WO2008090402A1

WO2008090402A1 - A system and method of transferring digital rights to a media player in a drm environment

Info

Publication number: WO2008090402A1
Application number: PCT/IB2007/002434
Authority: WO
Inventors: Martin Weiss; William Jacob Hayes; Eckart Zollner
Original assignee: Psitek (Proprietary) Limited
Priority date: 2007-01-25
Filing date: 2007-08-24
Publication date: 2008-07-31

Abstract

A system is provided in which a DRM service platform (2) is configured to dispense rights objects (RO) to media players (1) that are uniquely identifiable by way of unique identification data (GUID) with the digital media files encrypted into content objects (CO) that require a content object key (COk) in order to decrypt the content thereof and make it available, in real¬ time. The content object key is embodied in a rights object that is in turn transmitted to a particular media player in an encrypted format capable of decryption utilising at least some of the unique identification data of the particular media player and each media player has a processor capable of decrypting content objects in real-time to render the digital media files usable. Computer means (6) are interposed between a DRM service platform and a media player and are configured to share a unique interface key (IK) for communications with each unique media player and to decrypt a rights object received from the DRM service platform to retrieve the content object key contained therein and re-encrypt it with the unique interface key for onward transmission to the particular media player that is enabled to decrypt the content object key utilising its unique interface key.

Description

A SYSTEM AND METHOD OF TRANSFERRING DIGITAL RIGHTS TO A MEDIA PLAYER IN A DRM ENVIRONMENT

FIELD OF THE INVENTION

This invention relates to a system and method of transferring digital rights to a digital media player, typically a portable media player of the general type having suitable memory and processing ability such as those sold under the trade name "I-POD™" by or on behalf of Apple Computers, with the transfer taking place in a DRM (Digital rights management) environment.

More particularly, the invention relates to a system and method in which the processing ability of a media player may be reduced from that typically required in certain DRM environments, in particular ones such as that of the MICROSOFT™ Direct Digital Rights Management (DRM) solution.

It is to be understood that in this specification the term "digital rights" is intended to mean the relevant enablement to play certain encrypted content of a digital media file on a particular media player. The invention is concerned with a system in which limited entitlement is embodied in a rights object (RO) that also embodies an encrypted content object key (CO_k) that needs to be extracted by decrypting the rights object (RO) so that it can be used in real time to decrypt the digital media file contained in encrypted form in a content object (CO). The encryption of a digital media file to form the content object would typically take place in association with a DRM platform where the content object key is used and the content object key is embodied in the rights object (RO) generally at a subsequent time upon request received from a media player. The digital media player has a global unique identifier (GUID) that is also embodied in the rights object (RO) to render the rights object usable only on that particular media player. The content object and rights object may thus follow different commercial chains and are regularly acquired at different times.

BACKGROUND TO THE INVENTION

Currently, as indicated in Figure 1, a portable media player (1) that is operated in a DRM environment such as the MICROSOFT™ Direct Digital Rights Management (DRM) solution requires a relatively fast and powerful microprocessor to handle the initial decryption transactions when acquiring a rights object (RO) from a DRM service platform (2). Typically, such a DRM solution requires a media player to communicate with the DRM service platform via the internet or any other connection (3). When connected, the media player is able to transact with the DRM service platform and request a rights object (RO) that encapsulates the rights actually made available to the particular media player in respect of a particular content object (CO) being the encrypted data that encapsulates the particular audio, audiovisual or other work that has been requested. The transfer takes place with the media player directly connected (usually by way of a PC or other computer (4) as a host, conveniently using a USB or other suitable port) to the DRM service platform.

The rights object (RO) in the system under consideration, as indicated above, embodies an embedded content object key (CO_k) that is necessary in order to unlock the actual data from the particular content object (CO) with which it is associated in real-time to enable it to be played. The arrangement is such that only the particular media player can decrypt the rights object (RO) and thus retrieve the content object key (CO_k).

During the session of connectivity, the media player sends a number of packets of information to the DRM service platform including a public key (Pp), a digital certificate (P₀) and the global unique identifier (GUID) of the particular media player, as indicated in Figure 1. The DRM service platform authenticates the public key against the digital certificate and, if valid, at least in the instance of the proprietary MICROSOFT™ Direct Digital Rights Management (DRM) solution, the DRM service platform makes use of this unique information to encrypt the requested rights object (RO) that embodies the necessary content object key (CO_k). The encrypted rights object (RO) is then sent to the media player as indicated in Figure 2.

