WO2009104845A1

WO2009104845A1 - Method and apparatus for recording contents

Info

Publication number: WO2009104845A1
Application number: PCT/KR2008/004736
Authority: WO
Inventors: Kil-Soo Jung; Sung-Ryeul Rhyu; Joon-Hwan Kwon; Man-Seok Kang
Original assignee: Samsung Electronics Co., Ltd.
Priority date: 2008-02-19
Filing date: 2008-08-14
Publication date: 2009-08-27

Abstract

Provided are a method and apparatus for recording content. The method includes transmitting a first disc key of a first disc loaded into the recording apparatus to the server; receiving a first decryption key obtained by encrypting a title key of encrypted content with the first disc key, from the server; if a second disc loaded into the recording apparatus is not identical to the first disc, extracting the title key by decrypting the first decryption key with the first disc key; generating a second decryption key by encrypting the title key with a second disc key of the second disc; and recording the encrypted content and the second decryption key on the second disc. Accordingly, even if a title key encrypted with a disc key of a specific disc is recorded on a disc other than the specific disc, the content can be reproduced from the disc other than the specific disc.

Description

METHOD AND APPARATUS FOR RECORDING CONTENTS

Technical Field

[1] The present invention relates to a method and apparatus for recording content, and more particularly, to a method and apparatus for recording content by converting a title key encrypted with a disc key of a specific first disc into a title key encrypted with a disc key of a second disc and then recording the converted disc key on the second disc, so that even if the content is recorded on the second disc, the content can be reproduced from the second disc. Background Art

[2] Advances in digital technology have led to an increase in the amount and types of media signal recording apparatuses, such as digital televisions (DTV), digital versatile disc (DVD) players, and computers. Also, advances in communication technology have enabled a large amount of data to be sent or received within a short period of time via a wired/wireless communication network. Accordingly, a user can access a server managed by a content provider, including for example movie production companies and broadcasting companies, via a communication network, and then download content received from the server in the form of an audio signal, a video signal or a text signal to the user's recording apparatus. The user can use the downloaded content by recording the content on a hard disc included in the recording apparatus or an external storage unit inserted into the recording apparatus and then reproducing it therefrom. A storage medium on which a large amount of data can be recorded may be a DVD or a BD (Blue-ray disc).

[3] A digital rights management (DRM) technique is used in order to prevent a user from illegally copying or altering content downloaded from a server. The user can use the content after obtaining a right to revoke the DRM technique from a content provider. The DRM technique includes a content scrambling system (CSS) technique whereby content is reproduced through a multi-level decryption process using several keys. Through the CSS technique, it is possible to prevent content from being reproduced from a DVD by illegally copying the content to a hard disk driver (HDD), and prevent content stored in an HDD from being illegally recorded on and reproduced from another disc.

[4] FIG. 1 is a block diagram illustrating a method of reproducing content from a DVD

110 to which the CSS technique is applied. Referring to FIG. 1, encrypted disc keys, encrypted title keys and scrambled content are recorded on the DVD 110. A unique player key is allocated to a reproducing apparatus 120 that reproduces the content from the DVD 110. A player key is a value for decrypting an encrypted disc key. A unique player key is allocated to each reproducing apparatus that is to be capable of reproducing the content from the DVD 110. A disc key that is a unique disc value allocated to a disc, is information for decrypting an encrypted title key. The disc keys are encrypted with respective player keys which are allocated to reproducing apparatuses capable of recording data on or reproducing data from a disc, and are then recorded in a lead-in region of the DVD 110. The title key is a unique value allocated in a title of the content, and the title key is used to decipher all of the encrypted title or a part thereof. Each of the title keys is stored in a header section of the title in an encrypted form.

[5] If a user loads the DVD 110 into the reproducing apparatus 120 in order to reproduce the content from the DVD 110, the reproducing apparatus 120 reads the encrypted disc keys from the lead-in region of the loaded DVD 110. The reproducing apparatus 120 detects a disc key encrypted with the unique player key of the reproducing apparatus 120 from among the read disc keys being respectively encrypted using a plurality of player keys, and then decrypts the detected disc key with the unique player key of the reproducing apparatus 120 in order to extract the disc key. The reproducing apparatus 120 extracts a title key by deciphering an encrypted title key stored in the header section of a desired title by using the extracted disc key. Then, the reproducing apparatus 120 can reproduce the content from the DVD 110 by descrambling the scrambled content using the extracted title key.

[6] FIG. 2 is a diagram illustrating a CSS managed recording system. The CSS managed recording system allows content to be downloaded via a communication network and recorded on a blank disc by applying a system for protecting content which is equivalent to those used in commercially sold DVDs, i.e., the CSS technique. Referring to FIG. 2, the CSS managed recording system includes a recording apparatus 200, a server 220 and a communication network 210. The recording apparatus 200 is connected to the server 220 via the communication network 210. The server 220 is managed by a content provider, such as a broadcasting company or a movie production company, and stores an audio signal, a video signal, a text signal, or a meta data signal thereof.

