Patent Publication Number: US-9418376-B2

Title: Method and system to digitally sign and deliver content in a geographically controlled manner via a network

Description:
CLAIM OF PRIORITY 
     This application is a continuation of and claims the benefit of priority under 35 U.S.C. §120 to U.S. patent application Ser. No. 12/013,278, filed on Jan. 11, 2008, which is a divisional of U.S. application Ser. No. 10/321,062 filed on Dec. 16, 2002, which issued as U.S. Pat. No. 7,404,084, which claims the priority benefit of International Application No. PCT/US01/19271, filed on Jun. 15, 2001, and of U.S. Provisional Patent Application No. 60/212,215, filed Jun. 16, 2000, which applications are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to the field of network communications and, more specifically, to a method and system for digitally signing content for secure distribution and delivery via a communications network. 
     BACKGROUND OF THE INVENTION 
     The proliferation of networks, and the widespread acceptance of the Internet as a communication and distribution channel in particular, have presented a number of opportunities for pay media content distribution. Specifically, broadband Internet Protocol (IP) networking and satellite technologies have provided a number of new opportunities for publishing and media content distribution worldwide. The ability of networks to support resource-intensive media, such as streaming media multicasting, is growing rapidly as satellite and broadband IP technologies allow content and service providers to distribute high-quality video to millions of subscribers simultaneously. 
     However, these opportunities have been accompanied by concerns regarding content piracy and digital rights management (DRM). A challenge facing traditional pay media distributors is to enable content providers to control their proprietary content, while maintaining the flexibility to distribute media content widely. The increased distribution potential heightens the need to protect and secure media content. For example, a content provider may have particular concerns regarding preventative measures to minimize the possibility of premium content falling into wrong hands, and the enforcement of copyrights. 
     Conditional Access (CA) technology for traditional broadcasting systems is based on implementing business rules in a secure device (e.g., a smart card) located at the subscriber receiving device. Access to content is controlled by encrypting the content with a key. The secure device will only release this key to the decrypting device if the subscriber fulfills the access conditions set by the operator. A problem with such security systems is that the secure devices in the field need to be replaced when new business rules are introduced or when the security system is ‘hacked’. When a large number of secure devices in the field need to be updated, it will be appreciated that the cost implications are significant. In the case of large numbers this can be a very expensive exercise. 
     The Internet is becoming a platform for content delivery to millions of users worldwide. Using the Internet for secure content delivery introduces several problems. For example, standard Client/Server systems often cannot handle the load associated with large pay-per-view events, as a single central security server is typically not equipped to handle millions of events in a short time period. Further, standard Client/Server systems typically require that a single content encryption key be shared by all users, rendering such systems vulnerable to key hook piracy (extracting the key and distributing the key to unauthorized users). Distributed security systems to manage access to content (e.g., LDAP) partially address the first problem identified above, but do not protect the content encryption keys from unauthorized operators. 
     A rapidly growing broadband Internet audience is making the Internet an exciting place to stream audio and video directly to millions of users worldwide. To overcome Internet congestion, streaming media may be pushed to the edges of the Internet (e.g., to the ISP&#39;s), where it is cached and from where the media can be streamed at high quality to the end user. Content owners are increasingly using the Internet are a platform to deliver high quality programming to a large and rapidly growing audience. However, content providers are often reluctant to put premium content on the Internet, as digital content can easily be stored, forwarded and copied without any degradation by any user with a computer and a (broadband) Internet connection. Copy protection standards, such as those specified by 5C, at the end user device using a physical secure device for decryption are expensive and somewhat unsafe. An experienced hacker can typically break into the secure device and retrieve the decrypted content and redistribute the content anonymously or, in a worst-case scenario, retrieve a decryption key and redistribute the content anonymously. 
     Watermarking techniques at the end user device using a physical secure device may be expensive and unsafe, as any experienced hacker can break into the secure device and “catch” the content before it is watermarked. 
     When content is encrypted and distributed to a large group of subscribers via a communications network, there exists a danger that one of the subscribers may decrypt the content and, during the decryption process, extract a content (or product) encryption key that was used by a content provider to encrypt the content. Assuming the encrypted content is easily available for unauthorized users, this allows for so-called “key hook piracy” whereby the fraudulent, authorized user distributes the product key to unauthorized users, possibly together with the encrypted content. Distributing a single content encryption key over a communications network, such as the Internet, can be done very efficiently. 
     When a content provider wants to secure and sell premium content for distribution over a large worldwide network, such as the Internet, there are a number of functions and systems that may need to be installed for a successful implementation. For example, secure storage and distribution of content encryption (or product) keys may be required to prevent exposure of the content (or product) encryption keys to a fraudulent operator or user. The exposure of such content encryption keys may result in a significant loss of revenue because of piracy. Further, a secure and scaleable key distribution system, which can manage a large number of subscribers simultaneously, may need to be in place. A scalable key distribution system may become critical to distribute content associated with large-scale live events. The implementation and operational costs associated with system software and hardware required to implement these functions may be high for a single content provider. 
     Current hardware-based content security solutions typically combine user authentication and content security in one module (e.g., a single smart card or other tamper proof environment is used to authenticate the user and store/process content keys). This arrangement does not allow for situations in, which a user orders content, using a secure identification device (such as a PKI-enabled banking smart card or mobile device including a PKI-enabled SIM chip), and views the content using a copy-protected viewing device other than a viewing device that is integral with the secure identification device. For example, the user may wish to access the content utilizing a copy-protected device that is not linked with a specific user, and that can therefore not be used to identify the user. 
     Content licenses, such as those implemented by Microsoft Windows Media Digital Rights Management (DRM) technology and Intel ISIS, are signed by a private key of the license issuer as proof of the authenticity of the license to a content player (e.g., a set-top box). The signature of the content license with a private key prevents hackers from altering valid licenses and generating invalid licenses. However, assigning a license utilizing a private key operation is computationally expensive when a large number of simultaneous transactions are required. In addition, the implementation and operational costs of managing private keys and associated certificate authorities may be prohibitive. 
     Networks (e.g., the Internet) are becoming increasingly attractive to content providers as alternative distribution platforms for content, next to traditional TV broadcasting. It is desirable to provide a content distributor with a degree of geographic control over the distribution of content and to enable a content distributor to block users in certain countries or regions from accessing certain content. For example, a sports club may want to distribute a live game over the Internet worldwide, but may need to block users in certain countries from accessing the content due to exclusive broadcasting rights that have been sold to national broadcasters. 
     Traditional network-based pay media solutions require users to register payment information (e.g., credit card details) with a content distributor. This approach poses a number of burdens on users. Specifically, users may be required to provide financial information to companies (e.g., content distributors) that they do not trust. Further, users may be required to provide substantially identical financial information to a large number of content distributors if a user obtains content from a variety of sources. These burdens potentially create a barrier to entry for users. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided a method and system to digitally sign a content license associated with content. The content license is generated at a content provider. The content license is signed utilizing a symmetric key. In an exemplary embodiment, symmetric key encrypts the content. In an alternative exemplary embodiment, symmetric key encrypts a product key that in turn encrypts the content. 
     According to another aspect of present invention, there is provided a method and system to distribute content via a network in a geographically controlled manner. A request is received from a content requestor for delivery of content to the content requestor via the network. A content requestor authentication process is performed, the content requestor authorization process including determining a geographic location associated with the content requestor, determining geographic access criteria associated with the content, and determining whether the geographic location complies with the geographic access criteria. The content is released delivery to the content requestor if the content location complies with the geographic access criteria. In one exemplary embodiment, the determining of the geographic location includes determining a delivery address to which a copy-protected device associated with the content requestor was delivered. In an alternative exemplary embodiment, the determining of the geographic location includes determining a delivery address that a user authentication device associated with the content requestor was delivered. The determining of the geographic location may also include mapping a source network address of the request for the delivery of the content to a request source location. 
     Other features of the present invention will be apparent from the accompanying drawings and from the detailed description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements and in which: 
         FIG. 1  is a block diagram illustrating processing of content as it is communicated from a content provider, via a content distributor, to a content destination, according to an exemplary embodiment of the present invention. 
         FIG. 2  is a block diagram illustrating further details regarding software components that may reside at various locations of the content distribution system to facilitate distribution and delivery processes, according to an exemplary embodiment of the present invention. 
         FIG. 3  is a block diagram illustrating further architectural details regarding an exemplary embodiment of a content distribution system. 
         FIG. 4  is a diagrammatic representation of a number of real-time processes, databases and user interfaces that together provide the functionality of a conditional access server, according to an exemplary embodiment of the present invention. 
         FIG. 5  is a block diagram illustrating various processes that constitute a conditional access agent, according to an exemplary embodiment of the present invention. 
         FIG. 6A-6B  show a flowchart illustrating a method, according to an exemplary embodiment of the present invention, of processing a content request received from a content destination. 
         FIG. 7  is a flowchart illustrating a method, according to an exemplary embodiment of the present invention, of securely delivering content from a content provider to a content destination via a content distributor, where the content distributor performs an association operation relating to the content. 
         FIGS. 8A-8B  are block diagrams illustrating, at a high level and according to an exemplary embodiment of the present invention, a method of combating key-hook piracy by encrypting clear content with a relatively large number of random, time varying session keys. 
         FIG. 9  is a flowchart illustrating a method, according to an exemplary embodiment of the present invention, of encrypting content utilizing a random, time varying sequence of session keys to combat key-hook piracy. 
         FIGS. 10A-10B  show a flow chart illustrating a method, according to an exemplary embodiment of the present invention, of distributing cached content from a content distributor to a content destination, responsive to a request for the content from the content destination. 
         FIG. 11  is a block diagram illustrating a pay media conditional access service provider, according to an exemplary embodiment of the present invention, and illustrates an interaction of a conditional access service provider with multiple content providers, as well as with one of multiple conditional access agents. 
         FIG. 12  is a flowchart illustrating a method, according to an exemplary embodiment of the present invention, whereby a conditional access service provider provides security functions to multiple parties within a content distribution system. 
         FIG. 13  is a flowchart illustrating a method, according to an exemplary embodiment of the present invention, of generating a product key at a content provider and storing the product key at a conditional access provider. 
         FIG. 14  is a flowchart depicting a method, according to an exemplary embodiment of the present invention, of distributing an agent secret key from a condition access agent to an ASP conditional access server. 
         FIG. 15  is a flowchart illustrating a method, according to an exemplary embodiment of the present invention, of product key distribution from a conditional access service provider to a conditional access agent. 
         FIG. 16  is a block diagram illustrating a system, according to an exemplary embodiment of the present invention, that provides a product key to access content upon receipt and verification of two separate certificates, namely a user device certificate and a copy-protected device certificate. 
         FIG. 17  is a flowchart illustrating a method, according to an exemplary embodiment of the present invention, to secure content for distribution via a network by employing separate user device and copy-protected device authentication processes to protect content from unauthorized access. 
         FIG. 18  is a flowchart illustrating a method, according to an exemplary embodiment of the present invention, of communicating a product key, encrypted with the public keys of both a copy-protected device and a user authentication device. 
         FIG. 19  is a diagrammatic representation of a content license, according to an exemplary embodiment of the present invention. 
         FIG. 20  is a flowchart illustrating a method, according to an exemplary embodiment of the present invention, of signing a content license utilizing a symmetric key. 
         FIG. 21  is a diagrammatic representation of a further content license, according to an exemplary embodiment of the present invention, that is signed utilizing a digital signature in the form of a symmetric key. 
         FIG. 22  is a flowchart illustrating further details regarding a method, according to an exemplary embodiment of the present invention, of generating a digital signature for a license utilizing a symmetric key. 
         FIG. 23  is a flowchart illustrating a method, according to an exemplary embodiment of the present invention, of verifying a content license utilizing a digital signature that embodies a symmetric key. 
         FIG. 24  is a flowchart illustrating a method, according to an exemplary embodiment of the present invention, of distributing content via a network in a geographically controlled manner. 
         FIG. 25  is a flowchart illustrating a method, according to an exemplary embodiment of the present invention, to dynamically present a payment gateway to a content requestor. 
         FIG. 26  illustrates an exemplary sequence of interfaces that may be presented by a client application executing at a content destination to present an order list of payment gateways. 
         FIG. 27  is a block diagram illustrating a machine, in an exemplary form of a computer system, that may operate to execute a sequence of instructions, stored on a machine-readable medium, for causing the machine to perform any of the methodologies discussed in the present specification. 
     
