Abstract:
This invention describes a system and methods for media content subscription service distribution; typical services include cable television, premium content channels, pay-per-view, XM radio, and online mp3 services. Subscribers use portable electronic devices to store digital certificates certifying the subscriber&#39;s privileges and an assigned public key. The devices can communicate with specially enabled televisions, radios, computers, or other media presentation apparatuses. These, in turn, can communicate with central databases owned by the provider, for verification purposes. Methods of the invention describe media content subscription service privilege issuing and use. The invention additionally describes methods for protecting media content transmitted to users with a variety of encryption schemes. The invention also comprises methods for subscribed users to bestow a subset of their privileges to a number of secondary users, with appropriate permission from the media content subscription service provider.

Description:
RELATED U.S. APPLICATION DATA 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 14/305,904, filed on Jun. 16, 2014, which is a continuation of and claims priority to U.S. patent application Ser. No. 13/693,607, filed on Dec. 4, 2012, entitled “System and Methods for Assignation and Use of Media Content Subscription Service Privileges,” now issued as U.S. Pat. No. 8,788,813, which is a continuation of and claims priority to U.S. patent application Ser. No. 12/861,121, now U.S. Pat. No. 8,327,152, filed on Aug. 23, 2010, entitled “System and Methods for Assignation and Use of Media Content Subscription Service Privileges,” which is a continuation of and claims priority to U.S. patent application Ser. No. 10/858,336, now U.S. Pat. No. 7,783,892, filed on Jun. 1, 2004, entitled “System and Methods for Assignation and Use of Media Content Subscription Service Privileges,” which claims priority under USC 119(e) to U.S. Provisional patent Application Ser. No. 60/474,750, filed on May 30, 2003, entitled “Secure Biometric Identification Devices and Systems for Various Applications,” each of which are hereby incorporated by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates generally to the field of media content subscription services, and more specifically to portable and remotely controlled user privileges, and electronic/digital resource and asset management. 
         [0004]    2. Necessity of the Invention 
         [0005]    Media content subscription services are increasingly popular and profitable services. Common antenna (CATV), or cable television, subscriptions are found in millions of homes across America, and music services such as www.emusic.com and XM Radio are reporting increases in user levels. Most media content subscription services require an individual to apply for subscription, and if the media content subscription service provider wishes to accept the individual, he/she is provided with an appropriate service privilege-receiver. In the case of CATV, an accepted individual typically receives a set-top-box that is uniquely identified and associated with the individual. The set-top-box is capable of decrypting the CATV signal and supplies the decrypted version to the individual&#39;s television. 
         [0006]    However, once activated, these services typically require very little user identification, and an authorized user could unknowingly provide his benefits to other people. Most people have heard stories of ‘stealing cable from the neighbors’ and other rights-hijacking attempts. Additionally, because these services often expect use of a ‘home base’, such as a television set-top-box or a cookie on a computer, transporting subscription privileges from one location to another is anything from difficult to impossible. For example, it is very difficult for a cable subscriber to take his cable subscription service privileges to a friend&#39;s—and non-subscriber&#39;s—house for cable viewing at the friend&#39;s house. 
         [0007]    The necessity for administrative convenience and security has overwhelmed the subscriber&#39;s flexibility of subscription permissions. There is a definite need for a user-centric subscription service system, allowing for vendor, provider and user security, while allowing for greater user flexibility. 
       DESCRIPTION OF THE RELATED ART 
     Digital Rights Management Related Art 
       [0008]    U.S. Pat. No. 5,715,403 to Stefik discloses a system for controlling use and distribution of digital works. The invention allows the owner of a digital work to attach usage rights to their work. The usage rights define how the individual digital work may be used and distributed. Instances of usage rights are defined using a flexible and extensible usage rights grammar. Although the patent provides a network terminating device-based internal digital rights management system capability for managing and monitoring digital properties, the Stefik patent does not provide a user-oriented system for accessing digital rights and privileges. 