The media player may then use its unique secret key (Ps) to decrypt the rights object in a decryption process that is sophisticated (and, in this instance, proprietary to MICROSOFT™) as is indicated in Figure 3. Once the rights object (RO) has been decrypted, the player has access to the content object key (CO_k) that is required by the player to finally decrypt the content.

The player is then able to use the content object key (CO_k) in an algorithm that in real-time decrypts the content object thus exposing the media file that is able to be played by the electronics of the player, as indicated in Figure 4.

It can be seen that there are two decryption processes that take place within the media player, namely to decrypt the received rights object (RO) with the secret key (Ps) of the media player to expose the content object key (CO_k) as indicated Figure 3; and to decrypt the content object CO with the content object key (COk) to expose the playable media (5) in real time as indicated in Figure 4.

The decryption process for exposing the content object key (CO_k) requires a relatively powerful processor to handle the decryption algorithms that involve the manipulation of numbers with a large amount of digits (possibly up to 1024 bits). The decryption process for playing the content using the content object key (CO_k), on the other hand, is not as power intensive and can be performed by a relatively simple processor.

The result is that digital media of the type under consideration, may be unaffordable to a large sector of a population simply by virtue of the equipment required for decrypting the rights object being too costly. Applicant believes that such a situation is not in the interests of either the rights owners or would-be users of the rights.

OBJECT OF THE INVENTION

It is an object of this invention to provide a system and method of transferring digital media files to a digital media player that is less demanding on the processing power of a media player itself yet still honouring the DRM robustness.

SUMMARY OF THE INVENTION

In accordance with one aspect of this invention there is provided a system of the type in which a DRM service platform is configured to dispense rights objects to media players that are uniquely identifiable by way of unique identification data with the digital media files encrypted into content objects that require a content object key in order to decrypt the content thereof and make available, in real-time, the digital media files, and wherein a content object key is embodied in a rights object that is in turn transmitted to a particular media player in an encrypted format capable of decryption utilising at least some of the unique identification data of the particular media player, and wherein each media player has a processor capable of decrypting content objects in real-time to render the digital media files usable, the system being characterised in that computer means are interposed between a DRM service platform and a media player and are configured to share a unique interface key for communications with each unique media player and wherein the computer means is further configured to decrypt a rights object received from the DRM service platform to retrieve the content object key contained therein and re-encrypt it with a unique interface key for onward transmission to the particular media player that is enabled to decrypt the content object key utilising its unique interface key.

Further features of the invention provide for the computer means to include a computer and a uniquely identifiable memory unit, typically a smartcard but optionally any other secure processor unit with the decrypting and encrypting capabilities required in the event that it has been provided with unique identification data, in particular, a public key, a private key, and a certificate; for the unique identification data of the media player to include a global unique identifier, a media player public key and media player secret key, and a certificate; and for the generation of the interface keys to be carried out by an independent key management server.

It will be understood that, utilising a system as defined above, the power intensive initial decryption described above is handled by the computer means instead of by the media player, thus allowing the use of a less expensive and less power intensive processor in the media player itself. In the event that a smartcard is employed, the computer acts as a conduit for communications between the smartcard and the media player.

In order that the invention may be more fully understood an expanded description of one embodiment thereof will now follow. BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:-

Figure 1 illustrates schematically the transfer of a media player's unique identification data to a DRM service platform in an existing system;

Figure 2 illustrates the treatment of a rights object for transmission to a media player in an existing system;

Figure 3 illustrates the treatment in an existing system of a rights object in a media player to decrypt it;

Figure 4 illustrates the retrieval of the content object key and its use in association with the content object to release the digital media file;

Figure 5 illustrates the generation of an interface key for a particular media player in accordance with the present invention; and,

Figure 6 illustrates the acquisition and decryption of a rights object from a DRM service platform in terms of the present invention.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

In order to implement the invention and secure communications between a media player (1) and computer means (6) utilised according to the invention, it is required that the two devices share a common interface key so that each media player has a unique interface key (IK). The computer means would therefore have to securely cache a unique interface key for each player and in this embodiment of the invention a smartcard (7) is used as a cache facility with the smartcard being used in conjunction with a computer (8) only for the duration of the transaction. A smartcard is employed in this embodiment of the invention for security reasons, in particular, the perception of the high degree of security afforded by a smartcard.

It is envisaged that in a system in which multiple media dispensers are available for customers with media players to acquire content objects of their choice, one smartcard could be employed per media dispenser or, if a media dispenser is operated by a plurality of independent operators, each operator could use their own smartcard.

With reference in particular to Figure 5, a secure link between the media player and the smartcard is required and this is achieved in the following way.

