting device in step S1707, the key management device generates a master key based on the seed information generated in step S1703 (S1708).
The key management apparatus holds the master key generated in step S1708, and uses the master key from the next time (S1709).

In step S1702, if the master key is not to be updated (S1702, N), the key management device acquires the master key held in the ID / Km holding unit (S1710), and uses the master key for EMM. Is encrypted (S1711).
Thereafter, the key management device transmits the encrypted EMM to the broadcasting device (S1712).
[Operation of conditional access system]
Next, the operation of a conditional access system including the above-described playback device and key management device will be described. Since this embodiment is characterized by an operation for eliminating the viewing of content by an unauthorized playback device when the presence of an unauthorized playback device impersonating a regular playback device is detected, this situation will be described in particular.

FIG. 18 is a diagram illustrating the operation of each playback device when the unauthorized viewing of content by the unauthorized playback device is excluded.
The playback device 1 is owned by the user 1 who is authorized to view the content and has ID1 and a master key Km1. Similarly, it is assumed that the playback apparatus 2 is owned by the user 2 who is authorized to view the content and has ID2 and a master key Km2. Further, the unauthorized reproducing device is impersonating the reproducing device 2 and has ID2 and master key Km2.

In such a situation, a procedure will be described in which the broadcasting device knows the presence of the unauthorized playback device and excludes viewing of content by the unauthorized playback device.
The broadcast device transmits EMM1 to the playback device 1 (S1801).
The EMM includes an ID of a playback apparatus that should receive the EMM and an encrypted work key E (Kw, Km) obtained by encrypting the work key Kw with the master key Km. That is, EMM1 includes ID1 and encrypted work key E (Kw, Km1).

The playback apparatus 1 determines that the EMM is addressed to itself based on ID1 included in the EMM1, and decrypts E (Kw, Km1) using the stored Km1. As a result, the reproducing device 1 can acquire the work key Kw (S1802).
Also, the broadcasting device transmits EMM2 to the playback device 2 (S1803).
EMM2 includes ID2 and encrypted seed information E (Seed, Km2). Here, the encrypted seed information E (Seed, Km2) is obtained by encrypting the seed information Seed using the master key Km2.

The playback apparatus 2 determines that the EMM is addressed to itself based on ID2 included in the EMM2, and decrypts E (Seed, Km2) using the Km2 held. As a result, the reproducing device 2 can acquire the seed information Seed (S1804).
The unauthorized playback device also determines that it is an EMM addressed to itself based on ID2 included in EMM2, and decrypts E (Seed, Km2) using Km2 held. As a result, the unauthorized reproduction device can acquire seed information Seed (S1805).

  The playback device 2 generates a new master key Km2 'based on the seed information Seed (S1806). The algorithm for generating the master key Km2 'from the seed information Seed is individual, such as for each playback device, for each production lot, for each model, or for each manufacturer. Since this algorithm is also held in the key management device, the key management device can generate the master key Km2 'from the seed information Seed. Therefore, the same new master key Km2 'can be held between the playback device 2 and the key management device.

On the other hand, since the unauthorized reproducing apparatus does not have an algorithm for generating the master key Km2 ′ from the seed information Seed, it cannot generate the master key Km2 ′ (S1807).
The broadcast device transmits EMM2 ′ to the playback device 2 (S1808).
Here, EMM2 'includes ID2 and encrypted work key E (Kw, Km2').

The playback apparatus 2 determines that the EMM is addressed to itself based on ID2 included in the EMM2, and decrypts E (Kw, Km2 ′) using the Km2 ′ held therein. As a result, the reproducing device 2 can acquire the work key Kw (S1809).
On the other hand, the unauthorized reproduction device also determines that the EMM is addressed to itself by ID2 included in the EMM2, but cannot obtain the work key Kw because it does not hold the master key Km2 ′ (S1810).

The broadcast device transmits an ECM to the playback device 1 and the playback device 2 (S1811).
The ECM includes an encrypted scramble key E (Ks, Kw) obtained by encrypting the scramble key Ks with the work key Kw.
The playback device 1 receives the ECM and decrypts E (Ks, Kw) using the work key Kw acquired in step S1802. As a result, the reproducing device 1 can acquire the scramble key Ks (S1812).

The playback device 2 receives the ECM and decrypts E (Ks, Kw) using the work key Kw acquired in step S1809. As a result, the reproducing device 2 can acquire the scramble key Ks (S1813).
On the other hand, since the unauthorized reproducing apparatus cannot acquire the work key Kw in step S1810, it cannot acquire the scramble key Ks (S1814).

