JP2009015873A - Storage medium and content protection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a storage medium, capable of protecting contents by preliminarily registering revocation information in a specific storage area of the storage medium to thereby invalidate, when the storage medium is installed to unauthorized electronic equipment shown by the revocation information and used, the electronic equipment. <P>SOLUTION: A revocation list RL from which PD (recording and reproducing device) to be invalidated for content protection can be discriminated is preliminarily registered in a read-only disclosure ROM area 132 ensured on PM (storage medium) 13. When the PM 13 is installed to LCM (content use management system) or PD and used, a controller 130 provided on the PM 13 receives information showing the equipment from the LCM or PD, refers to the revocation list RL based on the information, and determines whether the equipment is invalidated or not according to the reference result. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a storage medium used for recording and reproducing various digital contents typified by image data and music data, and particularly suitable for suppressing recording and reproduction of contents by an unauthorized electronic device and The present invention relates to a content protection method.

  2. Description of the Related Art In recent years, with the development of computer technology, various electronic devices such as multimedia-compatible personal computers, set top boxes, players, and game machines have been developed. This type of electronic device can reproduce various digital contents such as image data and music data stored in a recording medium, and can also download and use digital contents through the Internet or the like.

  These digital contents can be copied or downloaded without degrading quality by adopting digital encoding technology such as MPEG2 and MP3. For this reason, recently, from the viewpoint of copyright protection, the need for a technique for protecting such digital contents from unauthorized use has been screamed.

  However, many storage media used in electronic devices such as personal computers, set-top boxes, players and the like can be recorded / reproduced even when moved to another device, and the specifications are basically open. For this reason, since the content can be freely moved / copied, it is practically difficult to protect the content stored in the storage medium from unauthorized copying / moving.

  Therefore, a storage medium in which the storage medium unit and the controller are integrated, such as a memory card, is provided with an inaccessible area (secret area) that can be accessed only by a specific procedure that is hidden and cannot be accessed by the user. It is conceivable to protect the content by storing important information necessary for using the content such as copy control information and movement control information.

  In this case, when content is copied / moved between an electronic device such as a personal computer, a set-top box, or a player and a storage medium, each of them has a predetermined mechanism relating to copyright protection (content protection). The content protection function) is mutually authenticated as to whether it is a legitimate one, and if it is authenticated, a common authentication key is obtained individually by exchanging keys according to the key generation algorithm shared with each other. The authentication key may be used for encryption (license encryption) / decryption of content key (content encryption key) or content encryption / decryption.

  However, since the information necessary for the mutual authentication is set in advance at the time of shipment of the device, for example, a mechanism for content protection by an attack in which the device (a program that operates on the device) is altered after the purchase of the device. In the case where the device becomes useless, this kind of problematic device cannot be detected only by the mutual authentication.

  The present invention has been made in consideration of the above circumstances, and its purpose is to have a configuration in which revocation information that can be discriminated by an electronic device to be invalidated for content protection is registered in advance in a specific storage area. An object of the present invention is to provide a storage medium and a content protection method capable of protecting content by invalidating the electronic device when used by being attached to the electronic device represented by the revocation information.

  According to one aspect of the present invention, a storage medium that can be used for recording or reproducing digital content by an electronic device having at least one of a digital content recording function and a reproducing function is provided. This storage medium is a read-only controller, a public ROM area pre-registered with revocation information that can be discriminated by electronic devices to be invalidated for content protection, and digital content is encrypted using a content key A recorded encrypted content and an encrypted content key obtained by encrypting the content key using a pre-stored media key unique to the storage medium used for exchanging digital content with the electronic device And a rewritable public R / W area used for the. When the storage medium is attached to an arbitrary electronic device and used for recording the encrypted content by the electronic device, the controller uses the revocation information registered in the public ROM area and the electronic device. It is determined whether or not the use of the storage medium by the electronic device should be invalidated according to the received information, and if it is determined that the use should not be invalidated, the encryption to be recorded in the rewritable public R / W area Causing the electronic device to acquire the media key specific to the storage medium used for generating the encrypted content key by the electronic device, and mounting the storage medium on an arbitrary electronic device to When used for decryption and playback, the revocation information registered in the public ROM area and the electronic device It is determined whether or not the use of the storage medium by the electronic device should be invalidated according to the information obtained, and if it is determined that the use should not be invalidated, the encrypted content recorded in the public R / W area The electronic device is caused to acquire the media key unique to the storage medium used for decryption by the electronic device.