    
    
     DETAILED DESCRIPTION 
     Methods and systems to digitally sign and distribute content in a geographically controlled manner via a network are described. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be evident, however, to one skilled in the art that the present invention may be practiced without these specific details and that these specific details are exemplary. 
     Overview—Content Distribution System 
       FIG. 1  is a diagrammatic representation of a content distribution system  10 , according to an exemplary embodiment of the present invention. The system  10  may conceptually be viewed as comprising a distribution process  12  and a delivery process  14 . Within the distribution process  12 , multiple content providers  16  (e.g., a content producer or owner) distribute content via a network  18  (e.g., the Internet (wireless or wired)) to content distributors (or distribution points)  20 . The distribution of content from a content provider  16  to a content distributor  20  may be as a multicast via satellite, as this provides an economic way to distribute content to a large number of content distributors  20 . 
     Each of the content distributors  20  caches content received from multiple content providers  16 , and thus assists with the temporary storage of content near the “edges” of a network so as to reduce network congestion that would otherwise occur were a content provider  16  to distribute content responsive to every content request received from a content consumer. Each content distributor  20  is equipped to respond to requests received via the network  18  from the multiple content destinations  22  (e.g., users) within a specified service area or conforming to specific criteria. Specifically, a content distributor  20 , after performing the necessary authorization and verification procedures, may forward content that it has cached to a content destination  22  or, if such content has not been cached, may issue a request for the relevant content to a content provider  16 . For example, if the content comprises a live “broadcast”, the content may be directly forwarded via the content distributor  20  to the content destination  22 . 
     Typically, a request for content from a content destination  22  is re-routed to content distributor  20  located nearby the requesting content destination  22 . The requested content is then streamed (or otherwise transmitted) from the content distributor  20  to a media terminal (e.g., a personal computer (PC), set-top box (STB), a mobile telephone, a game console, etc.) at the content destination  22 . 
       FIG. 1  illustrates, at a high-level, the processing of content as it is communicated from a content provider  16 , via a content distributor  20 , to a content destination  22 . At the content provider  16 , clear content  24  is encrypted utilizing, for example, a symmetric product key (or content key) to generate encrypted content  26 . It will thus be appreciated that the content provider  16  will be particularly concerned about security pertaining to the product key as access to this key potentially allows for regeneration of the clear content  24 . The encrypted content  26  (or cipher text) is then communicated from the content provider  16 , via the network  18 , to the content distributor  20 . A conditional access agent  28 , which represents the interests of the content provider  16  at the remote content distributor  20 , may perform a number of operations in a secure environment with respect to the encrypted content  26 . In one embodiment, the conditional access agent  28  decrypts the encrypted content  26  to regenerate the clear content  24  within a secure environment, and watermarks the clear content for distribution to a specific content destination  22 . Watermarked content  30  may then be distributed from the content distributor  20  via the network  18 , to a conditional access client  32  at the content destination  22 . In an alternative embodiment, the conditional access agent  28  at the content distributor  20  may re-encrypted the content with a public key of a copy-protected device at the content destination  22 . In any event, the clear and watermarked content  30  is then available for viewing and consumption at the content destination  22 . 
       FIG. 2  is a block diagram showing further details regarding software components that may reside at the various locations of the system  10  to facilitate the distribution and delivery processes  12  and  14 . The content provider  16  operates a content provider server  34  that is responsible for the actual distribution of content from the content provider  16 . For example, the content provider server  34  may comprise a streaming media server (e.g., the Real Networks streaming media server developed by Real Networks of Seattle, Wash. State or a Microsoft media server developed by Microsoft of Redmond, Wash. state). A conditional access server  36  (e.g., the Sentriq Server developed and distributed by Mindport Sentriq from San Diego, Calif.) operates to define and store access rights to content of the content provider  16 , to perform digital rights management, to encrypt content, and to manage and distributed product keys. To this end, the content provider server  34  and the conditional access server  36  are shown to communicate registration keys and access criteria. 
     While the conditional access server  36  is shown to reside with a content provider  16 , in an alternative embodiment, a conditional access server  37  may reside at a conditional access service provider (ASP)  38 . In this case, the conditional access server  37  may perform the above-described functions for multiple content providers  16 . 
     The exemplary content distributor  20  is shown to host a local content server  40  and a conditional access agent  28 . The local content server  40  may again be a streaming media server that streams cached (or freshly received) media. The conditional access agent  28  operates to provide intelligent content and revenue security to content providers  16  by processing access and revenue criteria, personalizing content for delivery to a content destination  22 , and personalizing and managing key delivery to a content destination  22 . Broadly, the conditional access agent  28  operates securely to authenticate a content destination  22  (e.g., utilizing secure tokens and X.509 certificates), securely to retrieve and cache product key information and access criteria, and to forward processed transactions to a commerce service provider  42  that provides billing and clearance services. For example, a conditional access agent  28  may evaluate a content request from a content destination  22  based on access criteria specified by a content provider  16 , local date and time information, and user credentials and authentication. If a content destination  22  is authorized and/or payment is cleared, requested content may optionally be decrypted, personally watermarked, personally re-encrypted and delivered to the content destination  22 . 
     A content destination  22  is shown to include a secure device  46  (e.g., a copy-protected device such as a set-top box (STB)) and to host a conditional access client  48 . The conditional access client  48  may reside on a personal computer or on the secure device  46 . Where the conditional access client  48  resides on a personal computer it may, for example, launch responsive to the issuance of a request from a further client program (e.g., a browser), for access certain content. The conditional access client  48  operates to communicate a public key of the secure device  46  to a conditional access agent  28  and also performs user authentication to verify that a particular user is authorized to initiate a transaction. The conditional access agent  28  utilizes copy-protected device technology to stream content to a viewing device. 
     To review, the content distribution system  10  is implemented by a distributed collection of conditional access servers  36 , conditional access agents  28 , and conditional access clients  48  that operate in conjunction with media servers and viewing devices (e.g., players) to protected the rights of a content provider  16  in specific content, while facilitating the widespread distribution of content. A conditional access server  36  enables the content provider  16  to encrypt and associated access criteria (e.g., pay-per-view, pay-per-time, subscription) with content. The conditional access server  36  also manages subscriptions and provides monitoring and statistic tools to a content provider  16 . A conditional access agent  28  is a cryptographic component that insures that access criteria, as defined by content providers  16 , are enforced. Conditional access agents  28  are located within a distribution network (e.g., at an edge server) and validate subscriber content requests against, for example, content access criteria, local date and time, and subscriber credentials. A conditional access client  48  is located at a destination device (e.g., the PC, a STB, and mobile phone, game console or the like) and manages an interface between a secure device  46  and a subscriber. 
       FIG. 3  is a block diagram showing further architectural details regarding an exemplary embodiment of a content distribution system  10 . The functioning of the various components of the content distribution system  10 , as shown in  FIG. 3 , will now be the described in the context of registration, content ordering and transaction processing operations. 
     The content distribution system  10  consists of a number of sub-systems that together provide a required functionality. In one embodiment, these sub-systems seek to enable the Internet infrastructure to be utilized as a safe and secure medium for online selling and buying of content, data, programs, products and services context, including video and audio encoders, servers, players, clearing systems and existing Web sites. 
     The content distribution system  10 , in one embodiment, seeks to provide at least the following functions:
         (1) Conditional access to management through various access criteria schemes.   (2) End-to-end content security and copy protection, using encryption and watermarking technology.   (3) Transaction and purse management, using Public Key Infrastructure (PKI) and eXtensible Markup Language (XML) technology.   (4) Pay-per-view, pay-per-time and subscription based access.   (5) Access control on the basis of region and date/time.   (6) Varying prices on the basis of region and date/time.   (7) Management of a variety of (debit and credit) purses.   (8) Scaling to many (simultaneous) subscribers using a highly distributed architecture.   (9) Secure device portability, using the standard PKCS#11 interface.   (10) User platform portability by defining an interface based on HTTP and XML, allowing a range of subscriber platforms (PC/STB/GSM).       

     The above listed functions, in one embodiment, are enabled primarily by the following components:
         (1) Conditional access clients  48  are located at content destinations  22  to sign content transactions and manage the content decryption process. The conditional access clients  48  each operate in conjunction with a secure device  46  (e.g., an e-Token or smart card).   (2) Conditional access servers  36  are located at content providers  16  or at conditional access service providers  38  as a content security ASP for merchants. In the conditional access service provider embodiment, a content provider  16  may access a website operated by the conditional access service provider  38  to secure content and to define access conditions (pay per view, subscription, etc) associated with the content.   (3) Conditional access agents  28  are located at various points within network to act as “brokers” enforcing the security settings that are associated with content by content providers  16 . Conditional access agents  28  may optionally include additional encryption and watermarking technology to increase the level of security ‘at the last mile’.   (4) Secure device servers  44  are located at commerce service providers  42  (e.g., pay-media operators) or payment gateways to manage the secure devices and associated purses in the field.       

     For the purpose of the immediately following description, assume that content has already been decrypted by a content provider  16 . Live content requires a slightly different approach at the initial stage of content protection (real-time encryption is required). 
     A content registration and protection operation is initiated by a content provider  16  that has a content item that needs to be secured from unauthorized access. In one embodiment, the content provider  16  accesses a Web server operated by the conditional access service provider  38 , from which the content provider  16  downloads a content security management application (not shown). The content security management application allows the content provider  16  to secure (encrypt) the content and associate the content with particular access criteria. The content is registered at the conditional access server  37 , operated by the conditional access service provider  38 , together with the access criteria and a product key that was used for encryption of the content. A unique Uniform Resource Locator (URL) linking to the access criteria is included in a content description file (ASX, SDP or SAP). The content is thus secured and may now be distributed using, for example, unicast or multicast. 
     A content ordering operation is commenced upon receipt of a request from a content destination  22  (e.g., a user) for specific content. The user may, for example, be running a browser on a personal computer and want to view a content item provided by of a particular content provider  16 . When selecting the content item, the browser detects a tag containing a URL. The browser passes the URL to the conditional access client  48 , also executing on the personal computer, to commence a transaction. 
     The conditional access client  48  initiates a secure session with a conditional access agent  28  to request an order for the relevant content item. If the content item is not cached at the content distributor  20  as cached content, the conditional access agent  28  retrieves access criteria for the requested content item from the conditional access server  36  and forwards a derived XML signing request to the conditional access client  48 . The conditional access client  48  parses the XML signing request, displays order information (such as a price) to the user and prompts for a Personal Identification Number (PIN) code and confirmation by way of a user interface. The user confirms the order, and the conditional access client  48  digitally signs the order confirmation using the secure device  46 . The signed order is sent to the conditional access agent  28  that verifies the signed confirmation order and the user credentials. The conditional access agent  28  manages the content security process (e.g., watermarking, re-encryption) until an access time has expired, after which the content destination  22  will no longer be able to access the content. 
     A transaction processing operation occurs concurrently with the content ordering operation. More specifically, the conditional access agent  28  will forward the signed confirmation order (i.e., transaction) to the secure device server  44  of the commerce service provider  42  to update a secure device purse and to prepare the transaction for clearing. The commerce service provider  42  processes the transaction and makes the appropriate money transfers. 
     The secure device server  44  interfaces with an external commerce service provider  42  to forward secured transactions. In one exemplary environment, a pay media operator or payment gateway is hosted by the service provider  42 . The value of the transaction may be negotiated between the various parties (content owner/provider, network provider/ISP, payment gateway, etc). 
     The conditional access client  48  interfaces with the secure device  46  at the content destination  22 . Example secure devices  46  are smart cards or e-Tokens. A secure device  46  may utilize the PKCS#11 interface to provided device independent. 
     The content destination  22  may also employ client devices utilizing non-PC client platforms, such as Set Top Boxes (STBs) and mobile telephones enabled with (smart card) PKI technology. A client device employed at a content destination  22  may run an interactive application (such as the OpenTV software suite) to order secure content items using a regular pay television smart card. 
     The conditional access client  48  and secure device  46  interface with the local content server  40  (e.g., a media server) and client applications to secure a control channel (such as RTSP or HTTP) and data channel (such as MPEG-4 over RTP). 
     The secure device server  44  provides an interface for external payment registration servers (such as used for regular web sites) to allow automated purse management. 
     Overview—Conditional Access Server  36   
     As stated above, a conditional access server  36  may reside at a content provider location, or may be deployed by a conditional access service provider  38 . A conditional access server  36  provides at least the following functions:
         (1) Allows content providers  16  to assign access criteria (or rule information) to content.   (2) Allows content providers  16  to create and manage content products (subscription types).   (3) Management of the content encryption keys and key distribution to the conditional access agents  28 .   (4) Management of subscriptions (generation, storage and distribution) and forwarding of signed subscription transactions to a commerce service provider (e.g. a payment gateway).   (5) Processing of transactional information (monitoring).       

     Each of the above functions will now briefly be described. The content provider  16  defines the access criteria (AC) using an access criteria profile editor (or Digital Rights Manager) (not shown) that generates a unique URL that is distributed together with the content. The generated access criteria are stored in a database together with the appropriate product key (optionally encrypted under a storage key), a digital signature and a content tag (i.e., a short description). A conditional access agent  28  retrieves the appropriate access criteria when subscribers request access to the associated content. The access criteria are stored in such a way that retrieval can be performed efficiently (e.g., the criteria are organized by content provider and location for which the access criteria is appropriate). 
     Conditional access agents  28  are assigned a certain location identifier (ID), according to the physical region that they serve. Multiple conditional access agents  28  may be assigned to the same location ID. The conditional access server  36  will map the conditional access agent ID to the appropriate region ID&#39;s to lookup the access criteria that are suitable for that agent, if any. 
     As locations may be assigned to multiple regions, and access criteria may be defined for multiple regions, there may be a conflict (one location may map to multiple conflicting access criteria sets). To address this conflict, the operator can associate a region priority code to indicate which region should be given priority. 
     A content provider  16  may also define new content products and manage subscription requests utilizing the conditional access server  36 . A content product may, for example, have an identifier, a name, duration (usually a month), a start date and end date. A subscription may be an “instance” of a content product associated with a certain secure device that ordered the product and a subscription start and end date. 
     A conditional access server  36  also processes incoming transactions and forwards them to the appropriate commerce service provider  42 . The content provider  16  may be able to monitor the processed transactions. 
       FIG. 4  is a diagrammatic representation of a number of real-time processes, databases and user interfaces that together provided the functionality of a conditional access server  36 , according to one embodiment of the present invention. The below described server processes of the conditional access server  36  communicate with external processes, such as a conditional access agent  28  and the secure device server  44 , utilizing the described interfaces. 
     A content rights manager  60  allows a content provider  16  to associated access rights and criteria with content items. Access rights are organized utilizing profiles in order to reduce operational efforts. Profiles may be created utilizing a profile rights manager  62 . The profile rights manager  62  allows a content provider  16  to create templates for access criteria, based on regional, time, payment and subscription parameters. A product manager  64  allows a content provider  16  to define content products that are available for subscription. 
     A cash monitor  66  is a user interface to monitor the value of transactions for a particular content provider  16 , potentially in real-time. An access criteria server  68  is a HTTP server providing access criteria and keys to conditional access agents  28 . 
     A subscription form server  70  is a HTTP server providing subscription forms (e.g., a signed list of subscriptions) for a specific secure device to conditional access agents  28 . Specifically, a subscription form is a clear XML text of a current subscription associated with a secure token, signed by the conditional access server  36 . A subscription form contains a signed list of time-constrained subscriptions bound to an issuer (e.g., a content provider  16 ) and a secure device serial number. A subscription form is signed by the conditional access server  36  to prove the authenticity thereof and maintain integrity. 
     A subscriber server  72  is a HTTP server that can securely process subscription requests. A transaction server is utilized to monitor transactions and update the real-time cash monitor  66 . 
     Below are set out a number of tables and fields, according to an exemplary embodiment of the present invention, which may be utilized by the conditional access server  36 . 
     A table Resource represents general resource values for the conditional access server  36 . This table is used to store system variables such as the port number for accepting AC server connections or the debug level. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                   
                 ResourceId 
               
               
                   
                 Name 
               
               
                   
                 Value 
               
               
                   
                 DefaultValue 
               
               
                   
                 Description 
               
               
                   
                   
               
               
                   
                 ResourceId is the unique key. 
               
            
           
         
       
     
     The table Product represents product information. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 ProductIssuerId 
                 Issuer of the product 
               
               
                   
                 ProductId 
               
               
                   
                 Name 
               
               
                   
                 Duration 
                 Used in combination with field below . . . 
               
               
                   
                 DurationUnit 
                 Subscription duration unit 
               
               
                   
                   
                 1 = minutes, 2 = hours, 3 = days, 4 = weeks, 
               
               
                   
                   
                 5 = months, 6 = years 
               
               
                   
                 Duration2 
                 Absolute value of the duration (future use 
               
               
                   
                   
                 only, when ‘Duration’ and ‘DurationUnit’ 
               
               
                   
                   
                 are not flexible enough) 
               
               
                   
                 ParentalCode 
                 Minimum age for accessing content 
               
               
                   
                 AutoRenewal 
                 Subscription is automatically renewed after 
               
               
                   
                   
                 expiration (future use) 
               
               
                   
                 StartDate 
                 Product becomes available for sale 
               
               
                   
                 EndDate 
                 Product no longer available 
               
               
                   
                 InfoURL 
                 URL to subscription information 
               
               
                   
                   
               
               
                   
                 ProductIssuerId and ProductId form the unique key. 
               
            
           
         
       
     
     The table ProductAC represents the access criteria (usually payment) for a subscription using a certain payment gateway or commerce service provider. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 ProductIssuerId 
                   
               
               
                   
                 ProductId 
               
               
                   
                 PGWId 
                 Payment gateway ID 
               
               
                   
                 ParentalCode 
                 Minimum age (future use, if you want to 
               
               
                   
                   
                 have parental rating control per payment 
               
               
                   
                   
                 gateway. I.e. nationality related) 
               
               
                   
                 Price 
                 Price in whole units 
               
               
                   
                   
                 (25, 50 is represented as 2550) 
               
               
                   
                   
               
               
                   
                 ProductIssuerId, ProductId and PGWId form the unique key. 
               
            
           
         
       
     
     The table Region represents regional information. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                   
                 CountryId 
               
               
                   
                 RegionId 
               
               
                   
                 Name 
               
               
                   
                   
               
               
                   
                 CountryId and RegionId form the unique key. 
               
            
           
         
       
     
     The table Country represents the geographical information. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 CountryId 
                   
               
               
                   
                 CountryCode 
                 3 character country code as defined by ISO 
               
               
                   
                 Name 
                 Like ‘Chello Amsterdam’ or ‘RoadRunner 
               
               
                   
                   
                 SD’ 
               
               
                   
                   
               
               
                   
                 CountryId is the unique key. 
               
            
           
         
       
     
     The table Merchant represents the content providers  16  that have access to the conditional access server  36 . 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 MerchantId 
                 Merchant 
               
               
                   
                 Name 
                 Name of the merchant 
               
               
                   
                 EMail 
                 E-mail address of merchant 
               
               
                   
                 InfoURL 
                 Link to information 
               
               
                   
                   
               
               
                   
                 MerchantId and PGWId form the unique key. 
               
            
           
         
       
     
     The table MerchantUser represents the users (operators) of content providers  16 . They possess a secure token to access the conditional access server  36 . This table is used to verify the identity of the content providers  16  when he or she logs on to the system. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 Serial 
                 Secure device serial number 
               
               
                   
                 MerchantId 
                 Content provider ID linked with the secure 
               
               
                   
                   
                 device. 
               
               
                   
                 EMail 
                 E-mail address of user 
               
               
                   
                 UserName 
                 (Optional) name of the user 
               
               
                   
                 AccessRights 
                 Integer representing user&#39;s access rights. 
               
               
                   
                   
                 This allows a way to distinguish the access 
               
               
                   
                   
                 rights of a certain user (for example: A user 
               
               
                   
                   
                 is allowed access to certain applications 
               
               
                   
                   
                 only). 
               
               
                   
                 SecretKey 
               
               
                   
                 PublicKey 
               
               
                   
                   
               
               
                   
                 Serial is the unique key. 
               
            
           
         
       
     
     The table MerchantPGW represents the payment gateways (or commerce service providers) that have a clearing agreement with the content providers  16 . 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 MerchantId 
                 Merchant 
               
               
                   
                 PGWId 
                 Payment gateway 
               
               
                   
                   
               
               
                   
                 MerchantId and PGWId form the unique key. 
               
            
           
         
       
     
     The table CAAgent represents information about the conditional access agents  28  in the field. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 NetworkId 
                 Network in which it is located (e.g. 
               
               
                   
                   
                 RoadRunner) 
               
               
                   
                 AgentId 
               
               
                   
                 CountryId 
                 Integer representing the country location 
               
               
                   
                 RegionId 
                 Integer representing the actual location (e.g. 
               
               
                   
                   
                 Amsterdam). 
               
               
                   
                 Type 
                 Type of agent (token, PCMCIA, etc) 
               
               
                   
                 Version 
                 Hardware/Software version 
               
               
                   
                 SerialNumber 
                 Serial number of CA Agent secure device 
               
               
                   
                 Host 
                 Host (address) of CA Agent 
               
               
                   
                 SecretKey 
                 CA Agent Secret key (encrypted with 
               
               
                   
                   
                 storage key) 
               
               
                   
                 PublicKey 
                 CA agent Public Key 
               
               
                   
                   
               
               
                   
                 NetworkId and CAAgentId form the unique key. 
               
            
           
         
       
     
     The table Network represents information about the network of conditional access agents  28 . 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 NetworkId 
                   
               
               
                   
                 Name 
                 Name of the network provider (e.g. 
               
               
                   
                   
                 @Home) 
               
               
                   
                 Notes 
                 Contractual notes 
               
               
                   
                 EMail 
                 E-mail address of network provider 
               
               
                   
                 InfoURL 
                 URL to information about network provider 
               
               
                   
                   
               
            
           
         
       
     
     The table PaymentGateway represents payment gateway information. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 PGWId 
                   
               
               
                   
                 Name 
               
               
                   
                 SdsHostName 
               
               
                   
                 Type 
                 Type of payment gateway (1 is reserved for 
               
               
                   
                   
                 anonymous payment gateway) 
               
               
                   
                 Format 
                 Currency format string for future use 
               
               
                   
                 ISOCurrency 
                 ISO currency code 
               
               
                   
                 EMail 
                 E-mail address of payment gateway 
               
               
                   
                 InfoURL 
                 URL to payment gateway information 
               
               
                   
                   
               
               
                   
                 PGWId is the unique key. 
               
            
           
         
       
     
     The table CountryPaymentGateway represents the payment gateways per country. This table is used to limit the number of selectable payment gateways depending on the selected country/region when assigning access criteria to an item. 
                                             Field   Description                          CountryId               PGWId                       CountryId and PGWId form the unique key.            
Subscription Tables
 
     The subscription tables are only accessed by the subscription form server  70  and subscriber server  72 . 
     The table SubscriptionForm represents the subscriptions that have been issued to subscribers on behalf of a content provider  16 . 
                                             Field   Description                          IssuerId   Either 0 (Entriq) or the merchant ID           DeviceSerial   Unique serial of secure device           SubscriptionForm   Digitally signed subscription form                       IssuerId and DeviceSerial form the unique key.            
Access Criteria Tables
 
     The table ItemAC links a particular item (content) with an access criteria profile and a key. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 MerchantId 
                 Merchant ID 
               
               
                   
                 ItemId 
                 Unique item (content) ID 
               
               
                   
                 Description 
                 Short description of content, displayed to 
               
               
                   
                   
                 subscriber at confirm. 
               
               
                   
                 ProfileId 
               
               
                   
                 Policy 
                 Policy indicating security parameters 
               
               
                   
                   
                 such as encryption algorithm, key length, 
               
               
                   
                   
                 etc. 
               
               
                   
                 ProductKey 
                 (Prime) Product key used for encryption 
               
               
                   
                   
                 of content 
               
               
                   
                 Format 
                 Encoding format such as MPEG-2/ 
               
               
                   
                   
                 MPEG-4, Real, Windows codec etc. 
               
               
                   
                 Bandwidth 
                 Bandwidth in bits/second 
               
               
                   
                   
               
               
                   
                 MerchantId and ItemId form the unique key. 
               
            
           
         
       
     
     There is an index on Description, to allow for quick searching on a description. 
     The table ACProfile represents a profile for access criteria and links to actual access criteria sets. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 MerchantId 
                   
               
               
                   
                 ProfileId 
               
               
                   
                 Name 
               
               
                   
                   
               
               
                   
                 MerchantId and ProfileId form the unique key. 
               
            
           
         
       
     
     The table ACProfileCountryBlackout represents the regions that are to be blacked out for a certain profile. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 MerchantId 
                   
               
               
                   
                 ProfileId 
               
               
                   
                 CountryId 
                 Country to be blacked out 
               
               
                   
                   
               
               
                   
                 MerchantId, ProfileId, and CountryId form the unique key. 
               
            
           
         
       
     
     The table ACProfileRegionBlackout represents the regions that are to be blacked out for a certain profile. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 MerchantId 
                   
               
               
                   
                 ProfileId 
               
               
                   
                 CountryId 
                 Country to be blacked out 
               
               
                   
                 RegionId 
                 Region to be blacked out 
               
               
                   
                   
               
               
                   
                 MerchantId, ProfileId, CountryId and RegionId form the unique key. 
               
            
           
         
       
     
     The table ACProfileSet represents an access criteria set (conditions) under which an item is provided to the subscriber. 
                                             Field   Description                          MerchantId               ProfileId           CountryId           RegionId           SetId   Sequence number (order is of importance)           SubscriptionFlag           ProductIssuerId           ProductId           PriceFlag           PGWId   Payment gateway ID           PurchasePrice           TimePriceFlag           Time   Viewing time associated with purchase               price           TimePrice   (Used for pricing such as 1$ per minute)           ViewTime   Viewing time associated with recurring               price (e.g. 1 minute in case of 1$ per               minute)           LoyaltyFlag   True if subscriber can earn loyalty points.           LoyaltySchemeId   Loyalty scheme such as air-miles or FFP               (future use)           LoyaltyPoints   Number of points (future use)           ParentalFlag   True if access is restricted to certain               minimal age           ParentalCode   Minimum age           TimeWindowFlag   True if access must be blocked during               certain hours           TimeWindowStart   Local time to start blocking access           TimeWindowEnd   Local time to stop blocking access           DateWindowFlag   True if access must be blocked before or               after certain date range           DateWindowStart           DateWindowEnd           FormattedAC   Formatted access criteria (future use for               improved performance)                       MerchantId, ProfileId, CountryId, RegionId and SetId form the unique key.            
Transaction Tables
 
     The table CashMonitor represents a credit counter for the subscriber transactions and is used for monitoring purposes only. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Field 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 MerchantId 
                 Merchant (content provider) 
               
               
                   
                 PGWId 
                 Payment gateway 
               
               
                   
                 ResetDate 
               
               
                   
                 Subscriptions 
                 Total subscription revenues since reset date 
               
               
                   
                 PayPerView 
                 Total PPV revenues since reset date 
               
               
                   
                   
               
               
                   
                 MerchantId and PGWId form the unique key. 
               
            
           
         
       
     
     The table Transaction contains all the transactions. 
                                                 Field   Description   Unique Key                          MerchantId   Merchant               Received           Type   Subscription/PPV           CaAgentId   (0 if subscription)           Transaction                       MerchantId and Received form the key.            
Overview—Conditional Access Agent  28 
 
     A conditional access agent  28  operates as a secure gatekeeper to actual content provided via a content distributor  20 . A conditional access agent  28 , in one exemplary embodiment of embodiment, is co-located with a local content server  40  to “police” local subscriber accesses to protected content stored on that media server. 
     A conditional access agent  28  provides at least two functions namely (1) a verification function that includes verification of content destination (e.g., subscriber) requests for secure content against access criteria defined by a content provider  16 , and (2) a gateway function including decryption, watermarking and re-encryption of secure content, depending on content security settings. 
     Dealing more specifically with the verification function and utilizing the example of a subscriber as a content destination  22 , a conditional access agent  28  manages subscriber access to the content by evaluating the access criteria and the subscriber credentials. The agent  28  verifies and processes the subscriber request before (and during) the provision of the requested content. Access criteria are defined by the content provider  16 , signed by a conditional access server  36  and distributed as described above. In one embodiment, the agent  28  selects the first appropriate access criteria set based on the user credentials. The selected access criteria set is sent to the subscriber for signature. This may require an explicit confirmation from the subscriber (in case of a payment) or this may be transparent (in case of a subscription). Subscription forms, originally generated by the subscription form server  70 , are cached locally at the conditional access agent  28 . If a subscription form is not available or out of date, the conditional access agent  28  retrieves the latest subscription form from the appropriate content provider  16 . 
     Signed pay per view transactions are also cached by the conditional access agent  28  to allow a subscriber to view a movie multiple times within the allowed time window without charge. 
     Not all conditional access clients may support all types of access criteria. The conditional access agent  28  therefore interprets the client type before suggesting a specific access criteria set. 
     Turning now to the gateway function performed by a conditional access agent  28 , after a subscriber (or user) has been granted access to the content, a request is sent to the local content server  40  to ‘release’ the content. This request contains all the necessary data, including the IP destination address/port, subscriber signed access criteria, the subscriber certificate and the key to decrypt the content (encrypted with the public key or secret group key of the conditional access agent  28 ). The content is then decrypted, watermarked and optionally re-encrypted with a different key (e.g., a unique user key). 
     The conditional access agent  28  interfaces with the secure device server  44  to:
         (1) Verify the current debit/credit level of the subscriber (e.g., in the cases of PPV or PPT transactions).   (2) (If required) verify the age of the user associated with the secure device server  44 .   (3) Forward the signed PPV/PPT transactions to the secure device server  46  for clearing and administration purposes.       

     For this interface, the agent  28  acts as the client. 
     The conditional access agent  28  interfaces with the conditional access server  36  to query subscriptions. For this interface, the conditional access agent  28  acts as the client. 
     The agent  28  also interfaces with the conditional access server  36  to query access criteria and keys and to forward transactional information statistics. 
     The conditional access agent  28  interfaces with the conditional access client  48  to send a payment request, receive a transaction (signed payment request) and to pass any result messages (such as service denial based on insufficient debit/credit, regional blackout, etc). For this interface, the conditional access agent  28  acts as the server. 
     The conditional access agent  28  interfaces, in one exemplary embodiment, with a media client  49  and the content server  40  using the Real Time Streaming Protocol over TCP/IP (for control interfacing) or UDP/IP (for data interfacing). In this case, the conditional access agent  28  usually acts as a transparent proxy, but will carry out specific actions when the subscriber attempts to access secured content (such as evaluating the access criteria and the subscriber credentials). 
     Architecturally, the conditional access agent  28  comprises a number of real-time processes that together provide the required functionality.  FIG. 5  is a block diagram illustrating various processes that constitute the conditional access agent  28 , according to an exemplary embodiment of the present invention. A conditional access agent server  80  communicates with external processes, such as the conditional access server  36 , the secure device server  44  and the conditional access client  48  utilizing a number of interfaces. The conditional access agent server  80  provides a server implementation of a conditional access agent  28  for the client/agent interface. A conditional access client  48  uses this interface to connect to the conditional access agent server  80  to complete a secure XML-based transaction based on access criteria associated with a requested content item. At the end of a successful session, a product key is transmitted to the conditional access client  48 . 
     A conditional access agent socket proxy  82  operates as a transparent proxy between a media player  84  and the content server  40  control channel, and is responsible for preventing unauthorized access to the content. 
     A conditional access agent transaction manager  86  forwards the transactions from a secure agent  88  to the secure device server  44  and sends the received receipt back to the secure agent  88  to delete the transactions. 
     The secure agent  88  is central to the conditional access agent  28 , performs the following functions:
         (1) Keeps track of all secure (user) sessions (session id, user IP address, timers, etc).   (2) Decrypts and watermarks content in a controlled fashion.   (3) Maintains Store and Forward transactions.   (4) Stores the conditional access agent private key, certificate and the conditional access server public key.   (5) Stores the registered payment gateways and associated Certificate Revocation Lists (CRLs).       

     The secure agent  88  may, in one embodiment, be implemented in hardware to increase the level of content and transaction security. 
     An exemplary operational scenario involving the conditional access agent  28  will now be described with reference to  FIG. 5 :
         (1) Content destination  22  (e.g., user) selects content.    The user requests a content description file, such as an ASX file, using a regular browser based on HTTP.   (2) Trigger conditional access client  48 .    A browser  90  identifies a unique tag included in the content description file and is configured to forward the URL of the content description file (e.g., the ASX file) to the conditional access client  48 . The client  48  sets up a connection with the conditional access agent server  80 , based on the URL, to start a secure ordering process utilizing regular HTTP messages.   (3) Retrieving content description file.    The conditional access agent  28  retrieves the content description file from a Web server  92  using a regular HTTP GET request. From this content description file, the access agent  28  retrieves an access criteria URL.   (4) Selecting access criteria.    The conditional access agent  28  retrieves the access criteria using a regular HTTP connection with a proxy (which may have the access criteria cached from a previous session). The conditional access agent  28  registers a new session with the secure agent  88  using the information it has received (subscriber information, access criteria, etc). At session creation, the secure agent  88  verifies:
           (1) That a payment gateway (associated with the user&#39;s token) is supported;   (2) That the serial number is not on the Certificate Revocation List; and   (3) The (default) host of the secure device server associated with the user&#39;s token.   
           (5) Retrieving token information.    The conditional access agent  28  retrieves the secure device information (such as purse information) from the secure device server host to verify purse levels and optionally check age restriction settings.   (6) Constructing the order request/proposal.    Based on the user credentials, access criteria and local time, the conditional access agent server  80  constructs an order request (the offer) and sends this to the conditional access client  48  for approval (or decides to refuse access to this particular user). The order request is also registered with the secure agent  88 , which stores this information together with the other session information.   (7) User signs order.    The user signs the order and sends the signature to the conditional access agent  28  using a regular HTTP POST message. The conditional access agent  28  forwards the signature to the secure agent  88 . The secure agent  88  will verify all session information (access criteria, user credentials, local time, signature etc.) before granting access.   (8) Opening of the content ‘gate’.    In a first exemplary embodiment, the content is stored in the clear and the security relies on the socket proxy to block unauthorized access. The socket proxy can query the secure agent  88  for session information. This is not secure as the content is not encrypted and there is no control over which files are streamed.    In a second embodiment, the content is encrypted and a key will therefore be required by the conditional access client  48  in order to decrypt the content. The socket proxy will now be a RTSP proxy to provide intelligent blocking to implement functionality such as Pay Per Time.    In case of personalized content security, the secure agent  88  controls the gate since the encrypted content will have to go through the to agent  88  to be decrypted, optionally watermarked, and re-encrypted. This feature is supported for standard compression algorithms, such as MPEG-2, MPEG-4 and MPEG-7.    The conditional access client  48  receives an OK (assuming a positive authentication and verification) from the conditional access agent  28  using a regular HTTP message, optionally including the session key encrypted under the user public key.   (9) Transaction forwarding.    Assuming all went well, the conditional access agent transaction manager  86  forwards the signed order to a secure device server for clearing purposes. The signed order is also sent to the conditional access server  36  for monitoring and statistics.
 
Overview—Conditional Access Client  32 
       

     The conditional access client  32  is executed on a subscriber terminal (e.g., a personal computer (or STB), and is responsible for presenting a user interface to a end user (e.g., a subscriber) and also for interfacing between the secure device  46  and other security sub-systems. 
     The conditional access client  48 , in one embodiment, allows external applications (e.g., web clients or plug ins) to manage the secure device  46 . The following management requests pertaining to the secure device  46  are, in one embodiment, supported:
         (1) Changing of a user Personal Identification Number (PIN);   (2) Querying the status of the secure device  46  (e.g., error not inserted, ready, etc.);   (3) Publishing the status of the secure device  46 ; and   (4) Querying the secure device serial number and certificate.       

     In addition to providing the above described management interface, the conditional access client  48  also operates to assign requests, received from the conditional access agent  28 , and to advise a user accordingly. A signing request that does not require a PIN may be transparent to a subscriber. 
     Receipt of a request that requires a PIN to sign the request causes the client  48  to display descriptive information regarding the request (e.g., a movie title) to the subscriber in conjunction with a payment amount. The subscriber is asked to enter a PIN code. If the request relates to a subscription, the client  48  updates a subscription counter on local storage and, in one embodiment, on the secure device  46 . This subscription counter is utilized by the conditional access client  48  to detect that new subscriptions may be available. If the secure device  46  and the conditional access client  48  do not allow for storage, the client  48  may maintain the subscription counter in memory. 
     If a subscription request is not successfully completed, the client  48  displays an error message to the user, the error message including an error code and an English-language error description. In one embodiment, the error code may be mapped to a local error string, instead of showing the English-language error description. The error message may also contain a URL, for example, identifying a site for which appropriate subscription may be obtained if the lack of such a subscription results in the error message. 
     Overview—Secure Device  46   
     A particular secure device  46  is, in one exemplary embodiment, associated with a particular end-user (e.g., a subscriber). In various exemplary embodiments, the secure device  46  may be a dedicated device specifically for use within the content distribution system  10 ; a shared device manufactured for use within a different system (e.g., a banking system), but also leveraged within the content distribution system  10 ; or an embedded device that is embedded within a closed media device (e.g., a smart card in a Set Top Box (STB)), or a SIM card in a mobile telephone that is again for use in alternative system, but leveraged within the content distribution system  10 . 
     A minimum requirement for the secure device  46 , in one exemplary embodiment, is that its supports digital signing using private/public key technology. Secure devices  46  embedded in close media devices need not adhere to specific requirements, other than providing sufficient security to warrant protection of a user private key. Shared secure devices (e.g., banking cards), in order to be utilized within the content distribution system  10 , are required to adhere to at least a subset of the requirements defined below, this subset of requirements varying depending on the commercial and technical issues. A set of requirements, according to one exemplary embodiment of the present invention, for dedicated secure device are set out below. 
     In one embodiment, a dedicated secure device  46  hosts at least two private keys, namely a first private key for encryption and a second private key for signing. The private key for key encryption is available to external applications without user PIN submission. The private key for signing is only available to external applications after PIN submission. 
     The secure device  46  may have a co-processor for secure RSA signing with the secure device unique private key. 
     Storage within the secure device  46 , in one embodiment, follows the PKCS#11 model and may offer:
         Public storage, available for guests (read), admin (read/write) and user (read/write). This storage is used for public keys (label: “Public key” and “Public key encrypt”), certificates (label: “Certificate”, 1500 bytes) and public free format system information (label: “System data”, 400 bytes). The free format system information shall contain a valid XML string with various Entriq and other system defined tags.   Private storage, available for admin (read) and user (read/write). This storage is used for free format user information (label: “User data”, 800 bytes). The free format user information shall contain a valid XML string with various Entriq and other defined tags.   Two-Factor secret, available for user (write/use). This storage is used for the signing private key (label: “Private key”).   One-Factor secret, available for guests (use), admin (use) and user (write/use).       

     This storage is used for the key decryption private key (label: “Private key decrypt”). 
     The secure device  46  may also be pre-configured with two public/private key pairs, and a certificate signed with the private key of a commerce service provider  42  (or payment gateway). This private key of the payment gateway is hosted by a secure device  46  manufacturer to allow the secure device  46  to be pre-loaded with a valid certificate by delivery into the field. The certificate may, in one embodiment, be X.509 compliant. 
     The secure device  46  is furthermore personalized with a fixed PIN code, and may allow a user to set a new PIN after submission of a current user PIN. 
     Distributed Secure Agents 
     The content distribution system  10 , as described above with reference to  FIGS. 1-3 , in one embodiment, proposes that content be encrypted at a content provider  16 , and then distributed to regional content distributors  20  (e.g., broadband Internet Service Providers (ISP&#39;s)). Conditional access agents  28  are deployed at these content distributors  20  to evaluate content requests from content destinations operating conditional access clients  32  before delivery of the requested content occurs. Upon appropriate authorization of a request, at the content distributor  20  and under control of the conditional access agent  28 , the requested content is decrypted and at least one association operation performed on the content before it is forwarded to the content destination  22 . The association operation performed at the content distributor  20  may include personal watermarking of the content and/or personal re-encrypting of the content, as will be described in further detail below. With respect to a watermarking operation, the identity of a specific consumer at the content destination  22  is “embedded” in the watermarked content, and the identity of the content consumer can accordingly be detected if the derivative copy of the content is distributed in an unauthorized manner. Accordingly, a content consumer will be discouraged from forwarding copies of the content to others if an unauthorized derivative copy of the content can be traced back to the relevant content consumer utilizing a watermark. 
     A content consumer (i.e., requesting user) is, in one embodiment, is verified utilizing a public/private key, and additional certificates, that may be stored on a tamper-proof device (e.g., a smart card or mobile telephone). The certificate contains information that may be utilized to identify a secure device  46  associated with the content consumer. A conditional access agent  28  trusts a number of Certification Authorities (CA) and maintain a Certification Revocation List (CRL) of a Certification Authority to prevent unauthorized access with compromised secure devices  46 . 
     The content distribution system  10 , which deploys distributed conditional access agents  28  to represent the interests of content providers  16 , provides a number of advantages. Firstly, moving security functionality, implemented by a conditional access agent  28  in the manner described below, away from an end user device (e.g., a secure device  46 ) increases security as this functionality is located outside the reach of hackers at a content destination  22 . Secondly, there are economic benefits, as certain security functionality is removed from the content destination  22 , and is thus more easily managed and maintained. 
     A further advantage is that personal re-encryption of content (e.g., utilizing a unique user key) requires that an unauthorized distributor redistribute the entire content, as opposed to just relevant keys. 
     Fourthly, personal watermarking of content at a remote conditional access agent  28  makes it difficult for a hacker to impact a watermarking process. 
     Fifthly, the use of public/private key technology at a conditional access agent  28 , in the manner described below, makes the solution scalable. 
     The content distribution system  10  provides security functionality in a distribution system that “pushes” content to the edges of a network before it is delivered, possibly on demand, to content consumers. 
     Finally, the content distribution system  10 , in one embodiment, utilizes secure tokens such as banking, GSM, or pay media smart cards that are already in wide distribution, thus allowing for a large content consumer network. 
       FIGS. 6A-6B  show a flow chart illustrating a method  120 , according to an exemplary embodiment of the present invention, of processing a content request received from a content destination  22 . When discussing the method  120 , it is assumed that the requested content is stored at, or redistributed from in the case of live multicasting, a local content server  40  (e.g., video file server or router) that operates in conjunction with a conditional access agent  28 . If a conditional access agent  28  is unavailable, a user will fail to obtain access to the required keys. 
     At block  122 , a content consumer, for example utilizing a secure device  46 , issues a request via the network  18  to a content distributor  20 , operating a conditional access agent  28 , to deliver (e.g., via streaming) particular content. In response to the issuance of such a request, a conditional access client  48  executing on a user viewing device (e.g., a PC or set top box) initiates communications with an appropriate conditional access agent  28 , via a network  18 , to obtain the necessary keys. Specifically, at block  122 , as part of the request, the conditional access client  48  communicates a user certificate (e.g., issued by a payment gateway) and optionally a copy-protected device certificate to the conditional access agent  28 . 
     At block  124 , the content distributor  20  utilizing the conditional access agent  28 , verifies the received user certificate and optionally the copy-protected device certificate by verifying a challenge communicated by the client  48  to the agent  28  in association with the user device and copy-protected device certificates. 
     At block  126 , the content distributor  20  utilizing the conditional access agent  28 , retrieves access criteria and a product key related to the requested content from a content provider  16 . As discussed above, the access criteria and the product key (S p ) are encrypted with a public key of the conditional access agent  28  so that only the specific conditional access agent  28  is able to access the product key. 
     The retrieval of the access criteria and product key involves the conditional access agent  28  issuing a request to a conditional access server  36 , responsive to which the server  36  verifies regional constraints associated with the requested content in order to return the appropriate access criteria. Specifically, access criteria may differ per region, and accordingly per conditional access agent  28 . 
     The conditional access server  36  secures the access criteria and product key by encrypting the product key with the public key of the conditional access agent  28 , and signs the access criteria, including the encrypted product key, with the conditional access server  36  private key. The product key will thus only be available to the intended conditional access agent  28 . 
     At block  128 , the content distributor  20 , and specifically the conditional access agent  28 , verifies the signature of the access criteria and the product key using a certificate of the content provider  16 , as provided by a trusted third-party. A public key of the trusted third-party would be well known, and embedded within the conditional access agent  28 . 
     In an alternative embodiment, performance constraints imposed by large live events (e.g., a popular soccer game) may require that the access criteria and the product key are signed utilizing a shared secret key as opposed to the private key of the conditional access private key. 
     At block  130 , the content distributor  16 , and specifically the conditional access agent  28 , decrypts the received product key associated with the requested content, utilizing a private key of the conditional access agent  28 . 
     Turning now to  FIG. 6B , at block  132 , the conditional access agent  28  of the content distributor  20  requests information concerning a secure device  46  of a content consumer from the secure device server  44  of a commerce service provider  42  (e.g., payment gateway). This information concerning the secure device  46  may include a purse value, date of birth, geographic location, etc., and is signed by the commerce service provider  42 . In an alternative embodiment, performance constraints imposed by a large live event may required that the information concerning the secure device  46  be signed utilizing a shared secret key as opposed to a private key of the commerce service provider  42 . 
     At block  134 , the conditional access agent  28  of the content distributor  20  receives subscription information from the conditional access server  36 , this subscription information having been signed by the content provider server  34 . 
     At block  136 , utilizing the required information (e.g., the secure device information, access criteria, subscriptions, etc.), the conditional access agent  28  of the content distributor  20  constructs an order request based on a current date and time, signs the order request, and transmits the order request to a conditional access client  48  of the content consumer for acceptance. The conditional access agent  28  utilizes a secure clock to validate the current time against the access criteria settings of the content provider server  34 . The order request may furthermore consist of a number of order options, if applicable (e.g., a pricing of $8.00, or $4.00 for a predetermined amount of time plus $1.00 per minute thereafter). 
     At block  138 , the conditional access client  48  of the content consumer verifies a signature of the conditional access agent  28  with which the order request has been signed and prompts the user for a PIN to confirm the order. The PIN is utilized to sign the order utilizing the secure device  46 , and a resulting order confirmation (signed) is transmitted back to the conditional access agent  28  of the content distributor  20 . 
     At block  140 , the conditional access agent  28  verifies the collected data (in a physically secure environment). The collected data includes access criteria, a user signature, a user certificate (signed by the commerce service provider  42 ), a copy-protected device certificate, subscriptions, current purse levels, and a user date of birth. 
     If the request passes the verification process, the conditional access agent  28  then establishes a secure session with the conditional access client  48 , and generates a unique user key (U k ). The unique user key (U k ) is then encrypted with a public key of a copy-protected device associated with the secure device  46 , and communicated to the conditional access client  48  using the secure session. If a copy-protected device is not available, and not required according to the access criteria, the unique user key may be encrypted utilizing a public key of the secure device  46 . 
       FIG. 7  is a flowchart illustrating a method  150 , according to an exemplary embodiment of the present invention, of securely delivering content from a content provider  16  to a content consumer via at least one content distributor  20 , where the content distributor  20  performs an association operation (e.g., watermarking or encryption) relating to the content. In the method  150 , the at least one content distributor  20  is uniquely authorized to perform the operation relating to the content. 
     The method  150  commences at block  152  with the encryption by a content provider  16 , and more specifically a conditional access server  36 , of content with a product key (S p ). This encrypting of the content is automatically performed prior to a scheduled distribution of particular content to multiple content distributors  20  for local distribution to content destinations  22 . Alternatively, the encryption of the content may be performed, in the event of a live event, on the fly and concurrently with provision of the content from the content provider  16  to a content distributor  20 . In yet a further embodiment, the encryption of the content may be performed responsive to receipt of a request, at the content provider  16 , for the specific content from a particular content destination  22 . 
     Having encrypted specific content with the product key (S p ), the conditional access server  36  of the content provider  16  then encrypts the product key (S p ) with a public key of a specific content distributor  20 . In one embodiment, the public key in which the product key is encrypted is the pubic key of a secure device accessed by a conditional access agent  28 . 
     The content provider  16  then transits the encrypted content and the encrypted product key to the content distributor  20 . 
     At block  154 , the content distributor  20 , and more specifically the conditional access agent  28 , operates to decrypt the product key within a secure, tamper proof environment. A tamperproof environment may be provided by tamperproof hardware, such as an nCypher cryptographic hardware card, tamperproof software, or by a regular PC physically protected from unauthorized access. 
     Having then decrypted the product key, the content distributor  20 , and specifically the conditional access agent  28 , proceeds to decrypt the content utilizing the product key, again within the secure, tamper proof environment facilitated by a secure device. 
     Having decrypted the content, the conditional access agent  28  then operates to perform an association operation relating to the content. In one exemplary embodiment, this operation constitutes watermarking a copy of the content for distribution to a specific content destination  22 , a specific content consumer, or an identified group of content destinations  22  or content consumers. Watermarking is a mechanism to, in one embodiment, embed arbitrary data into an audio or video signal, where the embedded data is not easily detectible and/or removable from the resulting signal. “Individual watermarking” is a process of watermarking a signal for a specific content destination  22  (e.g., a content consumer or user) such that the identity of the content consumer can be traced back in case the resulting signal is subject to unauthorized distribution. The watermarking of the content allows a content distributor  20  (or a content provider  16 ) to associate a specific copy of the content, uniquely watermarked, with a specific content destination  22 . 
     Having performed the operation relating to the content, the conditional access agent  28 , again within the secure tamper-proof environment, generates a unique user key (U k ), and re-encrypts the content with this unique user key. 
     As all operations within block  154  are performed within the secure, tamper-proof environment, it will be appreciated that the interests of the content provider  16  are well protected, and that the product key is not exposed outside the secure environment. Further, only an authorized entity (e.g., a specific conditional access agent  28 ) is authorized to reveal the product key within the secure environment as the private key of a secure device of the agent  28  is required to decrypt the product key. In this way, the content provider  16  exercises strict and rigorous control of which entity is able to decrypt the product key. 
     In one exemplary embodiment, at block  156 , the content distributor  20 , utilizing the conditional access agent  28  and within the secure tamper-proof environment, encrypts the product key with the unique user key (U k ). The content distributor  20  then also encrypts the unique user key with a public key of the content destination  22 . At block  158 , the content distributor  20  transmits the encrypted content, the encrypted product key, and the encrypted unique user key to the content consumer at a content destination  22 . 
     At block  160 , the content consumer at the content destination  22  decrypts the unique user key utilizing a private key of the secure device  46 , then decrypts the product key utilizing the unique user key, and finally decrypts the watermarked content utilizing the decrypted product key. 
     As discussed above, the method  150  is particularly advantageous in that it enables a content provider  16  to authorize a specific content distributor  20  to perform an operation relating to the content, and in one embodiment, to contribute to combating authorized distribution. Such operations may include, for example, watermarking or further encryption of the content. In addition to the authorization being specific to a content distributor  20 , the method  150  is also advantageous in that the operation is performed in a secure, tamper-proof environment within which the interests of the content provider  16  are protected and the product key is subject to very limited and controlled exposure. 
     In this way, a content provider  16  is provided with assurances that distributed secure agents (e.g., conditional access agents  28 ) located at various distribution points operate to protect the interests of the content provider  16 . The content provider  16  is thus provided with a degree of security and assurance regarding operations that are performed by content distributors  20  and the content provider  16  is thus likely to entrust distribution of sensitive and very valuable content to such a content distributor  20 . 
     Further, by performing the operation at block  154  (e.g., watermarking or encrypting) prior to actual delivery of the content to a consumer (i.e., within the network), the risks of piracy are reduced. Upgrades to a secure agent (e.g., the conditional access agent  28 ) are also more easily implemented than upgrades to processes at consumer locations. 
     In conclusion, the method  150  enables an association operation (e.g., a watermarking process) to be distributed to content distributors  20  located at ISPs and therefore closer to content consumers. This is advantageous in that it enables load management. The method  150  also addresses concerns of a content provider  16  regarding security resulting from that, in order to perform certain operations on the content (e.g., a watermarking operation) at a distributor  20 , the content must “be in the clear” in order to properly perform the operation. The method  150  addresses this concern by providing a secure environment in which the operation is performed, and providing the content provider  16  with control over which content distributors  20  are authorized to generate clear content within the secure, tamper-proof environment with the purposes of performing such operations. 
     Methodology—Variable Key Content Differentiation 
     So-called “key hook piracy” occurs when an authorized, but fraudulent, user distributes decryption keys, that may be utilized to decrypt content to unauthorized users. Distributing such a single decryption key over networks, such as the Internet, can be done effectively. 
       FIGS. 8A and 8B  are block diagrams illustrating, at a high level, a method, according to an exemplary embodiment of the present invention, of combating “key hook piracy”. With specific reference to  FIG. 8A , the present invention proposes encrypting clear content  24  with a relatively large number of session keys  98  to generate encrypted content  26 . In one embodiment, the session keys  98  comprise a sequence of random, time-varying session keys. 
       FIG. 8B  illustrates further details regarding the distribution of content and the session keys  98 , according to an exemplary embodiment of the present invention. The content provider  16  is shown to firstly distribute encrypted content  26  (i.e., clear content  24  encrypted with the session keys  98 ). In one embodiment, the content provider  16  may distribute the encrypted content  26  directly to a content destination  22 . In an alternative embodiment, the encrypted content  26  may be distributed to a local content server  40  at a content distributor  20 , and cached by the local content server  40  for eventual distribution to a content destination  22 . 
     The conditional access server  36  at the content provider  16  also operates to encrypt each of the session keys of the sequence of the time-varying session keys with a product key (S p ), and to distribute the encrypted session keys to the conditional access agent  28 , as indicated at  104 . The conditional access server  36  also operates to encrypt the product key (S p ) with the public key of a specific conditional access agent  28 , and then to distribute the encrypted product key to the specific conditional access agent  28 , as indicated in  FIG. 8B  at  106 . During delivery to a conditional access client  48 , the conditional access agent  28  replaces the session keys encrypted with the product key (S p ) with session keys encrypted with a unique user key (U k ), instead of the product key (S p ). Specifically, prior to deliver to a conditional access client  48 , the conditional access agent  28  decrypts the encrypted product key received from the conditional access server  36  utilizing the private key (or secret key) of the conditional access agent  28 , decrypts the sequence of session keys encrypted with the product key, and then re-encrypts the sequence of session keys utilizing the unique user key (U k ). The re-encrypted sequence of session keys is then distributed from the conditional access agent  28  to the conditional access client  48 , as indicated at  108 . The conditional access agent  28  also distributes the unique user key (U k ) to the conditional access client  48  via a secure authorization channel, as indicated in  FIG. 8B  at  110 . 
     At the conditional access client  48 , the user key (U k ) is utilized to decrypt the re-encrypted sequence of session keys, the decrypted session keys then in turn being available to decrypt the encrypted content  26 . 
     It will be appreciated, utilizing the above-described system, the product key (S p ) remains protected from access at a content destination  22  as it is only communicated from the conditional access server  36  to the conditional access agent  28 , and is at no time exposed to the conditional access client  48 . For additional security, the decrypting of the product key is performed at the conditional access agent  28  utilizing a tamperproof device (e.g., a smart card). 
     The user key (U k ) is by itself useless to users other than the recipient that receives this user key via the secure authorization channel. An authorized user is furthermore discouraged from performing “key hook piracy” in that such an authorized user will be required to send all session keys to an unauthorized user to enable the unauthorized user to access the encrypted content. By generating a large number of session keys, the effort to forward such session keys to unauthorized users approaches the effort of forwarding the entire encrypted content. 
       FIGS. 9-10  illustrate a number of flow charts providing further details regarding the operations performed at the conditional access server  36 , the conditional access agent  28  and the conditional access client  48 . 
       FIG. 9  is a flow chart illustrating a method  300 , according to an exemplary embodiment of the present invention, of encrypting content utilizing a random, time-varying sequence of session keys, so as to combat “key hook piracy”. The method  200  commences at block  202  with the generation, at a conditional access server  36 , of a sequence of random, time-varying session keys  98 . As described with reference to  FIG. 2 , the conditional access server  36  may be deployed at a content provider  16 , or at a conditional access service provider  38  that is accessed by a content provider  16 . 
     At block  204 , specific content is encrypted utilizing the random, time-varying sequence of session keys prior to distribution of the content from a content provider  16 . Content is typically but not necessarily encrypted using symmetric block or stream ciphers such as DES, AES (Rijndael) or RC4. 
     At block  206 , the conditional access server  36  encrypts each session key with a product key (S p ), the product key being uniquely associated with the relevant content. The session key is typically but not necessarily encrypted using symmetric block ciphers such as DES or AES (Rijndael). 
     At block  208 , the content provider  16  transmits the encrypted content to a content distributor  20 , for storage on the local content server  40 . Alternatively, the content provider  16  may, in one embodiment, distribute the encrypted content directly to a content destination  22 . 
     At block  208 , the content provider  16  distributes the encrypted sequence of session keys  98 , as indicated at  104  in  FIG. 8B , to one or more conditional access agents  28 , deployed at one or more content distributors  20 . 
     At block  210 , a content distributor  20  stores (or caches) the encrypted content on a local content (or media) server  40  that is associated with a conditional access agent  28 . 
     It will be appreciated that, upon completion of the method  200 , a content provider  16  has delivered to a content distributor  20  encrypted content that a content distributor  20  is uniquely enabled to access. The content distributor  20  is enabled o perform one or more operations with respect to the encrypted content and/or the sequence of session keys. 
       FIG. 9  describes the method  200  whereby a content provider  16  provides encrypted content, and an associated sequence of session keys, to a content distributor  20  for caching at the content distributor  20 .  FIGS. 10A-10B  show a flowchart illustrating a method  220 , according to an exemplary embodiment of the present invention, of distributing the cached content from a content distributor  20  to a content destination  22 , responsive to a request for the relevant content from the content destination  22 . Accordingly, the method  220 , in one embodiment, assumes that requested content is cached at a local content server  40  of a content distributor  20 . In an alternative embodiment, the method  220  may be performed where content is broadcast in a near real-time manner (e.g., for a live sporting event). 
     The method  220  commences at block  222  with the receipt of a request at a conditional access agent  28  of a content distributor  20  for content from a conditional access client  48 . The request includes a user device certificate, issued by a commerce service provider  42  (e.g., a payment gateway) to identify the requesting user. The request also includes a copy-protected device certificate to identify the viewing device and a client challenge that is used to authenticate the agent  28  to the client  48 . 
     At block  224 , the conditional access agent  28  transmits a request to a conditional access server  36 , associated with a content provider  16  that is an owner or provider of the requested content, for (1) the product key (S p ) in which to decrypt the content and (2) rule information or access criteria, associated with the requested content. 
     At block  226 , the conditional access server  36  verifies regional constraints associated with the content in order to return the appropriate access criteria. Specifically, access criteria may differ by region, and accordingly per conditional access agent  28 . 
     At block  228 , the conditional access server  36  encrypts the product key with a public key of a secure device associated with the requesting conditional access agent  28 , thereby ensuring that only the specific conditional access agent  28  is able to access the product key. 
     At block  230 , the conditional access server  36  attaches a signature to the rule information, or access criteria, and to the encrypted product key, to thereby cryptographically bind the access criteria with the product key. 
     At block,  232 , the conditional access agent  28  receives the access criteria and product key, and verifies the signature of the access criteria and the product key utilizing a supplied certificate for the conditional access server  36 , which is signed by a trusted third party. The public key of the trusted third party is well known and, in one embodiment, embedded within the conditional access agent  28 . 
     At block  234 , the conditional access agent  28  requests and receives from the commerce service provider  42  secured device information (e.g., a purse value, date of birth, regional control information, etc.). This secure device information pertains to the secure device  46  of the content consumer and is signed by the commerce service provider  42 . 
     At block  236 , the conditional access agent  28  requests and receives subscription information from the conditional access server  36 , this subscription information again being signed by the conditional access server  36 . 
     At block  238 , the conditional access agent  28  constructs an order request utilizing the acquired information (e.g., the secure device information, access criteria and subscription information), signs the order request, and communicates the order request to the conditional access client  48  associated with the content destination. 
     At block  240 , the conditional access client  48  verifies the signature of the conditional access agent  28 , confirms the order request, and signs and returns an order confirmation to the conditional access agent  28 . 
     Turning now to  FIG. 10B , at block  242 , the conditional access agent  28  verifies the collected data (e.g., access criteria, user signature, user device certificate, copy-protected device certificate, subscriptions, current purse levels and user date of birth) within a physically secure environment implemented at the content distributor  20 . 
     At block  244 , the conditional access agent  28  creates a secure session with the conditional access client  48 , and generates a unique user key. 
     At block  246 , the conditional access agent  28  encrypts the unique user key with (1) the public key of a copy-protected device or (2) a public key of the secure device  46  associated with a content consumer at the content destination  22 . 
     At block  248  the conditional access agent  28  processes the encrypted session keys  98  associated with the content, the sequence of encrypted session keys  98  having been received at the conditional access agent  28  at block  208  of the method  200  described above with reference to  FIG. 9 . Specifically, at block  248 , each session key, as encrypted with the product key, is decrypted and then re-encrypted with the unique user key. As will be recalled, the product key was encrypted with the public key of the conditional access agent  28 , and communicated to the conditional access agent  28  at block  228  shown in  FIG. 10A . The personal re-encryption of the sequence of session keys utilizing the unique user key is useful in that it requires a “hacker” to redistribute the entire sequence of session keys. 
     At block  250 , the conditional access agent  28  transmits the sequence of session keys encrypted with the unique user key to the conditional access client  48  at the content destination  22 . 
     At block  252 , the conditional access client  48  decrypts the sequence of session keys, utilizing the unique user key, which was received by the conditional access client  48  at block  256  from the agent  28 . 
     At block  254 , the conditional access client  48  then decrypts the encrypted content utilizing the decrypted session keys. 
     Conditional Access Service Provider  38   
     According to a further aspect of the present invention, and as described briefly above with reference to  FIG. 2 , a pay media conditional access service provider  38  operates to provide “outsourced” content security function to multiple content providers  16 . Utilization of security functions provided by such a service provider  38  may be attractive to content providers  16 , as the setup, maintenance and operational costs associated with providing such security functions in-house (e.g., by operating an in-house conditional access server  36 ) may be high for a single content provide  16   r.    
     The content security functions, according to an exemplary embodiment of the present invention, that may be provided by a conditional access service provider  38  include the secure storage and distribution of content encryption keys and associated access criteria (or rules), and also the provision of a secure and scalable key distribution system that is able to manage a potentially large number of content consumers. 
       FIG. 11  is a block diagram illustrating a pay media conditional access service provider  38 , according to an exemplary embodiment of the present invention, and shows an interaction of the conditional access service provider  38  with multiple content providers  16 , as well as one of multiple conditional access agents  28 . At a high level, content is encrypted at either the content provider  16  or alternatively at the service provider  38 , after which a key and access criteria (or rules) are registered with the conditional access service provider  38 . The service provider  38  thereafter assumes responsibility for management of user authentication and key distribution, in the manner described below. In this way, conditional access services are provided by the service provider  38 , instead of the traditional approach that requires a substantial investment from each content provider  16 . 
     As stated above, a number of advantages flow from having multiple content providers  16  share a common key storage and distribution infrastructure (e.g., the service provider  38 ). However, a number of challenges face such a service provider  38 . Specifically, a number of security issues require attention to secure product key creation, storage and distribution. Exemplary security issues that are addressed by the present invention include:
         1. Random product key generation: It will be appreciated that a product key generated by content provider  16 , in one embodiment, is random (i.e., approaching a true random key) and created in an environment trusted by the content provider  16 .   2. A product key is protected from access by a pay media conditional access provider  38  while stored in a database maintained by the service provider  38 .   3. A product key is protected during transport between the service provider  38  and the content provider  16 .   4. An association of a product key with access criteria (or rules) is restricted to authorized users only.       

     The specific methodologies by which the above issues are addressed are described in further detail below with reference to the flow charts shown in  FIGS. 12-15 . 
     Referring again to  FIG. 11  by way of architectural description, a pay media conditional access service provider  38  is shown to deploy an ASP conditional access server  37 , which cooperates with a server secure device  39 . The conditional access server  37  operates to perform substantially the same functions as a conditional access server  36  that may be deployed by a content provider  16 , and is described above. The server secure device  39  is utilized by the conditional access server  37  to provide a secure, tamper-proof environment within which to perform certain operations, as will be described in further detail below. 
     A conditional access agent  28  is also shown to deploy an agent secure device  29 , which is similarly used by the agent  28  to provide a secure, tamper-proof environment in which to perform certain operations. Each content provider  16  also deploys a provider secure device  17  to again provide a secure, tamper-proof environment for certain sensitive operations. 
       FIG. 12  is a flow chart illustrating a high level method  280 , according to an exemplary embodiment of the present invention, whereby a conditional access service provider  38  provides security functions to multiple parties within a content distribution system  10 . 
     At block  282 , a product key, and optionally the access criteria (or rules), are communicated from a content provider  16  to the service provider  38 , and specifically to the server secure device  39  of the service provider  38 . The product key and the access criteria are then encrypted, within the server secure device  39  with a storage key, and stored by the conditional access server  37 . 
     At block  284 , a secret agent key is communicated from a conditional access agent  28  to the secure server device  39  of the service provider  38 , encrypted with a storage key within the server secure device  39 , and stored at the service provider  38 . 
     At block  286 , a content provider  16  distributes content, encrypted with the product key, to a local content server  40  of a content distributor  20 . As described above, the local content server  40  operates to cache the encrypted content, in one exemplary embodiment, for regional distribution. As also illustrated in  FIG. 11 , the local content server  40  operates in conjunction with a conditional access agent  28  deployed by content distributor  20 . 
     Returning to  FIG. 12 , at block  288 , responsive to a request from a conditional access agent  28 , the product key, encrypted by the service provider  38  with the secret agent key, is communicated to the conditional access agent  28  from the ASP conditional access server  37 . 
     At block  290 , the conditional access agent  28  decrypts, and optionally performs a personalization (or association) operation with respect to the content so that the content is uniquely associated with a particular content destination  22  (e.g., a particular user). This personalization (or association) operation may comprise a watermarking operation to watermark the content and thereby generate a derivative of the original content that is unique to the relevant content destination  22 . 
     The personalization (or association) operation may also include re-encrypting the content with a unique user key, as described above. 
     At block  292 , the conditional access agent  28 , in conjunction with the local content server  40 , distributes the content to a content destination  22  (e.g., a user). 
       FIG. 13  is a flow chart illustrating a method  300 , according to an exemplary embodiment of the present invention, of generating a product key at a content provider  16  and storing the product key at a conditional access service provider  38 . 
     At block  302 , a product key is created at the content provider  16  utilizing a random number generator  19  and optionally a provider secure device  17 , to thereby provide a high degree of randomness for the product key. It would be appreciated that a high degree of randomness is desirable to provide an increased level of security for the product key. 
     At block  304 , the product key is encrypted utilizing a public key of the server secure device  39  of the pay media conditional access service provider  38 . 
     At block  306 , rule information (e.g., access criteria) associated with the content encrypted utilizing the product key is identified. The encrypted product key is then optionally combined with this rule information by signing both the product key and the rule information utilizing a private key of the content provider  16 . 
     At block  308 , a content provider certificate is attached to the encrypted product key (and optionally the combined rule information), and the encrypted product key, rule information, and provider certificate are communicated to the ASP conditional access server  37  operated by the service provider  38 . 
     Turning now to activities performed at the service provider  38 , at block  310 , the ASP conditional access server  37  verifies the content provider certificate and signature, and submits the encrypted product key to the server secure device  39 . 
     At block  312 , within the secure environment provided by the server secure device  39 , the encrypted product key is decrypted utilizing the private key of the secure server device  39 . It will be recalled that the product key was, at block  314 , encrypted utilizing the public key of the server secure device  39 . 
     At block  314 , the product key is re-encrypted with a symmetric storage key, and stored within a server database. Furthermore, within the database  41 , the encrypted product key (now encrypted with the storage key) is logically linked to the content provider  16  that submitted the product key. 
     In the event that rule information was submitted in conjunction with the product key, this rule information is similarly stored within the database  41 , and also linked with the content provider and product key within the database  41 . 
     By only revealing the product key in the clear within the secure environment provided by the server secure device  39 , and encrypting the product key with a symmetric storage key prior to storing the product key within the database  41 , it will be appreciated that access to the product key by the pay media conditional access service provider  38  is effectively prevented. The storage key is managed by the operator that hosts the conditional access server  37  (such as Sentriq) and is cycled on a regular basis for new product keys. The storage key must be securely managed since it used to protect many product keys that in turn can decrypt many content items. 
       FIG. 14  is a flowchart depicting a method  320 , according to an exemplary embodiment of the present invention, of distributing an agent secret key from a conditional access agent  28  to the ASP conditional access server  37 . 
     The method  320  commences at block  322 , with the receipt at the conditional access agent  28  of the public key of the server secure device  39 . 
     At block  324 , the agent  28  encrypts an agent secret key utilizing the public key of the server secure device  39 . The agent secret key is used to secure communication between the server  37  and the agent  28   
     At block  326 , the agent  28  signs the encrypted agent secret key utilizing the agent secure device  29 , and the encrypted agent secret key is transmitted to the ASP conditional access server  37 , together with an agent certificate of the agent  28 . 
     Turning now to activities performed by the ASP conditional access server  37 , at block  328 , the conditional access server  37  verifies the agent certificate and signature and, at block  330 , submits the encrypted agent secret key to the server secure device  39 . 
     At block  332 , the server secure device  39  operates to decrypt the agent key within a secure environment, and then re-encrypt the agent secret key utilizing the symmetric storage key. The re-encrypted agent key (encrypted utilizing the storage key) is stored within the database  41 , and logically linked to an associated conditional access agent  28 . 
       FIG. 15  is a flow chart illustrating a method  340 , according to an exemplary embodiment of the present invention, of product key distribution from the conditional access service provider  38  to a conditional access agent  28 . 
     At block  342 , a conditional access agent  28  issues a request for a product key to the ASP conditional access server  37 . This request may be for license generation purposes, or for the purpose of decrypting content, stored at local content server  40  in order to perform an association operation on clear content, or merely to distribute the clear content to a content destination  22 . 
     At block  344 , the server  37  transmits the encrypted product key (encrypted with the symmetric storage key) and the encrypted agent secret key (again encrypted with the symmetric storage key) to the server secure device  39 . 
     At block  340 , the server secure device  39 , within a secure environment, decrypts both the product and agent secret keys, so that these keys are only in the clear within the secure environment. 
     At block  348 , the server secure device  39  then encrypts the product key with the agent secret key. 
     At block  350 , the server secure device  39  returns the encrypted product key (encrypted with the agent secret key) to the ASP conditional access server  37 . At block  352 , the ASP conditional access server  37  transmits the encrypted product key to the requesting conditional access agent  28 . 
     At block  354 , the conditional access agent  28  receives the encrypted product key, decrypts the encrypted product key utilizing the agent secure device  29 . 
     Having now revealed the product key within a secure environment, the conditional access agent  28  may perform any one of a number of operations. In one embodiment, the conditional access agent  28  may, within the secure environment provided by the agent secure device  29 , re-encrypted product key with a secure device key of a secure device  46  at a content destination  22 , and communicate the re-encrypted product key (encrypted with a key for the secure device  46 ) to a content destination  22 . Alternatively, the conditional access agent  28  that utilized the decrypted product key to generate clear content then performs one or more operations relating to the clear content. For example, the clear content may be communicated directly to content destination  22 , may be watermarked and/or may be re-encrypted with a unique user key, before delivery to a content destination  22 . 
     As described above, a content provider  16  may optionally submit rules (i.e., access criteria) to the pay media conditional access service provider  38  for controlling access to a particular content. To this end, the ASP conditional access server  37  may require a valid digital signature of the rule information, generated utilizing the provider secure device  17  operated by the content provider  16 . The signed rule information may also include a recent time stamp in order to prevent replay. In an alternative embodiment, the content provider  16  may include a challenge (generated by the ASP conditional access server  37 ), in a rule change request. 
     In one embodiment, the pay media conditional access service provider  38  may also permit entities other than the content provider  16  to change or specify rule information, associated with a particular product key, as stored within the database  41 . Specifically, the service provider  38  may provide the ability to configure the rights of certain content providers  16 . This functionality allows a content provider  16   a  to modify rule information associated with a product key that was registered by another content provider  16   n . Further, this functionality allows a content provider  16   a  to introduce alternative rules for a product key that was previously registered by a further content provider  16   n . The pay media conditional access provider  38 , in one embodiment, provides the following functions:
         (1) Registration of a content item, and an associated product key, by a specific content provider  16 .   (2) Linking of a product key, associated with a particular content item, to additional, new rule information, and modification of the rule information for product keys associated with a particular content provider.   (3) Registration of a new content item utilizing the same product key that is already associated with a further, already registered content item. However, the new content item, while being registered with an already registered product key, may be registered with different rule information.       

     In summary, the rights of each content provider  16  are stored and managed by the pay media conditional access provider  38 . A content provider  16  may be authorized to register content items for one or more content providers (e.g., content providers  16   a ,  16   b  and  16   c . The same content provider  16   a  may be authorized to update rules for content providers  16   b  and  16   d . Finally, for example, content provider  16   b  may be authorized to create new content items, utilizing a pre-registered product key of a content item registered by further content provider  16   c  and  16   f . 
     Separating User Authentication and Content Security 
     As described above, current hardware-based content security solutions are based on combining (1) user authentication and (2) content security into a single module (e.g., a smart card). However, this lack of differentiation between copy-protected device authentication and specific user authentication can be undesirable in certain circumstances. For example, it does not necessarily allow user mobility across multiple-protected devices (e.g., copy-protected personal computers or STBs). Accordingly, a specific user is typically only able to access restricted content via a specific copy-protected device purchased by that user, and into which user authentication information is integrated. For example, an authorized user is currently not able to utilize a STB, owned by a friend or relative that the user may be visiting, to view content to which the relevant user is a subscriber. 
     According to one aspect of the present invention, this problem may be addressed by logically separating user authentication functionality from content security (i.e., copy-protected device authentication) functionality. To this end  FIG. 16  is a block diagram illustrating a system  400 , according to an exemplary embodiment of the present invention, that provides a product key to access content upon receipt and verification of two separate certificates, namely a first user device certificate for user authentication and a second secure copy-protected device certificate for content security authentication. More specifically, the system  400  includes a secure conditional access agent  28  that communicates, as described above, with a conditional access client  48 . The conditional access client  48 , in turn, accesses a secure user authentication device  402  (e.g., a PKI token, smart card or SIM card) and a secure copy-protected device  408  (e.g., a software based tamperproof decoder or hardware based set top box decoder). 
     The secure user authentication device  402  is, it will be appreciated, associated with a user, and is thus typically portable and carried on the person of a user. The secure copy-protected device  408 , on the other hand, is associated with a device within which the ability to copy a content is disabled (or restricted). Accordingly, the secure copy-protected device  408  is typically embedded within, or integrally formed with, a viewing device (e.g., a PC or STB). 
     Each of the secure user authentication and secure copy-protected devices  402  and  408  is shown to include a respective device certificate  404  and  410 , and a device public key  408  and  412 . 
       FIG. 17  is a flow chart illustrating a method  420 , according to an exemplary embodiment of the present invention, to secure content for distribution via a network  18  by employing separate user device and copy-protected device authentication processes to protect content from unauthorized access. At a high level, the method  420  includes associating a user device authentication process with content, and associating a separate, copy-protected device authentication process with the content. 
     Referring to  FIG. 17 , the method  420  commences at block  422  with the receipt by the conditional access client  48  of a signature and certificate  404  associated with the secure user authentication device  402 . The conditional access client  48  then forwards the user device signature and certificate  404  to the secure conditional access agent  28 . At block  424 , the conditional access client  48  receives a signature and certificate  410  associated with the copy-protected device  408  and transmits the copy-protected device signature and certificate  410  to the conditional access agent  28 . 
     At block  426 , the conditional access agent  28  verifies the secure user device signature and certificate  404  in a first user device authentication process. At block  428 , the conditional access agent  28  verifies user credentials against access criteria (or rule information) associated with content requested by the conditional access client  48 . The requested content, it will be appreciated, is presented to an authenticated user via the authenticated copy-protected device  408 . 
     At block  430 , the conditional access agent  28  verifies the certificate  410  of the secure copy-protected device  408 . At block  432 , assuming the verification operations is performed at blocks  426 - 430  are successfully completed, the conditional access agent  28  proceeds to encrypt the requested content with a public key of the copy-protected device  408 . At block  434 , the conditional access agent  28  authorizes transmission of the encrypted content to the conditional access client  48  for delivery to the secure copy-protected device  408 . 
     At block  436 , the conditional access client  48  initiates decryption of the requested content wherein a secure environment provided by the copy-protected device utilizing a private key (not shown) of the copy-protected device  408 . 
     In conclusion, it will be noted that two separate and distinct authentication processes are performed at blocks  426 - 428  and  430 . Further, it will be noted that each of these separate authentication processes verify separate and distinct user device and copy-protected device information (e.g., separate device certificates). By separating the authentication processes, an authorized user, in one exemplary use scenario, is enabled to utilize a copy-protected device of a third party to request and view content, for which that particular user is authorized. For example, the user authentication device may comprise a smart card, PKI token, SIM card or the like, that may be inserted into a personal computer, STB, PDA, cell phone or the like of a third party, thus enabling the authorized user to request content via a third party&#39;s copy-protected device  408 . 
     Associating a License with a Particular User 
     Content licenses, such as those implemented by Microsoft Windows Media DRM technology and Intel ISIS are typically linked in a cryptographic manner to a specific player (e.g., a user computer). However, such content licenses are not tied to a particular user, and thus can be utilized by any one with access to the relevant player. This situation is undesirable both from a content owner (license issuer) as well as a user (license holder) viewpoint. 
     At a high level, according to one aspect of the present invention, a method of associating a license with a particular user includes encrypt a product key, to be included within a license to particular content, with both the public key  412  of the copy-protected device and the public key  406  of a user authentication device. According to one aspect of the present invention, a method of securing content for distribution to a network would include the operations of method  420  described above with reference to  FIG. 17 , but differ in that at block  432 , the conditional access agent  28  would encrypt the product key with both the public keys  406  and  412 , as opposed to only the public key  412 . 
       FIG. 18  is a flow chart illustrating a method  450 , according to an exemplary embodiment of the present invention, of communicating a product key, encrypted with the public keys of both a copy-protected device and a user authentication device to a copy-protected device and a user authentication device. In one embodiment, the product key is firstly encrypted utilizing the public key of the copy-protected device  408 , and then again encrypted with the public key  406  of the user authentication device  402 . In this embodiment, it will be appreciated that, in order for the copy-protected device  408  to access the product key, the copy-protected device  408  requires the user authentication device  402  to first decrypt the product key. In order to prevent replay attacks, the copy-protected device  108  may append a challenge to the encrypted key when requesting the user to decrypt the product key. 
     Turning specifically now to the method  450  illustrated in  FIG. 18 , at block  452 , a user, via integrated or separate user-authentication and copy-protected devices  402  and  408 , selects particular encrypted content for viewing via the copy-protected device  408 . 
     At block  454 , the copy-protected device  408  loads a content license, associated with the requested content and required to decrypt the content.  FIG. 19  is a diagrammatic representation of an exemplary content license  470  that may be loaded at block  454 . As illustrated, the content license  470  includes a machine identification identifying the copy-protected device  408 , content identification identifying the requested content, a twice-encrypted product key  472 , license usage restrictions, a signature of the license issuer, and a certificate of the license issuer. 
     Returning to  FIG. 18 , at block  456 , the copy-protected device  408  detects that the product key  472  is encrypted with the public key  406  of the user authentication device  402 . This is indicated in the license usage restrictions. At block  458 , the copy-protected device  408  appends a random challenge to the encrypted product key  472  and, at block  460 , requests the user authentication device  402  to decrypt the encrypted product key, and also issues a challenge to the user authentication device  402  utilizing the private key (not shown) of the user authentication device  402 . 
     At block  462 , the copy-protected device  408  re-encrypts a result returned from the user authentication device  402  with the public key  406  of the device  402  to thereby verify the challenge. 
     At decision block  464 , a determination is made as to whether the challenge was successfully verified or not. If so, at block  466 , the copy-protected device  408  decrypts the encrypted product key utilizing the private key of the copy-protected device  408  to reveal the product key. At block  468 , the copy-protected device  408  then utilizes the revealed product key to decrypt the requested content. 
     The above-described aspect of the present invention may be utilized in one exemplary use scenario to secure highly confidential data that is delivered to, and stored on, a copy-protected device  408  (e.g., a user&#39;s computer). Depending upon the user&#39;s authentication mechanism, a user may be required to utilize a hardware PKI token to authenticate the user to the copy-protected device  408  prior to obtaining access to the encrypted content. 
     License Generation Utilizing Symmetric Keys 
     As noted above, the signing of content licenses utilizing a private key operation is computationally expensive when a large number of simultaneous transactions are required (e.g., when the content is live, broadcast event). Additionally, the operational costs of managing private keys, and associated certification authorities may be high. 
     With a view to addressing the above-identified problems, the present invention proposes, in one exemplary embodiment, signing a license utilizing a secret symmetric key. In one embodiment, the secret symmetric key comprises a product key that encrypts content to which the license pertains. In an alternative embodiment, the symmetric key constitutes a key that is utilized to encrypt a product key that is in turn utilized to encrypt the content. 
     Signing a content license utilizing a symmetric key is advantageous in that the computational costs of a symmetric key operation are substantially less than the computational costs of a private key operation. In this manner, the present invention allows a content distribution infrastructure to generate an increased number of licenses in a potentially shorter time period. A further benefit is that the additional costs of managing a public key infrastructure are substantially avoided, as in the embodiment where the symmetric key constitutes a product key, this product key is known to the license issuer anyway as a license will typically include such a products key. 
     Signing licenses with a symmetric key (e.g., the product key) rather than a private key allows anyone with access to the product key to create licenses, rather than restricting the creation of licenses to certified license issuers. 
       FIG. 20  is a flow chart illustrating a method  480 , according to an exemplary embodiment of the present invention, of signing a content license utilizing a symmetric key. 
     At block  482 , a content license is generated at a content provider  16 . At block  484 , the content provider  16  then signs the content license utilizing a symmetric key. In one embodiment, the symmetric key comprises a product key with which content, associated with the content license, is encrypted. In an alternative embodiment, the symmetric key is a symmetric key that the content provider  16  utilized to encrypt a product key that was utilized to encrypt the associated content. 
     At block  486 , the content provider  16  proceeds to encrypt the content, to which the content license pertains, with the symmetric product key. 
     At block  488 , the content provider  16  then distributes the content, and the associated content license, to a recipient (e.g., to a content distributor  20 , or directly to a content destination  22 ). 
     At block  490 , the content provider  16  distributes the symmetric product key to a recipient (e.g., a content distributor  20  or a content destination  22 ). The distribution of the symmetric key may be according to any one of the methodologies discussed. For example, the symmetric key may be encrypted utilizing the public key of a copy-protected device  408  associated with the recipient. 
     At block  492 , the recipient verifies the content license utilizing the symmetric key. For example, the recipient may decrypt the product key utilizing a private key for a copy-protected device  408  associated with the recipient, and then utilize the decrypted product key to verify the content license. 
     Having verified the content license at block  494 , the recipients may then optionally decrypt the content utilizing the symmetric product key. 
       FIG. 21  is a diagrammatic representation of a content license  496 , according to an exemplary embodiment of the present invention. As illustrated, the content license  496  is signed utilizing digital signature  498  in the form of a symmetric key. In one embodiment, the symmetric key is a product key with which associated content is encrypted. The content license  496  is shown to include substantially the same information as the content license  470  shown in  FIG. 19 , but differs in that the license  496  is signed by the product key, as opposed to being signed by a license issuer. 
       FIG. 22  is a flowchart providing further details regarding a method, according to an exemplary embodiment of the present invention, of generating the digital signature  498  for a license  496  utilizing a symmetric key (e.g., a product key). 
     As illustrated in  FIG. 22 , the license  496  is subject to a hash function  510  to generate a hash result  512 . The hash result  512  and a symmetric key in the exemplary form of a product key  500  provide input to a signature function  514  that generates a digital signature  498  for the license  496  from these two inputs. 
       FIG. 23  is a flowchart illustrating a method, according to an exemplary embodiment of the present invention, of verifying a content license  496 , utilizing a digital signature  498  generated utilizing a symmetric key (e.g., a product key). 
     The license  496  is again subject to the hash function  510  to regenerate the hash result  512 . A verification function  516  receives the three inputs, namely the hash result  512 , the symmetric key  500  and the digital signature  498 . As the digital signature  498  was generated utilizing the symmetric key  500 , the verification function  516  is able to verify the content license  496  utilizing these three inputs. 
     Geographic Control of Content Distribution 
     It is desirable to provide a content provider  16  with geographic control over the distribution of content for a number of reasons. For example, a content provider  16  may wish to distribute a live event over the Internet worldwide, but need to block certain countries (e.g., or reasons due to exclusive broadcasting rights having been sold to broadcasters in those regions). According to one aspect of the present invention, there is provided a method and system to provide content providers  16  with secure geographic distribution control. 
     At a high level, the present invention proposes that content providers  16  encrypt content before distribution of a network (e.g., the Internet). In order to view the encrypted content, a content destination  22  will need to retrieve the encrypted content and the associated encryption key (or keys). Prior to communicating such encryption keys and content, according to one aspect of the present invention, a user and/or a copy-protected device are authenticated with secure hardware devices (e.g., PKI-enabled hardware devices such as smart cards or USB e Tokens). Once a user or copy-protected device has been identified, a number of geographic location checks are then performed against geographic access criteria to determine whether or not to release content to a requesting content destination  22 . 
       FIG. 24  is a flowchart illustrating a method  550 , according to an exemplary embodiment of the present invention, of distributing content via a network (e.g., the Internet) in a geographically controlled manner. The method  550  commences at block  552  with the receipt of a request from a content requestor located at a content destination  22  for delivery of content via a network to the content destination  22 . The request may, for example, be received at conditional access agent  28 , as illustrated in  FIG. 2  from a conditional access client  48 , located at the content destination  22 . As described above with reference to FIG.  16 , the request to the conditional access agent  18  may include both a user authentication device certificate  404  and a copy-protected device certificate  410 . 
     At block  554 , the conditional access agent  28 , in the manner described above, retrieves access criteria associated with the request content from an appropriate conditional access server  36  operated via a content provider  16 , or by a service provider  38 . The retrieved access criteria includes geographic access criteria specifying geographic regions (e.g., countries, states, provinces, counties, towns, municipal areas, etc.) and access conditions associated with those geographic regions. For example, the geographic access criteria may prohibit, or alternatively authorize, distribution of the associated content to a specific geographic region or regions. For the purposes of the present specification the term “geographic location” shall be taken to include any geographic location identifiable by any criteria, including national, state, municipal, city, town, economic, demographic, historical, or a socio-economic criteria. 
     At block  554 , the conditional access agent  28  also commences a content requestor or authentication process that, in one embodiment, includes performing a lookup to determine the physical delivery address of the copy-protected device  408  utilizing the copy-protected device certificate. In an alternative embodiment, at block  554 , the conditional access agent  28  may perform a lookup of the delivery address of the user authentication device  402 , utilizing information contained in the user device certificate  440 . In yet a further embodiment, the conditional access agent  28  may lookup the delivery addresses for both the copy-protected and the user authentication devices. The delivery address information may be included in the certificate, or stored in the network as information linked with the user and/or device. 
