Patent Publication Number: US-8533458-B2

Title: Headend system for downloadable conditional access service and method of operating the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2007-0124226, filed on Dec. 3, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a headend system for a downloadable conditional access service and a method of operating the same. 
     This work was supported by the IT R&amp;D program of MIC/IITA. [2007-S-007-01, The development of downloadable conditional access system] 
     2. Description of Related Art 
     When users desire to watch a specific program in cable networks, a Conditional Access System (CAS) determines whether to provide a service based on a user authentication and enables only approved user to receive the program. 
     In a CAS in an initial stage, each manufacturing company uses standards different from each other, and thus a CAS is not compatible with other devices excluding a device of a particular company. Accordingly, a broadcasting service provider is required to directly provide a receiving terminal to a subscriber, which imposes a heavy burden on a broadcasting service provider and causes a difficulty in updating a CAS. 
     The OpenCable has provided a standard separating a Conditional Access module from a subscriber terminal to overcome such a disadvantage, that is, to prevent a monopoly of manufacturing company, boost competition, and cause a decline in a product price. Accordingly, a CAS separated from a subscriber terminal is standardized as a cable card of a Personal Computer Memory Card International Association (PCMCIA) card type. Also, a broadcasting service provider provides a subscriber with only cable card without lending a terminal to a subscriber, and thereby may provide a fee-based broadcasting service. However, an expected result of OpenCable has not been achieved due to an increase in a cable card price and management cost as well as failure in a retail market of terminals. 
     In such a circumstance, a technology related to a downloadable CAS (DCAS) is provided. The DCAS downloads a conditional access software to a subscriber terminal without a separate hardware conditional access module, and thereby enables a fee-based broadcasting service to be provided. 
     Thus, a technology which maintains a compatibility with a existing headend system for a cable broadcasting system and safely transmits a conditional access software to a receiver is required. 
     BRIEF SUMMARY 
     The present invention provides a headend system for a downloadable conditional access service and a method of operating the same where an Authentication Proxy (AP) server and Downloadable Conditional Access System (DCAS) host authenticate each other and generate a same session key, and thus an access validity of the DCAS host may be efficiently determined. 
     The present invention also provides a headend system for a downloadable conditional access service and a method of operating the same which is compatible with a Conditional Access System (CAS) in a conventional art without significantly changing the CAS in the conventional art. 
     The present invention also provides a headend system for a downloadable conditional access service and a method of operating the same which may safely download a software-based secure micro client to a DCAS host. 
     The present invention also provides a headend system for a downloadable conditional access service and a method of operating the same which enable a broadcasting service provider to manage a CAS with a relatively low cost and enable a subscriber to easily install and update the CAS. 
     According to an aspect of the present invention, there is provided a method of operating a headend system for a downloadable conditional access service, the method including: receiving, by an Authentication Proxy (AP) server, basic authentication information from a Downloadable Conditional Access System (DCAS) host, the basic authentication information being required to authenticate the DCAS host; transmitting, by the AP server, the basic authentication information to an external trusted authority device which authenticates the DCAS host; and generating, by the AP server, a session key for encrypting/decrypting a secure micro client using a session key sharing factor, wherein the AP server and DCAS host share the session key sharing factor generated by the external trusted authority device, and the DCAS host generates a same key as the session key. 
     According to an aspect of the present invention, there is provided a headend system for a downloadable conditional access service, the headend system including: an AP server receiving basic authentication information which is basis of an authentication of a DCAS host from the DCAS host, transmitting the basic authentication information to an external trusted authority device which authenticates the DCAS host, and generating a session key for encrypting/decrypting a secure micro client image using a session key sharing factor, wherein the session key sharing factor generated by the external trusted authority device is shared with the DCAS host. 
     According to an aspect of the present invention, there is provided a headend system for a downloadable conditional access service, the headend system including: an IPS server encrypting a secure micro client by a session key, receiving a command to download the secure micro client to a DCAS host from an AP server, and transmitting the secure micro client, encrypted by the session key, to the DCAS host in response to the command of the AP server. 
     According to an aspect of the present invention, there is provided a headend system for a downloadable conditional access service, the headend system including: a DPS transmitting download-related information to an AP server according to a request from the AP server, the download-related information including information about a download scheme of a secure micro client or information about an address of an IPS server. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects and advantages of the present invention will become apparent and more readily appreciated from the following detailed description, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a block diagram illustrating a headend system for a downloadable conditional access service according to an embodiment of the present invention; 
         FIG. 2  is a block diagram illustrating an Authentication Proxy (AP) server according to an embodiment of the present invention; 
         FIG. 3  is a flowchart illustrating a method of operating a headend system for a downloadable conditional access service according to an embodiment of the present invention; 
         FIG. 4  is a block diagram illustrating an Integrated Personalization System (IPS) server according to an embodiment of the present invention; 
         FIG. 5  is a block diagram illustrating a Downloadable Conditional Access System Provisioning Server (DPS) according to an embodiment of the present invention; and 
         FIG. 6  is a block diagram illustrating a Local Key Server (LKS) according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures. 
       FIG. 1  is a block diagram illustrating a headend system  110  for a downloadable conditional access service according to an embodiment of the present invention. 
     Referring to  FIG. 1 , the headend system  110  includes an Authentication Proxy (AP) server  111 , Local Key Server (LKS)  112 , Downloadable Conditional Access System Provisioning Server (DPS)  113 , and Integrated Personalization System (IPS) server  114 . 
     The headend system  110  is installed separately from a existing Conditional Access System (CAS) server  140 . Also, the headend system  110  is operated independently from the CAS server  140 , and thereby may be compatible with an existing cable broadcasting system. 
     The LKS  112  stores and manages information about keys of servers such as a key of a secure micro (SM), history of identification (ID) information of the SM, key of the AP server  111 , history of ID information of the AP server  111 , and history of key information of the IPS server  114 . Also, the DPS  113  manages download-related information and policy associated with a DCAS service. The IPS server  114  stores and manages an SM client to be downloaded to a DCAS host  160 . 
     When a DCAS host  160  connected to a cable network exists, the AP server  111  transmits information associated with an SM of the DCAS host  160  to a Trusted Authority (TA)  120  to authenticate the DCAS host  160 . The TA  120  is a reliable external authentication device. The TA  120  authenticates the DCAS host  160  using the received information associated with the SM. 
     The AP server  111  receives the download-related information from the DPS  113 . The download-related information may include information associated with a connection (mapping) between the IPS server  114  and DCAS host  160 , information associated with a download scheme of the SM, information associated with a DCAS operating policy, and download scheduling information. 
     In this instance, the AP server  111  commands the IPS server  114  to perform a process to download the SM client based on the download-related information. The IPS server  114  performs the process to download the SM client according to a download scheme corresponding to download-related information selected by the DPS  113  from a plurality of download schemes. The plurality of download schemes may correspond to a variety of transfer protocols such as a Carousel, Trivial File Transfer Protocol (TFTP), Hyper-Text Transfer Protocol (HTTP), and the like. 
     When an authentication of the DCAS host  160  is completed, the DCAS host  160  downloads and installs the SM client in the SM of the DCAS host  160 . The DPS  113  reports to the CAS server  140  an access authority of the authenticated DCAS host  160  to a program through a billing system  130 . In this instance, the CAS server  140  transmits an Entitlement Management Message (EMM) to the DCAS host  160  through a Cable Modem Termination System (CMTS)  150 . 
     The SM client downloaded and installed in the SM of the DCAS host  160  extracts a code word using the received EMM through a CAS messages processing operation. Also, the SM client transmits the extracted code word to a Transport Processor (TP). The TP decodes the encrypted and received program using the code word. 
       FIG. 2  is a block diagram illustrating an Authentication Proxy (AP) server  210  according to an embodiment of the present invention. 
     Referring to  FIG. 2 , the AP server  210  includes a DCAS network protocol interface  211 , session control module  212 , authentication management module  213 , key management module  214 , download control module  215 , and database  216 . 
     The DCAS network protocol interface  211  receives/transmits a DCAS protocol message through a Hybrid-Fiber Coaxial (HFC). The DCAS protocol message is transmitted from a DCAS host  220 . 
     The session control module  212  manages a state of every session and controls a session with respect to the DCAS host  220 . 
     The authentication management module  213  and an external authentication device, that is, TA  230 , authenticate an SM based on authentication information of the session control module  212 . The authentication management module  213  transmits information associated with an authentication result of the SM to the session control module  212 . 
     The key management module  214  stores key-related information, operated in the AP server  210 , in the database  216  while transmitting the key-related information to the LKS  260 . Also, in case of emergency, the key management module  214  requests for a backup of the key-related information to the LKS  260  for data restoration. 
     The download control module  215  stores information associated with a connection between the IPS server  250  and DCAS host  220 , download scheduling information, and information associated with a DCAS operating policy, received from the DPS  240 , in the database  216 . Also, the download control module  215  transmits a command received from the session control module  212  to the IPS server  250  in order to enable the SM client to be downloaded to an authenticated DCAS subscriber terminal sub system. The command indicates the IPS server  250  to perform a process to download the SM client. 
       FIG. 3  is a flowchart illustrating a method of operating a headend system for a downloadable conditional access service according to an embodiment of the present invention. 
     Referring to  FIG. 3 , an AP server continuously transmits a certificate of the AP server and SM client version information to a DCAS host via a DCAS network protocol interface. The certificate of the AP server and SM client version information, currently operated, are used to determine whether downloading of an SM client is necessary. The certificate of the AP server is used to authenticate a message received from the AP server by the DCAS host, and to confirm an identify of the AP server. 
     The DCAS host connected to a DCAS network determines whether to newly install or update the SM client using the received SM client version information. When the SM client is determined to be newly installed or updated, the DCAS host transmits basic authentication information to the AP server. 
     The basic authentication information includes information associated with a key pairing of a TP and SM, a certificate of the SM, and the like. The certificate of the SM may be used when the AP server authenticates a message received from the DCAS host and confirms an identity of the DCAS host. 
     The AP server transmits the basic authentication information to the TP, and the TP authenticates the SM. When the authentication of the SM is completed, the AP server generates a session key sharing factor, and transmits the generated session key sharing factor to the AP server. 
     The AP server shares the session key sharing factor with the DCAS host. The AP server and DCAS host sharing the session key sharing factor perform a mutual authentication. When the authentication is completed, each session key is generated. The session key may be used to encrypt or decrypt a DCAS message and SM client. 
     The AP server requests a DPS for download-related information. The download-related information may include information associated with a connection (mapping) between an IPS server and DCAS host, information associated with an address of the IPS server, and information associated with a download scheme of the SM or a name of an SM client. The AP server transmits the download-related information to the DCAS host. 
     The AP server commands the IPS server to perform a process to download the SM client according to a download scheme. The IPS server performs the process to download the SM client according to the selected download scheme. 
     The DCAS host transmits download state information to the AP server in association with whether the SM client is normally downloaded. The AP server determines whether the SM client is to be downloaded again based on the received download state information. When it is determined that the SM client is to be downloaded again, the AP server performs a process to download the SM client again. 
     The method of operating a headend system for a downloadable conditional access service according to the above-described embodiment of the present invention may be recorded in computer-readable media including program instructions to implement various operations embodied by a computer. The media may also include, alone or in combination with the program instructions, data files, data structures, and the like. The media and program instructions may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable media include magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD ROM disks and DVD; magneto-optical media such as optical disks; and hardware devices that are specially configured to store and perform program instructions, such as read-only memory (ROM), random access memory (RAM), flash memory, and the like. Examples of program instructions include both machine code, such as produced by a compiler, and files containing higher level code that may be executed by the computer using an interpreter. The described hardware devices may be configured to act as one or more software modules in order to perform the operations of the above-described embodiments of the present invention. 
       FIG. 4  is a block diagram illustrating an Integrated Personalization System (IPS) server  410  according to an embodiment of the present invention. 
     Referring to  FIG. 4 , the IP server  410  includes a download module  411 , database  412 , and network adapter  413 . 
     The download module  411  stores, in the database  412 , an SM client to be downloaded and information associated with a DCAS host  430  related to the download module  411 . Also, the download module  411  encrypts the SM client according to a request from the AP server  420 , and performs a process to download the encrypted SM client. The network adapter  413  performs a network interoperation to enable the download module  411  to transmit the SM client. 
     Also, the IPS server  410  stores and manages an SM client image, and performs a process to enable the SM client to be safely downloaded to the DCAS host  430 . Herein, a mutual authentication of the AP server  420  and DCAS host  430  is completed, and the SM client image is used to perform a conditional access function in a specific DCAS host  430 . 
     The safe download of the SM client refers to reducing data loss and data change and to transmitting SM client having an accurate version. For this, the SM client is encrypted using a session key generated through the authentication between the AP server  420  and DCAS host  430 . A download scheme with respect to the encrypted SM client may be a broadcast carousel, TFTP, HTTP, and the like. However, the IPS server  410  and the AP server  420  authenticate each other and the IPS server  410  is provided with session key and information about a download policy before encrypting the SM client or performing the process to download. 
     An example of downloading the SM client according to an embodiment of the present invention is described. 
     The AP server  420  transmits a download command with respect to the SM client, information associated with the DCAS host  430 , and session key to the IPS server  410 . The IPS server  410  encrypts the SM client using the session key generated through the authentication between the AP server  420  and DCAS host  430 . 
     The IPS server  410  performs a process to download the encrypted SM client using any one of a plurality of download schemes. 
     The DCAS host  430  receiving the SM client reports information about a download result to the AP server  420 . It is reported that information associated with installment and operation result of the SM client as well as the information about the download result. 
     The above-described operation is repeated a plurality of times, and thus a plurality of SM clients in a single session may be downloaded to the DCAS host  430 . 
       FIG. 5  is a block diagram illustrating a Downloadable Conditional Access System Provisioning Server (DPS)  510  according to an embodiment of the present invention. 
     Referring to  FIG. 5 , the DPS  510  includes a key management module  511 , policy management module  512 , database  513 , and billing system interface  514 . 
     The DPS  510  determines and maintains a DCAS policy of a cable service provider in a DCAS service structure, that is, the DPS  510  is performed as a central manager. The DPS  510  transmits/receives a message for a functional operation from/to an LKS  540 . Also, the DPS  510  communicates with a billing system  550  via the billing system interface  514 . 
     Main information required to determine and maintain the DCAS policy includes mapping information between an IPS server  520  and DCAS host, information associated with downloading an SM client, download scheduling information of the SM client, download-related information associated with a download scheme, and configuration information of DCAS headend system. 
     The policy management module  512  maintains and manages information required for the DCAS policy of the cable service provider in the database  513 . Also, the policy management module  512  manages a generation, deletion, or change of DCAS policy information to enable the AP server  530  to instantly apply a changed DCAS policy. Also, the policy management module  512  selects any one of a plurality of IPS servers. The IPS server  520  is used to perform a process to download the SM client. 
     The key management module  511  performs a backup of key-related information from an LKS  540  on a disaster recovery. 
     The billing system interface  514  transmits buying-related information transmitted via the AP server  530  to the billing system  550 . 
       FIG. 6  is a block diagram illustrating a Local Key Server (LKS)  610  according to an embodiment of the present invention. 
     Referring to  FIG. 6 , the LKS  610  includes a key management module  611  and database  612 . 
     The key management module  611  stores, maintains, and manages a key of every SM operated in a network of a service provider, history of ID information of an SM, key of an AP server  620 , history of ID information of the AP server  620 , and history of key information of an IPS server, in the database  612 . 
     The key management module  611  inquires key-related information in the database  612  according to a request from the AP server  620  and DPS  630 . Also, the key management module  611  transmits the inquired information to the AP server  620  or DPS  630 . The key management module  611  restores the key-related information of the database  612  of the LKS  610  using a key record stored in a TA  640  on a disaster recovery. 
     According to an embodiment of the present invention, in a headend system for a downloadable conditional access service and a method of operating the same, an AP server and DCAS host authenticate each other and generate a same session key, and thus an access validity of the DCAS host may be efficiently determined. 
     Also, according to an embodiment of the present invention, a headend system for a downloadable conditional access service and a method of operating the same is compatible with a CAS in a conventional art without significantly changing the CAS in the conventional art. 
     Also, according to an embodiment of the present invention, a headend system for a downloadable conditional access service and a method of operating the same may safely download a software-based secure micro client to a DCAS host. 
     Also, according to an embodiment of the present invention, a headend system for a downloadable conditional access service and a method of operating the same enable a broadcasting service provider to manage a CAS with a relatively low cost and enable a subscriber to easily install and update the CAS. 
     Although a few embodiments of the present invention have been shown and described, the present invention is not limited to the described embodiments. Instead, it would be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.