  According to the present invention, since the revocation information that can identify the electronic device to be invalidated for content protection is registered in advance in the specific storage area of the storage medium, the storage medium is represented by the above list. When the electronic device is used by being mounted on the electronic device, the electronic device can be invalidated to protect the content.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a configuration example of a content use management system 1 according to an embodiment of the present invention. In this example, music data is used as an example of content (digital content). However, the present invention is not limited to this, and data such as movies and game software may be used.

  An EMD (Electronic Music Distributor) is a music distribution server or a music distribution broadcast station.

  A content use management system (hereinafter referred to as LCM (Licence (SDMI-) Compliant Module)) 1 is realized using, for example, a personal computer (PC). The content protection method in the LCM 1 is based on the premise that the encryption / decryption of content is managed for each storage medium (storage medium) 13 on which the content is to be recorded, using the identification information (media ID) of the storage medium. It is said.

  The LCM 1 includes receiving units # 1 to # 3 corresponding to a plurality of EMDs (here, EMDs # 1 to # 3), and encrypted content distributed by the EMD through the receiving units # 1 to # 3 or The license (usage condition and encrypted content decryption key) is received. The receiving units # 1 to # 3 may have a reproduction function and a billing function. In addition, it is possible to purchase a favorite content using a billing function.

  The LCM 1 has a secure content server (here, Secure Music Server: SMS, hereinafter referred to as SMS) 2. The SMS 2 receives the encrypted content purchased by the user via the EMDI / F (interface) unit 3. The encrypted content (here, the music content) is decrypted by the EMDI / F unit 3 as necessary, and subjected to format conversion and re-encryption. When the SMS 2 receives the encrypted content, it stores it in the music data storage unit 10 and stores the music data decryption key (content decryption key) in the license storage unit 9. Here, the SMS 2 may have a playback function so that the user can listen to the distributed music content. In this case, the music content managed by the SMS 2 can be played on the PC.

  The SMS 2 also sends content data (digital content) to the storage medium 13 (hereinafter referred to as PM (Portable Memory)) such as a memory card that can be attached to the media I / F unit 6 via the I / F unit 6. It has a function to output. The PM 13 is used by being set on a dedicated recording / reproducing apparatus (hereinafter simply referred to as a PD (Portable Device)) 12 having the configuration shown in FIG. 2 to reproduce the content recorded on the PM 13 on the PD 12. be able to.

  Recording of content from the SMS 2 to the PM 13 can be performed directly through the media I / F unit 6 or via the PD 12.

Here, the check-in / check-out function by the LCM 1 will be briefly described.
Checkout means that the LMS 1 stores content as “parent” and copies the copy as “child” content to the PM 13. The “child” content can basically be freely reproduced by the PD 12, but it is not allowed to create the “grandchild” content from the “child”. The number of “children” that a “parent” can produce is defined as an attribute of the “parent”. Check-in means that, for example, the PM 13 is attached to the media I / F unit 6 of the LCM 1 and the LCM 1 erases (or cannot use) the “child” content. Is to restore the right to make one. This is also called checking in with the “parent”.

As shown in FIG. 3, the PM 13 includes a controller 130 and a storage media unit including a public area 131 and a secret area 134. The secret area 134 is a storage area that can be accessed only by a secret procedure (that is, a secret specific procedure) through the controller 130, and is used to store information necessary for content decryption. Secret area 134, corresponding PM13 unique medium identification information (hereinafter, referred to as the media key) and concealed ROM region constants are stored, such as K _M, (referred to as the media mark) is provided on a side to be licensed secret It consists of a secret R / W (read / write) area in which variables such as license decryption keys as data are stored. Medium key K _M is each PM13 may be a unique, it can be used a serial number or production number (PM13 individual serial number or lot number), various other identification information. Incidentally, the media key K _M, may be generated from the unique identification information and the license decryption key to each PM13. The secret ROM area is secured, for example, on a ROM (read-only nonvolatile memory), and the secret R / W area is secured, for example, in a specific area of a flash memory (rewritable nonvolatile memory).