         [0009]    U.S. Pat. Nos. 6,401,085, 6,356,905, and 6,199,099, all to Gershman, disclose a system that facilitates web-based information retrieval and display. A wireless phone or similar hand-held wireless device with internet protocol capability is combined with other peripherals to provide a portable portal into the Internet. The wireless device prompts a user to input information of interest to the user. This information is transmitted a query to a service routine running on a Web server. The service routine then queries the Web to find price, shipping and availability information from various Web suppliers. This information is available for use by various applications through an interface support framework. An “electronic valet” capability is also disclosed which represents a convenient mechanism for organizing user preferences, rights, privileges, etc. However, the patent, and the products it protects, does not provide a user-centric, media content subscription service system. 
         [0010]    A variety of other U.S. Patents discuss securely or privately accessed systems, digital rights management systems, and other remotely, wirelessly, or portably accessed or controlled systems or resources, including U.S. Pat. Nos. 6,135,646, 6,256,393, 6,289,445, 6,327,622, 6,449,367, 6,499,099, 6,330,770, 6,535,871 and others. None of these patents provide a user-centric media content subscription service system. 
         [0011]    U.S. Pat. No. 6,516,412 to Wasilewski discloses a CATV system that provides conditional access to services. The cable television system includes a head-end from which service “instances” are broadcast, and provides set-top units for receiving the instances and selectively decrypting the instances for display to system subscribers. These service instances are encrypted using public and/or private keys provided by service providers or central authorization agents. Keys used by the set-top units for selective decryption may also be public or private in nature, and such keys may be reassigned at different times to provide a cable television system in which piracy concerns are minimized. The Wasilewski patent appears not to perceive or articulate a need for portable, user-centric privileges. The Wasilewski patent is silent, vague, or incomplete on several features, including hierarchies of access privileges or verification of authenticated user privileges. There is also no mention of users porting their privileges between different remotely controlled devices and machinery. 
       REMOTE CONTROL RELATED ART 
       [0012]    U.S. Pat. No. 4,005,428 to Graham discloses a patent relating to private remote control communication systems. In Graham&#39;s patent, coded messages, e.g., for use in remote control of equipment, are transmitted and received in a system which purports to preclude unauthorized or accidental activation of a control associated with the receiving means. This presumed secure communication is accomplished by generating a plurality of carrier frequencies in a predetermined sequence and by modulating each carrier frequency in accordance with a digital code. The receiving means, which is primarily tuned to receive the first carrier in a transmission sequence, detects and decodes the received signals and stores the decoded message. The equipment to be controlled includes a receiver that is retuned to another carrier frequency after each bit of a coded message is detected, in a system that appears to resemble a “spread spectrum” type of a communications system, insofar as Graham&#39;s patent notes that the equipment is expected to be responsive to the entire received message. 
         [0013]    The Graham patent appears to be one of many re-articulations of spread-spectrum communications systems, which can be fundamentally different, yet generically are well known in the art. Graham is primarily directed to communications by radio from a base transmitter to a radio-controlled station or to remote radio station equipment, where message privacy and security are important. Graham does not disclose media content subscription service applications. 
         [0014]    U.S. Pat. No. 4,847,542 to Clark discloses an automatic garage door operator with remote load control. The apparatus of the invention is a remote control device comprising a two button portable controller that features a “secure mode.” In accordance with the normal operation of the secure mode button, actuation when the garage door is closed toggles the remote controller between either a secure state or a non-secure state. In the secure state, the automatic garage door operator does not move the door upon receipt of a door signal. To open the door when in the secure state, the garage door operator must first press the secure button to enter the non-secure state and then press the door button to open the door. The secure button has a secondary function when the garage door is open and the secure state is prohibited. Actuation of the secure button when the door is open toggles the state of a load remote from the automatic garage door operator between an on state and an off state. This control is achieved via a signal modulated on the electric power main. Clark is limited to the control of garage doors and other doors, and does not anticipate or suggest applications outside of the narrow focus of the patent. 
         [0015]    U.S. Pat. No. 5,473,318 to Martel discloses a car door operator that purports to provide enhanced security for controlled vehicle access by employing transmitters having unique identity codes that are fixed at the time of manufacture. A receiver includes a nonvolatile read/write identity code memory for storing the authorized identity codes. If a received identity code is found within this memory, then the user is authorized and the door is opened. Otherwise, the user is not authorized and entry is refused. A remotely disposed memory controller controls the authorized identity codes stored in the identity code memory, which is preferably electrically erasable programmable read only memory (EEPROM). The memory controller is preferably a desktop computer including a data base program with the identity of authorized users. The identity code of a transmitter held by a formerly authorized user can be determined via the data base program and deleted from the identity code memory without requiring return of the transmitter. “Pass back” is restricted by preventing additional door accesses for a predetermined time following each access. In an alternative embodiment, a two-button transmitter includes a fixed identity code and a user selectable identity code. One button transmits the selectable identity code to individualized receiver/operators also having a user settable identity code. 
