Abstract:
Methods, devices and systems for providing content providers with a secure way to multicast their data flows only to legitimate end users. By making a specific decision for each potentially legitimate end user requesting a specific data flow, differing subscriber profiles may be taken into account. Furthermore, end to end encryption is avoided by having a switch and/or router control the specific data flow to a specific end user. Each end user sends a request DTU to the switch and/or router asking for permission to join a multicast group. The switch and/or router extracts identification data from the request data transmission unit (DTU) and determines whether the requesting end user is cleared for the requested specific data flow. This determination may be made by sending a query DTU containing the identification data to a policy server which checks the identification data against preprogrammed criteria in its databases. The policy server then sends a response DTU to the switch and/or router confirming or denying the authenticity or legitimacy of the request based on the identification data. In the meantime, after the switch and/or router sends the query DTU to the policy server, the switch and/or router allows the specific requested data flow to proceed to the requesting end user. If, based on the response from the policy server, the request is determined to not be legitimate or authentic, the specific data flow is terminated. If the request is legitimate or authentic, then the data flow is allowed to flow uninterrupted by the switch and/or router.

Description:
FIELD OF THE INVENTION 
     The present invention relates to networking technologies and, more specifically, to technologies for providing a secure multicast flow between a multicast source and an end user receiving the multicast. The present invention is particularly applicable but is not limited to methods and devices for providing authentication and verification services to multicast providers. 
     BACKGROUND TO THE INVENTION 
     The increasing spread of computer technology and its application to all aspects of daily life has led to new and complex issues and problems. With the advent of broadband access to the Internet, an increasing number of content providers are using multicast technologies to deliver their content to subscribers. This usually involves establishing a continuous data flow between the content source and an end user device with the data flow containing the content. More often that not, such content takes the form of multimedia data with both voice and video content encoded in the data flow. 
     To simplify matters for end users, these data flows can be accessed by end user devices such as set top boxes. This technology has been used to deliver not only varied multimedia content but even regular television signals. Such TV signals are quite amenable to multicast technology as such signals are essentially broadcast to multiple end user devices simultaneously. All an end user device has to do to receive a TV signal multicast over the Internet is to receive the data flow emanating from the content source. 
     However, to prevent unauthorized access to these multicasts, content providers currently encrypt the multicast data at the source end. Legitimate end users can receive the data flow and are provided with appropriate decryption keys to decrypt the data flow. Such end-to-end encryption unfortunately can be inconvenient. Specifically, encryption and decryption capabilities are required at each end of the data flow link. Furthermore, the encryption and decryption keys and algorithms need to be periodically replaced or updated to prevent unauthorized users elements from breaking into the system. Clearly, such a system for preventing access to multicast data is inconvenient and can be costly. It is an object of the present invention to provide alternatives which overcomes or mitigates the disadvantages of the prior art. 
     It should be noted that the term data transmission unit (DTU) will be used in a generic sense throughout this document to mean units through which digital data is transmitted from one point in a network to another. Thus, such units may take the form of packets, cells, frames, or any other unit as long as digital data is encapsulated within the unit. Thus, the term DTU is applicable to any and all packets, cells, frames, or any other units that implement specific protocols, standards or transmission schemes. It should also be noted that the term digital data will be used throughout this document to encompass all manner of voice, multimedia content, video, binary data or any other form of data or information that has been digitized and that is transmitted from one point in a network to another. 
     SUMMARY OF THE INVENTION 
     The present invention provides methods, devices and systems for providing content providers with a secure way to multicast their data flows only to legitimate end users. By making a specific decision for each potentially legitimate end user requesting a specific data flow, differing subscriber profiles may be taken into account. Furthermore, end to end encryption is avoided by having a switch and/or router control the specific data flow to a specific end user. Each end user sends a request DTU to the switch and/or router asking for permission to join a multicast group. The switch and/or router extracts identification data from the request data transmission unit (DTU) and determines whether the requesting end user is cleared for the requested specific data flow. This determination may be made by sending a query DTU containing the identification data to a policy server which checks the identification data against preprogrammed criteria in its databases. The policy server then sends a response DTU to the switch and/or router confirming or denying the authenticity or legitimacy of the request based on the identification data. In the meantime, after the switch and/or router sends the query DTU to the policy server, the switch and/or router allows the specific requested data flow to proceed to the requesting end user. If, based on the response from the policy server, the request is determined to not be legitimate or authentic, the specific data flow is terminated. If the request is legitimate or authentic, then the data flow is allowed to flow uninterrupted by the switch and/or router. 
     In a first aspect the present invention provides a method for authenticating a request for a specific data flow from an end-user device, the method comprising:
     a) receiving a request data transmission unit (DTU) from the end user device, said request DTU requesting said specific data flow for said end user device;   b) extracting identification data from said DTU, said identification data identifying said end user device and said specific data flow;   c) determining if said request DTU is legitimate based at least a portion of said identification data; and   d) executing a predetermined set of steps based on whether said request DTU is legitimate as determined in step c).   

