Abstract:
A method and system are provided for securely storing and retrieving live off-disk media programs. Events delineate media segments, each of which are encrypted with a different key so as to be streamable to a remote device via digital living network alliance (DLNA) or HTTP live streaming protocols. Media segments and identifiers for managing the storage and retrieval of such media segments are compatible with live streaming data structures, obviating the need to re-encrypt data streams.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. Provisional Patent Application No. 61/801,260, entitled “SECURE HANDLING OF LIVE OFF DISK (LOD) CONTENT USING DRM SYSTEM,” by Rafie Shamsaasef, William Franks, Geetha Mangalore, and Paul Moroney, filed Mar. 15, 2003, which application is hereby incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to systems and methods for recording and playing back media programs embodied in media streams, and in particular to a system and method for secure storage and retrieval of media programs temporarily stored in live buffer. 
         [0004]    2. Description of the Related Art 
         [0005]    Compression technologies have made the storage and transmission of media programs having audiovisual information to consumers feasible. Such video compression techniques (hereinafter generically referred to as compressed packetized transport (CPT) techniques typically break the media program into a plurality of frames that are compressed using spatial and/or temporal encoding techniques. Typically, some of the frames are identified as index (or I) frames, which are only spatially encoded. Such frames can be decoded without requiring data from any of the other frames, and serve as a datum for other frames. Other frames (known as predictive or P frames) also use temporal compression techniques, wherein the data recorded for the frame represent changes from an earlier frame. Since frame-to-frame differences are often small, such frames are substantially more efficiently compressed than the I frames. P frames, however, cannot be decoded without reference to another (e.g. I) frame. Still other frames (known as bi-predictive or B frames) also use spatial and temporal compression, but obtain their values from multiple frames. B frames offer higher compression than 1 frames or P frames, but must reference those frames to be reproduced. MPEG-2, MPEG-3, MPEG-4, H.264, H.265, and AVC are examples of CPT paradigms. 
         [0006]    Compressed media programs can be transmitted via satellite, cable, terrestrial wireless transmission, or the Internet, or received in analog form and compressed locally. Once received by a suitable device such as a set top box (STB) or receiver, the media programs may be decoded and/or decrypted (if encoded and/or encrypted by the headend or source of the media program) and provided to a display device for presentation to the user. 
         [0007]    Such media programs may also be locally recorded for later playback using devices such as a digital video recorder (DVR), which may be integrated with the receiver or a separate device. Such recordings are typically stored on a large capacity storage device such as an internal or external hard disk drive (HDD). 
         [0008]    DVRs typically include a RAM buffer that stores media program streams as they are received and plays them back a user controllable short time later. Such buffers are known as “live off disk” or LOD buffers. These buffers provide a “live pause” capability that allows the user to pause the playback of the received media program, while the LOD buffer continues to store the media streams as they are received. When the user thereafter selects “play,” playback from the LOD buffer resumes from the temporal point where the pause command was received. The LOD buffer also offers playback of the media program(s) stored therein from any randomly selected temporal point, and thus enables trick play and other features. The LOD buffer is typically implemented in a partition of the same hard disk drive (HDD) used to permanently store media programs, although separate memory devices may also be used. 
         [0009]    In most cases, storage of incoming media programs into the LOD buffer is not initiated upon the selection of the “pause” command. Rather, media streams received by the DVR are routinely sent to the LOD buffer where they are stored, retained, and written over on a first-in-first out (FIFO) basis without user intervention or command. LOD buffers typically include enough memory to store two or more hours of program material, hence it is possible for several programs to be stored in the DVR LOD buffer at a time. However, since the LOD buffer operates on a FIFO basis, any programs stored in the LOD buffer are subject to being erased or written over to make room for newer media programs unless they are designated for permanent storage. Hence, there is a need to provide a means for selecting recordings within the LOD buffer for permanent (e.g. indeterminate) storage. 
         [0010]    It is desirable for DVRs to have the capacity to transmit data to client devices such as cellphones, laptops, or tablet computers. DVRs that are capable of such functionality are commonly known as gateway DVRs. The transmission of such information is often accomplished by use of a HTTP live streaming (HLS). HLS is an HTTP (hypertext transfer protocol) based media streaming protocol that is used in selected client devices. HLS works by breaking up an incoming media stream into a sequence of small HTTP-based file downloads known as chunks, with each chunk being a small portion of a potentially unbounded transport stream. At the start of the streaming session, the client device receives a playlist or manifest (*.m3u8), and uses that playlist or manifest to determine which chunks to request in which order. The playlist may also contain other metadata, and may be continually updated as additional media chunks become available. Typically, such streams are secure with before transmission, for example, using a Digital Transmission Licensing Administrator (DTLA) approved technology such as Internet Protocol Rights Management (IPRM). 