         [0016]    U.S. Pat. No. 5,721,583 to Harada, discloses an interactive television system for providing TV and CATV-based entertainment services and other TV-based services to authorized users, apparently primarily focused on electronic polling of users. The invention is based on a “central site” apparatus, apparently a high-capacity computer. Terminal devices bi-directionally communicate with the central computer via a digitally linked two-way CATV network, to provide video and audio inputs to a display apparatus thereto, with each of the terminal apparatuses being wirelessly controllable by one or more remote control apparatuses. Additionally, using remote controllers, users can request services or participate in TV-centric polling, with the TV being the communications medium in conjunction with a digital link to a central site, via a television-attached terminal, such as a set-top box. Message data issued by a remote control apparatus is automatically accompanied by apparatus identifier information, then read out from a memory of the remote control apparatus for identifying that remote control apparatus, and may also be accompanied by personal information concerning a registered user of the remote control apparatus. Onboard user recognition can be implemented by a plug-in IC card interface section or fingerprint recognition section, for enabling restriction of each remote control apparatus to use by only a specific registered user, or to enable only a specific registered user to access certain services. 
         [0017]    Harada&#39;s patent does not lend itself to user-centric applications. In the Harada product, primary and apparent last resort placement of application intelligence appears centralized. Harada&#39;s “terminal” is apparently a set-top controller connected into the TV. However, set-top terminals appear effectively slaved to the central computer. They do not appear to recognize classes of devices allowed to access them. Implicitly, Harada&#39;s central computer is managing and authorizing the enabling of his terminal and by extension, the central site is effectively, (indirectly) managing remote control devices communicating with the terminal attached to the TV, all of which are controlled by and digitally linked to the central site. 
         [0018]    The Harada patent does not disclose hierarchies of remote control devices or user privileges, optional identity credential verification subsystem flexibility, and pre-definable security options on a mobile, portable, application-by-application basis. There is also no mention of authorized users porting their remote controllers and their associated privileges between different remotely controlled devices and machinery. 
         [0019]    U.S. Pat. No. 5,900,867 and U.S. Pat. No. 6,396,544, both to Schindler, et al, teach a self-identifying remote control device having a television receiver for use in a computer. An entertainment system is disclosed which has a personal computer as the heart of the system with a large screen VGA quality monitor as the display of choice. The entertainment system has digital satellite broadcast reception, decompression and display capability with multiple radio frequency remote control devices that transmit self-identifying signals and that have power adjustment capabilities. These features are used to provide context-sensitive groups of keys that are defined to affect only selected applications running in a windowing environment. The remote control devices of this invention claim to combine television and VCR controls with standard PC computer keyboard controls. A user of the Schindler invention is not subject to strict authentication and different levels of privilege to operate the remote control or the remote-controlled resource. Schindler is utilitarian for its stated applications and does not completely disclose or suggest use for one or more authorized users of the remote controller. 
         [0020]    U.S. Pat. No. 6,369,693 to Gibson teaches a method of, and system for, transferring secure data. The method of transferring secure data in a remote control system includes a remote controller and a controlled apparatus that is operable in response to commands relayed by the remote controller. The controlled apparatus has a receiver for receiving transmissions from the remote controller. The remote controller has a transmitter, a memory for storing secure data and commands and a keypad. The embedded transmitter is controlled so that in response to a user wishing to transfer secure data to the user apparatus, it transmits this data at a power level lower than that which is normally used for sending other commands. The link between the remote controller user apparatus can be radio frequency wireless or infrared wireless. 