  The public area 131 is an area accessible by a normal procedure other than the secret area, and is a read-only public area (hereinafter referred to as public ROM area) 132 and a rewritable public area (hereinafter public R / R). 133) (referred to as W region). The public ROM area is secured on the ROM, for example, and the public R / W area is secured on the flash memory, for example. The public ROM area and the public R / W area may be secured on the ROM in which the previous secret ROM area is secured and the flash memory in which the secret R / W area is secured.

  In the public ROM area 132, revocation information directly related to the present invention is registered in advance at the shipping stage of the corresponding PM13. This revocation information is a digital content that targets the device (LCM, PD) whose use of the PM 13 should be invalidated to protect the content, more specifically, the PM 13 (the public R / W area 133 in the PM 13). This is information that can be identified by the device (LCM, PD) that should invalidate the access request for recording or reproduction. In the present embodiment, the revocation information is a list of identification information (device ID) of devices to be invalidated. Therefore, in the following description, the term “revocation list RL” is used instead of “revocation information”. That is, the revocation list RL is registered in the public ROM area 132 in advance.

The public R / W area 133 stores an encrypted content key (content decryption key), encrypted content, and the like as appropriate. The encrypted content key is obtained by encrypting the content key K _C (specific to the content C) for decrypting the content C with the media key K _M depending on the PM 13. Further, encrypted content (where encrypted content doubly) encrypts the media key K _M which depends on the PM13 the encrypted content (K _C [C]) by K _C ( K _M [K _C [C]]).

The LCM 1 and PD 12 also have the same storage area as the PM 13 as shown in FIG.
That is, the LCM 1 has storage areas of a public area 111 including a public ROM area 112 and a public R / W area 113, and a secret area 114 that can be accessed only by a private procedure. In the public R / W area 113, the music data storage unit 10 shown in FIG. In the secret area 114, identification information (device ID) ID _{LCM of the LCM 1} is stored in advance. The secret area 114 also stores a content key K _{C for} each content as appropriate. Further, the secret book 114 has a guest book storage unit 8 shown in FIG. All music contents held in the music data storage unit 10 (public R / W area 113) under the management of the SMS 2 are a content ID (TID) as identification information and a predetermined number of duplicatable contents, That is, it has the remaining number of children and the checkout list as its attribute information. This attribute information is called a hotel book, and is stored in the hotel book storage unit 8 (in the secret area 114). The LCM 1 performs a secret area driver 7 for reading data from the hotel book storage unit 8 (the secret area 114 that provides the private book storage unit 8) after a specific procedure that is concealed for accessing the hotel book storage unit 8 is performed in the SMS 2. have. In addition, since this hotel book is not directly related to the present invention, description of the details of the method of use is omitted.

On the other hand, the PD 12 has storage areas of a public area 121 including a public ROM area 122 and a public R / W area 123, and a secret area 124 that can be accessed only by a private procedure. In the secret area 124, the identification information ID _{PD of the PD 12} is fixedly stored in advance. The secret area 124 also stores a content key K _{C for} each content as appropriate.

FIG. 2 shows a configuration example of the PD 12.
The PM 13 is used by being mounted on the media I / F unit 12f of the PD 12. When the LCM 1 reads / writes to / from the PM 13 via the PD 12, the secret area 134 (FIG. 3) of the PM 13 via the PDI / F unit 5 in the LCM 1, the LCMI / F unit 12e in the PD 12, and the media I / F unit 12f. Browse). The media I / F unit 12 f includes a secret area access unit (not shown) for accessing the secret area 134 of the PM 13. The public R / W area 123 and the secret area 124 (see FIG. 4) in the PD 12 are secured on the flash memory 12d, for example. The public ROM area 122 (see FIG. 4) is secured on the ROM 12c. A program for performing mutual authentication with the PM 13 is written in the ROM 12c. In the PD 12, under the control of the CPU 12a, processing such as mutual authentication with the PM 13 is executed according to this program.

  Next, with respect to the operation of the present embodiment, the encrypted music content distributed from the EMD is received by the EMDI / F unit 3 of the LCM 1 and temporarily stored in the music data storage unit 10 by the SMS 2. ”As a“ child ”content, for example, an operation at the time of check-out recording (copying) to the PM 13 mounted on the media I / F unit 6 will be described with reference to the flowchart of FIG.

  In this case, when a checkout instruction is given via, for example, the user interface (I / F) unit 15 of the LCM1 and the PM 13 is mounted on the media I / F unit 6 of the LCM1, the media I / F unit of the LCM1 6 and a known mutual authentication between the controller 13 of the PM 13 are performed (step S101). This mutual authentication is generally performed as follows, assuming that the LCM 1 is the device A and the PM 13 is the device B.

  First, it is assumed that device A authenticates device B. Here, if the device A holds the public key kp and the device B shares a predetermined content protection function with the device A, the device A holds the secret key ks corresponding to the public key kp. ing. Device A generates a random number R and sends it to device B. Upon receiving the random number R generated by the device A, the device B encrypts it with the secret key ks and returns the encrypted random number (represented as ks [R]) to the device A. In the device A, ks [R] is decrypted using the public key kp, and if the decryption result is equal to the previously generated random number R, it is determined that the device B is a correct partner.

  Thereafter, mutual authentication can be performed by performing the same operation as described above from the device B to the device A. In this case, device B holds the public key, device A holds the secret key, device A encrypts the random number generated by device B with the secret key, and device B decrypts it using the public key. Check if it is equal to the previously generated random number.

As a result of the mutual authentication (S101), when it is confirmed that both the LCM1 and the PM13 are legitimate parties, a key exchange is performed between the media I / F unit 6 of the LCM1 and the controller 130 of the PM13. , The same authentication key (K _X1 ) is shared. This key exchange is performed, for example, by a method using a random challenge / response represented by CSS (Content Scrambling System) used as a content encryption algorithm of DVD-ROM. The authentication key (K _X1 ) is a time-varying key that changes every time.

The media I / F unit 6 of the _{LCM 1} reads out its own identification information ID _LCM that is concealed (stored) in the concealed area 114, encrypts the ID _LCM with the authentication key (K _X1 ), and the encrypted ID _LCM (= K _X1 [ID _LCM ]) is sent from the media I / F unit 6 to the PM 13 (step S102).

The controller 130 of the PM 13 decrypts K _X1 [ID _LCM ] from the LCM 1 side with the authentication key (K _X1 ) acquired in the previous key exchange to obtain an ID _LCM (step S103).
Next, the controller 130 of the PM 13 refers to the revocation list RL in the public ROM area 132 based on the decrypted identification information ID _LCM of the LCM 1 and determines whether the identification information matching the ID _LCM is registered. It is determined whether to invalidate the use of the PM 13 (step S104).

If the identification information matching the ID _LCM is registered in the revocation list RL, the controller 130 determines that the use of the PM 13 by the corresponding LCM 1 should be invalidated (revoked), and stops the subsequent processing. To do.

On the other hand, if the identification information that matches the ID _LCM is not registered in the revocation list RL, the controller 130 determines that the use of the PM 13 by the corresponding LCM 1 is permitted and is concealed in the secret area 134. The media key KM _being read is output (step S105). The controller 130 exchanges keys with the media I / F unit 6 of the LCM 1 (via the media I / F unit 6 of the LCM 1) and shares the same authentication key (K _X2 ). The read media key K _M is encrypted with the authentication key (K _X2 ), and the encrypted K _M (= K _X2 [K _M ]) is sent to the LCM 1 (step S106).

The media I / F unit 6 of the LCM 1 decrypts K _X2 [K _M ] from the PM 13 side with the authentication key (K _X2 ) acquired by the previous key exchange to obtain the media key K _M (step S107).
Then the media I / F unit 6 of LCM1 encrypts the media key K _M which has obtained the content key K _C that is concealed in the concealed region 114, the encrypted _{K C (= K M [K} C] ) Is written in the public R / W area 133 of the PM 13 (step S108).

As described above, in this embodiment, the (encrypted) Disabling never passed from PM13 If it is (Riboketo) according revocation list RL media key K _M, LCM 1 is received from the PM13, the the contents key K _C that is concealed in the concealed region 114 of LCM1 encrypted by the medium key K _M, are to be written in the public R / W region 133 of PM13. Therefore, the invalidation target LCM specified in the revocation list RL is compared with the method in which the authentication key is exchanged between the LCM 1 and the PM 13 and the content key is encrypted / decrypted using the recognition key. It is possible to reliably invalidate (exclude) the electronic device that intends to use PM13. Incidentally, when sending a public R / W area encrypted content stored in the music data storage unit 10 secured in the 113 LCM1 (K _{C [C])} to PM13, further encrypted with the acquired K _M You may make it.