[7] A user can access and log in the server 220, and then select and download desired content in a scrambled form from the server 220. The user loads a disc (not shown) into the recording apparatus 200 in order to record the downloaded scrambled content on the disc. The recording apparatus 200 reads an encrypted disc key from a lead-in region of the loaded disc. The recording apparatus 200 extracts a disc key by decrypting the encrypted disc key by using a unique player key of the recording apparatus 200, and transmits the extracted disc key to the server 220 via the communication network 210. The server 220 generates an encrypted title key by encrypting the disc key received from the recording apparatus 200 by using the title key of the content that is to be recorded by the user, and then transmits the encrypted title key to the recording apparatus 200 together with or without the scrambled content. The recording apparatus 200 can download the encrypted title key and the scrambled content from the server 220, and record, on the disc, the scrambled content and the encrypted title key that is used to decrypt the scrambled content in order to reproduce the content.

[8] As described above, the recording apparatus 200 transmits a disc key of a specific disc on which content is to be recorded to the server 220, downloads a title key encrypted with the disc key from the server 220, and then records the encrypted title key together with scrambled content on the disc, so that the scrambled content can be descrambled and reproduced. However, the encrypted title key and the scrambled content downloaded from the server 220 may not be successfully recorded on the disc due to a problem of the recording apparatus 200. In this case, the user may record the downloaded encrypted title key and scrambled content on a new disc. Also, if the user transmits a disc key of a specific disc to the server 220 and downloads the encrypted title key and the scrambled content from the server 220 by using the transmitted disc key, the encrypted title key and the scrambled content may be recorded, by the user's mistake, on a new disc other than the specific disc.

[9] In this case, a reproducing apparatus decrypts the encrypted title key by using a disc key allocated to the new disc. However, the encrypted title key has been encrypted using the disc key of the specific disc. Thus, if the encrypted title key is decrypted using the disc key of the new disc that is different from that of the specific disc, a title key whose value is different from that of the original title key is obtained. Since the scrambled content cannot be deciphered using the title key having a value different from that of the original title key, the reproducing apparatus will not be able to reproduce the content. Accordingly, when the encrypted title key generated using the disc key of the specific disc is recorded on a disc other than the specific disc, the content cannot be reproduced, thus leading to waste of the disc. Disclosure of Invention Technical Solution

[10] The present invention provides a method and apparatus for recording content in such a manner that even if a title key encrypted with a disc key of a specific disc is recorded on a disc other than the specific disc, the content can be reproduced from the disc other than the specific disc.

[11] The present invention also provides a method and apparatus for recording content in such a manner that a title key encrypted with a disc key of a specific disc can be recorded a predetermined number of times on a disc other than the specific disc. Advantageous Effects

[12] According to the above embodiments of the present invention, it is possible to provide a method and apparatus for recording content in such a manner that the content can be reproduced, even if a title key encrypted with a disc key of a specific disc is recorded on a disc other than the specific disc.

[13] Also, it is possible to provide a method and apparatus for recording content in such a manner that a title key encrypted using a disc key of a specific disc can be recorded on a disc other than the specific disc. Description of Drawings

[14] The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

[15] FIG. 1 is a block diagram illustrating a method of reproducing content from a disc to which a content scrambling system (CSS) technique is applied;

[16] FIG. 2 is a diagram illustrating a CSS managed recording system;

[17] FIG. 3 is a block diagram of a content recording apparatus according to an embodiment of the present invention;

[18] FIG. 4 is a flowchart illustrating a content recording method performed by the recording apparatus of FIG. 3, according to an embodiment of the present invention; and

[19] FIG. 5 is a flowchart illustrating a content recording method performed by the recording apparatus of FIG. 3, according to another embodiment of the present invention. Best Mode

[20] According to an aspect of the present invention, there is provided a content recording method performed by a recording apparatus communicating with a server with a communication network, the method comprising transmitting a first disc key of a first disc loaded into the recording apparatus to the server; receiving a first decryption key obtained by encrypting a title key of encrypted content with the first disc key, from the server; if a second disc loaded into the recording apparatus is not identical to the first disc, extracting the title key by decrypting the first decryption key with the first disc key; generating a second decryption key by encrypting the title key with a second disc key of the second disc; and recording the encrypted content and the second decryption key on the second disc.