         [0021]    U.S. Pat. No. 6,424,285 to Perdue, et al, discloses a communications system for transmitting and receiving remote control messages in an electronic remote control system. This communications system uses a message protocol that is purportedly suited for transmitting RF remote control messages with IR remote control messages in a time multiplexed fashion, wherein the RF remote control messages are transmitted during the pause intervals between IR remote control message transmission intervals. A plurality of data fields begins with a data field for specifying a destination device address. A security code data field allows a specific remote control transmitter to control a specific destination device. A status field specifies codes associated with the message. A keycode field carries a message payload. A checksum field verifies the transmission integrity of the remote control message. A remote control message based on the present message protocol may be expanded to include additional data fields and to expand pre-existing data fields. While the Purdue patent, and products it protects, appears utilitarian for applications requiring both RF and infrared data communications, there is no mention of using the remote controller apparatus for media content subscription services. 
         [0022]    Russell, in U.S. Pat. Nos. 5,481,265, 5,729,220, 6,201,484, and 6,441,770 describes a ‘secure access transceiver.’ The invention illustrates a hand-held electronic device that incorporates wireless technology with a button-oriented user interface. The device is used to provide both identification of an individual and a device to a receiving device or system. 
         [0023]    International Application No. PCT/US00/42323 describes a Biometric Personal Identification Device (BPID). A BPID is a hand-held electronic device that provides multi-factor authentication and allows its enrolled operator to control the release and dissemination of stored information such as financial accounts, medical records, passwords, personal identification numbers, and other sensitive data and information. The device has tamper-resistant packaging with form factors ranging from credit card size to key fobs. Various embodiments also include a biometric scanner, a liquid crystal display (LCD) and buttons for user interaction, and a wireless interface for communication with other electronic devices. The device has been developed so that the fingerprint cannot be physically or electronically removed or transmitted from the device, and information cannot be physically or electronically removed or transmitted from the device unless released by the operator of the authorizing biometric. All data and processing is performed securely. The BPID can store a variety of data and applications, though it is primarily intended for point-of-sale or other financial transactions. However, the BPID does not describe means for secure remote control access. 
       BRIEF SUMMARY OF THE INVENTION 
       [0024]    This invention describes a system and methods for media content subscription service distribution; typical services include CATV, premium content channels, pay-per-view, XM radio, and online music services. Subscribers use portable electronic devices, such as a handheld computer or a laptop, to store digital certificates certifying the subscriber&#39;s privileges and an assigned public key. These certificates are issued and signed by the media content subscription service provider. The devices can communicate with specially enabled televisions, radios, computers, or other media presentation apparatuses. These, in turn, can communicate with central databases owned by the provider, for verification purposes. In some embodiments of the invention the media presentation apparatus can examine the privilege certificate; in other embodiments the media presentation apparatus forwards the privilege certificate to the central database for verification. 
         [0025]    Methods of the invention describe media content subscription service privilege issuing and use. The invention additionally describes methods for protecting media content transmitted to users with a variety of encryption schemes. The invention also comprises methods for subscribed users to bestow a subset of their privileges to a number of secondary users, with appropriate permission from the media content subscription service provider. The system is designed for portability and security of issued privileges. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Master Reference Numeral List 
         [0026]      FIG. 1 : System 
           [0027]      101  Personal identification device 
           [0028]      102  Media presentation apparatus 
           [0029]      103  Media content subscription service database 
           [0030]      FIG. 2 : Assigning Primary Applicant Privileges 
           [0031]      251  Specify media content subscription service privilege 
           [0032]      252  Determine if the primary applicant possesses a public/private key pair 
           [0033]      253  Assign a public/private key pair to the primary applicant 
           [0034]      254  Store the public key and the primary applicant&#39;s name in a database 
           [0035]      255  Find the primary applicant&#39;s public key in a database 
           [0036]      256  Create and store a media content subscription service privilege certificate 
           [0037]      FIG. 3 : Using Primary User Privileges 
           [0038]      351  Select a media content subscription service privilege certificate 
           [0039]      352  Authenticate the primary user 
           [0040]      353  Present the media content subscription service privilege certificate 
           [0041]      354  Prove ownership of the certificate 
           [0042]      355  Verify the media content subscription service provider&#39;s digital signature 
