Patent Application
20100166189
This application is based upon and claims the benefit of priority from Japanese Patent Applications No. 2008-334642, filed Dec. 26, 2008; and No. 2009-131285, filed May 29, 2009, the entire contents of both of which are incorporated herein by reference.
1. Field
One embodiment of the invention relates to a key management apparatus and a key management method, which are capable of managing an encrypted content and a key of the encrypted content in separate media.
2. Description of the Related Art
A Secure Digital (SD) card (trademark) that stores an encrypted content in a user data area, and also stores an encrypted content key, which is obtained by encrypting a content key used for encrypting content with a card-specific user key stored in a protected area, in the user data area is known (e.g., paragraphs [0004]-[0009] of Jpn. Pat. Appln. KOKAI Publication No. 2006-14035).
A new digital rights management (DRM) system, which is capable of protecting digital contents such as music, videos, and books against illegal copying and securely distributing the digital contents by utilizing a copyright protection function of the SD card to combine a key stored in an SD card and a corresponding viewer soft, has been designed.
Features of the above system are creating a secure key which is obtained by encrypting a key (right) itself for using a content, and distributing the key and the content separately, by utilizing the copyright protection function of the SD card and identification numbers (ID) unique to respective SD cards.
With the above features, distribution of content to users through any manners such as delivery of CD/DVD, download from the internet, and a super-distribution system became possible. Convenience for both of distributors distributing contents and users purchase content is thereby developed. The super-distribution system is a system wherein ease of distribution and copying being the characteristic of digital content is taken advantage for freely distributing encrypted content, and users are charged on the basis of actual use.
According to the DRM system, read and development of content for browsing the content becomes possible only when encrypted content and an encrypted key are together. Therefore, if only the content itself is copied and there is no key for the content, it is not possible to use the copied content. It becomes possible to distribute the content itself between individuals, as a development of the super-distribution. Also, a key to be stored in an SD card is encrypted in such a manner that it is related to an identification number (ID) unique to every SD card. Even if information on a key is copied, the key will not function without the SD card being the copy source, and content therefore cannot be used.
Now, in this DRM system, distribution of digital content by writing encrypted content and an encrypted key to an SD card will be considered. A conventional SD card has high confidentiality of a key. However, it has a disadvantage that, while an encrypted content wherein separate delivery for distributing a key and content separately is supported can be copied or moved to another medium, a key cannot be copied or moved to another medium. Therefore, when a plurality of contents are moved from a respective plurality of SD cards to other media, it becomes laborious to look for SD cards respectively storing encrypted content keys for respective encrypted contents. Furthermore, in the worst case, an SD card storing a key for an encrypted content moved to another medium may not be possible to be specified and the moved encrypted content cannot be reproduced.
A general architecture that implements the various feature of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention.
Various embodiments according to the invention will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment of the invention, a key management apparatus configured to access an information storage medium comprising a user data area for storing encrypted content and encrypted content key, the encrypted content being encrypted with a content key in a plain version and the encrypted content key being encrypted on the basis of a media unique key unique to the medium, and a hidden area for storing the media unique key, the apparatus comprises a decrypting module configured to read a first media unique key and an encrypted content key which corresponds to a selected content from a first information storage medium and to decrypt the encrypted content key with the first media unique key in order to obtain a content key in a plain version; an encryption module configured to read a second media unique key from the second information storage medium and to encrypt the content key in the plain version with the second media unique key in order to obtain an encrypted content key for the second information storage medium; and a write module configured to write the encrypted content key for the second information storage medium to a user data area of the second information storage medium.
According to an embodiment,
A storage area of an SD card 12 is divided into a system area 14, a hidden area 16, a protected area 18, and a user data area 20. The SD card 12 also includes an encryption/decryption module 22.