[21] The transmitting of the first disc key to the server may include extracting an encrypted first disc key from the first disc; and extracting the first disc key by de- crypting the encrypted first disc key with a player key. The method may further include storing the first decryption key to belong to a group, together with the encrypted first disc key and the encrypted content. The method may further include extracting an encrypted second disc key from the second disc; and determining whether the encrypted second disc key is identical to the stored, encrypted first disc key, wherein if the encrypted second disc key is not identical to the encrypted first disc key, it is determined that the second disc is not identical to the first disc. The extracting of the title key may include determining whether the first decryption key and the encrypted content have ever been recorded on the first disc; and if the first decryption key and the encrypted content have never been recorded on the first disc, extracting the title key. The method may further include after the generating of the second decryption key, updating the stored first decryption key with the second decryption key, and updating the stored, encrypted first disc key with the encrypted second disc key; and after the recording of the encrypted content, the second decryption key on the second disc, deleting the second decryption key and the encrypted second disc key from the recording apparatus. The determining of whether the first decryption key and the encrypted content have ever been recorded may include determining that the first decryption key and the encrypted content have never been recorded on the first disc, when the first decryption key and the encrypted first disc key are stored in the recording apparatus. The group may include a recording indication identifier indicating whether the first decryption key and the encrypted content have ever been recorded on the first disc. The extracting of the title key may include extracting the recording indication identifier belonging to the group; determining whether the first decryption key and the encrypted content have ever been recorded on the first disc, using the recording indication identifier; and if the first decryption key and the encrypted content have never been recorded on the first disc, extracting the title key. The method may further include after the generating of the second decryption key, updating the stored first decryption key with the second decryption key, and updating the stored, encrypted first disc key with the encrypted second disc key; and after the recording of the encrypted content and the second decryption key on the second disc, updating the recording indication identifier so as to indicate that the encrypted content and the second decryption key are recorded.

[22] According to another aspect of the present invention, there is provided a recording apparatus for communicating with a server via a communication network, the apparatus comprising a communication unit exchanging information with the server via the communication network; a disc key decryption unit respectively extracting a first disc key and a second disc key from a first disc and a second disc which are loaded into the recording apparatus; a title key extraction unit extracting a title key of encrypted content by decrypting a first decryption key received from the server by using the first disc key, where the first decryption key is obtained by encrypting the title key with the first disc key; a decryption key generation unit generating a second decryption key by encrypting the title key with a second disc key of the second disc; a disc comparison unit determining whether the second disc loaded into the recording apparatus is identical to the first disc; a recording unit recording the content and the second decryption key on the disc; and a controller controlling the overall operation of the recording apparatus.

[23] According to another aspect of the present invention, there is provided a computer readable medium having recorded thereon a computer program for executing a content recording method performed by a recording apparatus communicating with a server with a communication network, the method comprising transmitting a first disc key of a first disc loaded into the recording apparatus to the server; receiving a first decryption key obtained by encrypting a title key of encrypted content with the first disc key, from the server; if a second disc loaded into the recording apparatus is not identical to the first disc, extracting the title key by decrypting the first decryption key with the first disc key; generating a second decryption key by encrypting the title key with a second disc key of the second disc; and recording the encrypted content and the second decryption key on the second disc. Mode for Invention

[24] This application claims the benefit of Korean Patent Application No.

10-2008-0014911, filed on February 19, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

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

[26] FIG. 3 is a block diagram of a content recording apparatus 200 according to an embodiment of the present invention. Referring to FIG. 3, the content recording apparatus 200 includes a user interface 310, a controller 320, a communication unit 330, a local storage unit 340, a recording unit 350, a storage medium 360, a disc key decryption unit 370, a disc comparison unit 380, a title key extraction unit 390, and a second decryption key generation unit 400. In some cases, although not shown, the recording apparatus 200 may further include a reading unit that reads data from the storage medium 360 or the local storage unit 340, and an output unit that performs signal processing on the read data and outputs the processing result.

[27] The recording apparatus 200 is connected to a server 220 via a communication network 210. The recording apparatus 200 can record content received from the server 220 on the storage medium 360 and may be a digital television (DTV), a computer, or a digital versatile disc (DVD) player. In the current embodiment, the recording apparatus 200 can perform a read operation in order to reproduce content from the storage medium 360 but the present invention is not limited thereto. That is, the recording apparatus 200 may be formed to only perform a write operation and not the read operation. The communication network 210 includes a wired/wireless communication network.

[28] The server 220 is managed by a content provider, such as a broadcasting company, a movie production company, or a general content creating company. The server 220 stores an audio signal, a video signal, a text signal, or a meta data signal thereof. In the present application, a title is used to be equivalent to content. In the present invention, since content contains an audio signal, a video signal, a text signal, or a meta data signal thereof, a title is used as an inclusive term including not only a video signal but also an audio signal, a text signal, and a meta data signal thereof. The server 220 scrambles various titles using at least one title key and stores the scrambled titles. Also, the server 220 stores title keys for decrypting the scrambled titles. Although FIG. 3 illustrates that the server 220 has a function of providing content, but a database (not shown) may perform the function of the server 220 in some cases.

[29] A user can receive user authentication by accessing and logging in the server 220, and then select and download desired content. If the desired content is not charge free, the user can download the content from the server 220 after paying a fee by transmitting payment information to the server 220.