           [0043]      356  Transmit the encrypted media content feed 
           [0044]      357  Decrypt the encrypted media content feed 
           [0045]      358  Display the decrypted media content feed 
           [0046]      FIG. 4 : Assigning Secondary Applicant Privileges 
           [0047]      451  Specify media content subscription service privilege 
           [0048]      452  Verify primary user possesses media content subscription service privilege 
           [0049]      453  Determine if the secondary applicant possesses a public/private key pair 
           [0050]      454  Assign a public/private key pair to the secondary applicant 
           [0051]      455  Store the public key and the secondary applicant&#39;s name in a database 
           [0052]      456  Find the secondary applicant&#39;s public key in a database 
           [0053]      457  Create a media content subscription service privilege certificate for the secondary applicant 
           [0054]      458  Store the secondary applicant&#39;s and the primary applicant&#39;s media content subscription service privilege certificate 
           [0055]      FIG. 5 : Using Secondary User Privileges 
           [0056]      551  Select a media content subscription service privilege certificate 
           [0057]      552  Authenticate the secondary user 
           [0058]      553  Present the secondary user&#39;s media content subscription service privilege certificate 
           [0059]      554  Prove ownership of the certificate 
           [0060]      555  Verify the primary user&#39;s digital signature 
           [0061]      556  Present the primary user&#39;s media content subscription service privilege certificate 
           [0062]      557  Verify the media content subscription service provider&#39;s digital signature 
           [0063]      558  Transmit the encrypted media content feed 
           [0064]      559  Decrypt the encrypted media content feed 
           [0065]      560  Display the decrypted media content feed 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0066]    This invention describes a system for accessing portable media content subscription service privileges, and/or other privileged or protected content or resources. Media content subscription services include CATV, premium content cable channels such as Home Box Office® (HBO®) and Showtime®, pay-per-view, online music services such as www.emusic.com, and satellite radio services such as XM and Sirius radio. These services are increasingly popular, but do not typically allow for portability or distribution of services to other qualified users. The invention described herein addresses both of these issues. 
         [0067]    A Portable Media Content Subscription Service System 
         [0068]    The system of this invention can be seen in  FIG. 1 , and comprises at least one personal identification device  101 , a media presentation apparatus  102 , and a media content subscription service database  103 . The personal identification device  101  is a portable device that is capable of identifying its user and providing proof of this identification, and that is also capable of encryption, decryption, and digital signature generation. For example, the personal identification device  101  may be a handheld personal digital assistant, such as Hewlett-Packard&#39;s iPAQ or Palm&#39;s Palm Pilot, the biometric personal identification device described in Russell, Johnson, Petka, and Singer, a laptop computer, or any other comparable device. 
         [0069]    The media content subscription service provider establishes the level of identification required by the device. User identification is required in order to allow user access to a cryptographic key pair. Digital signatures generated by this key pair are considered binding to the individual, so the level of authentication and identification should be adjusted accordingly. Devices that incorporate local biometric authentication are preferable, given their ability to uniquely identify users. However, some services may only require a password, or a PIN. Other systems may wish to use the personal identification device  101  in conjunction with a smart card or a magnetic stripe card. 
         [0070]    A media presentation apparatus  102  is a unit that is capable of presenting media content to a user that is adapted for communicating with a personal identification device  101  and possibly a remote database  103 . This may be a television, computer, radio, stereo, or other comparable device. In preferred embodiments, the media presentation apparatus  102  is also capable of performing encryption, decryption, and verification of digital signatures. This may require addition of a “set-top-box,” or other peripheral, capable of performing these cryptographic processes. 
         [0071]    The media content subscription service database  103  is used to associate users with assigned cryptographic keys, and required billing information. The distribution of cryptographic keys is described in further detail below. 
         [0072]    Applying for and Assigning Media Content Subscription Service Privileges 
         [0073]    Individuals must apply to media content subscription service providers for privileges (this individual is referred to as the ‘primary applicant’). The application and distribution of privileges can be seen in  FIG. 2 , steps  251 - 256 . For example, individuals wishing to watch HBO must request the privilege from their CATV distributor for the premium content channel (step  251 ). If the distributor decides to authorize the service, the distributor searches its database—the media content subscription service database  103 —for the applicant&#39;s unique identifier (step  252 ). For ease of discussion the unique identifier will be the applicant&#39;s name, but this selection has no impact on the scope of the invention. 
