KR20090019660A - Method and apparatus for storing digital content in storage device - Google Patents

Abstract

A method for storing the digital contents in the storage instrument and apparatus therefore are provided to reduce the amount of the information for safe management. The apparatus for storing the digital contents in the storage instrument ciphers the contents to the contents key(307). The apparatus ciphers the contents key to the storage key which is the inherent key about the storage instrument(308). The apparatus stores the contents key file and the encrypted contents including the encrypted contents key in the storage instrument(309).

Description

TECHNICAL FIELD AND APPARATUS FOR STORAGE DIGITAL CONTENT IN STORAGE DEVICE

The present invention relates to a method of protecting digital content, and more particularly, to a method of storing digital content in a storage device and managing the stored storage device.

With the development of communication technology, digital content is becoming more and more large, and accordingly, a lot of high-capacity storage devices for storing digital content are released. Since digital content can theoretically be reproduced indefinitely without quality degradation, it is necessary to prevent digital content from being used by unauthorized persons. For example, if a set-top box receiving digital content receives broadcast content and stores it on a storage device connected to the set-top box, the content stored on that storage device must not be played when connected to another set-top box. .

As such, a variety of digital right management (DRM) technologies are being researched to protect digital content. Storage devices are generally non-intelligent devices that do not have the computing power required to protect content. The host (set-top box, digital TV, etc.) copying the content to the content must perform an appropriate encryption process on the content before storing the content on the storage device.

1 is a flowchart illustrating a process of storing digital content in a storage device by a host according to the related art.

In step 110, the host generates a content key.

In step 120, the host encrypts the content to store in the storage with the content key.

In operation 130, the encrypted content is stored in a storage device connected to the host.

In step 140, the content key is encrypted with the device key of the host. The device key of the host is a key that is unknown to devices other than the host.

In step 150, the host stores the encrypted content key in a secure place within the host. Of course, the information that maps the content key and the corresponding content will also be stored at this time.

If the content is stored in the storage device by the above process, the content cannot be played even if the storage device is connected to another host. Because the content key is kept on the host, the encrypted content cannot be decrypted by other devices. Thus, the content can only be played back on the original host, hereinafter this environment will be referred to as "binded" to the host.

However, according to such a prior art, there is a problem that the host has to manage a lot of content. In other words, since the host must keep the content key for all the contents that are encrypted and stored, overload may occur over time.

In addition, in order to play content bound to a host on another host or to move to another storage device, a host to which the content is bound is required. Since the host is generally not easy to carry, content portability and The problem is that mobility is very low.

It is an object of the present invention to provide a method in which a host does not keep all content keys when storing digital content on a storage device, and also provides a method for easily moving content bound to one host to another device.

According to an aspect of the present invention, there is provided a method for a host to store digital content in a storage device, the method comprising: encrypting the content with a content key; Encrypting the content key with a storage key that is a unique key for the storage device; And storing the encrypted content key file including the encrypted content key and the encrypted content in the storage device.

The storage key is a first storage key, which is a key generated by a portable security device connected to the host, and the storing method further includes deleting the first storage key from the host when the storing is completed. .

The storage method may include determining whether a second storage key, which is a key generated by the host, for the storage device already exists in the host; Extracting or newly generating the second storage key from the host based on the determination result; Updating the content key file using the second storage key; Encrypting the second storage key with a device key of the host; And storing the encrypted second storage key on the host.

The updating may include decrypting the encrypted first storage key using a device key of the host; Decrypting a content key included in the content key file using the decrypted first storage key; Encrypting the decrypted content key with the second storage key; And replacing the content key encrypted with the second storage key with the content key encrypted with the first storage key.

The storage key is a second storage key which is a key generated by the host, and the storage method includes: encrypting the second storage key with a device key of the host; And storing the encrypted second storage key on the host.

The storage method may further include receiving a first storage key which is a key generated by the portable security device for the storage device from the portable security device connected to the host; And updating the content key file using the first storage key.

 The updating may include decrypting the encrypted second storage key using a device key of the portable security device; Decrypting a content key included in the content key file using the decrypted second storage key; Encrypting the decrypted content key with the first storage key; And replacing the content key encrypted with the first storage key with the content key encrypted with the second storage key.

The storage method may include retrieving the storage key from the host or a portable security device connected to the host when a play request for the content is received; And selectively playing the encrypted content based on the search result.

The reproducing may include decrypting a content key included in the content key file using the storage key when the storage key is found as a result of the search; And decrypting the encrypted content using the decrypted content key.

The storage device is a first storage device, and the storage method includes: receiving a command for moving the content from the first storage device to a second storage device; Decrypting the encrypted content key using the first storage key; Encrypting the decrypted content key with a second storage key that is a storage key for the second storage device; Storing a content key file including the content key encrypted with the second storage key and the encrypted content in the second storage device; And deleting the content key file and the encrypted content stored in the first storage device.

Preferably, the content key file further includes a value for checking integrity of the content key file.

The content key file may further include a recovery key which is a value obtained by encrypting the storage key with a third party's public key or the host's public key.

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

In addition, the present invention provides a host for storing digital content in a storage device, comprising: a content encryption unit for encrypting the content with a content key; A content key encryption unit encrypting the content key with a storage key which is a unique key for a storage device connected to the host; And a storage controller configured to store a content key file including the encrypted content key and the encrypted content in the storage device.

According to the present invention, since the host only needs to manage one storage key per storage, the amount of information to be managed securely can be reduced.

In addition, if the user only has a portable security device that stores the storage key together with the storage device where the content is stored, the user can freely play or move the content bound to the portable security device to another storage device by connecting the storage device to any host. .

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2A is a diagram illustrating a structure of information stored in a host and a storage according to an embodiment of the present invention.

As shown in FIG. 2A, the storage information 220 is stored in the host 220 in the present embodiment, and the storage ID file 240 and the encrypted content (not shown) are stored in the storage device 230. The content key file 250 is stored. The communication interface between the host 210 and the storage device 230 is not limited to a specific one.

The host 210 generates a storage ID file 240 for each storage device connected to the storage device, and stores the storage ID file 240 in the corresponding storage device. When the storage device is connected, the host 210 identifies the storage device by looking at the storage ID file included in the storage device.

The storage ID file 240 includes a host ID 241, a storage ID 242, and a message authentication code (MAC) 243. The digital signature value may be used instead of the MAC.

The host ID 241 is an identifier of the host 210 itself, the storage ID 242 is an identifier of the storage device 230, and the MAC 243 is a value for checking the integrity of the storage ID file 240.

Since extracting a unique identifier from all storage can be difficult, the storage ID 242 is generated by the host 210 with a unique value that can be distinguished from other storage devices by the storage device 230 to the storage device 230. ). Since the storage ID 242 is also included in the storage information 220, the host may be used as index information when the host finds a storage key for the storage device 230 in the storage information 220. When the storage device 230 is connected, the host 210 searches for a storage ID file for the storage device 230 and creates a new one if the storage ID file does not exist.

The storage information 220 includes a storage ID, a storage key, and a nonce. Of course, the storage ID has the same value as the storage ID 242 included in the storage ID file 240 and the storage ID 252 included in the content key file 250.

Nonce is a value generated by the host 210 for each storage device, and a nonce generated for one storage device is generated such that a previously used value does not appear even if it is updated later. When the nonce is stored in the host 210, the nonce is preferably stored encrypted with the device key of the host 210. Meanwhile, the nonce is also included in the content key file 250 included in the storage device 230.

This nonce can be exploited to prevent disk cloning attacks. That is, when the content stored in the storage device 230 moves to another storage device, the host 210 deletes the content key file for the content moved from the storage device 230, and stores the corresponding storage device in the storage information 220. The storage information element 221 having the storage ID of 230 is found and the corresponding storage nonce is updated. In addition, the updates of the remaining content key files stored in the corresponding storage device 230 are the same as those of the storage information 220.

In this way, even if an attacker copies the original storage to a bit by bit and backs up the storage device before the content has moved, the moved content cannot be played on the host. However, to this end, the host should compare the nonce of the storage information 220 with the nonce of the content key file 250 to play the corresponding content only when the host matches.