[30] A user loads the storage medium 360, such as a disc, on which content is to be recorded into the recording apparatus 200. The recording apparatus 200 reads an encrypted disc key from a lead-in region of the loaded storage medium 360. The recording apparatus 200 extracts a disc key by decrypting the encrypted disc key with a unique player key of the recording apparatus 200, and transmits the extracted disc key to the server 301 via the communication network 210. The server 220 encrypts a title key of the content that is to be recorded by the disc key received from the recording apparatus 200, and then transmits the encrypted title key to the recording apparatus 200. Hereinafter, a disc key that is transmitted from the recording apparatus 200 to the server 220 and is used for the server 220 to encrypt a title key of content selected by a user, will be referred to as a 'first disc key', and a disc from which an encrypted first disc key is extracted will be referred to as a 'first disc'. Also, the result of encrypting the title key of the content with the first disc key will be referred to as a 'first decryption key'.

[31] The recording apparatus 200 downloads the title key encrypted using the first disc key, and encrypted (scrambled) content to the local storage unit 340, and stores them therein. The encrypted content may be downloaded either together with or separate from the first decryption key. [32] Then, upon receiving from the user a command that the encrypted title key and the encrypted content be recorded on a disc being currently loaded into recording apparatus 200, the recording apparatus 200 determines whether the current disc is identical to the first disc. A disc that is currently loaded into the recording apparatus 200 and on which the user instructs the encrypted content and encrypted title key stored in the local storage unit 340 to be recorded, will be referred to as a 'second disc', to be distinguished from the first disc.

[33] The recording apparatus 200 determines whether the second disc is identical to the first disc, and records the encrypted content and title key to the second disc only when they are identical to each other. If the second disc is not identical to the first disc, the recording apparatus 200 extracts a title key by decrypting the first decryption key with the first disc key. Since the first decryption key is obtained by encrypting the title key with the first disc key, the original title key can be extracted by decrypting the first decryption key by using the first disc key. The recording apparatus 200 encrypts the extracted title key with a second disc key of the second disc loaded into the recording apparatus 200. Hereinafter, a key obtained by encrypting a title key of content with a second disc key will be referred to as a 'second decryption key', so that the key can be distinguished from the first decryption key. The recording apparatus 200 records a second decryption key on the second disc, together with the encrypted content.

[34] The constitutional elements of the recording apparatus 200 will now be described in detail. The user interface 310 that acts as an interface with a user, delivers the user's command to the controller 320. The user interface 310 includes a physical transducer, such as a keyboard mouse, a touch screen, or a microphone, and receives a command, characters, numbers or voice information from the user and delivers it to the controller 320.

[35] The communication unit 330 accesses the server 220 or the database via the wired/ wireless communication network 210. Although not shown, if the communication unit 330 performs a radio communication, it may include a radio signal transceiving unit, a base-band processor, and a link controller. The base-band processor and the link controller exchange a control command and data with the controller 320 by exchanging host control interface (HCI) packets with the controller 320 while being connected to the controller 320 via an HCI. The radio communication may use a wireless local area network (WLAN), bluetooth, zigbee, or WiBro.

[36] The local storage unit 340 stores information downloaded from the server 220 or the data base by the communication unit 330. In the current embodiment, the local storage unit 340 downloads an encrypted content and a first decryption key from the server 220 and stores them, where the first decryption key is obtained by encrypting the title key with a first disc key. As described above, the first disc key is a disc key that the recording apparatus 200 transmits to the server 220, and is used for the server 220 to encrypt a title key for predetermined content.

[37] The local storage unit 340 stores the first decryption key and the encrypted content to belong to the same group as the encrypted first disc key. In some cases, each of a plurality of groups may further include a recording indication identifier indicating whether a decryption key and encrypted content belonging to the same group as the recording indication identifier are recorded on a disc. The recording indication identifier prevents an unauthorized user from illegally recording the content stored in the local storage unit 340 on a plurality of discs. Once encrypted content and a decryption key thereof are recorded on a predetermined disc, the value of the recording indication identifier is changed in order to indicate that they have been recorded. For example, the value of the recording indication identifier is set to zero (0) when the encrypted content and the decryption key belonging to the same group as the recording indication identifier have never been recorded on the predetermined disc. After the encrypted content and the decryption key are recorded on the predetermined disc, the value of the recording indication identifier is changed to T. If the recording indication identifier has a value of T, the controller 320 determines that the encrypted content and the decryption key have already been recorded and then does not give a command that they be recorded on a disc. In some cases, the controller 320 may control the output unit to create and output an image indicating that a decryption key and encrypted content belonging to a group having a recording indication identifier whose value is T cannot be further recorded on a disc.

