KR20090012979A - Method and apparatus for forbidding consuming digital contents against copy control information - Google Patents

Abstract

A method and an apparatus for forbidding the use of digital contents against copy control information are provided to prevent disc cloning attack by allowing the use of contents only when the nonce stored in the memory coincides with the nonce stored in the corresponding storage. A method for forbidding the use of digital contents against copy control information comprises a step of creating nonce for each storage connected to a protective device and storing it in a separate memory and the corresponding storage, a step of updating the nonce stored in the memory and the nonce stored in the storage to the identical value when content is moved from the original storage, and a step of, when the use of at least one of the contents in the storages is requested, selectively allowing the use of the requested content depending on whether the nonce stored in the storage including the requested contents and the nonce of the corresponding storage stored in the memory.

Description

TECHNICAL FIELD AND APPARATUS FOR FORBIDING consuming digital contents against copy control information

The present invention relates to a method for processing digital content, and more particularly, to a method for preventing unauthorized use of copy-limited digital content.

Recently, a technology for a method of receiving and storing broadcast content and various PVR / DVR systems supporting the technology have been developed.

When content including copy control information is stored in one device, it may be prohibited to be copied later through another device and a digital interface. That is, the content whose copy control information is "copy-once" (only one copy is allowed) is stored in the storage and the copy control information is changed to "copy-no more" (copy prohibited). Thus, this content can no longer be copied to other storage but can only be moved. Here, move means that the content is copied from the original storage to another storage while being deleted from the original storage (hereinafter, the same). Therefore, if you move this content to another storage, the content must no longer be able to play on any storage other than the one to which the content has moved (including the original storage).

However, after copying the original storage at a bit level (bit by bit) to back up the storage in the state before the content movement occurs, the content can be played back using the backed up storage after moving the content. There is a risk of unauthorized distribution. This attack is called a disk cloning attack.

Therefore, there is a need for a new content management mechanism that can ensure that copy-protected content cannot be played from storage other than new storage if it is moved from one storage to another.

It is an object of the present invention to provide an apparatus and method for preventing content that is prohibited from copying from being played simultaneously on two or more separate storages.

In order to achieve the above object, the present invention provides a method for processing content by a security device that restricts the use of content, by generating a nonce for each of the storage devices connected to the security device. Storing in a predetermined predetermined memory and corresponding storage; Updating a nonce for the original storage stored in the memory and a nonce stored in the original storage to the same value when content is moved from the original storage; And if permission to use at least one of the contents of the storages is requested, selectively permitting the use of the requested contents according to whether a nonce stored in the storage having the requested content and the nonce of the corresponding storage stored in the memory match. Characterized in that it comprises a.

The content processing method includes encrypting content using content keys; Encrypting each of the content keys using device keys of the storage where the content is stored; Storing the encrypted content and the encrypted content keys in the storages; Encrypting device keys of the storages with a device key of the secure device; And storing the encrypted device keys in the memory, wherein the memory is embedded in the security device.

The content processing method includes encrypting content using content keys; Encrypting each of the content keys using device keys of the storage where the content is stored; Storing the encrypted content and the encrypted content keys in the storages; And storing the device keys of the storages in a portable device that can be separated from the secure device, wherein the memory is embedded in the portable device, and the device keys of the storages are stored in the portable device. It is encrypted by the portable device and then stored in the memory.

In the storing of the nonce, the nonce is encrypted using a device key of a corresponding storage, and then stored in the memory.

Storing the nonce in the corresponding storage and storing the encrypted content keys in the corresponding storage include recording the nonce and the encrypted content keys in content key files for the corresponding content, wherein the content key The files preferably contain a message authentication code (MAC) or signature for integrity checking.

The content processing method may further include updating a MAC or signature value of the content key files based on the updated nonce when the nonce included in the content key files is updated.

The present invention also provides a recording medium on which a computer program for executing the content processing method is recorded.