The broadcast device transmits the scrambled content to the playback device 1 and the playback device 2 (S1815).
The scrambled content E (Content, Ks) is the content scrambled with the scramble key Ks.
The playback device 1 decrypts E (Content, Ks) using the scramble key Ks acquired in step S1812. As a result, the playback device 1 can acquire content (S1816).

The playback device 2 decrypts E (Content, Ks) using the scramble key Ks acquired in step S1813. As a result, the playback device 2 can acquire content (S1817).
On the other hand, since the unauthorized playback device cannot acquire the scramble key Ks in step S1814, it cannot acquire the content (S1818).

In this way, when the presence of an unauthorized playback device impersonating a legitimate playback device is detected, the broadcasting device updates the same master key held by the key management device and the playback device, so that the unauthorized playback device It is possible to eliminate the viewing of content by.
Further, in this embodiment, since the master key is updated using the EMM transmitted by broadcasting, it takes less days than the method of updating the master key using portable media such as an IC card. Therefore, the legitimate user does not suffer the disadvantage that the user cannot view the content he / she wants to view until the portable media arrives.

Furthermore, even if the ID and the master key Km are not assigned to each playback device, but are assigned to each production lot, model, manufacturer, etc., the key management device is applicable. There is no need to bear the burden of sending portable media to all playback devices.
(Embodiment 2)
[Outline of conditional access system]
FIG. 19 is a diagram showing an outline of the conditional access system in the present embodiment.

The conditional access system in this embodiment includes a key management device 1901, a manufacturing device 1902, a playback device 1903, and a broadcasting device 1904.
The procedure in which the key management device 1901 and the playback device 1903 have the same ID and master key Km and the procedure in which the playback device 1903 acquires the work key Kw are the same as in the first embodiment.

The difference between the present embodiment and the first embodiment is a method of updating the master key Km.
In the present embodiment, the master key Km is updated as follows.
The broadcast apparatus 1904 stores trigger information indicating that the ID of the reproduction apparatus to be updated and the master key Km should be updated in the EMM and broadcasts. Then, the playback device to be updated recognizes that the master key Km should be updated using the update information, and transmits device information such as its own ID to the key management device 1901. The key management device 1901 transmits seed information that is the source of the new master key to the playback device. The playback device updates the master key Km using the seed information.

  Here, since the algorithm for generating a new master key Km ′ from the seed information is the same only for the key management device and the legitimate user, only the key management device and the legitimate user reproduction device are the same. Can hold a new master key Km ′. Therefore, the conditional access system according to the present embodiment can eliminate unauthorized viewing by other users after updating the master key.

In the first embodiment, seed information is stored in the EMM and transmitted. On the other hand, this embodiment is different in that trigger information for starting a simple master key update is stored in the EMM and transmitted, and the seed information is transmitted by means other than the EMM.
A reproducing apparatus that implements such a conditional access system will be described in detail below.
[Configuration of playback device]
The playback apparatus in the present embodiment is different from the playback apparatus of the first embodiment only in the Km update unit. Therefore, only the Km update unit will be described, and description of other configurations will be omitted.

FIG. 20 is a diagram illustrating a detailed configuration of the Km update unit according to the second embodiment.
The Km updating unit includes a device information holding unit 2001, a device information transmitting unit 2002, a seed information receiving unit 2003, a Km generating unit 2004, and a Km storing unit 2005.
The device information holding unit 2001 holds individual device information in a playback device such as an ID, for example, and inputs the device information to the device information transmitting unit 2002 in response to a notification from the update information determining unit.

The device information transmission unit 2002 transmits the device information held by the device information holding unit 2001 to the key management device as a seed information acquisition request signal. When receiving the device information, the key management device returns seed information.
The seed information receiving unit 2003 receives the seed information and inputs the seed information as an argument of the master key generation algorithm of the Km generation unit 2004. Here, the device information and the seed information are transmitted using a telephone line.

The Km generation unit 2004 generates a new master key Km ′ using an incorporated algorithm. This algorithm differs for each playback device, each production lot, each model, or each manufacturer, and is also held in the key management device.
The Km storage unit 2005 stores the master key Km.
In the present embodiment, the following two methods are used depending on the timing of generation of a new master key, either of which may be adopted.

The first method is a method for generating a new master key as soon as seed information is acquired.
The second method is a method in which seed information is held as it is after obtaining seed information, and a new master key generation process is performed as necessary. In this case, for example, when an EMM is input to the EMM decryption unit, a new master key generation process may be started after receiving a signal from the EMM decryption unit.

FIG. 21 is a diagram showing a data structure of the EMM for updating the master key Km.
In the present embodiment, an identifier is stored in the data part, and this identifier itself becomes trigger information.
[Configuration of key management device]
FIG. 22 is a diagram illustrating a configuration of a key management apparatus in the conditional access system.