Whenever the host 210 stores one content in the storage device 230, the host 210 generates a content key file 250 for the corresponding content and stores the content key file 250 in the storage device 230. The content is encrypted with the content key and stored in the storage device 230. The content key is encrypted with a storage key which is a device key of the storage device 230 and inserted into the content key file 250. As such, since the content key is included in the content key file 250 stored in the storage device 230 rather than stored by the host 210, the host 210 needs to directly manage the content key for all contents. There is no need to manage storage keys for each storage device.

The content key file 250 includes a host ID 251, a storage ID 252, a nonce 253, a content key 254, a recovery key 255, and a MAC 256. The recovery key 255 encrypts the storage key of the storage device 230 with a public key of a third party, for example, the host device 210 manufacturer. Alternatively, the content may be encrypted with the public key of the device to which the corresponding content is bound (in this embodiment, the host 210). This is in case the storage key cannot be recovered, such as when the host 210 is lost or the storage information 220 is erased.

The description of the other information included in the content key file 250 has been described above, and thus will be omitted here. In addition, CCI (Copy Control Information) and Content ID may be further included.

2B is a diagram illustrating the structure of information stored in a host and a storage according to another embodiment of the present invention.

As shown in FIG. 2B, in the present embodiment, unlike the embodiment of FIG. 2A, the storage information 321 is included in the portable security device 320. The portable security device 320 connects to the host 310, generates a storage ID and a nonce for the storage device 330, and inserts the storage ID and nonce into the storage information 321. Hereinafter, such a portable security device 320 will be referred to as a portable security component (PSC). The storage key is preferably stored encrypted by the device of the PSC (320).

The storage information 321, the storage ID file 331 and the content key file 332 are almost identical in structure as in FIG. 2A, but include a PSC ID instead of a host ID. Although not shown, the encrypted content is, of course, also stored in the storage device 330.

According to this embodiment, the content is bound to the PSC 320 rather than the host 310. Therefore, when the user plays the storage device 330 on another host, only the PSC 320 may be connected to another host to freely use the content stored in the storage 330.

3 is a flowchart illustrating a process in which a host stores content in a storage device according to an embodiment of the present invention.

In step 301, a storage device is connected to the host.

In step 302, the host determines if an appropriate storage ID file exists in the storage device. At this time, the host ID (PSC ID) and storage ID in the storage ID file are referenced.

In step 303, if there is no appropriate storage ID file, a storage ID file and storage information is generated. When the content is bound to the PSC, the storage ID file and the storage ID included in the storage information are received from the PSC.

In step 304, the host detects a storage key from the storage information.

In step 305, a content storage request is received via the user interface.

In step 306, the host generates a content key.

In step 307, the content is encrypted with the generated content key and stored in the storage device.

In step 308, the content key is encrypted with the storage key.

In step 309, the storage key is stored in the host or PSC. It is preferable to encrypt and store with the device key of the host or PSC.

4 is a flowchart illustrating a process of binding content bound to a PSC to a host according to an embodiment of the present invention.

Step 401 is a process of binding the content to the PSC using the first storage key generated by the PSC for the storage device. Description of this process has been described above in FIG. 3 and will not be described herein.

In step 402, the host searches storage information for the storage device to determine whether a storage key for the storage device is already stored in the host. If yes, the storage key is extracted from the corresponding storage information element. If not, create one. The storage key generated by the host will be referred to as a second storage key.

In step 403, the host decrypts the content key included in the content key file using the first storage key, that is, the storage key generated by the PSC.

In step 404, the host updates the content key file using the second storage key. That is, the content key decrypted in step 403 is encrypted using the second storage key, and the content key encrypted with the second storage key is replaced with the existing content, that is, the content key encrypted with the first storage key. Also, the PSC ID included in the content key file and the storage ID file is replaced with the host ID.

In step 405, the second storage key is encrypted with the device key of the host.

In step 406, the encrypted second storage key is stored in non-volatile memory of the host.

By this process, since the second storage key stored in the host is required to decrypt the encrypted content stored in the storage device, the content may be said to be bound to the host.

5 is a flowchart illustrating a process of binding content bound to a host to a PSC according to an embodiment of the present invention.

Step 501 is a process of binding the content to the host by using the second storage key generated by the host for the storage device. The description of this process is replaced with the description of FIG. 3.

In step 502, the host searches for storage information of the PSC to determine whether a storage key for the corresponding storage device is already stored in the PSC. If the PSC and the storage device have connected before, the storage information will be on the PSC. If the storage key already exists in the PSC, the storage key is extracted from the storage information. If not, the storage key is requested to the PSC to receive the newly generated storage key. The storage key generated by the PSC will be referred to as a first storage key.

In step 503, the host decrypts the content key included in the content key file using the second storage key, that is, the storage key generated by the host.

In step 504, the host updates the content key file using the first storage key. That is, the content key decrypted in step 503 is encrypted using the first storage key, and the content key encrypted with the first storage key is replaced with the existing content, that is, the content key encrypted with the second storage key. This may mean creating a new content key file and deleting an existing content key file.

Also, the host ID included in the content key file is replaced with the PSC ID.

In step 505, the first storage key is deleted from the host. This is because if the first storage key remains in the host, the host can play the content bound to the PSC.

By this process, since the first storage key stored in the PSC is needed to decrypt the encrypted content stored in the storage device, the content may be said to be bound to the PSC. That is, the user can play the content stored in the storage on any host with the PSC.

6 is a flowchart illustrating a process of playing content stored in storage by a host according to an embodiment of the present invention.

In step 601, the host receives a playback request for content stored in a storage device through a user interface.

In step 602, the host checks the host ID or PSC ID of the content key file and, accordingly, searches for its storage information element by searching its nonvolatile memory or PSC connected to the host. That is, the storage information element is retrieved by using the storage ID included in the storage ID file or the content key file as index information.

In step 603, it is determined whether a storage information element with a matching storage ID exists.

In step 604, if the corresponding storage information element does not exist, output an error message to the user and exit.

In step 605, if there is a corresponding storage information element, the storage key is extracted from the storage information.

In step 606, the content key included in the content key file is decrypted using the storage key.

In operation 607, the content stored in the storage device is decrypted using the decrypted content key.

In step 608, the decrypted content is played back.

7 is a flowchart illustrating a process of moving content stored in storage according to an embodiment of the present invention. That is, in the present embodiment, the device to which the content is bound is not changed, but the storage device in which the content is stored is changed. At this time, the content should be bound to a host performing the following procedure or a PSC connected to the host.

In step 701, the host receives a request to move content from a first storage device to a second storage device through a user interface.

In step 702, the host detects or newly generates a second storage key that is a storage key for the second storage device. That is, if there is a second storage key in the existing storage information, the second storage key is extracted from the corresponding storage information element, otherwise, a new storage key is generated.

In step 703, the host decrypts the content key included in the content key file of the first storage using the first storage key. The first storage key may be extracted from nonvolatile memory in the host or from a PSC connected to the host.

In step 704, the host encrypts the content key with the second storage key and generates a content key file. The newly generated content key file has a different storage ID, nonce, recovery key, MAC, etc. than the content key file existing in the first storage device.

In step 705, the generated content key file and the encrypted content are stored in the second storage device.

In operation 706, the content key file and the encrypted content stored in the first storage device are deleted.

8 is a diagram showing the structure of a host according to an embodiment of the present invention.

As shown in FIG. 8, the host 800 according to an embodiment of the present invention includes a content encryptor 801, a PSC controller 802, a content key encryptor 803, a content movement controller 804, and a storage device. The controller 805, the update unit 810, the storage key generator 820, the playback unit 830, the search unit 840, and the storage key manager 850 are included.

The content encryption unit 801 encrypts the content using the content key.

The content key encryptor 803 encrypts the content key using the storage key of the storage device 900.

The storage controller 805 stores the content key file and the encrypted content in the storage device 900.

The PSC controller 802 receives the storage key generated by the PSC for the storage device 900 from the PSC 1000, and when the operation of binding the content to the PSC is completed, the PSC controller 802 deletes the storage key from the host 800. .