According to another aspect of the present invention, there is provided a security device for restricting use of content, the security device comprising: a nonce processing unit for generating a nonce for each storage connected to the security device to store in a predetermined memory separate from the storage and the storage; An update unit for updating a nonce of the original storage stored in the memory and the nonce stored in the original storage to the same value when a content is moved from the original storage; And when a use of at least one of the contents of the storages is requested, selectively permitting the use of the requested content according to whether a nonce stored in the storage having the requested content and a nonce of the corresponding storage stored in the memory match. It characterized in that it comprises a restriction.

According to the present invention, even if the copy-protected content has been disk-cloned in the state before the move from the storage, the content cannot be reproduced using the cloned storage after the movement of the content. This can prevent the use of content.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, "content" denotes a plural form of "content", and for convenience, "digital content (tsu)" is referred to as "content (tsu)".

1A to 1C are diagrams for describing a method of storing content according to an embodiment of the present invention. Here, it is assumed that content 1 is content that is prohibited from copying.

In FIG. 1A, the set top box STB stores content in the storage HDD 1 and restricts use of the content stored in the storage. Hereinafter, such a device will be referred to as a security device.

As shown in Fig. 1A, a security device stores content in storage connected to it, which stores information about the storages (hereinafter referred to as storage information) in a predetermined memory in the security device. A structure of storage information according to an embodiment of the present invention is shown in FIG. 1B.

As shown in FIG. 1B, the storage information according to an embodiment of the present invention includes an identifier (HDD_ID) of a storage, a device key (HDD_Key) of the storage, and a nonce (HDD_Nonce) generated for the storage. Here, the nonce is a value generated by the security device for each storage, and the nonce for one storage is generated so that a previously used value does not overlap even if it is updated later. In addition, as shown in FIG. 1B, the device key HDD_Key and the nonce HDD_Nonce of the storage are preferably stored encrypted by the device key MK of the security device.

On the other hand, the security device generates a content key file for all content, binds to the content and stores it. Thus, when content is moved to another storage, the content key file of the content as well as the content is deleted from the original storage. The structure of a content key file according to an embodiment of the present invention is shown in FIG. 1C.

As shown in FIG. 1C, a content key file according to an embodiment of the present invention includes an encrypted content key, a nonce of storage in which content is stored, copy control information, a message authentication code (MAC), and the like. do. The signature value may be used instead of the MAC. The content key is encrypted using the device key of the storage where the content is stored. Since content 1 is assumed to be content that is prohibited from copying, the copy control information of content 1 will be "Copy No-more".

Referring back to FIG. 1A, when the content 1 stored in the HDD 1 is moved from the HDD 1 and the content 1 and the content key file 1 are deleted from the HDD 1, the security device for the HDD 1 as shown in the figure on the right. Update the storage information and the remaining content key files stored on HDD 1.

More specifically, the HDD_Nonce included in the storage information of the HDD 1 and the HDD_Nonce of the remaining content key files stored in the HDD 1 are updated to the same value. It also updates the MAC or signature values of the remaining content key files based on the updated HDD_Nonce. As mentioned above, the updated HDD_Nonce should not be the same as the value previously used, and this property will be apparent to those skilled in the art from the term Nonce even if there is no explanation.

On the other hand, the security device according to an embodiment of the present invention restricts the use of contents stored in storages managed by the security device, and uses HDD_Nonce. That is, use is allowed only when the nonce included in the content key file of the content requested for use and the nonce included in the storage information of the corresponding storage are matched. Such a security device can protect against disk cloning attacks.

For example, even if an attacker copies HDD 1 in the state shown in the left figure of FIG. 1A by disk cloning, after content 1 moves, the attacker accesses the copied storage to the security device and requests the playback. Rejects the use of content 1. This is because the HDD_Nonce is updated in the storage information for the HDD 1 after the content 1 is moved, and thus has a different value from the HDD_Nonce included in the content key file 1 of the copied storage.

On the other hand, since the HDD_Nonce of the remaining content key files stored in the HDD 1 is updated in the same manner as the storage information of the HDD 1, it can be seen that the reproduction of the remaining files is not affected even after the content 1 is moved.

2 is a flowchart illustrating a process of processing content by a security device according to an embodiment of the present invention.

In operation 210, the security device stores content received through a broadcast channel or the like in storage.