The key management device 2201 includes an EMM reception unit 2202, a key update determination unit 2203, a seed information generation unit 2204, a Km update unit 2205, an ID / Km holding unit 2206, an EMM encryption unit 2207, an encrypted EMM transmission unit 2208, and device information reception. Part 2209 and seed information transmission part 2210.
The key management device in this embodiment is different from the key management device in the first embodiment in a seed information generation unit 2204, a device information reception unit 2209, and a seed information transmission unit 2210. Therefore, only different configurations will be described, and descriptions of the same configurations will be omitted.

In response to the notification from the key update determination unit 2203, the seed information generation unit 2204 generates seed information and inputs it to the Km update unit 2205, and inputs the seed information to the seed information transmission unit 2210. The seed information is information that is a source of a new master key. For example, a generation number or a random number that represents the generation of the master key Km can be considered.
The device information receiving unit 2209 receives device information such as an ID from the playback device, and specifies from which playback device the device information is transmitted based on the device information.

The seed information transmission unit 2210 transmits seed information to the playback device specified by the device information reception unit 2209.
As described above, the key management apparatus according to the present embodiment transmits seed information in accordance with an acquisition request for seed information from the playback apparatus. Further, the playback device knows that the master key should be updated based on the trigger information included in the EMM, and transmits a seed information acquisition request to the key management device.

Thereby, the playback device and the key management device have the same seed information, and generate new master keys from the seed information using the same algorithm.
In this embodiment, the playback device must always communicate with the key management device when updating the master key. As a result, the key management device can identify the playback device that is the source of the unauthorized playback device.

For example, if the playback device has a specification for transmitting its own ID as an acquisition request signal, the same ID is transmitted to the key management device multiple times when there is an unauthorized playback device. As a result, the key management device can determine that the playback device with that ID has become the source of an unauthorized playback device.
In this embodiment, the device information and the seed information are transmitted using a telephone line. However, the present invention is not limited to this and may be sent offline. Moreover, seed information may be transmitted using EMM.
(Embodiment 3)
[Outline of conditional access system]
FIG. 23 is a diagram showing an outline of the conditional access system in the present embodiment.

The conditional access system in this embodiment includes a key management device 2301, a manufacturing device 2302, a playback device 2303, and a broadcast device 2304.
The procedure in which the key management device 2301 and the playback device 2303 have the same ID and master key Km and the procedure in which the playback device 2303 acquires the work key Kw are the same as in the first embodiment.

The difference between the present embodiment and the first embodiment is a method of updating the master key Km.
In the present embodiment, the master key Km is updated as follows.
The broadcast device 2304 broadcasts the ID of the playback device 2303 to be updated and the seed information that is the source of the new master key Km ′ in the EMM.
Then, the playback device 2303 recognizes that the master key should be updated with the seed information, generates event information, and generates a new master key Km ′ from the seed information and event information. Here, the event information is information having an individual value for each update. In the present embodiment, random numbers are used as event information.

The playback device 2303 further transmits device information including its own ID and random number to the key management device 2301. The key management device 2301 updates the master key using the seed information and the random number.
Here, since the algorithm for generating a new master key Km ′ from the seed information and the random number is included only in the key management device and the playback device of the authorized user, only the key management device and the playback device of the authorized user have the new master. The key Km ′ can be acquired.

Therefore, the conditional access system according to the present embodiment can eliminate unauthorized viewing by other users after updating the master key.
A reproducing apparatus that implements such a conditional access system will be described in detail below.
[Configuration of playback device]
The playback apparatus in the present embodiment is different from the playback apparatus of the first embodiment only in the Km update unit. Therefore, only the Km update unit will be described, and description of other configurations will be omitted.

FIG. 24 is a diagram illustrating a detailed configuration of the Km update unit according to the third embodiment.
The Km update unit includes a seed information acquisition unit 2401, a device information generation unit 2402, a Km generation unit 2403, a Km storage unit 2404, and a device information transmission unit 2405.
The seed information acquisition unit 2401 acquires seed information from the update information determination unit, and inputs the seed information as an argument of the master key generation algorithm of the Km generation unit 2403.

The device information generation unit 2402 generates a random number in response to the notification from the update information determination unit, and generates individual device information for the playback device in combination with the ID held in advance. The device information is input to the Km generation unit 2403 and the device information transmission unit 2405.
The Km generation unit 2403 generates a new master key Km ′ using an incorporated algorithm. This algorithm differs for each playback device, each production lot, each model, or each manufacturer, and is also held in the key management device.