Next, the operation when the encrypted content stored in the PM 13 is decrypted and reproduced on the PD 12 will be described with reference to the flowchart of FIG.
First, when a playback instruction is given to the PD 12, for example, and the PM 13 is mounted on the media I / F unit 12f of the PD 12, between the CPU 12a of the PD 12 and the controller 130 of the PM 13 (the same as the step S101) ) Mutual authentication is performed (step S201). When the mutual authentication (S201) confirms that both the PD 12 and the PM 13 are legitimate parties, a key exchange is performed between the CPU 12a of the PD 12 and the controller 130 of the PM 13, and the same authentication is performed. The key (K _X3 ) is shared.

The CPU 12a of the _{PD 12} reads its identification information ID _PD concealed in the concealment area 124, encrypts the ID _PD with the authentication key (K _X3 ), and the encrypted ID _PD (= K _X3 [ID _PD ]) From the media I / F unit 12f to the PM 13 (step S202).

The controller 130 of the PM 13 decrypts K _X3 [ID _PD ] from the _PD 12 side with the authentication key (K _X3 ) acquired in the previous key exchange to obtain the ID _PD (step S203).
Next, the controller 130 of the PM 13 refers to the revocation list RL in the public ROM area 132 based on the decrypted identification information ID _PD of the _{PD 12,} and determines whether the identification information matching the ID _PD is registered. It is determined whether or not the use of the PM 13 is invalidated (step S204).

If the identification information matching the ID _PD is registered in the revocation list RL, the controller 130 determines that the use of the PM 13 by the corresponding PD 12 should be invalidated (revoked), and stops the subsequent processing. To do.

On the other hand, if the identification information matching the ID _PD is not registered in the revocation list RL, the controller 130 determines that the use of the PM 13 by the corresponding PD 12 is permitted and is concealed in the concealment area 134. The media key KM _being read is output (step S205). The controller 130 exchanges keys with the CPU 12a of the PD 12 (via the media I / F unit 12f of the PD 12), shares the same authentication key (K _X4 ), and then reads the read media key. K _M is encrypted with the authentication key (K _X4 ), and the encrypted K _M (= K _X4 [K _M ]) is sent to the PD 12 (step S206).

The CPU 12a of the PD 12 decrypts K _X4 [K _M ] from the PM 13 side with the authentication key (K _X4 ) acquired by the previous key exchange, and obtains the media key K _M (step S207).
Next, the CPU 12a of the PD 12 reads the encrypted content key K _C (= K _M [K _C ]) stored in the public R / W area 133 of the PM 13, and the media key K _M acquired in step S207. The decrypted content key K _C is written into the secret area 124 to be concealed (step S208). Accordingly, the PD 12 uses the decrypted content key K _C (and the previously decrypted media key K _M if necessary) to store the encrypted content stored in the public R / W area 133 of the PM 13. Can be decoded and reproduced.

As described above, in this embodiment, the (encrypted) Disabling never passed from PM13 If it is (Riboketo) according revocation list RL media key K _M, PD 12 is received from the PM13, the PM13 encrypted content key that is concealed in the concealed region 134 of the _{(K M [K C])} , and decoded by the media key K _M, are to be written in the secret area 124 of the PD 12. Therefore, the authentication key exchange between PD 12 and PM 13 and the decryption target PD (specified in the revocation list RL) are compared with decryption of the encrypted content key using the recognition key. The electronic device that intends to use PM13 can be reliably invalidated.

In the above embodiment, when the information concealed in the secret area or the information to be concealed in the secret area is exchanged between the LCM 1 and the PM 13 and between the PD 12 and the PM 13, the information is used as the authentication key. Although encryption is performed using (K _Xi ), encryption using an authentication key is not necessarily required. However, in order to ensure content protection, it is preferable to perform encryption with an authentication key.

  In the above embodiment, the revocation list RL has been described as being registered in the public ROM area 132. However, the revocation list RL may be an area where the revocation list RL is not tampered with. It may be registered in the secret area 134 that cannot be performed.