         [0074]    If the primary applicant&#39;s name is in the database, the distributor accesses an associated public key (step  255 ). If not, the distributor assigns a unique and unused public/private key pair to the applicant and stores the public key in the distributor&#39;s database with the applicant&#39;s name (step  253 ). The distributor now creates a primary media content subscription service privilege certificate for the applicant, including the HBO privilege, the public key (either the stored key or the newly generated key), and a digital signature signed by the distributor (step  254 ). The certificate may also store a secret, shared symmetric key that can be used by the applicant&#39;s television to decrypt the HBO feed. This key will be described in further detail below. 
         [0075]    The primary media content subscription service privilege certificate is downloaded to the primary applicant&#39;s personal identification device  101  upon completion (step  256 ). The individual can now present the certificate to access HBO at any location with a television and a cable connection. The individual may also bestow a subset of his privileges to a secondary applicant. This process is also described in further detail below. 
         [0076]    Although this example describes the use of HBO premium content, this process can be used for subscription to online video or music streams, or any of the other media content subscription services described above or known in the art. 
         [0077]    Primary User Use of Media Content Subscription Service Privileges 
         [0078]    A user authentication process is performed in a manner supportive of the individual&#39;s right to privacy, in accord with the application accessed and the stipulations of the remote-controlled resource or application owner, if any. In one embodiment, a tamper-resistant memory within the remote control apparatus stores a pre-enrolled biometric template of the authorized individual. The template is never authorized to leave the device, and is “zeroed-out” upon unauthorized attempted physical or logical access. When an individual wishes to access controlled resources, he/she submits another biometric template through a reader on the device. If the submitted identity credential matches the template stored therein, the user is granted access to operate the remote controller and the machinery it controls. 
         [0079]    In one embodiment, the remote controlled apparatus includes is a transmitter adapted for generating and transmitting a basic, “standalone,” simplex, one-way “identity credential verification signal” transmission from a user&#39;s remote controlled device to a target device after successful initial user authentication. In this embodiment, the remote control apparatus performs the user authentication process, displays the results in the form of a user “identity credential verification display,” generates and transmits as appropriate, a user “identity credential verification signal” and also transmits user control signals to the remotely controlled device. 
         [0080]    Upon receipt of media content subscription service privileges, an individual may use the personal identification device  101  to use the privileges. This discussion uses the previous example, in which a primary applicant (now, the ‘primary user’) receives HBO privileges, and can be seen in  FIG. 3 , steps  351 - 358 ; again, however, this description can be expanded to cover any of the discussed services. In this example, the primary user wishes to watch a movie showing on HBO with a friend, at the friend&#39;s house. He arrives at his friend&#39;s house and selects the HBO privilege on his personal identification device (step  351 ). The device prompts the individual to authenticate himself (step  352 ), and upon authentication presents the primary media content subscription service privilege certificate to the television (step  353 ). 
         [0081]    In one embodiment of the invention, the television forwards the certificate to the cable distributor. Note that the television must be enabled to send and receive messages, as well as perform encryption and decryption, as described above. This may necessitate a peripheral device that can be attached to the television to perform this task, such as a special set-top-box, or a “futurized” television that incorporates the capability. For purposes of further discussion, the television is assumed to have this capability. The cable distributor sends back a response to the personal identification device via the television, prompting the primary user to prove ownership of the private key corresponding to the public key in the certificate (step  354 ). This is typically accomplished by sending a string to the personal identification device, encrypting the string with the private key, transmitting the encrypted data back to the distributor, decrypting the message with the public key, and verifying that the decrypted message matches the original string. The cable distributor now verifies that it signed the certificate (step  355 ). If the cable distributor has already assigned a symmetric private key in the individual&#39;s certificate, it uses this key to encrypt the HBO feed, and transmits the encrypted feed to the television (step  356 ). The television saves the symmetric key and uses it to decrypt the feed (step  357 ), and presents HBO to the individual (step  358 ). 
         [0082]    In a second embodiment of the invention, the television has been pre-programmed with the public key of the cable distributor. After receiving the primary media content subscription service privilege certificate, the television challenges the personal identification device to ensure that it has ownership of the private key (step  354 ), and is able to verify that the cable distributor signed the certificate without further communication with the distributor (step  355 ). Again, if the distributor has already included a symmetric key in the certificate, the television can use it to decrypt the HBO feed (step  357 ). 