In step 220, a nonce is generated for each of the storages.

In step 230, the secure device stores the generated nonce in memory and corresponding storage in the secure device. That is, the initial value of the nonce of the storage is the same value stored in the storage and the value stored in the security device.

The nonce stored in the secure device is included in the storage information, and the nonce stored in the storage is included in the content key files.

In step 240, if the content is moved out of the original storage, the nonce for the original storage stored in the secure device and the nonce stored in the original storage are equally updated. That is, the storage information about the original storage and the content key files stored in the original storage are updated.

In operation 250, the secure device receives a use request for at least one of the contents stored in the storage.

In step 260, the security device determines whether to permit use of the requested content based on the nonce of the storage in which the requested content is stored. That is, it is determined whether the nonce of the storage stored in the security device and the nonce stored in the storage match. Therefore, it will be necessary to analyze the storage information for the storage and the content key file of the requested content.

In step 270, if the nonce of the storage stored in the security device and the nonce stored in the storage device match with the determination result of step 260, the use of the content is allowed. If it does not match, the request for use of the content is rejected.

3 is a diagram illustrating a structure of a security device for restricting use of content according to an embodiment of the present invention.

As shown in FIG. 3, the security device 300 according to the present invention includes a content key generation unit 301, a first encryption unit 302, a second encryption unit 303, a content storage control unit 304, and a memory. 305, a third encryption unit 307, a nonce processor 308, an update unit 309, a usage limiter 310, and a storage interface 311.

The content key generator 301 generates content keys for encrypting content to be stored in the storages.

The first encryption unit 302 encrypts the content with the content keys.

The second encryption unit 303 encrypts the content keys using the device keys of the storages.

The content storage control unit 304 stores the encrypted content and the encrypted content keys in the storages. At this time, the encrypted content key is recorded in the content key file of the corresponding content, and the content key file is stored in association with the corresponding content.

The third encryption unit 307 encrypts the device keys of the storages with the device key of the security device 300 and is stored in the memory 305. At this time, the device keys of the encrypted storages are recorded in the storage information.

The nonce processor 308 generates a nonce for each of the storages and stores the nonce in the memory 305 and the corresponding storage. At this time, the nonce stored in the storage is recorded in all content key files stored in the storage, and the nonce stored in the memory 305 is recorded in the storage information of the corresponding storage. When storing the nonce in the memory 305, it is preferable to encrypt and store the device key of the security device 300.

Meanwhile, the content key file may include a device key of encrypted storage, a nonce of storage, a content ID, copy control information of the corresponding content, and the like. Message Authentication for Integrity Check of the content key file Code) or signature value.

When the content stored in the storage is moved to the outside (the content key file is also moved because the content key file is bound to the content), the updater 309 sets the same value as the nonce stored in the memory 305 and the storage. Update with That is, the storage information of the storage stored in the memory 305 and the remaining content key files stored in the storage are updated. Of course, when updating the content key files, the MAC or signature value included in the content key files is also recalculated based on the new nonce.

The usage limiter 310 selectively limits the use of content stored in the storages based on the nonce value stored in the memory 305 and the storages. That is, when a use request for content is received, the content key file of the content and storage information of the storage in which the content is stored are analyzed. If the nonce included in the content key file and the nonce included in the storage information match, the use of the corresponding content is allowed;

The storage interface 311 is an interface that enables communication between the security device 300 and the storages.

4A to 4B are diagrams for describing a security device according to another embodiment of the present invention.

The security device described so far uses the device key of the device to encrypt the device key of the storage and the nonce of the storage, and stores the device key and the encrypted nonce of the encrypted storage in the storage information of the corresponding storage. That is, it is stored in the memory 305 in FIG.

However, in such an environment, both the storage and the security device that stores the storage information must be available to use the content stored in the storage. In order to use the content, the license must be obtained from the security device, because the nonce included in the storage information of the storage must be referenced to determine whether the security device is licensed. Therefore, even if a user carries the storage and moves it to another security device, the content stored in the storage cannot be played back.

In this embodiment, the storage information is stored in a separate portable device 450 separated from the security device 400 in preparation for such a case. Hereinafter, the portable device 450 will be referred to as a portable security component (PSC).