[38] Alternatively, a decryption key and an encrypted disc key belonging to a group may be deleted in order to indicate whether the decryption key and encrypted content belonging to the group are recorded on a disc. As described above, encrypted content, a group includes a decryption key for decrypting the encrypted content, and an encrypted disc key which is used to generate the decryption key. Once the encrypted content and the decryption key are recorded on a predetermined disc, the recording apparatus 200 can delete the decryption key and the encrypted content from the local storage unit 340. If a group from which a decryption key and an encrypted disc key are deleted is detected from among groups stored in the local storage unit 340, the controller 320 determines that encrypted content and the decryption key belonging to the detected group cannot further be recorded on a disc. In some cases, the controller 340 may control the output unit to create and output an image indicating that encrypted content belonging to a group from which a decryption key and an encrypted disc key are deleted cannot be further recorded on a disc.

[39] The recording unit 350 records the first decryption key and encrypted content stored in the local storage unit 340 on the storage medium 360 loaded into the recording apparatus 200.

[40] The disc key decryption unit 370 extracts the disc key from the storage medium 360 loaded into the recording apparatus 200. If the first disc is loaded into the recording apparatus 200, the disc key decryption unit 370 extracts the encrypted first disc key from the first disc, and obtains the first disc key by deciphering the encrypted first disc key with the unique player key of the recording apparatus 200. The disc key decryption unit 370 transmits the obtained first disc key to the server 220 via the communication unit 330. Then, if the second disc is loaded into the recording apparatus 200, the disc key decryption unit 370 extracts an encrypted second disc key from the second disc, and transmits it to the disc comparison unit 380. Also, the disc key decryption unit 370 obtains the first disc key from the encrypted first disc key stored in the local storage unit 340 and transmits it to the title key extraction unit 390, so that the title key extraction unit 390 can decipher the first decryption key with the first disc key. Also, the disc key decryption unit 370 obtains the second disc key by deciphering the encrypted second disc key extracted from the second disc by using the unique player key of the recording apparatus 200 and then transmits the second disc key to the second decryption key generation unit 400, so that the second decryption key generation unit 400 can generate the second decryption key by encrypting the title key with the second disc key.

[41] The disc comparison unit 380 determines whether the second disc loaded into the recording apparatus 200 is identical to the first disc. To this end, the disc comparison unit 380 receives the encrypted second disc key from the disc key extraction unit 380, reads the encrypted first disc key from the local storage unit 340, and determines whether the encrypted second disc key is identical to the encrypted first disc key. The disc comparison unit 380 provides the result of determining to the controller 320.

[42] If a command that content be recorded on the second disc loaded into the recording apparatus 200 is given from a user and the second disc is not identical to the first disc, the title key extraction unit 390 receives the first disc key from the disc key decryption unit 370, reads the first decryption key from the local storage unit 340, and decrypts the first decryption key with the first disc key. The first decryption key stored in the local storage unit 340 has been encrypted with the first disc key, and thus, the original title key can be obtained by decrypting the first decryption key with the first disc key. The title key extraction unit 90 extracts the title key and transmits it to the second decryption key generation unit 400.

[43] The second decryption key generation unit 400 receives the title key from the title key extraction unit 390 and the second disc key from the disc key decryption unit 370. The second decryption key generation unit 400 generates the second decryption key by encrypting the title key with the second decryption key. The second decryption key generation unit 400 transmits the second decryption key to the local storage unit 340.

[44] The controller 320 controls the overall operation of the recording apparatus 200 in order to perform a content recording method according to the present invention. The controller 320 includes an arithmetic logic unit (ALU) that makes a calculation, and a register that temporarily stores data and commands.

[45] The controller 320 controls the disc key decryption unit 370 to extract the first disc key from the loaded storage medium 360. The controller 320 transmits the first disc key to the server 220 via the communication unit 330. The recording apparatus 200 downloads the title key for the content encrypted with the first disc key from the server 220. The local storage unit 340 stores the downloaded first decryption key and encrypted content to belong to the same group, together with the encrypted first disc key.

[46] Next, upon receiving a command that the encrypted content and the decryption key stored in the local storage unit 340 be recorded on the currently loaded second disc, from a user via the user interface 310, the recording apparatus 200 determines whether the second disc is identical to the first disc. To this end, the controller 320 controls the disc comparison unit 370 to determine whether the encrypted first disc key stored to belong to the same group as the scrambled content and the first decryption key is identical to the encrypted second disc key of the second disc. When the encrypted first disc key is identical to the encrypted second disc key, the controller 320 determines that the first disc is identical to the second disc, and controls the recording unit 350 to record the encrypted content and first decryption key on the second disc.

