Method of transferring rights object and electronic device

A method of transferring a rights object (RO) and an electronic device are provided. The method includes generating a secure RO by encrypting an RO including usage rights information regarding digital content and transferring the secure RO from a first device to a second device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Methods consistent with the present invention relate to transferring a rights object (RO) and an electronic device, and more particularly, to transferring an RO and an electronic device which can prevent an RO from being copied during the transfer of the RO.

2. Description of the Related Art

In recent years, research has been vigorously conducted on Digital Rights Management (DRM), which is a technology for protecting digital content that can be easily copied and distributed, and various services adopting DRM technology have been or are currently being commercialized.

Related art techniques of protecting digital content generally focus on the prevention of illegitimate access to digital content. For example, in the related art, only users who have paid charges for digital content are allowed to access the digital content, whereas users who have not paid any charges for the digital content are not allowed to access the digital content.

Due to the characteristics of digital data, digital content can be easily reused, processed, copied, and distributed. Therefore, if digital content is illegitimately copied or distributed by users who have access to the digital content, the digital content can be used even by users who have not paid any charges for the digital content and are thus not eligible for the digital content.

In order to address this, DRM technology requires encryption of digital content for safe distribution of digital content and also requires a predetermined license, called a Rights Object (RO), for the use of digital content.

Referring toFIG. 1, a user who wishes to use digital content may be provided with desired digital content by a content provider120with a host device110. The digital content provided by the content provider120is encrypted. In order to use encrypted digital content (hereinafter referred to as a content item), an RO is necessary.

The user may purchase an RO including the right to execute a content item from an RO issuer130using the host device110. The right to execute the content item may be a content encryption key that is necessary to decrypt the content item.

The RO issuer130may report a statement regarding the issuance of ROs to the content provider120. The RO issuer130may be the same entity as the content provider120.

A user can use a content item by acquiring an RO corresponding to the content item.

A content item can be freely copied to or distributed to a number of users without an RO. An RO includes usage restriction information regarding the number of times that a content item can be used, a period of time for which the content item can be used, and/or the number of times that the RO can be copied, and thus imposes restrictions on the reuse or copy of content.

In short, it is possible to effectively protect digital content using DRM technology

A user may store an RO in a host device such as a mobile phone or a personal digital assistant (PDA) which can execute multimedia data.

In order to facilitate the maintenance and distribution of content items and ROs, methods of storing ROs in portable storage devices such as memory sticks or multimedia cards (MMCs) have been developed.

FIG. 2illustrates a flowchart of a related art method of transferring an RO present in a host device110to a portable storage device140. When the portable storage device140is connected to the host device110, a user can execute an RO transfer command for transferring an RO from the host device110to the portable storage device140.

Referring toFIG. 2, in operation S110, the host device110transfers an RO to the portable storage device140upon execution of an RO transfer command. In operation S120, when the transfer of the RO is complete, the portable storage device140notifies the host device110of the completion of the RO transfer. In operation S130, the host device110removes the RO present therein upon being notified that the transfer of the RO has been completed.

If the method is terminated abnormally at a time A between operation S110and operation S120, the host device110cannot be notified of whether the transfer of the RO has been completed and thus may not be able to decide when to remove the RO present therein. As a result, the RO remains in both the host device110and the portable storage device140. That is, the RO is copied during the transfer of the RO.

SUMMARY OF THE INVENTION

The present invention provides a method of transferring an RO and an electronic device which can prevent an RO from being copied during the transfer of the RO.

According to an aspect of the present invention, there is provided a method of transferring a RO including usage rights information regarding digital content, the method including generating a secure RO by encrypting the RO and transferring the secure RO from a first device to a second device.

According to another aspect of the present invention, there is provided an electronic device, including a storage module which stores an RO including usage rights information regarding digital content, an encryption module which generates a secure RO by encrypting the RO, an interface module which enables the electronic device to interface with an external device, and a control module which controls the encryption module to generate the secure RO and transfers the secure RO to the external device via the interface module.

According to another aspect of the present invention, there is provided an electronic device, including an interface module which enables the electronic device to interface with an external device that transmits an encrypted RO, a storage module which stores the encrypted RO, a decryption module which decrypts the encrypted RO, and a control module which controls the decryption module to decrypt the encrypted RO and stores a decrypted RO obtained by the decryption performed by the decryption module in the storage module.