     In a second aspect the present invention provides a network device for routing multiple data flows from data servers to end user devices, the device comprising:
     means for receiving a request data transmission unit (DTU) from an end user device, said request DTU requesting a specific data flow for said end user device;   means for extracting identification data from said request DTU, said identification data identifying said end user device and said specific data flow;   means for transmitting a query regarding an authentication of said request DTU to a policy server capable of authenticating said request DTU based on at least a portion of said identification data, said query containing said at least a portion of said identification data;   means for receiving a response from said policy server, said response being related to said query; and   means for routing said specific data flow to said end user device, wherein said network device allows or prevents access to said specific data flow by said end user device based on whether said request DTU is legitimate.   

     In a third aspect the present invention provides computer readable media having encoded thereon a computer software product comprising:
     a software module for receiving a request data transmission unit (DTU) from an end user device, said request DTU requesting a specific data flow for said end user device;   a software module for extracting identification data from said request DTU, said identification data identifying said end user device and said specific data flow;   a software module for determining if said request DTU is legitimate based on at least a portion of said identification data; and   a software module for allowing a transmission of said specific data flow to said end user device.   

     In a fourth aspect the present invention provides a method of authenticating an end user device capable of coupling to a network, the method comprising:
     a) receiving a data transmission unit (DTU) from said end user device, said DTU containing identification data identifying said end user device and specific data to which said end user device is supposed to have access;   b) extracting said identification data from said DTU; and   c) determining if said end user device is entitled to access said specific data based on at least a portion of said identification data and a set of predetermined business rules.   

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the invention will be obtained by considering the detailed description below, with reference to the following drawings in which: 
         FIG. 1  is a block diagram of a system for providing secure multicast flow; 
         FIG. 2  is a flow chart illustrating the steps taken by a switch and/or router in providing secure multicast flow; and 
         FIG. 3  is a block diagram of software modules and submodules which may be used to implement aspects of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a block diagram of a system for providing secure multicast flow is illustrated. The system  10  has multicast content servers  20 A,  20 B,  20 C along with end user devices  30 A,  30 B,  30 C. A switch and/or router  40  is also present along with a policy server  50 . The content servers  20 A,  20 B,  20 C transmit multicast data flows  60 A,  60 B,  60 C to the switch and/or router  40  for distribution to end user devices  30 A,  30 B,  30 C. The switch and/or router  40  also communicates with policy server  50 . 
     The system  10  works with the content servers transmitting data flows  60 A,  60 B,  60 C to the switch and/or router  40 . Each data flow may be directed or routed to any number of end user devices of which end user devices  30 A,  30 B,  30 C are representative. It is for this reason that the data flows  60 A,  60 B,  60 C are referred to as multicast—each data flow may be broadcast to any number of recipient end user devices. However, only legitimate or authentic end user devices, those which subscribe to specific services provided by the operators of the content servers  20 A,  20 B,  20 C are allowed access to the data flows. As an example, end user device  30 A may subscribe to the data flows  60 A and  60 C but not to data flow  60 B. Similarly, end user device  30 B may be a legitimate subscriber to data flow  60 B and  60 C while end user device  30 C may be a subscriber to all the data flows  60 A,  60 B,  60 C. 
     To access the data flows to which they are subscribed, each end user device  30 A,  30 B,  30 C independently sends a request to the switch and/or router  40  requesting a specific data flow. For our example, end user device  30 A may request data flow  60  B while both end user devices  30 B and  30 C may both request data flow  60 A. When the switch and/or router  40  receives the request, usually in the form of a request data transmission unit (DTU) that contains not only the identity of the requesting end user device but also the requested data flow, the switch and/or router  40  extracts this identification data from the request DTU. A determination must then be made whether the requesting end user device is allowed access to the specific requested data flow. For this determination, the switch and/or router  40  formulates a query DTU to be sent to the policy server  50  for each requested data flow. The query DTU is then forwarded to the policy server  50 . 
     While the switch and/or router  40  is waiting for a response DTU from the policy server  50  containing a response to the query DTU, the switch and/or router  40  will allow the requested data flow to proceed to the requesting end user device. Thus, in  FIG. 1  and returning to our example, end user devices  30 A,  30 B,  30 C each sends a request DTU (represented by arrow  70 A,  70 B,  70 C respectively) to the switch and/or router  40 . Switch and/or router  40  then allows the requested data flows (represented by arrows  80 A,  80 B,  80 C) to the requesting end user devices as the switch and/or router  40  communicates (arrow  90 ) with the policy server  50  by way of at least one query DTU. The switch and/or router  40  then receives at least one response DTU (arrow  100 ) from the policy server  50 . 
     Once the switch and/or router  40  receives the relevant response DTU from the policy server  50 , the switch and/or router  40  will then either terminate the data flow to the end user device associated with the response DTU received or let the data flow continue uninterrupted. As noted above in our example and referring to  FIG. 1 , end user device  30 C is a subscriber to all three data flows  60 A,  60 B,  60 C so its requested data flow  60 A is allowed to continue uninterrupted. However, end user device  30 B is not a subscriber to its requested data flow  60 A and end user device  30 A is not a subscriber to its requested data flow  60 B. As such, both of these data flows (data flows  80 A,  80 B) are terminated by switch and/or router  40 . 
     It should be noted that the policy server  50 , once it receives a query DTU from the switch and/or router  40 , can apply whatever preprogrammed security checks are required to authenticate the correlation between the requesting end user device and the requested specific data flow. For example, the policy server may check with an internal subscriber table to determine if the requesting end user device is a subscriber to the requested data flow. Similarly, the policy server  50  may also check its databases to determine if the requesting end user device is implementing minimum required security measures to receive the requested data flow. As another alterative, the policy server  50  may check with accounting records to determine if the end user using the requesting end user device is current with his or her accounts. If the account is delinquent, the policy server  50  may then return a reject for the requested data flow. Another option is for the policy server to implement predetermined and preprogrammed business rules in conjunction with the identification data extracted from the request DTU to determine whether a requested data flow is to be allowed. Many other criteria may be implemented by the policy server to determine whether a specific request by a specific end user device for a specific data flow is to be allowed or not. The legitimacy or whether the request DTU is legitimate is therefore dependent on the policies implemented by the policy server. To assist in the tracking of the response DTUs from the policy server, each response DTU may have the identification data that was originally contained in the query DTU to which the response DTU is responding. The switch and/or router  40  then merely has to cross-reference its record of query DTU sent with the received response DTUs to determine which data flows are to be left uninterrupted and which ones are to be terminated. 
     As an option, and to reduce the amount of traffic between the policy server and the switch and/or router, the switch and/or router  40  could be provided with a default position and the policy server need only send a response when the default position is no longer operable. For example, the default position could be for the switch and/or router to allow the requested data flow to go through. If the query DTU sent to the policy server results in an authentication/legitimization of the requesting end user device, the policy server does not have to send a response DTU to the switch and/or router. In the absence of a request DTU from the policy server, the switch and/or router will let the allowed requested data flow to continue. However, if the policy server sends a response DTU in response to a query DTU, then the previously allowed data flow is to be interrupted. It should be clear that this alternative scheme, if implemented, must have a timer which determines how long the switch and/or router will wait for a response DTU. 
     Another alternative to the above would be to, instead of allowing a requested data flow to proceed, the requested data flow is prevented from continuing unless a positive response DTU is received in a given amount of time. For this alternative, the switch and/or router waits for a positive response DTU from the policy server before allowing the requested data flow to proceed. Again, this scheme will require a timer which will determine how long the switch and/or router will wait for a response DTU from the policy server. 
     A further alternative would be for the policy server to log query DTUs it has received while the switch and/or router allows the requested data flows to continue. The logged query DTUs will then be analysed at a later time by the policy server and if any of these logged query DTUs fail the check and analysis, its corresponding data flow is then terminated. 
     For specific implementations of the above, it is preferred that the request DTU sent by the end user devices to the switch and/or router  40  be an IGMP (Internet Group Management Protocol) join message. IGMP (details of which may be found in Internet Engineering Task Force (IETF) RFC 2236 and RFC 1112) is an Internet protocol which provides a way for an Internet computer to report its multicast group membership to adjacent routers. Thus, an IGMP join message from end user device  30 A merely requests that end user device  30 A be added to the multicast group membership for a specific multicast data flow. 
     The use of the IGMP protocol may also simplify the extraction of the identification data from the request DTU. Because each MAC (Media Access Control) identification number is unique for every network access device (e.g. network cards), this MAC number can be used as one of the identification data to extracted. This MAC address is a hardware unique to each piece of equipment, and specifically identifies each hardware device. Another possible component of the identification data to be extracted can be the unique IP (Internet Protocol) or network address of the requesting end user device. Both the MAC address and the IP address can be extracted from the IGMP join message as all IGMP messages have the following format: 
                                                     MAC Header   IP Header   IGMP Payload                        
The IGMP payload would contain data identifying the requested data flow. This can include the identity or address of the source of the requested data flow. Thus, returning to the example above, the end user device  30 A, when requesting data flow  60 B, may not only refer specifically to data flow  60 B, but also to content server  20 B that is the origin of data flow  60 B.
 
     It should further be noted that the functions of the switch and/router  40  need not be executed by a switch or a router. Any IGMP routing contact point can execute these functions. Thus, a generic device that can receive the request DTU and can pass a query DTU to a policy server and, consequently, direct or affect the data flow to the end user device, can be used. 
     The above system is particularly applicable to applications where the end user devices are set top boxes (STB). Such applications, where the STBs can automatically send the request DTUs to the switch and/or router  40 , are usually found in systems where the data flows have multimedia content such as television channel feeds from specific TV stations with the data flows being distributed to the subscribing end users by way of a broadband link to the Internet. 
     To prevent denial of service (DoS) attacks from hackers or illegitimate end users, the switch and/or router  40  may be provided with the capability to cache or store previous response DTUs from the policy server. With such a capability, repeated requests from an illegitimate end user device will not result in repeated query DTUs to the policy server. 
     As another alternative, the functions of the policy server  50  may be integrated into the switch and/or router  40 . Such an integrated device can not only perform the routing of the data flows but also the function of determining whether the request DTUs are legitimate or not. The integrated device would therefore have the wherewithal to perform security checks and account checks for the multiple of end user devices. 
     If, on the other hand, a separate policy server is desired, a server implementing any of the following protocols/standards may be used:
     RADIUS (Remote Authentication Dial-In User Service)   

     (See IETF RFC 2138 and 2139 for details)
     LDAP (Light Weight Directory Access Protocol)   SNMP (Simple Network Management Protocol)   

     As a process, the system above, can be implemented as shown in  FIG. 2 , a flowchart illustrating the steps taken by a switch and/or router  40  in providing secure multicast flow. As can be seen in the figure, the process begins with step  500 —receiving a request DTU from an end user device. Step  510  is that of extracting the identification data from the request DTU. This request data includes not only the data identifying the requesting end user device (such as its MAC address and IP address) but also data identifying the requested data flow. Steps  520  and  530  are performed either concurrently or in succession. Step  520  is that of allowing the requested data flow to reach the requesting end user device. In step  530 , the switch and/or router  40  creates a query DTU containing the identification data extracted in step  510 . Also in step  530 , the switch and/or router  40  sends the query DTU to a policy server for authentication/validation of the request from the end user device. Step  540  is a check whether a response DTU has been received from the policy server. Since, for this implementation, the default position is to allow the data flow transmission to continue absent any response from the policy server, all that is required is to determine whether a response DTU corresponding to the query DTU, sent in step  530 , has been received. If a corresponding response DTU has been received, then (step  550 ) the data flow transmission must be terminated as the response DTU means that the request DTU has not been authenticated/legitimized. On the other hand, if a response DTU has not been received by the switch and/or router, the data flow transmission is allowed to continue uninterrupted (step  560 ). 
     It should be noted that the above process has many variants which are still covered by the concepts disclosed above. As noted earlier, the default position may be either to allow the transmission or to prevent the transmission absent any response from the policy server. However, it has been found that, for Internet TV based applications, allowing access to the data flow absent any negative response DTUs is preferable. 
     The process above may be adjusted for applications involving periodic authentication checks by the end user devices. For such application, the end user devices receiving their data flows would periodically transmit a DTU containing their identification data to the switch and/or router. The switch and/or router will then authenticate the end user device. If the authentication fails for whatever reason, the data flow to the end user device is terminated, regardless of whether the end user device was previously allowed access to the data flow or not. Such a scheme will allow for changing conditions in the databases of the policy server to be taken into account. As an example, if a business rule in the policy server commands that any subscriber who is more than 60 days overdue in his payments is to be cut off, up to the 59 th  day that subscriber will be allowed access. On the 60 th  day, however, conditions will have changed and the subscriber is no longer allowed access. As such, on the 60 th  day, any data flow to that subscriber is to be terminated by the switch and/or router. 
     The system/method outlined above may be used not only in set top box applications but also in satellite based delivery of digital cable signals. Also, other applications which require authentication, either one time or periodical authentication, of end user devices may use the above system. Thus, satellite, cable, wireless, or any other means for delivering digital media services (such as digital television or digital radio) are particularly adaptable to the above system. 
     As a software product, the above can be implemented with different modules executing different functions (see  FIG. 3 ). As an example, each of the following functions can be implemented by different modules:
     receiving a request DTU from the end user device (module  1000 );   extracting the identification data from the request DTU (module  1010 ):   determining the authenticity of the request DTU by creating and sending a query DTU to the policy server and receiving the response DTU from the policy server (module  1020  and submodules  1020 A and  1020 B);   routing the requested data flow to the requesting end user device (module  1030 ); and   terminating the data flow to the end user device (module  1040 )   allowing the data flow to the end user device (module  1050 ).
 
These modules communicate with each other to pass data and DTUs between them so that each module may execute its function. It should be noted that modules  1040  and  1050  are merely two options to the same end result—disallowing access to the data flow to unauthorized end user devices.
   

     As can be seen, the end user device  30 A sends a request DTU to the module  1000 . The module  1000  then sends the request DTU to module  1010  so the identification data can be extracted. The extracted identification data can then be sent to module  1020  where submodule  1020 A creates a request DTU and submodule  1020 B sends the request DTU to the policy server  50 . Depending on the implementation and on the results of the authentication check on the policy server, the policy server  50  may or may not send a response DTU. Based on whether a response DTU is received or not or based on the contents of a received response DTU, module  1020  sends a command to module  1040  or to module  1050  (depending on the implementation). If module  1050  is used in the implementation, a message is sent to module  1030  which routes the data flow to the end user device  30 A. On the other hand, if the default action is to allow the data flow to proceed and module  1040  is used in the implementation instead of module  1050 , module  1030  has already routed the data flow to the end user device  30 A. A message can then come from module  1020  instructing module  1040  to terminate the data flow. This message would cause module  1030  to stop the data flow to end user device  30 A. 
     Embodiments of the invention may be implemented in any conventional computer programming language. For example, preferred embodiments may be implemented in a procedural programming language (e.g. “C”) or an object oriented language (e.g. “C++”). Alternative embodiments of the invention may be implemented as pre-programmed hardware elements, other related components, or as a combination of hardware and software components. 
     Embodiments can be implemented as a computer program product for use with a computer system. Such implementation may include a series of computer instructions fixed either on a tangible medium, such as a computer readable medium (e.g., a diskette, CD-ROM, ROM, or fixed disk) or transmittable to a computer system, via a modem or other interface device, such as a communications adapter connected to a network over a medium. The medium may be either a tangible medium (e.g., optical or electrical communications lines) or a medium implemented with wireless techniques (e.g., microwave, infrared or other transmission techniques). The series of computer instructions embodies all or part of the functionality previously described herein. Those skilled in the art should appreciate that such computer instructions can be written in a number of programming languages for use with many computer architectures or operating systems. Furthermore, such instructions may be stored in any memory device, such as semiconductor, magnetic, optical or other memory devices, and may be transmitted using any communications technology, such as optical, infrared, microwave, or other transmission technologies. It is expected that such a computer program product may be distributed as a removable medium with accompanying printed or electronic documentation (e.g., shrink wrapped software), preloaded with a computer system (e.g., on system ROM or fixed disk), or distributed from a server over the network (e.g., the Internet or World Wide Web). Of course, some embodiments of the invention may be implemented as a combination of both software (e.g., a computer program product) and hardware. Still other embodiments of the invention may be implemented as entirely hardware, or entirely software (e.g., a computer program product). 
     Although various exemplary embodiments of the invention have been disclosed, it should be apparent to those skilled in the art that various changes and modifications can be made which will achieve some of the advantages of the invention without departing from the true scope of the invention. 
     A person understanding this invention may now conceive of alternative structures and embodiments or variations of the above all of which are intended to fall within the scope of the invention as defined in the claims that follow.