The system area 14 stores key management information Media Key Block (MKB) and a media identifier IDm. The hidden area 16 stores a media unique key Kmu. The protected area 18 stores an encrypted user key Enc (Kmu, Ku). The user data area 20 stores an encrypted content key Enc (Ku, Kc) and an encrypted content Enc (Kc, C). Description of Enc (A, B) indicates, in the present specification, that data (also referred to as a key) B encrypted by data A. A user key Ku is an encryption/decryption key for a content key Kc, and, in the SD card 12, this user key Ku is commonly used for a plurality of encrypted content keys Enc (Ku, Kc1), and Enc (Ku, Kc2), . . . etc.
The system area 14 is a read only area to which a reproduction device 32 or the like can access from outside of the SD card. The hidden area 16 is a read only area to which the SD card itself refers, and this area can never be accessed from outside. The protected area 18 is an area which is readable/writable from outside of the SD card when authentication is successful. The user data area 20 is an area which is freely readable/writable from outside of the SD card. The encryption/decryption module 22 is for performing authentication, key exchange, and encryption communication between the protected area 18 and outside of the SD card, and it has an encryption/decryption function.
With respect to the above-explained SD card 12, the reproduction apparatus 32, which is a key management apparatus as well as a user terminal for reproduction, operates logically as explained below. That is to say, in the reproduction apparatus 32, key management information MKB read from the system area 14 the SD card 12 is subjected to an MKB process (S2) by a preliminarily-set device key Kd, and a media key Km is thereby obtained. The reproduction apparatus 32 then subjects the media key Km and a media identifier IDm read from the system area 14 of the SD card 12 to a hash process (S4) for obtaining a media unique key Kmu.
Subsequently, the reproduction apparatus 32 executes, on the basis of the media unique key Kmu, authentication and key exchange (Authentication Key Exchange [AKE]) process (S6) between the reproduction apparatus 32 and the encryption/decryption module 22 of the SD card 12, and shares a session key Ks with the SD card 12. The authentication and key exchange process of step S6 is successful when the media unique key Kmu in the hidden area 16 to which the encryption/decryption module 22 refers and the media unique key Kmu generated by the reproduction apparatus 32 match, and then the session key Ks is to be shared.
Next, the reproduction apparatus 32 reads the encrypted user key Enc (Kmu, Ku) from the protected area 18 through encrypted communication (S8) using the session key Ks, and subjects the encrypted user key Enc (Kmu, Ku) to a decryption process (S10) by using the media unique key Kmu, and thereby obtains the user key Ku.
Then, the reproduction apparatus 32 reads the encrypted content key Eric (Ku, Kc) from the user data area 20 of the SD card 12, and subjects the encrypted content key Enc (Ku, Kc) to a decryption process (S12) by using the user key Ku, and thereby obtains the content key Kc. The reproduction apparatus 32 reads the encrypted content Enc (Kc, C) from the user data area 20 of the SD card 12, and subjects the encrypted content key Enc (Kc, C) to a decryption process (S14) by using the content key Kc, and reproduces thereby obtained content C.
In the above basic example, the encrypted content Enc (Kc, C) is stored in the data area 20 of the SD cards 12. According to the present embodiment, however, a case where an encrypted content Enc is moved to another storage medium such as a hard disk will be explained. In other words, in decryption process (S14), encrypted content Enc (Kc, C) read from another storage medium is decrypted by using the content key Kc, which is obtained by decrypting the encrypted content key read from the SD card 12.
The SD card 12 is inserted into a card slot 52 of the reproduction apparatus 32. Inside the reproduction apparatus 32, an encryption/decryption module 54, a built-in memory 56, a CPU 58, a card slot 52, a user key table 62, a display 64, an input device 66, and a USB terminal 68 are connected to one another via a system bus. The encryption/decryption module 54 includes a process of decrypting encrypted content keys read from respective SD cards by using user keys of the respective SD cards and again encrypting the decrypted content key by using a user key of a specific SD card. Therefore, the reproduction apparatus 32 includes the user key table 62 which manages the user key of the specific SD card. The CPU 58 includes special software for key management. A user interface for guiding user's operation is displayed on the display 64, and user's operation is inputted via the input device 66. The input device 66 may employ a touch panel system wherein the display 64 is combined therewith. The HDD 40 is connected to the USB terminal 68.