The Km storage unit 2404 stores the master key Km.
The device information transmission unit 2405 transmits the device information from the device information generation unit 2402 to the key management device. Here, the device information is transmitted using a telephone line.
In the present embodiment, the following two methods are used depending on the timing of generation of a new master key, either of which may be adopted.

The first method is a method for generating a new master key as soon as seed information is acquired.
The second method is a method in which seed information is held as it is after obtaining seed information, and a new master key generation process is performed as necessary. In this case, for example, when an EMM is input to the EMM decryption unit, a new master key generation process may be started after receiving a signal from the EMM decryption unit.
[Configuration of key management device]
FIG. 25 is a diagram illustrating a configuration of a key management apparatus in the conditional access system.

The key management apparatus according to the present embodiment is different from the key management apparatus according to the first embodiment in a device information receiving unit 2505 and a Km updating unit 2506. Therefore, only the device information receiving unit will be described, and description of other configurations will be omitted.
The device information receiving unit 2505 receives device information from the playback device. Here, the device information includes the ID of the playback device and a random number generated by the playback device. The device information receiving unit 2505 identifies from which playback device the device information is transmitted based on the ID.

The Km update unit 2506 updates the master key using the seed information generated by the seed information generation / insertion unit 2504 and the random number received by the device information reception unit 2505.
The new master key is generated using the same algorithm as that of the playback device.
As described above, the key management device according to the present embodiment includes the seed information in the EMM, transmits the seed information to the playback device, and receives a random number from the playback device. Also, the playback device knows that the master key should be updated based on the seed information included in the EMM, and transmits the random number generated at that time to the key management device.

As a result, the playback device and the key management device acquire the same seed information and the same random number, and generate new master keys from the seed information and the random number using the same algorithm.
In this embodiment, the playback device must always communicate with the key management device when updating the master key. As a result, the key management device can identify the playback device that is the source of the unauthorized playback device.

For example, if the playback device has a specification for transmitting its own ID as an acquisition request signal, the same ID is transmitted to the key management device multiple times when there is an unauthorized playback device. As a result, the key management device can determine that the playback device with that ID has become the source of an unauthorized playback device.
In the present embodiment, the device information is transmitted using a telephone line, but is not limited to this and may be sent offline.

In all the embodiments, the playback device and the key management device update only the master key, but the ID may be updated together with the master key. The update of the master key and ID may be overwritten, or a part of the ID may be retained and the part of the retained ID may be valid, or all of the IDs may be retained and valid. Also good.
In all the embodiments, the algorithm for generating a new master key is managed by the key management device. However, the algorithm is not limited to this as long as the security is ensured. For example, when there are a plurality of manufacturers and each manufacturer manages the algorithm of the playback apparatus that the manufacturer itself has manufactured, the algorithm is distributed and managed, so that there is an effect of risk dispersion.

In the first embodiment, the master key update method is applied to the playback device of the conditional access system. However, as in the case of an SD card, DVD playback device, etc., it corresponds to an ID to protect various information. It can also be applied to a device having a key. An example of application to a DVD playback apparatus will be described below.
FIG. 26 is a diagram showing the configuration of a DVD playback apparatus.

The playback device 2601 includes a reading unit 2602, a type determination unit 2603, a device key holding unit 2604, a media key decryption unit 2605, an update information determination unit 2606, a content key decryption unit 2607, a content decryption unit 2608, and a content playback unit 2609.
Various types of information on the DVD are read by the reading unit 2602 and sorted by type by the type determining unit 2603.

The media key decryption unit 2605 decrypts the data using the device key held in the device key holding unit 2604 and inputs the data to the update information determination unit 2606.
The update information determination unit 2606 inputs the data to the device key update unit 2610 if the update information is included in the data, and inputs the data to the content key decryption unit 2607 if the update information is not included. .

The device key update unit 2610 generates a new device key using the update information, and updates the device key held in the device key holding unit 2604.
As described above, the playback apparatus 2601 can update the device key using the update information determination unit 2606 and the device key update unit 2610.
(1) A playback apparatus for playing back content according to the present invention acquires a storage unit that holds a secret key, and encryption key information that is encrypted by a secret key encryption method, and is held by the holding unit. A key information decrypting means for decrypting the encrypted key information using a secret key, and obtaining key information, and the key information obtained by the key information decrypting means is key update information used for updating the secret key A new secret key is generated based on the key update information, and the secret information used in the key information decryption unit is held in the holding unit, and the key information obtained by the key information decryption unit is the content When it is a decryption key for decrypting a key, an encrypted content key encrypted by a secret key encryption method is obtained, and the content key is decrypted using the decryption key to obtain a scramble encryption method Ri obtains the scrambled content, characterized in that it comprises a content reproducing means for reproducing the content by descrambling using the content key.