         [0083]    Depending on the embodiment of the invention and the nature of the media content subscription service provider, the provider may choose to use to issue the symmetric secret key in one of several ways. In a first method, the cable distributor may wish to use the same symmetric key for all authorized users of a service, and issue this as part of the primary media content subscription service privilege certificate. In a similar method, the cable distributor may wish to use the same symmetric key for all authorized users, but update the symmetric key on a daily, weekly, monthly, random, or other time interval basis. This could be used to make it more difficult for non-subscribers to access the secret symmetric key. Alternatively, each individual may be assigned a unique symmetric secure key. This may be stored in the primary media content subscription service privilege certificate or may be changed and provided each time the individual attempts to access the privilege. 
         [0084]    Assigning Media Content Subscription Service Privileges to a Secondary Applicant 
         [0085]    A recipient of media content subscription service privileges may wish to allow other persons to use his privileges. For example, a father who has initially applied for and received privileges for HBO (the primary user) may wish to allow his teenage son (the secondary user) to subsequently watch the channel in his absence. The father may want to restrict the son&#39;s access to movies airing on HBO with a certain MPAA rating, or may wish to restrict the son&#39;s access to HBO at certain times. However, it may be necessary to impose a limit on the number of allowable secondary users per primary media content subscription service privilege certificate—for example, a cable distributor probably does not want a primary user to bestow his rights upon an entire neighborhood. Accordingly, the media content subscription service provider may establish a governing system that states a primary user can only issue a certain number of secondary certificates. This is left to the discretion of the media content subscription service provider. 
         [0086]    The distribution process can be seen in  FIG. 4 , steps  451 - 458 . The father instructs his personal identification device to create a secondary media content subscription service privilege certificate for his son, who is now the ‘secondary user’, and to incorporate any additional restrictions that he has selected, such as the MPAA ratings. This step determines the rights appropriate for the son (step  451 ). The device verifies that the father is only assigning a subset of his privileges to the son (step  452 ). The father now needs a public key for the son (step  453 ). If the father has issued a certificate to the son before, he may already have a public key for the son on file in his personal identification device or other storage location that he can retrieve and use accordingly (step  456 ). If not, a public/private key pair is created for the son and the father stores the public key in a local database (step  454 ). This database may reside anywhere that the primary user wishes to keep it. 
         [0087]    The father then creates and signs the secondary certificate using his (the father&#39;s) private key, and provides it to the son (step  457 ). He also provides the primary media content subscription service privilege certificate to the son (step  458 ). These certificates may be stored in the son&#39;s personal identification device, or may be stored as part of the son&#39;s user account in the father&#39;s personal identification device. 
         [0088]    Secondary User Use of Media Content Subscription Service Privileges 
         [0089]    In the example described above, a father elects to bestow his HBO privileges on his son. Once the son has received his secondary certificate he is free to make use of the privileges as stipulated by his father. This process is seen in  FIG. 5 , steps  551 - 560 . If the son wishes to watch HBO, he selects the secondary certificate on his personal authentication device (step  551 ). He is prompted to authenticate, in order to prove that he is authorized to use the certificate (step  552 ). The son then presents the secondary certificate; depending on implementation of the system, the son&#39;s personal identification device may perform analysis of this certificate (step  553 ). Alternatively, the secondary certificate could be transmitted to the television or even to the cable provider as described above. The son proves ownership of the private key corresponding to the public key in his certificate (step  554 ), and the recipient verifies the digital signature signed by the primary user, the father (step  555 ). 
         [0090]    The son then presents the primary certificate (issued to his father) (step  556 ), and the recipient verifies that the cable provider signed the certificate (step  557 ). The two certificates together demonstrate the son&#39;s ability to use the HBO service; without both, the son cannot access the channel. As described in the system above, the cable provider distributes a symmetric key that is used to encrypt and decrypt the HBO feed. This key is provided in the same manner as for the primary user. The distributor sends the encrypted HBO feed to the son&#39;s television (step  558 ), and the feed is decrypted and displayed (step  559  and  560 ). 
         [0091]    While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention.