NO20093404A1 - Method for transmitting rights criteria for multi-domain and trans-domain distribution of video and other media content - Google Patents

Abstract

A method is presented in which a set of criteria for accessing video or other media content is merged into the content itself before that content is encrypted and sent to or retrieved by a user terminal. The user terminal has a security model that decrypts the content as well as retrieves a copy of the embedded set of criteria. The criteria that were contained in the content are then compared with access rights or privileges in the security module, and if the comparison means that access to the content is to be given then the security module releases the content for the user to utilize it. Several such sets of criteria can be merged into the content so that the same content can be used on many types of user terminals. A further aspect of the method is the simplified secure transfer of content between different types of user terminals or server machines' security domains.

Description

TECHNICAL AREA

The invention relates to architecture for end-to-end protection of digital media content in different domains and between media forms and formats.

BACKGROUND AND KNOWN METHODS

Television, video, audio and other media content may be protected to enforce payment ("pay TV"), confidentiality ("closed user groups") or copyright ("for private use only"). The protection mechanisms used in such contexts are called access control systems ("Conditional Access Systems - CAS") and digital rights management systems ("Digital Rights Management - DRM").

The usual architecture for the protection of media content that is mass distributed to consumers and subscribers based on broadcasting or multi-casting techniques involves: i) Encryption of the content using an encryption algorithm and associated electronic (content) keys. These are most often called "control words - CW" or "Traffic Encryption Keys - TEK".

Inclusion of the content keys in special messages that are attached to, but not within, the content. These messages are encrypted with a higher order key. Such messages are often called "Entitlement Control Messages - ECM" or "Key Stream Messages - KSM".

The ECM/KSM usually also contains the access criteria associated with the content. Access criteria are references and parameters associated with the right or privilege users must have in order to make use of the content.

ii) Sending the encrypted content and messages to receiver units such as so-called decoders ("Set Top Boxes - STB"). One variant is that the recipient devices themselves retrieve the encrypted content and messages.

iii) The receiving units will then first decrypt the messages, interpret these, and then

compare the access criteria with the receiving device's rights and privilege information. If the criteria for access to the content are met, the content keys are released so that the content can be decrypted.

iv) The content is decrypted and it can be presented to the user.

In this architecture, there are also messages to transport rights and privileges as well as different types of keys to the users' receiving devices. Such messages are often called "Entitlement Management Messages - EMM" or "Rights Messages".

To enforce content protection, all types of messages, i.e. ECM/KSM, EMM, Rights Messages and the like, must be processed in, and all related rights, privileges and keys stored in, a secured environment.

Such an environment is typically offered by dedicated security modules such as intelligent cards ("Integrated Circuit Cards - ICC"), i.e. so-called smart cards, "Subscriber Identity Modules - SIM", or micro SD cards and USB devices containing a security module or specially protected software running in the receiving device .

Decryption of the content is done in the receiving device, but usually outside the security module that performs the message processing. This is partly because most types of security modules have not been able to decrypt content at high enough bit rates.

Systems based on this architecture represent a complete environment for content protection. Examples of systems are the Digital Video Broadcasting (DVB) framework for CAS with associated proprietary CAS from various vendors and the Open Mobile Alliance's (OMA) DRM.

Network convergence, multifunction terminals and high-capacity memory in portable devices today allow easy transfer of content from one medium to another, storage for later use, storage before transfer and use, and so on.

It would be most user-friendly if one could allow the movement of content from the domain in which it was received under the control of the access control system in this domain to another domain controlled by another access control system. This is generally not possible with current methods.

In order to achieve such trans-domain control over the content, one must, based on common (basically mono-domain) methods, in addition to decrypting the content with the content key and re-encrypting the content for the new domain, either: a) Translate the access criteria assigned to the content of the first domain to access criteria compatible with the next domain, or b) Sending access criteria for both domains, and possibly more domains, in parallel together with the encrypted content of the first domain.

Neither a) nor b) are in practice simple solutions:

Ad a): There exists a relatively large number of proprietary CAS/DRM systems, a) thus requires that a relatively large number of consistent translations be put in place for each of all relevant transitions between two domains.

An alternative is to develop some standard translations, but CAS/DRM actors have historically shown little desire for detailed standardization.

Ad b): Transfer formats for a given domain usually include security protocols and security messages only for that domain.

Transferring access criteria for other domains is therefore generally not supported.

The same problem with transition between domains also exists in principle for EMM/Rights Messages, but the transport of such messages is generally decoupled from the transport of the content itself. EMM/Rights Messages can be sent both before and after the transfer of the content, as well as via other means than the content. This differs from access criteria which must have a direct connection to the encrypted content.

The fact that both a) and b) are difficult to realize in practice prevents the secure transfer of protected content between domains. In other words, either the content must be opened and thus no longer protected, or the users must be refused to transfer the content between domains.

Two-way content distribution networks ease some of the restrictions imposed by one-way content distribution networks and the off-line transfer of content between domains as described above by allowing the sending side (also used server or source) to evaluate access criteria based on the receiver (also used client) identifying or authenticating to the sending side, whereupon the sending side either denies the recipient access to the content or releases the content for the recipient. Several variants of two-way mechanisms exist, and one of these is described in US patent US2008/0249946 A1. However, the degrees of freedom one achieves with two-way networks do not solve the challenges for one-way networks

content distribution network.

The invention proposes a new way of transporting access criteria that makes secure transfer of content to multiple domains and between domains easier.

DESCRIPTION OF THE INVENTION

The purpose of the invention is to simplify being able to use digital media content in several domains, and to simplify the transfer of access criteria from one domain to another.

According to the invention, by embedding or embedding the access criteria in the content itself, one can ensure that one or more sets of access criteria are with the content regardless of where it is transferred, including transfer to a different domain than the one in which the content was received. The embedded access criteria are then used of security modules to decide whether the content should be made available to the user.

While the original access criteria are added to the content by a rights and content issuer, the invention also includes that the user's security modules can change or add information about use, such as the number of times the content has been consumed, in the embedded access criteria as well as enter the identity of the user receiver unit or security module. Such identities are often referred to as (digital) fingerprints.ffingerprinting").

Methods for the invention are described in relation to the attached independent patent claims.

Other advantages, details and aspects of the invention appear from the associated independent patent claims.

Brief description of figures

The description of the invention refers to the following attached figures:

Figure 1: is a block diagram illustrating the main mechanism of the invention. Figure 2: shows how the invention supports the secure transfer of content from one

domain to another.

Figure 3: shows where user-specific information can be woven into the content before further transmission or use.

DESCRIPTION OF RECOMMENDED IMPLEMENTATION

With reference to the accompanying figures, the invention is discussed in the following through a description of the recommended implementation. Professionals will also be able to find other applications and variants within the scope of the invention as described by the independent patent claims.

According to the invention, a method is presented for how to enter or weave in access criteria into a stream of or a quantity of television/video content, music content, or other audiovisual content so that the access criteria are included in the content regardless of where the content is transferred or located.

Figure 1 shows a block diagram that illustrates an exemplary implementation of the invention. The figure shows the transfer of content from a content source, encryption, decryption and formatting for presenting the content to a user. Original content is marked a and comes from a camera or other type of source. The access criteria are generated by an access criteria generator A. The access criteria are a data structure that provides information on how the content can be used, stored and copied. Typical access criteria are the time and date of the last use of the content - "expiry date", the number of times the content can be used, whether the content is permitted to be copied in multiple copies, and so on. The access criteria should be secured with a cryptographic message checksum, possibly supplemented by an error-correcting code against intentional or unintentional alteration.

The content a and the access criteria (3) are sent to the function B which embeds the access criteria into the content. Such embedding can be simply placing the access criteria in a part of the content where it causes the least disruption (simple embedding) to interweaving the access criteria information using so-called watermarking techniques ( "watermarking").The use of watermarking techniques makes it difficult to retrieve the access criteria without destroying or degrading the content, which can be used to detect whether the access criteria really belong to the given content and have not, for example, been taken from other content.

Function B will typically not only enter the access criteria at the beginning of the content, but will do this continuously or repeatedly over the whole or sufficient parts or blocks of the content. The inclusion of the access criteria in the content should be done in a way that does not interfere with the user's use of the content. In other words, function B should work so that the access criteria do not need to be removed from the content before it is used.

The content with entered access criteria, e, is then encrypted by an encryption function C based on cryptographic keys, here referred to as content keys.

The content keys \ i used by C are generated by a key generator D. The key generator produces keys by deriving them from higher order keys (often called master keys or root keys) or by using a random number generator. The key generator can also carry out tests of whether the content keys have acceptable characteristics.

The content keys \ jl are also themselves encrypted using a

content key encryption function E with a domain key a. The resulting domain key encrypted content key 0 is normally sent alongside the content, but may also have been sent beforehand or sent after the content has been transmitted, in the same or in a different channel than the content. The content can be sent in parallel to different domains with different encryption functions C and content keys. The content keys are then encrypted in parallel with different domain keys to produce an encrypted content key for each domain. Some or all domains may also have shared domain or content keys.

The encrypted content p and the encrypted content key 0 are transmitted to the receiver unit R via a transmission format and network, typically satellite, cable or terrestrial transmissions in DVB format and broadband and Internet transmissions in Internet Protocol (IP) format.

The receiver unit contains a security module such as a secured chip mounted inside a decoder/STB or other types of receiver units or separate security modules such as a secure USB device, micro SD card or PCMCIA card. The security module S can also be specially security-hardened software.

The security module S also contains the domain key a. When the security module S has received the encrypted content key 6, it uses the domain key a and the decryption function T to regenerate the content key

The security module S uses the content key \jl and

the content decryption function U to decrypt p to retrieve the content e containing the access criteria.

The security module S has a function V that extracts a copy of the access criteria (3) from the content8. V does not remove the access criteria from the content.

The access control function W checks whether the access criteria are genuine and not manipulated, and if they are accepted, interprets and compares p with the relevant rights and privileges x stored in the security module.

If the access criteria p copied from the content match the rights and privileges x stored in the security module, then the security module can release the content in plaintext digital format e for use by the user.

The receiving unit's performance of these operations constitutes the invention's mode for direct use of the content.

Figure 2 shows another mode of the invention where the receiving unit R prepares the content for further distribution and use in a different domain than the domain in which the content was received. In connection with such trans-domain transfer, the invention has a particular advantage compared to other strategies for moving content between devices that can use or store the content. In this mode, the security module S does not release the content in plaintext digital format e. Instead, a function X will re-encrypt the content with generally a different content key co associated with a different domain to produce X.

The second content key co may be a local device key such as a High-bandwidth Digital Content Protection (HDCP) key or it may be a content key from a different CAS or DRM system than the CAS/DRM system used to protect the content during transfer to the safety module S.

In the same way that the first content key \ jl was encrypted with a domain key a, so co can be encrypted by a function Y with another domain key y with r| as a result.

The security module S sends out the encrypted content X and the encrypted content key r|. X and ri can (possibly be stored and) forwarded to other types of security modules in other types of receiver units/terminals which, by knowing \\ r, X, Y or their inverse, can produce and send out the plaintext content e for use by the user.

Another possibility that the invention offers is that the security module S adds additional information to the content or changes the access criteria information before the content is released or re-encrypted. Such additional information can be usage-oriented, for example indicating how many times and at what time the content has been used. The additional information may also be an identification of the security module used to process the access criteria and content. Insertion of additional information is illustrated in Figure 3 as the function Z. Z takes in the content8, and delivers the content% including the additional information in plain text.

The invention differs from other methods in that the access criteria are tied to the content instead of what is common, namely to tie the access criteria to the content keys. While other methods have the advantage of not being able to decrypt the content before a decision is made as to whether the content should be released, the invention, in that the content can contain access criteria for several domains, has precisely the advantage that the same content can be used in several domains, and the further advantage that a do not need to translate access criteria when transferring the content from one domain to another because the invention simplifies such transfer to only include decryption in one domain and re-encryption for the next domain.

The invention therefore allows the issuer of the content to enter (several sets of) access criteria that follow the content as it traverses and is used in different domains.

If one could do such traversal based on common techniques for transferring access criteria, then a sufficiently compatible translation of rights would have to exist for each domain-to-domain combination. Today, no or only a few such translations exist, which prevents secure traversal of content through domains. One could possibly have sent access criteria for all relevant domains alongside the content, but existing transfer protocols are generally not prepared for such multiple access criteria transport. For example, there is no prepared translation or performance of access criteria formatted and sent according to the DVB standard over in the Microsoft Protected Broadcast Driver Architecture.

The invention is also compatible with existing solutions in that existing solutions' methodology of sending access criteria next to the content can be combined with the invention's method of sending the access criteria inside the content. In this way, existing solutions can be used as before in their domains, for example to protect content distributed in DVB format via satellite. If the user then wishes to transfer and/or store the content, for example, in his home network, then the content can be decrypted and re-encrypted in a security module, and transferred to the other domain according to the invention. When the content is to be used in the other domain, the access criteria in the content are used as a basis for deciding whether and how access to the content should be granted.

Claims (11)

1. Method for transferring criteria for access to digital TV, digital video, digital audio or other digital audiovisual content that is subject to access control characterized by the fact that the access criteria (P) are incorporated into or woven into the digital content itself (a ) whereupon the digital content (e) is encrypted and the encrypted content (p) is sent to a receiving unit/user terminal (R) or is retrieved by a receiving unit/user terminal (R) containing a permanently mounted or detachable security module (S) as at de-encrypting the encrypted content (p) regenerates the plaintext content (e) and which extracts relevant access criteria (p) from the content (e) and which only releases the content (e) in plaintext for use by the user if the extracted access criteria (P) matches corresponding rights information or privileges (?) in the security module (S). 2. Method according to claim 1, characterized in that the security module (S) instead of, or in addition to, releasing the content (e) in clear text form re-encrypts the content (e) with the access criteria (P) still lying in the content (e) with the same or a different encryption algorithm (X) and keys (co) than those (C, \ i) used for the encrypted content (p) entering the security module (S). 3. Method according to claim 1, characterized in that the method is used in parallel/together with a conventional access control system (CAS) or digital rights management system (DRM) for which the access criteria are sent alongside the encrypted content. 4. Method according to claims 1,2 and 3, characterized in that the encryption algorithm (C) and the content keys tø) used to encrypt the content (e) are those used for the access control system as described in claim 3. 5. Method according to claim 1, characterized in that the security module (S) inserts / weaves in (Z) into the content (e) information that reflects the use the user has had of the content (e), where such information can be indicators of when the content was first used, the number of times it has been used, with more to enable control of, among other things, the number of times or within which time frame the content is used. 6. Method according to claim 1, characterized in that the security module (S) inserts / weaves in (Z) into the content (e) a representation of the security module's (S) unique identity before the content (e) is released for use according to claim 1 or for re-encryption according to claim 2 . 7. Method according to claims 1, 5 and 6, characterized in that watermarking techniques are used to weave in access criteria (p), usage information or representation of identity (Z) in the content (e). 8. Method according to claim 1, characterized in that several sets of access criteria (p) are inserted / woven into the content (e) so that the same representation of the content can be used by different types of security modules (S) where each set of access criteria (p) is compatible with a type of safety modules (S). 9. Method according to claim 1 and claim 2, characterized in that the keys thaw) which are used in connection with encryption of the content (e) are made available to the security module (S) in the terminal (R) so that the security module (S) can decrypt the content either by thawing the keys ): - is encrypted and sent alongside the encrypted content (p) to the security module (S). - generated in advance or afterwards and sent to the security module (S) either in the same channel as the content or via other channels, - re-generated by the security module (S) when necessary and based on a seed or master key. 10. Method according to claim 3 and claim 4, characterized in that the security module (S) in the terminal (R) can be realized as a physical module that handles access based on conventional CAS/DRM and a module that performs residual processing according to the requirements, and that the two modules are connected or communicate in a secure way. 11. Method according to claims 1, 5 and 6, characterized in that the access criteria (P), usage information or representation of identity (Z) can be entered continuously or repeatedly over all or sufficient parts of or blocks of the content.