According to the above configuration, the playback device acquires key information, generates a new secret key when the key information is key update information, and plays back content using the decryption key when the key information is a decryption key. I do. Thus, by generating a new secret key based on the key update information, it is possible to properly decrypt the key information encrypted with the new secret key from the next time.
Therefore, after the secret key is updated, only a valid reproduction device can reproduce the content, and the reproduction of the content by an unauthorized reproduction device can be excluded.
(2) Further, an identifier indicating that the key information is key update information or an identifier indicating a decryption key is added to the key information, and the playback device is further obtained by the key information decryption means. The key information may be provided with determination means for determining whether the key information is key update information or a decryption key based on the identifier.

According to the above configuration, the playback apparatus can identify whether the key information is key update information or a decryption key by an identifier.
(3) In addition, the key information is included in EMM (Entitlement Management Messages), and the playback device further receives broadcast data including EMM encrypted by the secret key, and is encrypted. Broadcast receiving means for obtaining key information may be provided, and the key information decrypting means may obtain encrypted key information obtained by the broadcast receiving means.

  As a secret key update method, a method in which a secret key manager sends a portable medium in which a new secret key is recorded to a legitimate user is also conceivable. However, this method requires a considerable number of days until a legitimate user receives the portable media, and during that time, there is a possibility that the user may suffer disadvantages such as being unable to view the content. Further, from the viewpoint of the secret key manager, when updating the secret keys of a plurality of playback devices, the portable media must be individually sent to a plurality of users, which is expensive.

However, according to the above configuration, the playback apparatus can acquire the key update information by receiving the broadcast. Since the key update information is transmitted by broadcasting, the secret key is updated instantly.
Therefore, a legitimate user does not suffer from the above disadvantages.
Also, since the key update information is transmitted by broadcasting, the update of the secret key is notified to a plurality of playback devices at once.

Therefore, the administrator of the secret key can reduce the cost burden as described above.
(4) In addition, the generation unit may generate a new secret key based on a predetermined conversion that differs for each playback device, each production lot of the playback device, each model of the playback device, or each manufacturer of the playback device. It is good.
According to the above configuration, the secret key is updated based on a predetermined conversion that differs for each playback device, each production lot of the playback device, each model of the playback device, or each manufacturer of the playback device.

As a result, even if the playback device is illegally analyzed by reverse engineering and the secret key conversion method is leaked, the playback devices targeted for countermeasures are narrowed down.
(5) The key update information may include seed information that is a source of a new secret key, and the generation unit may perform a predetermined conversion on the seed information to generate a new secret key. .
According to the above configuration, the key update information includes seed information.

Therefore, the playback apparatus can acquire a new secret key only by acquiring seed information and performing predetermined conversion on the seed information.
(6) Further, the key update information is trigger information for instructing update of a secret key, and the generation unit further sends a source of the secret key to a key management device that manages the secret key according to the trigger information. Transmitting means for transmitting a seed information acquisition request signal, and seed information receiving means for receiving seed information transmitted by the key management apparatus in response to the acquisition request signal, wherein the generating means includes the seed information. The seed information received by the receiving means may be subjected to predetermined conversion to generate a new secret key.

According to the above configuration, the playback apparatus acquires the trigger information and knows that the secret key should be updated using the trigger information. Thereafter, the playback device requests the key management device to acquire seed information, receives the seed information, and performs a predetermined conversion on the seed information to acquire a new secret key.
Thus, communicating with the key management apparatus after receiving the key update information has the following two advantages.

One is that the key management device can identify the playback device that is the source of the unauthorized playback device.
For example, if the specification is such that the ID of the playback device is transmitted as an acquisition request signal, if there is an unauthorized playback device, the same ID is transmitted to the key management device multiple times. As a result, the key management device can determine that the playback device with that ID has become the source of an unauthorized playback device.

The other is that the key management device can know that the playback device is performing a master key update process. For example, if the seed information is simply transmitted by broadcasting, the key management device cannot know that the playback device is updating the master key. However, according to the above configuration, since communication is performed from the playback device, the key management device can at least recognize that the playback device has received the key update information.
(7) Further, the key update information includes seed information that is a source of a new secret key, and the generation unit further includes an output unit that outputs different event information once or multiple times, The generation means generates a new secret key based on the seed information and the event information by a predetermined conversion, and the playback device further manages the event information output by the output means. It is good also as providing the transmission means to transmit to the key management apparatus to do.

According to the above configuration, the playback device generates a new secret key from the seed information and event information. In addition, event information is transmitted to share a new secret key with the key management device.
Thus, communicating with the key management apparatus after receiving the key update information has the following two advantages.
One is that the key management device can identify the playback device that is the source of the unauthorized playback device.

For example, if the specification is such that the ID of the playback device is transmitted as an acquisition request signal, if there is an unauthorized playback device, the same ID is transmitted to the key management device multiple times. As a result, the key management device can determine that the playback device with that ID has become the source of an unauthorized playback device.
The other is that the key management device can know that the playback device is performing a master key update process. For example, if the seed information is simply transmitted by broadcasting, the key management device cannot know that the playback device is updating the master key. However, according to the above configuration, since communication is performed from the playback device, the key management device can at least recognize that the playback device has received the key update information.
(8) The holding means may hold individual secret keys for each playback device, each production lot of the playback device, each model of the playback device, or each manufacturer of the playback device.

According to the above configuration, the secret key is different for each playback device, each production lot of the playback device, each model of the playback device, or each manufacturer of the playback device.
As a result, even if the playback device is illegally analyzed by reverse engineering and the secret key conversion method is leaked, the playback devices targeted for countermeasures are narrowed down.
(9) Further, the playback device has an individual ID for each playback device, each production lot of the playback device, each model of the playback device, or each manufacturer of the playback device, and the generation means includes the seed information and the The ID may be subjected to predetermined conversion to generate a new secret key.

According to the above configuration, the ID is different for each playback device, each production lot of the playback device, each model of the playback device, or each manufacturer of the playback device.
As a result, even if the playback device is illegally analyzed by reverse engineering and the secret key conversion method is leaked, the playback devices targeted for countermeasures are narrowed down.
(10) According to the present invention, a playback method in which a playback device having a storage unit for storing a secret key plays back content acquires encryption key information encrypted by a secret key encryption method, and stores the secret key A key information decryption step for decrypting the encrypted key information to obtain key information, and the key information obtained by the key information decryption step is key update information used for updating the secret key. A new secret key is generated based on the information, and a holding step is held in the holding unit as a secret key used in the key information decryption step, and the key information obtained by the key information decryption step decrypts the content key An encrypted content key encrypted by a secret key encryption method, and using the decryption key to obtain a content key, and a scramble encryption method Get more scrambled content, characterized in that it comprises a content reproduction step of reproducing the content by descrambling using the content key.

According to the above configuration, the playback device acquires key information, generates a new secret key when the key information is key update information, and plays back content using the decryption key when the key information is a decryption key. I do. Thus, by generating a new secret key based on the key update information, it is possible to properly decrypt the key information encrypted with the new secret key from the next time.
Therefore, after the secret key is updated, only a valid reproduction device can reproduce the content, and the reproduction of the content by an unauthorized reproduction device can be excluded.
(11) A program for causing a computer having a secret key holding unit to reproduce content according to the present invention acquires encryption key information encrypted by a secret key encryption method, and uses the secret key to perform the encryption. A key information decrypting step for decrypting key information to obtain key information, and when the key information obtained by the key information decrypting step is key update information used for updating the secret key, a new information is created based on the key update information. Generating a secret key and generating the secret key used in the key information decryption step in the holding unit, and the key information obtained by the key information decryption step is a decryption key for decrypting the content key When the encrypted content key encrypted by the secret key encryption method is acquired, the content key is obtained by decrypting using the decryption key, and the scramble encryption method Ri obtains the scrambled content, characterized in that it comprises a content reproduction step of descrambling reproduces the content by using the content key.

According to the above configuration, the computer acquires key information, generates a new secret key when the key information is key update information, and reproduces content using the decryption key when the key information is a decryption key. Do. Thus, by generating a new secret key based on the key update information, it is possible to properly decrypt the key information encrypted with the new secret key from the next time.
Therefore, after the secret key is updated, only a valid reproduction device can reproduce the content, and the reproduction of the content by an unauthorized reproduction device can be excluded.
(12) A key management apparatus for managing a secret key in a secret key cryptosystem according to the present invention is generated by a key update information generation unit that generates key update information used for updating the secret key, and the generation unit. Key update information or a decryption key for reproducing content as key information, transmitting means for encrypting the key information with the secret key and transmitting it to the playback device; and a new secret key based on the key update information And a secret key generation unit that generates and uses a secret key used in the transmission unit.

According to the above configuration, the key management device transmits the encrypted key information to the playback device. As a result, the key management device and the playback device can have the same key information.
The key management device can update the secret key with the key update information included in the key information.
Therefore, after the secret key is updated, only a valid reproduction device can reproduce the content, and the reproduction of the content of the unauthorized reproduction device can be excluded.
(13) The transmission unit may further transmit the key information with an identifier indicating that the key information is key update information or an identifier indicating that the key information is a decryption key.