Movement of key according to the present invention will be described with reference to
Similarly, when another SD card 94 is inserted into the card slot 52 of the reproduction apparatus 32, the reproduction apparatus 32 displays the menu screen for allowing the user-selected content to be moved. Assume a case in which content C2 is selected, an encrypted content Enc (Kc2, C2) is moved from the SD card 94 to the HDD 40 as shown in
By repeating operation shown in
When the keys dispersedly stored in a plurality of SD cards are to be brought together in one SD card, the reproduction apparatus 32 activates special software for key management. The display 64 displays a user interface for prompting the user to insert an SD card being a movement source into the card slot 52.
When the first SD card 92 is inserted into the card slot 52 of the reproduction apparatus 32, the reproduction apparatus 32 reads various information (MKB, media identifier IDm, media unique key Kmu1, encrypted user key Enc (Kmu1, Ku1), encrypted content key Enc (Ku1, Kc1)) from the first SD card 92, as shown in
Afterward, the display 64 displays an user interface for prompting the user to insert the second SD 94 card into the card slot 52. When the first SD card 92 is unplugged from the card slot 52 and the second SD card 94 is inserted into the card slot 52 of the reproduction apparatus 32, the reproduction apparatus 32 reads various information (MKB, media identifier IDm, media unique key Kmu2, encrypted user key Enc (Kmu2, Ku2), encrypted content key Enc (Ku1, Kc1)) from the second SD card 94, as shown in
Subsequently, as shown in
If free space of the second SD card 94 is small and it is not possible to write the encrypted content key Enc (Ku2, Kc1) for the second SD card 94 thereto, the display 64 displays a user interface for prompting the user to insert another SD card into the card slot 52.
By repeating operations shown in
During reproduction of contents, the display 64 displays an user interface for prompting the user to select content in the HDD 40. When a content is selected (here, a case in which the encrypted content Enc (Kc1, C1) is selected is assumed), the display 64 displays an user interface for prompting the user to insert an SD card storing the key into the card slot 52.
When the second SD card 94 is inserted into the card slot 52, the reproduction apparatus 32 reads various information (MKB, media identifier IDm, media unique key Kmu2, encrypted user key Enc (Kmu2, Ku2), encrypted content key Enc (Ku2, Kc1) for the selected content) from the SD card 94, as shown in
The reproduction apparatus 32 reads a specified encrypted content Enc (Kc1, C1) from the HDD 40, and decrypts the encrypted content Enc (Kc1, C1) by using the content key Kc1, thereby obtaining and reproducing content C1.
As explained above, according to the first embodiment, the encrypted content key is decrypted by using the user key of the SD card being the movement source for obtaining a content key, then the decrypted content key is encrypted with a user key of the specific SD card being the movement destination, and thereby encrypted content key is written to the user data area of the specific SD card being the movement destination. With this process, even in a case in which encrypted contents stored in a plurality of SD cards, which also store encrypted content keys, are intensively moved to a large-capacity storage device, the encrypted content keys are able to be intensively moved to a specific SD card. Therefore, when the encrypted contents stored in the large-capacity storage device are to be reproduced, there is no need for looking for SD cards respectively storing encrypted content keys for the respective encrypted contents to be reproduced. In other words, the encrypted contents can be surely reproduced. Furthermore, even if a third party steals an encrypted content key, the encrypted content key cannot be decrypted and a content corresponding to the encrypted content key cannot be decrypted accordingly, and the content can be thereby protected.
Other embodiments of the key management apparatus according to the present invention will now be explained. In the other embodiments, parts similar to those in the first embodiment are designated by the same reference numerals and detailed explanations are omitted.