[47] When the encrypted first disc key is not identical to the encrypted second disc key, the controller 320 determines that the first disc is not identical to the second disc, and controls the recording unit 350 to not record the encrypted content and first decryption key on the second disc. The controller 320 controls the disc key decryption unit 370 to extract the second disc key from the second disc key and transmit it to the title key extraction unit 390. The controller 320 controls the title key extraction unit 390 to obtain the title key by decrypting the first decryption key, which is stored in the local storage unit 340, with the second key. The controller 320 controls the second decryption key generation unit 400 to generate the second decryption key by encrypting the title key with the second disc key. If the second decryption key is generated, the controller 320 updates the first decryption key stored in the local storage unit 340 with the second decryption key. That is, the controller 320 controls the local storage unit 340 to cancel the stored first decryption key and store the second decryption key instead of the first decryption key. Also, the controller 320 allows the encrypted first disc key to be canceled from the local storage unit 340 and the encrypted second disc key to be stored in the local storage unit 340 instead of the encrypted first disc key. Thus, the encrypted content, the second decryption key, and the encrypted second disc key are stored to belong to the same group in the local storage unit 340. As described above, a recording indication identifier may further be included in the group. The controller 320 controls the recording unit 350 to record the encrypted content and the second decryption key on the second disc. After the encrypted content and the second decryption key are recorded on the second disc, the controller 320 deletes them from the group, or updates a recording indication identifier to a value indicating that the encrypted content and the second decryption key have already been recorded when the recording indication identifier is included in the group.

[48] The reading unit reads data from the local storage unit 340 or the storage medium

360 and transmits the read data to the output unit. The output unit decodes the read data in order to convert it in a format in which the data can be output, and then outputs the converted signal. Also, the output unit outputs the overall state of the recording apparatus 200 or information input by a user via the user interface 310, using a screen or a speaker. Although not shown, the output unit includes a display unit that outputs a video signal and a speaker that outputs an audio signal. The output unit may include an on-screen display (OSD) processor that creates and outputs a user controlled list. In some cases, the out unit may create and output an image indicating that data requested by a user cannot be recorded on the second disc.

[49] FIG. 4 is a flowchart illustrating a content recording method performed by the recording apparatus 200 of FIG. 3, according to an embodiment of the present invention. Referring to FIG. 4, the recording apparatus 200 extracts an encrypted first disc key from a first disc loaded into the recording apparatus 200, and obtains a first disc key by decoding the encrypted first disc key with a unique player key of the recording apparatus 200. The recording apparatus 200 transmits the first disc key to the server 220 via the communication unit 330 (operation 401).

[50] A user can select and download content to be recorded on the storage medium 360 by accessing the server 220. The server 220 generates a first decryption key by encrypting the selected content with the first disc key. The recording apparatus 200 receives the first decryption key from the server 220 (operation 403).

[51] The recording apparatus 200 stores the first decryption key to belong to the same group, together with encrypted content, an encrypted first disc key, and a recording indication identifier (operation 405). As described above, the recording indication identifier indicates whether the encrypted content and the first decryption key belonging to the group are recorded on a first disc. The recording indication identifier is set to '0' before the encrypted content and the first decryption key are recorded on the first disc, and is set to T after the encrypted content and the first decryption key are recorded on the first disc. [52] Upon receiving a command that the first decryption key and the encrypted content be recorded on a currently loaded second disc from a user (operation 407), the recording apparatus 200 determines whether they have ever been recorded on a predetermined disc (operation 409). To this end, the recording apparatus 200 extracts the recording indication identifier stored in the local storage unit 340, together with the first decryption key and the encrypted content, and then determines whether the value of the recording indication identifier is '0' or T. If the value of the recording indication identifier is T, the recording apparatus 200 determines that the first decryption key and the encrypted content have been recorded on the predetermined disc and does not record them on the second disc any more. In some cases, the recording apparatus may create and output an image indicating that recording cannot be performed.

[53] If the value of the recording indication identifier is '0', the recording apparatus 200 determines that the first decryption key and the encrypted content have never been recorded, and then determines whether the first disc is identical to the second disc (operation 411). In order to determine whether the first disc is identical to the second disc, the recording apparatus 200 extracts the encrypted first disc key from the local storage unit 340, and obtains the first disc key by decrypting the encrypted first disc key with a player key of the recording apparatus 200. The recording apparatus 200 extracts a second disc key from the second disc key loaded thereinto, and compares the first disc key with the second disc key.

[54] If the first disc key is identical to the second disc key, the recording apparatus 200 records the first decryption key and the encrypted content on the second disc (operation 423). If the first disc key is not identical to the second disc key, the recording apparatus 200 extracts the first decryption key from the local storage unit 340, and obtains a title key by decrypting the first decryption key with the first disc key (operation 413). The recording apparatus 200 generates a second decryption key by encrypting the title key with the second disc key (operation 415). The recording apparatus 200 respectively updates the first decryption key and the encrypted first disc key stored in the local storage unit 340 with the second decryption key and the encrypted second disc key, and then stores the second decryption key and the encrypted second disc key (operation 417). The recording apparatus 200 records the second decryption key and the encrypted content on the second disc (operation 419). After operation 419, the recording apparatus updates the value of the recording indication identifier with T (operation 421). Accordingly, even if a user gives a command that the second decryption key and the encrypted content be recorded on the second disc, the recording apparatus 200 does not record them on the second disc by checking that the value of the recording indication identifier is T.