4b illustrates the structure of the security device 400 and the PSC 450 in more detail. Hereinafter, the description of the block having the same function as FIG. 3 among the blocks included in the security device 400 will be omitted.

As shown in FIG. 4B, unlike the security device in FIG. 3, the security device 400 does not include a memory in which storage information is stored, but instead includes a PSC controller 409. This is because the memory 453 in which the storage information is stored is built in the PSC 450.

The nonce of the storages generated by the nonce processor 405 is transferred to the PSC controller 409, and the PSC controller 409 transmits it to the PSC 450. In addition, the PSC controller 409 delivers the device keys of the storages to the PSC 450.

The encryption unit 451 of the PSC 450 encrypts the nonce of the received storages and the device keys of the storages to generate storage information, and then stores the stored information in the memory 453 embedded in the PSC 450.

On the other hand, when the movement of the content occurs, the update unit 406 notifies the PSC 450 of the information (for example, the storage identifier) and the updated nonce of the storage, and the PSC 450 receives the new nonce received. Update the storage information stored in memory by using the value.

The usage limiting unit 407 requests the PSC 450 for the nonce of the storage when a request for using the content is received. The decryption unit 452 of the PSC 450 decodes the nonce of the storage information and sends the decrypted nonce to the PSC control unit 409, and the PSC control unit 409 transmits it to the usage limiting unit 407. The usage restriction unit 407 compares the nonce received from the PSC control unit 409 with the nonce included in the content key file of the corresponding content, and determines whether to use the content.

5 is a flowchart illustrating a process of defending a disk cloning attack according to an embodiment of the present invention.

In the present embodiment, the embodiment in FIG. 4 is assumed. That is, the security device is connected to the PSC, and storage information is stored in the PSC.

In step 501, the secure device generates a nonce of storage A, and stores the nonce of content and storage A in storage A.

In step 502, the security device also provides a nonce to the PSC.

In step 503, the PSC encrypts the nonce of storage A with its device key to generate storage information of storage A.

In step 504, a move to content C of storage A occurs. Before the movement of content C occurs, the attacker copies storage A to the low level to make storage A '.

In step 505, because content C has moved, the secure device updates the remaining content key files stored in storage A. That is, the nonce stored in the storage A is updated.

In step 506, since the nonce included in the content key files has been updated, the MAC or signature value of the content key files is also updated.

In step 507, the security device notifies the PSC of the updated nonce.

In step 508, the PSC updates the storage information of storage A using the new nonce received from the security device.

In step 509, the secure device receives a playback request for content C of storage A '. In FIG. 5, the dotted line indicates that the security device has been separated, and the solid line indicates that the security device has been connected.

That is, the storage A is separated from the secure device, and the storage A 'is requested to use the content C while connected to the secure device. Since storage A 'is a disk clone of storage A before the movement of content C occurs, the security device recognizes storage A' as storage A in a previous state.

In operation 510, the security device requests and receives a content key file of content C from storage A '. At this time, the received content key file is a content key file before the content C moves.

In step 511, the security device requests a nonce of storage A from the PSC.

In step 512, the PSC decrypts the nonce from the storage information of the storage A using its device key. At this time, it should be noted that the decoded nonce is not the nonce in step 502 but the new nonce delivered in step 507.

In step 513, the PSC sends a nonce of storage A to the secure device.

In step 514, the security device compares the nonce contained in the content key file received in step 510 with the nonce received from the PSC in step 513. The nonce received from the PSC is the updated nonce, and the nonce stored in the storage A 'is non-updated so the two will not match.

In step 515, the secure device indicates to the attacker that playback for Content C has failed.

Meanwhile, the above-described embodiments of the present invention can be written as a program that can be executed in a computer, and can be implemented in a general-purpose digital computer that operates the program using a computer-readable recording medium.

The computer-readable recording medium may be a magnetic storage medium (for example, a ROM, a floppy disk, a hard disk, etc.), an optical reading medium (for example, a CD-ROM, a DVD, etc.) and a carrier wave (for example, the Internet). Storage media).