In the first embodiment, when an abnormal process such as powering off while a content key is moved from the first SD card to the second SD card, there is a possibility that, depending on kinds of anomaly, the content key is lost, losing one opportunity out of an allowed number of times to move or copy, and furthermore, an effective content key is stored in both of the movement source and movement destination.
According to a second embodiment, a non-volatile storage is provided to the reproduction apparatus 32 for avoiding the above-mentioned problem.
When the first SD card is inserted into the card slot 52 in block #12, an encrypted content key Enc (Ku1, Kc1) is read from the first SD card. The encrypted content key Enc (Ku1, Kc1) is decrypted in block #14 and content key Kc1 is obtained. Details of decrypting a content key are similar to those of the process of the first embodiment explained with reference to
The content key Kc1 is encrypted with unique information Kp on the reproduction apparatus 32 (e.g., a serial number of the apparatus) in block #18, and an encrypted content key Enc (Kp, Kc1) is thereby obtained. The encrypted content key Enc (Kp, Kc1) is written to the non-volatile memory 70 in block #20, and at the same time, “being moved” is written to move status information, which indicates whether or not a key preliminarily stored in the non-volatile memory 70 is being moved.
The encrypted content key Enc (Ku1, Kc1) is deleted from the first SD card in block 422.
In block #24, the first SD card is unplugged from the card slot 52 and the second SD card is inserted into the card slot 52.
In block #26, whether or not data is stored in the built-in memory 56 is determined. This determination indicates whether or not the reproduction apparatus 32 has ever been powered off during a period of time between start of content movement (to be precise, after process of block 416) and the determination. If the data is stored, that data is determined to be the content key Kc1. In this case, block #30 is executed.
If no data is stored, it can be determined that the reproduction apparatus 32 is once powered off. In this case, the encrypted content key Enc (Kp, Kc1) is read from the non-volatile memory 70 of the reproduction apparatus 32 and decrypted by using Kp, and the content key Kc1 is thereby obtained in block #28. This content key Kc1 is to be stored in the built-in memory 56.
After block #28, or in a case where a determination result is YES in block #26, the content key Kc1 is read from the built-in memory 56 and encrypted with unique information on the second SD card (e.g., encrypted user key Ku2), and the encrypted content key Enc (Ku2, Kc1) is thereby obtained in block #30. Details of this encryption are similar to those of the process of the first embodiment explained with reference to
The encrypted content key Enc (Ku2, Kc1) is written to the second SD card in block #32. The content key Kc1 is deleted from the built-in memory 56 in block #34. “Move completed” is written to move status information that is preliminarily stored in the non-volatile memory 70, in block #36. The encrypted content key Enc (Kp, Kc1) is deleted from the non-volatile memory 70 in block #38.
According to the process of
When the apparatus is powered on, it is determined in block #42 whether or not the move status information in the non-volatile memory 70 indicates “being moved”. If it is determined not being moved, it can be determined that the key movement is completed normally, and the operation of
If the move status information indicates “being moved”, it can be determined that the apparatus might be once powered off during a period of time between block #22 to block #36 of
In block #48, the encrypted content key Enc (Ku1, Kc1) is deleted from the first SD card.
Subsequent process is similar to the process in
In block #26, whether or not data is stored in the built-in memory 56 is determined. If data is stored, block #30 is executed. If no data is stored, in block #28, the encrypted content key Enc (Kp, Kc1) is read from the non-volatile memory 70 of the reproduction apparatus 32 and decrypted by using Kp, for obtaining the content key Kc1. This content key Kc1 is written to the built-in memory 56.
In block #30, the content key Kc1 is read from the built-in memory 56 and encrypted with unique information Ku2 of the second SD card, and the encrypted content key Enc (Ku2, Kc1) is thereby obtained.
In block #32, the encrypted content key Enc (ku2, Kc1) is written to the second SD card. The content key Kc1 is deleted from the built-in memory 56 in block #34. In block #36, “move completed” is written to the move status information preliminarily stored in the non-volatile memory 70. In block #38, the encrypted content key Enc (Kp, Kc1) is deleted from the non-volatile memory 70.