According to the above configuration, the key management apparatus can transmit two types of information, that is, a decryption key and key update information, using the same format.
(14) In addition, the key information may be included in EMM (Entity Management Messages), and the transmission unit may transmit the key information to a playback device by broadcasting.

According to the above configuration, the key management apparatus can transmit key update information by broadcasting. Since the key update information is transmitted by broadcasting, the secret key is updated instantly.
(15) In addition, the key update information includes seed information that is a source of a new secret key, and the secret key generation unit performs predetermined conversion on the seed information to generate a new secret key. Also good.

According to the above configuration, the key update information includes seed information.
Therefore, the key management apparatus can acquire a new secret key only by generating seed information and performing predetermined conversion on the seed information.
(16) The key update information is trigger information for instructing an update of a secret key, and the secret key generation unit further includes a seed information generation unit that generates seed information that is a source of a new secret key. A transmission means for receiving an acquisition request signal transmitted from the reproduction apparatus that has acquired the trigger information, and transmitting the seed information generated by the seed information generation means to the reproduction apparatus in response to the acquisition request signal; In addition, the secret key generation means may generate a new secret key by performing predetermined conversion on the seed information.

According to the above configuration, the key management device generates trigger information and notifies the playback device that the secret key should be updated based on the trigger information. Thereafter, it receives a seed information acquisition request signal from the playback device, and transmits the seed information to the playback device accordingly. Also, a new secret key can be obtained by performing predetermined conversion on the seed information.
Thus, communicating with the key management apparatus after transmitting the key update information has the following two advantages.

One is that the key management device can identify the playback device that is the source of the unauthorized playback device.
For example, if the specification is such that the ID of the playback device is transmitted as an acquisition request signal, if there is an unauthorized playback device, the same ID is transmitted to the key management device multiple times. As a result, the key management device can determine that the playback device with that ID has become the source of an unauthorized playback device.

The other is that the key management device can know that the playback device is performing a master key update process. For example, if the seed information is simply transmitted by broadcasting, the key management device cannot know that the playback device is updating the master key. However, according to the above configuration, since communication is performed from the playback device, the key management device can at least recognize that the playback device has received the key update information.
(17) Further, the key update information includes seed information that is a source of a new secret key, and the secret key generation unit is further configured to transmit one or more times transmitted from the reproducing apparatus that has acquired the seed information. Receiving means for receiving different event information every time, and the secret key generating means may generate a new secret key based on the seed information and the event information by a predetermined conversion.

According to the above configuration, the key management device receives the event information from the playback device, and generates a new secret key from the seed information and the event information.
Thus, communicating with the key management apparatus after receiving the key update information has the following two advantages.
One is that the key management device can identify the playback device that is the source of the unauthorized playback device.

For example, if the specification is such that the ID of the playback device is transmitted as an acquisition request signal, if there is an unauthorized playback device, the same ID is transmitted to the key management device multiple times. As a result, the key management device can determine that the playback device with that ID has become the source of an unauthorized playback device.
The other is that the key management device can know that the playback device is performing a master key update process. For example, if the seed information is simply transmitted by broadcasting, the key management device cannot know that the playback device is updating the master key. However, according to the above configuration, since communication is performed from the playback device, the key management device can at least recognize that the playback device has received the key update information.
(18) A key management system according to the present invention is a key management system including a playback device that plays back content, and a key management device that manages a secret key in a secret key cryptosystem of the playback device, the key management device The key update information generating means for generating key update information used for updating the secret key, and the key update information generated by the key update information generating means or the decryption key for reproducing the content as key information, Transmission means for encrypting key information with the secret key and transmitting it to the playback device; and a first generation means for generating a new secret key based on the key update information and using it as a secret key used in the transmission means And the reproducing apparatus obtains the encryption key information transmitted by the transmission means, decrypts the encryption key information using the stored secret key, and obtains the key information. And second generation means for generating a new secret key based on the key update information when the decrypted key information is key update information.

According to the above configuration, the playback device and the key management device acquire key information, update the secret key when the key information is key update information, and use the decryption key when the key information is a decryption key. Play back. In this way, by updating the secret key with the key update information, it is possible to properly decrypt the key information encrypted with the new secret key from the next time.
Therefore, after the secret key is updated, only a valid reproduction device can reproduce the content, and the reproduction of the content of the unauthorized reproduction device can be excluded.

  The present invention can be used for a conditional access system or the like.