     At block  556 , the conditional access agent  28  determines the source IP address of the request received from the content requestor at the content destination  22 , and attempts to map the source IP address to a geographic location. To this end, the conditional access agent  28  may have access to an external geographic location service, such as those offered by Quova, Inc., or Digital Envoy, Inc. that provide sophisticated IP geographic location services. 
     At block  558 , the conditional access agent  28  examines the geographic access criteria, included in the access criteria retrieved from the conditional access server  36 . 
     At decision block  560 , the conditional access agent  28  makes a determination as to whether the delivery address (or addresses) determined at block  554  and/or the geographic location associated with the source IP address determined at block  556  comply with the geographic access criteria. Following a positive determination at decision block  560 , the conditional access agent  28  releases the requested content, stored on the local content server  40  for delivery to the content destination  22  of the content requestor. On the other hand, following a negative determination at block  560 , delivery of the requested content to the content requestor at the content destination  22  is blocked. 
     It will be appreciated that the above-described methodology may find broad application in digital rights management and exercising geographic control over content distribution. For example, a content provider  16  (or distributor  20 ) may distribute USB eTokens in the U.S.A. for immigrants that wish to access sports events broadcast over the Internet from a country of origin. The sports clubs (e.g., the content providers  16 ) can, utilizing the above method  550 , verify that a content requestor is located at a content destination  22  in the U.S.A. by verifying the content requestor&#39;s digital certificate and signature, for distributing encrypted content and in appropriate key. 
     By checking that both the delivery address of a user authentication or copy-protected device, and the source IP address of a content request are located within an authorized geographic location, the present invention seeks to prevent a user from utilizing a secure device, properly authorized, within an unauthorized geographic location. Specifically, the IP source address check decreases the ability of a fraudulent user to access content from a “blocked” geographic location. Content and keys are only delivered if a user has access to a user authentication and/or copy-protected device that is not officially distributed to any blocked region, and the source IP address of the content requestor is not mapped to any blocked region. 
     Dynamic Selection of Payment Gateways 
     Traditional Internet-based payment solutions may require a user to provide financial information to companies which they do not have a trust relationship, and also to provide financial information to a wide range of content providers  16  from which the user may wish to obtain content. This potentially creates barriers to entry for a user. 
     According to one aspect of the present invention, these problems are addressed by having a content provider  16 , and more specifically a conditional access server  36 , order a list of payment gateways through which the content provider  16  will accept payment such that a preferred payment gateway is highly ranked in the ordered list, and a least preferred payment gateway is ranked low within the ordered list. 
     Upon receiving a user request for access to content of a particular content provider  16  at a conditional access agent  28 , the conditional access agent  28  may reorder (or re-rank) the list of accepted gateways to leverage existing trust relationships between the content requestor and, for example, a content distributor  20  hosting the conditional access agent  28 . In one embodiment, the list of payment gateways presented by the conditional access agent  28  to the content requestor is dictated by the content provider  16 . The content distributor  20  is not authorized to add payment gateways to this list, but merely to reorder the list to reflect an existing trust relationship that the content requestor may have established. In an alternative embodiment, the content distributor  20  may modify a list of payment gateways, by adding or subtracting payment gateways to that list. Specifically, the content distributor  20  may have established relationships with additional payment gateways that have no relationship with the content provider  16 . In this case, the content distributor  20  may include such further additional payment gateways in the list presented to the content requestor. In this case, the content distributor  20  will assume responsibility for the appropriate transfer of the funds to the content provider  16 . 
     Dealing more specifically with payment gateways, as stated above, a commerce service provider  42 , such as that illustrated in  FIG. 2 , may act as a payment gateway with respect to a content provider  16 , a content distributor  20  and/or a content destination  22 . For the purposes of the present invention, the term “payment gateway” will be taken to include any party that acquires transactions from a further party, and processes such transactions through a financial system (e.g., a banking or credit card system). Merely for example, a payment gateway may be used to link a banking network with the Internet. A payment gateway may furthermore link a number of banking systems together (e.g., Visa, MasterCard and American Express), and may typically not be vendor or bank specific, although occasionally this is the case. In providing an interface between a merchant (e.g., a content provider  16  or a content distributor  20 ) and a bank&#39;s payment processing system, a payment gateway may operate to translate messages into other formats (e.g., VisaNet) that are utilized for authorization and settlement of merchant transactions. A payment gateway typically acquires a transaction, certifies it and routes it. Many payment gateways are based on Secure Electronic Transaction (ACT) technology. 
       FIG. 25  is a flowchart illustrating a method  600 , according to an exemplary embodiment of the present invention, to dynamically present a payment gateway to a content requestor (e.g., as a content destination  22 ). 
     The method  600  commences at block  602  at a content provider  16 , which performs a ranking operation to generate an ordered list of payment gateways according to relationships established between the content provider  16  and such payment gateways. More specifically, as discussed above, a conditional access server  36  may utilize a number of tables to support functionally supplied to a content provider  16 . Such tables include, as discussed above, the table PaymentGateway that is populated with records for each of a number of payment gateways with which a content provider  16  has established relationships. The table PaymentGateway, in one embodiment of the present invention, is provided with an additional “rank” field that indicates the ranking within an ordered list of payment gateways attributed to the relevant payment gateway by a content provider  16 . The ranking operation performed at block  602  includes the identification of a preferred payment gateway that is identified by the content provider  16  as being its first choice of a payment gateway through which to receive payment for access to content that it provides. 
     At block  604 , each of a number of content distributors  20  may optionally rank a number of payment gateways according to relationships established between each of the respective content distributors  20  and the payment gateways, and again each identify a preferred payment gateway. In the simplest implementation, the content distributor  20  itself may implement a payment gateway, and not have established any relationships with third party gateways. For example, Excite@Home may operate both as a content distributor  20 , and a payment gateway. In this case, Excite@Home may simply identify an “Excite@Home wallet” as the preferred payment gateway. In a more complex implementation, a content distributor  20  may have established relationships with a number of payment gateways, and in this case may maintain a table similar to the table PaymentGateway of the conditional access server  36 . 
     At blocks  606 , responsive to receipt of a content request at a content distributor  20 , and more specifically a conditional access agent  28 , the conditional access agent  28  requests certain information as described, from a conditional access server  36  of a content provider  16 . According to the present invention, the information communicated from the conditional access server  36  to the conditional access agent  28  as part of this communication includes a list of payment gateways accepted by the content provide  16 . This list of payment gateways includes the ordered ranking of payment gateways and the identification of the provider-preferred payment gateway. At block  606 , the conditional access agent  28  also makes a determination as to whether a ranked list of payment gateways (or at least a preferred payment gateway) has been specified by the content distributor  20 . 
     Following a positive determination at block  608  (i.e., the content distributor  20  has identified a preferred payment gateway), at block  610 , the conditional access agent  28  causes the preferred payment gateway of the content distributor  20  to be presented to the content requestor, if appropriate. More specifically, in one embodiment, the conditional access agent  28  may reorder the list of provider-accepted payment gateways to reflect relationships established between the content distributor  20  and appropriate payment gateways, or to reflect trust relationships established between the content requestor and the content distributor  20  (e.g., in the case of Excite@Home) or another third-party payment gateway. This reordered list of provider-accepted gateways is then communicated from the conditional access agent  28  to the conditional access client  48  for presentation to the content requestor (e.g., via a browser). 
     In an alternative embodiment, at block  610 , the conditional access agent  28  may modify the list of accepted payment gateways to include payment gateways with which the content distributor  20  has relationships, but with which the content provider  16  does not have relationships. In this way, the list of accepted payment gateways may be expanded or reduced, depending on relationships established by the content distributor  20 . In this case, the modified list of accepted payment gateways will again be communicated to the conditional access client  48  for presentation to the content requestor, with a preferred payment gateway being identified for presentation to the content requestor as such. 
     On the other hand, following a negative determination at decision block  608  (i.e., the content distributor  20  has no preference with respect to payment gateways), the conditional access agent  28  forwards the provider-accepted list of payment gateways, unaltered, to the conditional access client  48  for presentation to the content requestor. In this case, the preferred payment gateway, as identified by the content provider  16 , will be presented to the content requestor as such. 
     In one embodiment of the present invention, the actual preferred payment gateway that is presented to the content requestor at block  610  or  612  is presented as a default payment gateway. In one embodiment, this may involve presenting only the preferred payment gateway to the content requestor, without presenting other options. In an alternative embodiment, a list of payment gateways, with the preferred (or default) payment gateway being selected in the absence of selection of the content requestor to the contrary, may be presented to the content requestor. 
       FIG. 26  illustrates an exemplary sequence of user interfaces that may be presented by a client (e.g., a browser), executing on a client device (e.g., a personal computer) at a content destination  22 , and also hosting a conditional access client  48 . The sequence of interfaces includes a first content selection interface  620 , according to an exemplary embodiment of the present invention, which allows a content requestor to select particular content. To this end, the exemplary content selection interface  620  presents titles for each a number of content items, and a check box adjacent to each of these titles that the user may check to indicate selection of a content item. 
     A payment selection interface  622 , according to an exemplary embodiment, presents a number of payment gateways, in the exemplary form of “wallets” from which the content requestor may select a wallet via which payment for one or more content items may be made. As illustrated in the exemplary payment selection interface  622 , Excite@Home wallet is indicated as a preferred, default payment gateway as a radio button displayed adjacent a listing for this wallet is pre-selected. Additional wallets are listed below the Excite@Home wallet in an order determined by the content distributor  20 , or in the absence of any preference by the content distributor  20 , by the content provider  16 . 
     The methodology as described above enables the following illustrative exemplary scenario. The National Basketball Association (NBA) may distribute a live basketball game over a network (e.g., the Internet). The NBA, as a content provider  16 , may accept payment utilizing a NBA wallet, an Excite@Home wallet, and an English “British Telecom” wallet, and may designate the NBA wallet as a preferred, default wallet. 
     When an Excite@Home user requests access to the game via a conditional access agent  28  deployed by Excite@Home, operating as a content distributor  20 , the relevant conditional access agent  28  may, in the manner described above, reorder a list of payment gateways, accepted by the NBA and received from a conditional access server  36  operated by the NBA, to reflect the Excite@Home wallet as the preferred and default wallet. Accordingly, the Excite@Home wallet would in this case be presented to the end user as the default wallet. 
     Alternatively, when a British Telcom user requests access to the game via a conditional access agent  28  deployed by British Telcom in its capacity as a content distributor  20 , the preferred and default payment gateway may be switched to the British Telcom wallet by the relevant conditional access agent  28 . 
     Finally, if a user requests content to the game outside the Excite@Home and British Telcom networks, the payment gateway communicated to the content requestor as the default and preferred payment gateway (in the absence of a reconfiguring by the appropriate content distributor  20 ) will be the NBA wallet, as specified by the NBA in its capacity as a content provider  16 . 
     This enables a content provider  16  (e.g., the NBA) to sell access to a basketball game with minimal user inconvenience for Excite@Home and British Telcom users, as these users are not required to establish an account with the NBA. Such users will then be spared the inconvenience of having to re-supply confidential information to the NBA. 
     With a view to implementing the method  600  described above, both a content provider  16  and a content distributor  20  may maintain an ordered (or ranked) list of payment gateways. To enable the content distributor  20  to determine which payment gateways should be presented to a user, the ranked list of payment gateways may be communicated from the content provider  16  to the content distributor  20 . Similarly, in one embodiment, the content distributor  20  may maintain a similarly ranked list of payment gateways. 
     In one embodiment, the content distributor  20  may present both the first and second ranked lists of payment gateways to a user for selection. In a further embodiment, the content distributor  20  may operate to only present payment gateways within the lists that correspond. In other words, only payment gateways that appear on the list of the content distributor  20  are presented to the requestor, with other payment gateways that do not appear on the list maintained by the content distributor  20  being filtered out. 
     In yet a further embodiment, the content distributor  20  may reorder payment gateways communicated in the ranked list of the content provider  16  to reflect relationships established between the content distributor  20  and at least one payment gateway. 
     In yet a further embodiment of the present invention, a content distributor  20  may be authorized to only present payment gateways that are included in the ranked list generated by the content provider  16 , and communicated to the content distributor  20 . Nonetheless, in this embodiment, the content distributor  20  is presented with the option of re-ordering, or only displaying selected payment gateways, in accordance with relationships that may have been established between the content distributor  20  and the payment gateways, or relationships that may have been established between the end user and the payment gateways. 
     Computer System 
       FIG. 27  is a diagrammatic representation of a machine in the form of computer system  700  within which software, in the form of a series of machine-readable instructions, for performing any one of the methods discussed above may be executed. The computer system  700  includes a processor  702 , a main memory  704  and a static memory  706 , which communicate via a bus  708 . The computer system  700  is further shown to include a video display unit  710  (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)). The computer system  700  also includes an alphanumeric input device  712  (e.g., a keyboard), a cursor control device  714  (e.g., a mouse), a disk drive unit  716 , a signal generation device  718  (e.g., a speaker) and a network interface device  720 . The disk drive unit  716  accommodates a machine-readable medium  722  on which software  724  embodying any one of the methods described above is stored. The software  724  is shown to also reside, completely or at least partially, within the main memory  704  and/or within the processor  702 . The software  724  may furthermore be transmitted or received by the network interface device  720 . For the purposes of the present specification, the term “machine-readable medium” shall be taken to include any medium that is capable of storing or encoding a sequence of instructions for execution by a machine, such as the computer system  700 , and that causes the machine to perform the methods of the present invention. The term “machine-readable medium” shall be taken to include, but not be limited to, solid-state memories, optical and magnetic disks, and carrier wave signals. 
     If written in a programming language conforming to a recognized standard, the software  724  can be executed on a variety of hardware platforms and for interface to a variety of operating systems. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein. Furthermore, it is common in the art to speak of software, in one form or another (e.g., program, procedure, process, application, module, logic . . . ), as taking an action or causing a result. Such expressions are merely a shorthand way of saying that execution of the software by a machine, such as the computer system  700 , to perform an action or a produce a result. 
     Thus, methods and systems to distribute content via a network utilizing distributed conditional access agents and secure agents, and to perform digital rights management (DRM) have been described. Although the present invention has been described with reference to specific exemplary embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.