When the storage device 900 is connected, the storage key generator 820 determines whether a corresponding storage information element exists in a nonvolatile memory (not shown) of the host 800. If present, the storage key is extracted from the corresponding storage information element. Otherwise, it is generated.

The storage key manager 830 encrypts the storage key generated by the storage key generator 830 using the device key of the host 800, and stores the storage key in a nonvolatile memory (not shown).

The updater 810 binds the content bound to the host 800 to the PSC, or vice versa, and updates the content key file stored in the storage device 900. As shown in FIG. 8, the updater 800 includes a key changer 811, a content key encryptor 812, a content key decryptor 813, and a storage key decryptor 814.

First, the storage key decryption unit 814 extracts a storage key stored in the host 800 or the PSC 1000.

The content key decryption unit 813 decrypts the content key included in the content key file using the storage key.

The content key encryptor 812 encrypts the content key again using the storage key generated by the device to which the content is bound. For example, assuming that the content bound to the host 800 is bound to the PSC, the content key encryption unit 812 encrypts the content key using the storage key generated by the PSC for the storage device 900. Ha ha.

The key replacement unit 811 replaces the existing encrypted content key included in the content key file with the content key encrypted by the content key encryption unit 812.

When the search unit 840 receives a playback request for the content of the storage device 900 through the user interface, the search unit 840 searches for the host 800 or requests the PSC 1000 connected to the host 800 to display the storage device 900. Find the storage key for.

The playback unit 830 selectively plays the content of the storage device 900 based on the result of the search unit 840. That is, if the storage key is found, the storage key is finally decrypted using the storage key, and if the storage key does not exist anywhere in the host 800 and the PSC 1000, an error message is output.

The content movement control unit 804 controls the movement of content stored in the storage device 900. That is, when a command for moving content from the first storage device to the second storage device is received, the encrypted content key is decrypted using the storage key of the first storage device, and the storage key of the second storage device is used. Encrypt the decrypted content key again.

Then, after storing the content key file including the content key encrypted with the storage key of the second storage device and the newly encrypted content in the second storage device, the content key file and the encrypted content stored in the first storage device are deleted. do.

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.

1 is a flowchart illustrating a process in which a host stores content in a storage device according to the prior art;

2A illustrates a structure of information stored in a host and a storage according to an embodiment of the present invention;

2b is a diagram showing the structure of information stored in a host and storage according to another embodiment of the present invention;

3 is a flowchart illustrating a process in which a host stores content in a storage device according to an embodiment of the present invention;

4 is a flowchart illustrating a process of binding content bound to a PSC to a host according to an embodiment of the present invention;

5 is a flowchart illustrating a process of binding content bound to a host to a PSC according to an embodiment of the present invention;

6 is a flowchart illustrating a process of playing content stored in storage by a host according to an embodiment of the present invention;

7 is a flowchart illustrating a process of moving content stored in storage according to an embodiment of the present invention.

8 is a diagram showing the structure of a host according to an embodiment of the present invention.

Claims (25)