For a better understanding of the present invention, the definitions of the terms frequently used in this disclosure will be given below.

The term ‘transfer’ denotes a process of moving a file from one device to another. During the transfer of a file, the file may exist in two devices at the same time. However, once the transfer of a file from a first device to a second device is completed, the file must not exist in the first device any longer, but must exist only in the second device.

The term ‘copy’ denotes a process of duplicating a Rights Object (RO) so that the RO can become available in two or more devices.

The present invention is described hereinafter with reference to flowchart illustrations of user interfaces, methods, and computer program products according to exemplary embodiments of the invention. It will be understood that each block of the flowchart illustrations, and combinations of blocks in the flowchart illustrations, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which are executed via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart block or blocks.

FIG. 3illustrates a block diagram of a system for transferring an RO according to an exemplary embodiment of the present invention. Referring toFIG. 3, the system includes a host device10in which an RO is stored and a portable storage device20which can be connected to the host device10.

The host device10reproduces and manages digital content according to the rights defined in the RO present in the host device10. The host device10may be a multimedia device such as a mobile phone, a personal digital assistant (PDA), a laptop computer, a desktop computer, or a digital television.

The portable storage device20includes a nonvolatile memory such as a flash memory which can read, write, and erase data. The portable storage device20has data processing capabilities and can be easily connected to or detached from the host device10. The portable storage device20may be a Smart Media (SM) card, a memory stick, a Compact Flash (CF) card, an eXtreme Digital (XD) card, or a multimedia card.

The host device10includes a storage module12which stores an RO, an encryption module14which encrypts an RO, an interface module16which enables the host device10to interface with the portable storage device20, and a control module18which controls the storage module12, the encryption module14, and the interface module16.

The RO present in the storage module12is a type of license including rights information regarding the right to use a content item, use restriction information regarding restrictions imposed on the use of the content item, copy restriction information regarding restrictions imposed on the copy of an RO, an identifier of the RO, and an identifier of the content item.

The rights information regarding the right to use a content item may be a content encryption key (CEK) which is necessary to decode a content item.

The encryption module14encrypts the RO present in the storage module12upon the request of the control module18and generates an encrypted RO.

More specifically, the encryption module14extracts a CEK from an RO, and encrypts the RO by encrypting the CEK using an encryption key. However, the present invention is not restricted to this. The encryption module14may extract one or more pieces of information, other than the CEK, from an RO and encrypt the extracted pieces of information. Once an RO is encrypted, content corresponding to the RO cannot be used until the RO is decrypted. Hereinafter, the RO having some specific fields encrypted by the encryption key, which only host device knows, is referred to as the secure RO.

The interface module16enables the host device10to interface with the portable storage device20. The host device10transmits data to or receives data from the portable storage device20through the interface16. When the host device10is connected to the portable storage device20, the interface module16of the host device10may be electrically connected to an interface module22of the portable storage device20. However, the present invention is not restricted to this. That is, when the host device10is connected to the portable storage device20, the interface module16of the host device10may not necessarily be directly connected to the interface module22of the portable storage device20, and may communicate with the interface module22of the portable storage device20with the aid of a wireless medium. In addition, the interface module16of the host device10and the interface module22of the portable storage device20may conduct mutual authentication and secure communication apart from processing the secure RO. The secure communication means that the transferred data, including the secure RO, are encrypted by the session key generated during the mutual authentication step.

When an RO transfer command is received from a user, the control module18controls the encryption module14to encrypt the RO present in the storage module12and stores a secure RO obtained by the encryption performed by the encryption module14in the storage module12. Thereafter, the control module18transfers the secure RO to the portable storage device20via the interface module16. The RO transfer command may be received from the user by an input module (not shown). Alternatively, the control module18may transfer the RO present in the storage module12to the portable storage device20upon connecting the portable storage device20to the host device10.

When the portable storage device20notifies the control module18, via the interface module16, that the transfer of the secure RO has been complete, the control module18removes the secure RO present in the storage module12.

Thereafter, the control module18issues a request for decryption of the secure RO to the portable storage device20via the interface module16. In this case, the control module18transmits the encryption key used to produce the secure RO to the portable storage device20.

The portable storage device20includes the interface module22, a storage module24, a decryption module26, and a control module28.

The interface module22enables the portable storage device20to interface with the host device10. The portable storage device20transmits data to or receives data from the host device10via the interface module22.

The storage module24stores a secure RO received by the interface module22. A secure RO may have an identification module (not shown) by which the secure RO can be distinguished from an RO yet to be encrypted. Alternatively, an identification module capable of distinguishing a secure RO from an RO yet to be encrypted may be provided as an independent module.

The decryption module26decrypts the secure RO present in the storage module24upon the request of the control module28. In detail, the decryption module26decrypts the secure RO present in the storage module24using the encryption key received from the host device10via the interface module22.

The control module28identifies a secure RO received by the interface module22and stores the secure RO in the storage module24. When a request for decryption of the secure RO is issued by the host device10, the control module28controls the decryption module26to decrypt the secure RO and stores a decrypted secure RO obtained by the decryption module26in the storage module24. Also, the control module28notifies the host device10, via the interface module22, that the decryption of the secure RO has been completed.

FIG. 4illustrates a flowchart of a method of transferring an RO according to an exemplary embodiment of the present invention. Referring toFIG. 4, in operation S10, when an RO transfer command is received from a user, the encryption module14of the host device10generates a secure RO by extracting a CEK of an RO present in the storage module12and encrypting the CEK with a encryption key under the control of the control module18. In operation S12, the control module18stores the secure RO in the storage module12. The RO stored in the host device10needs to be prevented from being used by the host device10before successfully transferring the RO to the portable storage device20because it is not desirable that the state information of the transferred secure RO differs from the state information of the RO stored in the host device10. That is, the host device10stores the secure RO instead of the existing RO to maintain the consistency of two ROs stored in the host device10and the portable storage device20. But, the control module18may not store the secure RO in the storage module12. If the state information of the transferred secure RO differs from the state information of the RO stored in the host device10, the transferred secure RO may be removed, and the transfer process may restart. In operation S14, the control module18transmits the secure RO to the portable storage device20via the interface module16.

In operation S16, the control module28of the portable storage device20receives the secure RO transmitted by the control module18of the host device10via the interface module22and stores the secure RO in the storage module24. In operation S18, the control module28notifies the host device10, via the interface module22, that the transfer of the secure RO has been completed.

In operation S20, the control module18of the host device10removes the secure RO present in the storage module12upon being notified that the transfer of the secure RO has been completed.

In operation S22, the control module18issues a request for decryption of the secure RO to the portable storage device20via the interface module16. In this case, the control module18transmits the encryption key used to produce the secure RO to the portable storage device20.

In operation S24, the control module28of the portable storage device20controls the decryption module26to decrypt the secure RO using the encryption key transmitted by the control module18of the host device10. In operation S26, the control module28stores a decrypted RO obtained by the decryption performed by the decryption module26in the storage module24. In operation S28, the control module28notifies the host device10, via the interface module22, that the decryption of the secure RO has been completed.

Even if the method is terminated abnormally at a time B between operation S16and operation S18, an RO present in the host device10and the portable storage device20, respectively, cannot be used because the RO is still encrypted. Therefore, it is possible to prevent an RO from being copied.

If the host device10does not remove the secure RO present in the storage module12in operation S20, the secure RO can be used later by decrypting the secure RO. However, the secure RO present in the portable storage device20can be transferred to but not used by other devices. In order to use the secure RO present in the portable storage device20, the user must perform the above-described method of transferring an RO.

In the above-described exemplary embodiments, a CEK of an RO is encrypted before the transfer of the RO so that the RO cannot be used unless decrypted. Therefore, even if an RO exists in two devices at the same time, the copy of the RO can be prevented, and the use of the RO can be allowed only when the transfer of the RO is properly completed. In the above-described exemplary embodiments, an RO present in the host device10is encrypted, and the encrypted RO is transferred to the portable storage device20. However, the present invention is not restricted to this and the present invention may be applied to the transfer of an RO from a portable storage device to a host device, from one host device to another host device, and from one portable storage device to another portable storage device.

As described above, according to the present invention, it is possible to prevent an RO from being copied during the transfer of the RO.