[55] FIG. 5 is a flowchart illustrating a content recording method performed by the recording apparatus 200 of FIG. 3, according to another embodiment of the present invention. Referring to FIG. 5, the recording apparatus 200 extracts an encrypted first disc key from a first disc loaded thereinto, and obtains a first disc key by decrypting the encrypted first disc key with its player key. The recording apparatus 200 transmits the first disc key to the server 220 (operation 501). The server 220 generates a first decryption key by encrypting a title key of desired content by using the first disc key and transmits it to the recording apparatus 200. The recording apparatus 200 receives the first decryption key from the server 220 (operation 503). The recording apparatus 200 stores the first decryption key to belong to a group identified by a content identifier, together with encrypted content and the encrypted first disc key (operation 505). When receiving from a user a command that a first decryption key and encrypted content belonging to a group identified by a specific content identifier be recorded on a second disc (operation 507), the recording apparatus 200 determines whether the first decryption key and the encrypted content have ever been recorded on a predetermined disc (operation 509). The recording apparatus 200 may determine whether the first decryption key and the encrypted content have been recorded on the predetermined disc by checking whether the first decryption key and the encrypted first disc key are stored in the local storage unit 340. If the first decryption key and the encrypted content have yet to be recorded on the predetermined disc, the recording apparatus 200 determines whether the second disc is identical to the first disc (operation 511). If the second disc is identical to the first disc, the recording apparatus 200 records the first decryption key and the encrypted content on the second disc (operation 523). Then, the first decryption key and the encrypted first disc key are deleted from local storage unit (operation 525). [56] If the second disc is not identical to the first disc, the recording apparatus 200 extracts the first decryption key from the local storage unit 340, and extracts a title key by decrypting the first decryption key with the first disc key (operation 513). The recording apparatus 200 generates a second decryption key by encrypting the title key with a second disc key (operation 515). The recording apparatus 200 respectively updates the first decryption key and an encrypted first disc key stored in the local storage unit 340 with the second decryption key and an encrypted second disc key (operation 517). The recording apparatus 200 records the second decryption key and the encrypted content on the second disc (operation 519). After completing the recording, the recording apparatus deletes the second decryption key and the encrypted second disc key from the local storage unit 340 (operation 521). Thus, even if a command that the second decryption key and the encrypted content be recorded on the second disc is later given from a user, the recording apparatus 200 does not perform the recording by checking that the second decryption key and the encrypted second disc have been deleted from the local storage unit 340.

[57] The present invention can be embodied as computer readable code in a computer readable medium. Here, the computer readable medium may be any recording apparatus capable of storing data that is read by a computer system, e.g., a read-only memory (ROM), a random access memory (RAM), a compact disc (CD)-ROM, a magnetic tape, a floppy disk, an optical data storage device, and so on. Also, the computer readable medium may be a carrier wave that transmits data via the Internet, for example. The computer readable medium can be distributed among computer systems that are interconnected through a network, and the present invention may be stored and implemented as computer readable code in the distributed system. A function program, code and code segments for embodying the present invention may be easily derived by computer programmers skilled in the art to which the present invention pertains.

[58] While this invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

[1] L A content recording method performed by a recording apparatus communicating with a server with a communication network, the method comprising: transmitting a first disc key of a first disc loaded into the recording apparatus to the server; receiving a first decryption key obtained by encrypting a title key of encrypted content with the first disc key, from the server; if a second disc loaded into the recording apparatus is not identical to the first disc, extracting the title key by decrypting the first decryption key with the first disc key; generating a second decryption key by encrypting the title key with a second disc key of the second disc; and recording the encrypted content and the second decryption key on the second disc.

[2] 2. The method of claim 1, wherein the transmitting of the first disc key to the server comprises: extracting an encrypted first disc key from the first disc; and extracting the first disc key by decrypting the encrypted first disc key with a player key.

[3] 3. The method of claim 2, further comprising storing the first decryption key to belong to a group, together with the encrypted first disc key and the encrypted content.

[4] 4. The method of claim 3, further comprising: extracting an encrypted second disc key from the second disc; and determining whether the encrypted second disc key is identical to the stored, encrypted first disc key, wherein if the encrypted second disc key is not identical to the encrypted first disc key, it is determined that the second disc is not identical to the first disc.

[5] 5. The method of claim 4, wherein the extracting of the title key comprises: determining whether the first decryption key and the encrypted content have ever been recorded on the first disc; and if the first decryption key and the encrypted content have never been recorded on the first disc, extracting the title key.