A method for a host to store digital content on a storage device, Encrypting the content with a content key; Encrypting the content key with a storage key that is a unique key for the storage device; And Storing a content key file containing the encrypted content key and the encrypted content on the storage device. The method of claim 1, The storage key is a first storage key which is a key generated by a portable security device connected to the host, And deleting the first storage key from the host when the storage is complete. The method of claim 2, Determining whether a second storage key, which is a key generated by the host, for the storage device already exists in the host; Extracting or newly generating the second storage key from the host based on the determination result; Updating the content key file using the second storage key; Encrypting the second storage key with a device key of the host; And Storing the encrypted second storage key on the host. The method of claim 3, wherein The updating step, Decrypting the encrypted first storage key using a device key of the portable security device; Decrypting a content key included in the content key file using the decrypted first storage key; Encrypting the decrypted content key with the second storage key; And Replacing the content key encrypted with the second storage key with the content key encrypted with the first storage key. The method of claim 1, The storage key is a second storage key which is a key generated by the host, The storage method, Encrypting the second storage key with a device key of the host; And Storing the encrypted second storage key on the host. The method of claim 5, Receiving a first storage key which is a key generated by the portable security device for the storage device from the portable security device connected to the host; And Updating the content key file using the first storage key. The method of claim 6, The updating step, Decrypting the encrypted second storage key using a device key of the host; Decrypting a content key included in the content key file using the decrypted second storage key; Encrypting the decrypted content key with the first storage key; And Replacing the content key encrypted with the first storage key with the content key encrypted with the second storage key. The method of claim 1, Retrieving the storage key from the host or a portable security device connected to the host when a play request for the content is received; And Selectively playing the encrypted content based on the search results. The method of claim 8, The reproducing step, Decrypting the content key included in the content key file using the storage key when the storage key is found as a result of the search; And  Decrypting the encrypted content using the decrypted content key. The method of claim 1, The storage device is a first storage device, The storage method, Receiving a command to move the content from the first storage device to a second storage device; Decrypting the encrypted content key using the first storage key; Encrypting the decrypted content key with a second storage key that is a storage key for the second storage device; Storing a content key file including the content key encrypted with the second storage key and the encrypted content in the second storage device; And And deleting the content key file and the encrypted content stored in the first storage device. The method of claim 1, The content key file further comprises a value for checking the integrity of the content key file. The method of claim 1, The content key file further comprises a recovery key that is a value obtained by encrypting the storage key with a third party's public key or the host's public key. A host for storing digital content on a storage device, A content encryption unit encrypting the content with a content key; A content key encryption unit encrypting the content key with a storage key which is a unique key for a storage device connected to the host; And And a storage control unit for storing the encrypted content key file and the encrypted content key in the storage device. The method of claim 13, The storage key is a first storage key which is a key generated by a portable security device connected to the host, The host, And receiving the first storage key from the portable security device, and deleting the first storage key from the host when the storage is completed. The method of claim 14, A storage key generation unit for determining whether a second storage key, which is a key generated by the host, for the storage device already exists in the host, and extracting or newly generating the second storage key according to the determination result; An updater to update the content key file using the second storage key; And And a storage key management unit encrypting the second storage key with the device key of the host and storing the second storage key in the host. The method of claim 15, The update unit, A storage key decryption unit that decrypts the encrypted first storage key using a device key of the portable security device; A content key decryption unit that decrypts a content key included in the content key file by using the decrypted first storage key; A content key encryption unit encrypting the decrypted content key with the second storage key; And And a key replacement unit for replacing the content key encrypted with the second storage key with the content key encrypted with the first storage key. The method of claim 13, The storage key is a second storage key which is a key generated by the host, The host, And storing the second storage key in the host by encrypting the second storage key with a device key of the host. The method of claim 17, And updating the content key file by using a first storage key which is a key generated by the portable security device connected to the host to the storage device. The method of claim 18, The update unit, A storage key decryption unit to decrypt the encrypted second storage key using a device key of the host; A content key decoder which decrypts a content key included in the content key file by using the decrypted second storage key; A content key encryption unit encrypting the decrypted content key with the first storage key; And And a key replacement unit for replacing the content key encrypted with the first storage key with the content key encrypted with the second storage key. The method of claim 13, A retrieval unit for retrieving the storage key from the host or a portable security device connected to the host when a reproduction request for the content is received; And And a content reproducing unit for selectively reproducing the encrypted content based on the search result. The method of claim 20, The content playback unit, And if the storage key is found as a result of the search, decrypts the content key included in the content key file using the storage key, and decrypts the encrypted content using the decrypted content key. The method of claim 13, The storage device is a first storage device, When a command for moving the content from the first storage device to the second storage device is received, the encrypted content key is decrypted using the first storage key and is a storage key for the second storage device. Encrypting the decrypted content key with a second storage key, storing the content key file including the content key encrypted with the second storage key and the encrypted content in the second storage device, and then storing the encrypted content key in the first storage device. The apparatus further comprises a content movement control unit for deleting the stored content key file and the encrypted content. The method of claim 13, The content key file further comprises a value for checking the integrity of the content key file. The method of claim 13, The content key file further comprises a recovery key which is a value obtained by encrypting the storage key with a third party's public key or the host's public key. A recording medium having recorded thereon a computer program for executing the method according to any one of claims 1 to 12.

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