During personalization of the smartcard it is programmed with a public key (Sp), a private key (Ss) and a certificate (S₀) such that when it is connected to a computer, and the media player sends its global unique identifier (GUID) to the computer a communications channel is set up between the computer and the smartcard whereupon the computer requests the smartcard's public key (Sp) and certificate (Sc).

The computer then establishes a communications channel with a key management server (KMS) (9) (back end server) and the computer forwards the global unique identifier of the media player as well as the smartcards' public key (Sp) and certificate (Sc) to the key management server. The key management server uses the received global unique identifier as a look-up index for that particular media player's interface key (IK). The key management server uses the smartcards' certificate to authenticate the smartcard's public key. The key management server, using a strong security framework such as a public key infrastructure (PKI) like RSA or ECC, encrypts the player's interface key using the smartcard's public key (Sp) and forwards it to the smartcard via the computer. The smartcard is able to decrypt the message using its private key and thereby extract the media player's interface key.

The interface key is then used to encrypt and decrypt all communications between the media player and the smart card. A secure communications channel has thus been created between the media player and the smartcard.

The smartcard then acts as a secure proxy for the media player when requesting a rights object (RO) from the DRM service platform, extracting the content object key (CO_k) and forwarding the content object key (CO_k) to the media player as follows:

The media player encrypts its secret key with its interface key and sends it securely to the smartcard via the computer. The smartcard uses the interface key to decrypt the players' secret key. The smartcard requests a rights object (RO) from the DRM service platform via the computer by forwarding the media players' public key, certificate and global unique identifier. The DRM service platform authenticates the players' public key using the players' certificate; encrypts the rights object (RO) using the players public key as well as any other operation that is required by the DRM service platform. This encrypted rights object (RO) package is forwarded to the smartcard via the computer.

The smartcard uses the media players' secret key and any other operation required by the DRM service platform to decrypt the rights object (RO) thus exposing the content object key (CO_k). The smartcard encrypts the content object key (CO_k) and other rights object information using the interface key and the smartcard forwards this data via the computer to the media player. The media player decrypts this data using the interface key and the media player uses the content object key (CO_k) to access the content in the content object, namely the digital media file.

The player stores the content object key (CO_k) in a secure area of its memory.

The content object itself, encrypted in the usual way, may be sent to the media player via the computer prior to the above process so that it is available when the content object key becomes available, or it may be acquired in any other permissible manner.

It will be appreciated that all DRM steps and functions required in order to fulfil licensing requirements are still present, the only difference being that the power intensive initial decryption portion is handled externally of the media player, thus allowing the use of a less expensive, less power intensive processor to be incorporated in the player. Also, implementation of the invention does not adversely affect any report back function between a media player and the relevant DRM platform, particularly as regards compliance with terms of the rights object, communications simply being conducted by way of the interposed computer means.

Numerous variations may be made to the system described above without departing from scope hereof.

Claims

CLAIMS:

1. A system of the type in which a DRM service platform (2) is configured to dispense rights objects (RO) to media players (1) that are uniquely identifiable by way of unique identification data (GUID) with the digital media files encrypted into content objects (CO) that require a content object key (CO_k) in order to decrypt the content thereof and make available, in real-time, the digital media files, and wherein a content object key is embodied in a rights object that is in turn transmitted to a particular media player in an encrypted format capable of decryption utilising at least some of the unique identification data of the particular media player, and wherein each media player has a processor capable of decrypting content objects in real-time to render the digital media files usable, the system being characterised in that computer means (6) are interposed between a DRM service platform and a media player and are configured to share a unique interface key (IK) for communications with each unique media player and wherein the computer means is further configured to decrypt a rights object received from the DRM service platform to retrieve the content object key contained therein and re-encrypt it with the unique interface key for onward transmission to the particular media player that is enabled to decrypt the content object key utilising its unique interface key.

2. A system as claimed in claim 1 in which the computer means include a computer (8) and a uniquely identifiable memory unit.

3. A system as claimed in claim 2 in which the uniquely identifiable memory unit is a smartcard (7).

4. A system as claimed in either one of claims 2 or 3 in which the uniquely identifiable memory unit has a processor unit with required decrypting and encrypting capabilities.

5. A system as claimed in claim 4 in which unique identification data of the uniquely identifiable memory unit includes a public key (Sp), a private key (Ss) and a certificate (Sc).

6. A system as claimed in any one of the preceding claims in which the unique identification data of the media player includes a global unique identifier (GUID), a media player public key (P_p), and media player secret key (Ps), and a digital certificate (Pc).

7. A system as claimed in any one of the preceding claims in which the interface keys are retained and managed by an independent key management server (9).