According to the process of
As explained above, according to the second embodiment, it is possible to prevent failures such as losing the content key, losing one opportunity out of the allowed number of times to move or copy even if the apparatus is powered off while the key is being moved. It is because the content key can be reissued by using the encrypted content key stored in the non-volatile memory 70. Furthermore, after reading the key from the first SD card, the key is deleted therefrom, and after writing to the key to the second SD card, the key is deleted from the non-volatile memory. Thus, the effective key can be prevented from being written to both of the movement source and the movement destination.
An example of the purchase history information 78 is shown in
In the key movement process according to the third embodiment, the account server 76 is accessed in block #52 for investigating move status information on the purchase history information 78.
In block #54, whether or not the move status information indicates “being moved” is determined. If determined that “being moved”, there is a possibility that the key is lost, and whether or not media ID of the first SD card being inserted in the card slot matches the media ID of the purchase history information 78 is determined in block #56. If the media IDs match, it is possible that after reading the content key from the first SD card being inserted in the card slot, the reproduction apparatus 32 may be powered off before the first SD card is exchanged to the second SD card and the key may be therefore lost. Thus, the content key is reissued in block #58. In other words, the account server 76 writes the content key Kc1 to the built-in memory 56.
Subsequently, key movement is resumed in block #60. More specifically, block #30 and block #32 of
If a determination result is NO in block #54, it represents that the apparatus was powered off not during the key movement, and the process of
If the media IDs do not match in block #56, it means that the SD card being the movement source is already unplugged from the reproduction apparatus 32. Therefore, the key does not have to be reissued and the process is terminated.
As explained above, according to the third embodiment, when the apparatus is powered off during the key movement, the content key is reissued. Thus, it is possible to prevent failures such as losing the content key, and losing one opportunity out of the allowed number of times to move or copy.
Although only one card slot 52 is provided according to the above explanation, two card slots may be provided. If the apparatus is provided with two card slots, a specific SD card to which the keys are intensively moved can be always inserted. Therefore, it is possible to save the trouble of looking for an SD card exclusively provided for the keys and convenience improves. Furthermore, the SD card exclusive for the keys may be embedded in the reproduction apparatus, since the exclusive SD card does not have to be inserted to/unplugged from the reproduction apparatus unless a target reproduction apparatus changes. Although it is explained in the above explanation that the reproduction apparatus 32 comprises a special hardware, it may be realized by using a personal computer executing special software.
The above-described embodiments explained aggressive movement of keys, however, the keys may be deleted moved) in accordance with movement of content. For example, in a case where licensing of content stored in the first SD card allows only movement, the content of the first SD card is moved to an HDD, and an encrypted content key for a second SD card corresponding to the moved content is written to the second SD card, and subsequently, the encrypted content key corresponding to the content is deleted from the first SD card. With this process, content is securely moved. Also, in a case where licensing of content in the first SD card allows only limited number of times to copy, an encrypted content key for the second SD card corresponding to the content is written to the second SD card, and subsequently, a sum of an allowed number of times to copy (stored in the protected area) with respect to the content in the first SD card and an allowed number of times to copy (stored in the protected area) with respect to the content in the second SD card is set equal to an original limited allowed number of times to copy. With this process, copying exceeding the limited allowed number of times can be prevented.
As explained above, a plurality of keys for a plurality of contents, which are dispersedly purchased and stored in a plurality of information storage media, can be brought together in one information storage medium. Therefore, in a case where a plurality of contents are to be reproduced after being brought together in one storage, a user is free from the trouble of looking for information storage media respectively storing keys corresponding to contents to be reproduced.
While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The various modules of the systems described herein can be implemented as software applications, hardware and/or software modules, or components on one or more computers, such as servers. While the various modules are illustrated separately, they may share some or all of the same underlying logic or code. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-334642 | Dec 2008 | JP | national |
| 2009-131285 | May 2009 | JP | national |