1 is a block configuration diagram of a content use management system according to an embodiment of the present invention. FIG. The block block diagram of PD (recording / reproducing apparatus) 12 in FIG. The block block diagram of PM (storage medium) 13 in FIG. The figure which shows the storage area structural example of LCM1 and PD12. The figure for demonstrating the operation | movement procedure at the time of the content recording from LCM1 to PM13. The figure for demonstrating the operation | movement procedure in the case of decrypting | regenerating and reproducing | regenerating the encryption content stored in PM13 on PD12.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... LCM (content use management system), 2 ... SMS (secure content server), 5 ... PDI / F part, 6 ... Media I / F part, 7 ... Secret area driver, 8 ... Inner book storage part, 9 ... License storage unit, 10... Music data storage unit, 11... CDI / F unit, 12... PD (recording / playback apparatus), 13... PM (storage medium, storage medium), 112, 122, 132. 123, 133: Public R / W area, 114, 124, 134: Secret area, 130: Controller.

Claims (5)

A storage medium that can be used for recording or playback of digital content by an electronic device having at least one of a digital content recording function and a playback function,
A controller,
A public ROM area pre-registered with revocation information that is read-only and is identifiable by an electronic device to be invalidated for content protection;
Encrypted content obtained by encrypting digital content using a content key and the content key encrypted using a prestored media key unique to the storage medium used for exchanging digital content with the electronic device A rewritable public R / W area used for recording with the encrypted content key
When the storage medium is attached to an arbitrary electronic device and used for recording the encrypted content by the electronic device, the controller uses the revocation information registered in the public ROM area and the electronic device. It is determined whether or not the use of the storage medium by the electronic device should be invalidated according to the received information, and if it is determined that the use should not be invalidated, the encryption to be recorded in the rewritable public R / W area Causing the electronic device to acquire the media key specific to the storage medium used for generating the encrypted content key by the electronic device, and mounting the storage medium on an arbitrary electronic device to When used for decryption and playback, the revocation information registered in the public ROM area and the electronic device It is determined whether or not the use of the storage medium by the electronic device should be invalidated according to the information obtained, and if it is determined that the use should not be invalidated, the encrypted content recorded in the public R / W area A storage medium characterized by causing the electronic device to acquire the media key unique to the storage medium used for decryption by the electronic device. The storage medium according to claim 1, wherein when the controller determines that the use of the storage medium by the electronic device should be invalidated, the controller stops subsequent processing. The information received from the electronic device by the controller is encrypted information,
The controller receives the encrypted information by performing an authentication process with the electronic device, and decrypts the encrypted information based on the authentication process to identify the electronic device If the revocation information registered in the public ROM area includes information that matches the acquired identification information, the use of the storage medium by the electronic device is invalidated. The storage medium according to claim 1 or 2, characterized in that A secret ROM area that is read-only and accessible in a private procedure through the controller;
4. The storage medium according to claim 1, wherein the media key unique to the storage medium is stored in the secret ROM area in advance. A content protection method used for a storage medium that can be used for recording or playback of digital content by an electronic device having at least one of a digital content recording function and a playback function,
The storage medium is
A controller,
A public ROM area pre-registered with revocation information that is read-only and is identifiable by an electronic device to be invalidated for content protection;
Encrypted content obtained by encrypting digital content using a content key and the content key encrypted using a prestored media key unique to the storage medium used for exchanging digital content with the electronic device A rewritable public R / W area used for recording with the encrypted content key
The content protection method includes:
When the storage medium is attached to an arbitrary electronic device and used for recording the encrypted content by the electronic device, the controller uses the revocation information registered in the public ROM area and the electronic device. It is determined whether or not the use of the storage medium by the electronic device should be invalidated according to the received information, and if it is determined that the use should not be invalidated, the encryption to be recorded in the rewritable public R / W area Causing the electronic device to acquire the media key unique to the storage medium used for generating the encrypted content key by the electronic device,
When the storage medium is attached to an arbitrary electronic device and used for decryption and playback of the encrypted content by the electronic device, the controller revokes the revocation information registered in the public ROM area and the electronic It is determined whether or not the use of the storage medium by the electronic device should be invalidated according to the information received from the device, and if it is determined that it should not be invalidated, the encryption recorded in the public R / W area A content protection method, comprising: causing the electronic device to acquire the media key unique to the storage medium used for decrypting content by the electronic device.

Images