[6] 6. The method of claim 5, further comprising: after the generating of the second decryption key, updating the stored first decryption key with the second decryption key, and updating the stored, encrypted first disc key with the encrypted second disc key; and after the recording of the encrypted content, the second decryption key on the second disc, deleting the second decryption key and the encrypted second disc key from the recording apparatus.

[7] 7. The method of claim 6, wherein the determining of whether the first decryption key and the encrypted content have ever been recorded comprises determining that the first decryption key and the encrypted content have never been recorded on the first disc, when the first decryption key and the encrypted first disc key are stored in the recording apparatus.

[8] 8. The method of claim 3, wherein the group comprises a recording indication identifier indicating whether the first decryption key and the encrypted content have ever been recorded on the first disc.

[9] 9. The method of claim 8, wherein the extracting of the title key comprises: extracting the recording indication identifier belonging to the group; determining whether the first decryption key and the encrypted content have ever been recorded on the first disc, using the recording indication identifier; and if the first decryption key and the encrypted content have never been recorded on the first disc, extracting the title key.

[10] 10. The method of claim 9, further comprising: after the generating of the second decryption key, updating the stored first decryption key with the second decryption key, and updating the stored, encrypted first disc key with the encrypted second disc key; and after the recording of the encrypted content and the second decryption key on the second disc, updating the recording indication identifier so as to indicate that the encrypted content and the second decryption key are recorded.

[11] 11. A recording apparatus for communicating with a server via a communication network, the apparatus comprising: a communication unit exchanging information with the server via the communication network; a disc key decryption unit respectively extracting a first disc key and a second disc key from a first disc and a second disc which are loaded into the recording apparatus; a title key extraction unit extracting a title key of encrypted content by decrypting a first decryption key received from the server by using the first disc key, where the first decryption key is obtained by encrypting the title key with the first disc key; a decryption key generation unit generating a second decryption key by encrypting the title key with a second disc key of the second disc; a disc comparison unit determining whether the second disc loaded into the recording apparatus is identical to the first disc; a recording unit recording the content and the second decryption key on the disc; and a controller controlling the overall operation of the recording apparatus.

[12] 12. The apparatus of claim 11, wherein the disc key decryption unit extracts an encrypted first disc key from the first disc, and extracts the first disc key by decrypting the encrypted first disc key with a player key.

[13] 13. The apparatus of claim 12, further comprising a local storage unit storing the received first decryption key to belong to a group, together with the encrypted first disc key and the encrypted content.

[14] 14. The apparatus of claim 13, wherein the disc key decryption unit extracts an encrypted second disc key from the second disc, and the disc comparison unit determines that the second disc is not identical to the first disc when the encrypted second disc key is not identical to the encrypted first disc key.

[15] 15. The apparatus of claim 14, wherein the controller determines whether the first decryption key and the encrypted content have ever been recorded on the first disc, and controls the title key extraction unit to extract the title key, when the first decryption key and the encrypted content have never been recorded on the first disc.

[16] 16. The apparatus of claim 15, wherein the local storage unit updates the stored first decryption key with the second decryption key and the stored, encrypted first disc key with the encrypted second disc key when the second decryption key is generated, and deletes the second decryption key and the encrypted second disc key from the recording apparatus when the encrypted content and the second decryption key are recorded on the second disc.

[17] 17. The apparatus of claim 16, wherein the controller determines that the first decryption key and the encrypted content have never been recorded on the first disc, when the encrypted second disc key is not identical to the encrypted first disc key.

[18] 18. The apparatus of claim 13, wherein the group comprises a recording indication identifier indicating whether the first decryption key and the encrypted content have ever been recorded on the first disc.

[19] 19. The apparatus of claim 18, wherein the controller determines whether the first decryption key and the encrypted content have ever been recorded on the first disc by extracting the recording indication identifier belonging to the group, and controls the title key extraction unit to extract the title key when the first decryption key and the encrypted content have never been recorded on the first disc. [20] 20. The apparatus of claim 19, wherein the local storage unit updates the stored first decryption key with the second decryption key and the stored, encrypted first disc key with the encrypted second disc key when the second decryption key is generated, and updates the recording indication identifier so as to indicate that the encrypted content and the second decryption key are recorded on the second disc when the encrypted content and the second decryption key are recorded on the second disc. [21] 21. A computer readable medium having recorded thereon a computer program for executing a content recording method performed by a recording apparatus communicating with a server with a communication network, the method comprising: transmitting a first disc key of a first disc loaded into the recording apparatus to the server; receiving a first decryption key obtained by encrypting a title key of encrypted content with the first disc key, from the server; if a second disc loaded into the recording apparatus is not identical to the first disc, extracting the title key by decrypting the first decryption key with the first disc key; generating a second decryption key by encrypting the title key with a second disc key of the second disc; and recording the encrypted content and the second decryption key on the second disc.