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

1A is a diagram for explaining data change when content is moved according to one embodiment of the present invention;

1B is a diagram showing the structure of storage information according to an embodiment of the present invention;

1C illustrates the structure of a content key file according to an embodiment of the present invention;

2 is a flowchart illustrating a process of processing content by a security device according to an embodiment of the present invention;

3 is a view showing the structure of a security device according to an embodiment of the present invention;

4a to 4b is a view showing the structure of a security device according to another embodiment of the present invention,

5 is a flowchart illustrating a process of defending a disk cloning attack according to an embodiment of the present invention.

Claims (13)

In the method for processing the content by a security device for restricting the use of the content, Generating a nonce for each of the storage devices connected to the security device and storing the nonce in a predetermined memory and corresponding storage; Updating a nonce for the original storage stored in the memory and a nonce stored in the original storage to the same value when content is moved from the original storage; And If use of at least one of the contents of the storage is requested, selectively permitting the use of the requested content according to whether a nonce stored in the storage in which the requested content resides matches a nonce of the corresponding storage stored in the memory. Method comprising a. The method of claim 1, Encrypting the content using the content keys; Encrypting each of the content keys using device keys of the storage where the content is stored; Storing the encrypted content and the encrypted content keys in the storages; Encrypting device keys of the storages with a device key of the secure device; And Storing the encrypted device keys in the memory, And the memory is embedded in the security device. The method of claim 1, Encrypting the content using the content keys; Encrypting each of the content keys using device keys of the storage where the content is stored; Storing the encrypted content and the encrypted content keys in the storages; And Storing the device keys of the storages in any portable device that can be separated from the secure device, The memory is embedded in the portable device, and the device keys of the storages are stored in the memory after being encrypted by the portable device. The method of claim 1, The step of storing the nonce, And encrypting the nonce using a device key of a corresponding storage and storing the nonce in the memory. The method of claim 2, Storing the nonce in the corresponding storage and storing the encrypted content keys in the storage include recording the nonce and the encrypted content keys in content key files bound to the content, And the content key files include a message authentication code (MAC) or a signature value for integrity checking. The method of claim 5, If a nonce included in the content key files is updated, updating the MAC or signature value of the content key files based on the updated nonce. A recording medium on which a computer program for executing the method according to any one of claims 1 to 6 is recorded. A security device for restricting the use of content, A nonce processor configured to generate a nonce for each of the storage devices connected to the security device, and store the same in a predetermined memory separated from the storage and the corresponding storage; An update unit for updating a nonce of the original storage stored in the memory and the nonce stored in the original storage to the same value when a content is moved from the original storage; And When the use of at least one of the contents of the storage is requested, a usage restriction selectively permitting the use of the requested content according to whether the nonce stored in the storage having the requested content and the nonce of the corresponding storage stored in the memory match. Apparatus comprising a portion. The method of claim 8, A first encryption unit encrypting the content using the content keys; A second encryption unit encrypting each of the content keys using device keys of storages for storing the corresponding content; A content storage control unit which stores the encrypted content and the encrypted content keys in the storages; And A third encryption unit encrypting the device keys of the storages with a device key of the security device and storing the device keys in the memory; And the memory is embedded in the security device. The method of claim 8, A first encryption unit encrypting the content using the content keys; A second encryption unit encrypting each of the content keys using device keys of storages for storing the corresponding content; A content storage control unit which stores the encrypted content and the encrypted content keys in the storages; And A portable device controller which stores the device keys of the storages in a predetermined portable device that can be separated from the security device, The memory is embedded in the portable device controller, and the device keys of the storages are stored in the memory after being encrypted by the portable device. The method of claim 8, The nonce processing unit, And encrypting the nonce using a device key of a corresponding storage and storing the nonce in the memory. The method of claim 9, The nonce processing unit and the content storage control unit respectively record the nonce and the encrypted content keys in content key files bound to the corresponding content, And the content key files include a message authentication code (MAC) or a signature value for integrity checking. The method of claim 12, And if the nonce included in the content key files is updated, updating the MAC or signature values of the content key files based on the updated nonce.

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