It is a figure which shows the outline of a conditional access system. It is a figure which shows the structure of the reproducing | regenerating apparatus in a conditional access system. It is a figure which shows operation | movement of the reproducing | regenerating apparatus in a conditional access system. It is a figure which shows the outline of the conditional access system in a some reproducing | regenerating apparatus. It is a figure which shows operation | movement of the some reproducing | regenerating apparatus in a conditional access system. It is a figure which shows the outline of the conditional access system in case an unauthorized reproduction | regeneration apparatus exists. It is a figure which shows the operation | movement of each reproduction | regeneration apparatus in the case of preventing unauthorized reproduction | regeneration of the content by an unauthorized reproduction | regeneration apparatus. 1 is a diagram showing an outline of a conditional access system in Embodiment 1. FIG. It is a figure which shows the structure of the reproducing | regenerating apparatus in a conditional access system. FIG. 3 is a diagram showing a detailed configuration of a Km update unit in the first embodiment. It is a figure which shows the data structure of normal EMM. It is a figure which shows the data structure of EMM for the update of the master key Km. It is a figure which shows the example of the algorithm in a Km production | generation part. It is a figure which shows operation | movement of the reproducing | regenerating apparatus in a conditional access system. It is a figure which shows the structure of the key management apparatus in a conditional access system. The example of management of ID and master key Km in a key management apparatus is shown. It is a figure which shows operation | movement of the key management apparatus in a conditional access system. It is a figure which shows operation | movement of each reproducing | regenerating apparatus when the illegal viewing of the content by an unauthorized reproducing | regenerating apparatus is excluded. 10 is a diagram illustrating an outline of a conditional access system in Embodiment 2. FIG. It is a figure which shows the detailed structure of the Km update part in Embodiment 2. FIG. It is a figure which shows the data structure of EMM for the update of the master key Km. It is a figure which shows the structure of the key management apparatus in a conditional access system. FIG. 11 is a diagram illustrating an outline of a conditional access system in a third embodiment. FIG. 10 is a diagram illustrating a detailed configuration of a Km update unit according to Embodiment 3. It is a figure which shows the structure of the key management apparatus in a conditional access system. It is a figure which shows the structure of the reproducing | regenerating apparatus of DVD.

Explanation of symbols

901 Playback device 902 Receiving unit 903 Type determining unit 904 ID / Km holding unit 905 EMM decoding unit 906 Update information determining unit 907 Kw updating unit 908 Kw holding unit 909 ECM decoding unit 910 Ks updating unit 911 Ks holding unit 912 Content decoding unit 913 Content output unit 914 Km update unit 1001 Seed information acquisition unit 1002 Km generation unit 1003 Km storage unit 1501 Key management device 1502 EMM reception unit 1503 Key update determination unit 1504 Seed information generation insertion unit 1505 Km update unit 1506 ID / Km holding unit 1507 EMM encryption unit 1508 Encrypted EMM transmission unit 2001 Device information holding unit 2002 Device information transmission unit 2003 Seed information reception unit 2004 Km generation unit 2005 Km storage unit 2201 Key management device 2202 EMM reception unit 22 03 Key update determination unit 2204 Seed information generation unit 2205 Km update unit 2206 ID / Km holding unit 2207 EMM encryption unit 2208 Encrypted EMM transmission unit 2209 Device information reception unit 2210 Seed information transmission unit 2401 Seed information acquisition unit 2402 Device information generation unit 2403 Km generation unit 2404 Km storage unit 2405 device information transmission unit 2504 seed information generation insertion unit 2505 device information reception unit 2506 Km update unit

Claims (1)

A playback device that is used in a digital broadcast conditional access system and decrypts various encrypted information transmitted by broadcast and displays it on a video receiver,
A holding means for holding a unique secret key and ID for each playback device, each production lot, each model or each manufacturer,
Key information decryption means for obtaining encrypted encryption key information and decrypting the encryption key information using the secret key to obtain key information;
Determining means for determining whether the key information is key update information used for updating based on leakage of the secret key or a decryption key for decrypting a content key based on an identifier added to the key information; ,
When the determination unit determines that the key information is key update information, the storage unit stores the key update information that is the source of the secret key;
If the determination means determines that the key information is the decryption key, obtains an encrypted content key, decrypts the encrypted content key using the decryption key, and obtains a content key Content reproducing means for acquiring scrambled content and descrambling the content key to reproduce the content;
After the key update information is held in the holding unit, each time the key information decrypting unit acquires new encryption key information, a hash function unique to each manufacturer incorporated in the playback apparatus and the holding unit are stored. Generating means for generating a new secret key based on the held key update information,
The holding means holds an initial state secret key,
The key update information includes a generation number of a new secret key, and the generation unit generates at least the generation number and the ID into the hash function to generate the new secret key .

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