         [0011]    To assure that stored media program recordings are not subjected to unauthorized use, they are encrypted before storage, even media program recordings that are only to be temporarily stored in the LOD buffer. Such recordings are typically encrypted using techniques different than those used for secure streaming. Hence, the gateway DVR is required to retrieve the encrypted media program from storage, decrypt it, then re-encrypt the media program for transmission via HLS. This presents processing challenges that can result in more expensive gateway DVRs or gateway DVRs that are less responsive to client requests. 
         [0012]    In view of the foregoing, there is a need for systems and methods for securely storing the contents of LOD buffers in a form that permits their conversion to permanent storage and later transmission to clients without requiring decryption and re-encryption of the media stream. This disclosure describes systems and methods that satisfy that need. 
       SUMMARY OF THE INVENTION 
       [0013]    To address the requirements described above, the present invention discloses a method and apparatus for providing at least a portion of a buffered media program for long term storage. In one embodiment, the method comprises receiving a media stream comprising at least a portion of the media program and content rights data defining one or more rights to use the at least a portion of the media program, generating media stream indexes from the received media stream, each media stream index associated with one of a plurality of media stream blocks, generating event indexes delimiting media stream indexes that correspond to events occurring temporally during reception of the media stream, the events defining one of a plurality of media stream segments therebetween, generating a content key for each media segment according to the content rights data and a key seed, encrypting each media segment according to the content key associated with each media segment, generating media program rights data comprising the key seed and the event index for each media segment, and buffering each media segment and the media program rights data associated with each media segment. In another embodiment, an apparatus comprises a processor communicatively coupled to a memory storing instructions for performing the foregoing operations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Referring now to the drawings in which like reference numbers represent corresponding parts throughout: 
           [0015]      FIG. 1  is a diagram illustrating one embodiment of a gateway DVR; 
           [0016]      FIG. 2  is a diagram illustrating exemplary operations that can be used to securely store and retrieve live off-disk media programs; 
           [0017]      FIG. 3  is a diagram illustrating the generation of indexes and media stream blocks. 
           [0018]      FIG. 4  is a diagram illustrating exemplary operations performed when the user wishes designate at least a portion of a media program stored in the LOD buffer for long term storage; 
           [0019]      FIG. 5  is a diagram illustrating the foregoing process of moving media program from buffered storage into long term storage; 
           [0020]      FIG. 6  is a diagram illustrating exemplary operations by which a media program stored as described above may be transmitted to a requesting client and thereafter played back; 
           [0021]      FIG. 7  is a drawing illustrating the gateway DVR transmitting a media program to a client playback device; 
           [0022]      FIG. 8  is a diagram depicting the indexing of the media stream using an HLS streaming protocol; 
           [0023]      FIG. 9  is a diagram illustrating elements analogous to those of  FIG. 7 , in an HLS and IPRM context; and 
           [0024]      FIG. 10  is a diagram illustrating an exemplary computer system  1000  that could be used to implement elements of the present invention, including elements of the gateway DVR  100  and client playback device  700 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0025]    In the following description, reference is made to the accompanying drawings which form a part hereof, and which is shown, by way of illustration, several embodiments of the present invention. It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. 
       Storage and Streaming Playback of Media Programs Temporarily Buffered in LOD Buffer 
       [0026]      FIG. 1  is a diagram of a typical gateway DVR  100 . The gateway DVR  100  comprises a receiver  102 , an indexer  104 , a security module  106 , an encryption module, and a memory  112 . 
         [0027]    The receiver  102  receives data streams from headends such as satellite television providers such as DIRECTV or ECHOSTAR, cable television providers such as TIME WARNER CABLE, broadcast television providers such as ABC or on-line television providers such as HULU or NETFLIX. As such, the receiver  102  may comprise a set top box (STB) designed specifically to receive the data stream, or may comprise a general purpose processing device such as a desktop or laptop computer. 
         [0028]    Data streams are typically in packetized format, and the media programs within the data streams are typically compressed as well. Media program packets may also be encrypted so as to restrict access to authorized subscribers. In such cases, the receiver  102  comprises a conditional access system that includes an decryptor  103  for decrypting the program stream. 
         [0029]    The gateway DVR  100  also receives data that describes the rights associated with the media program transmitted in the data stream. Such rights may include, for example, the right to play the media program and/or the right to copy the media program. Such data may be provided from the headend to the gateway DVR as a part of the data stream (as shown in  FIG. 1 ), but may also be provided by means independent from the data stream 
         [0030]    The gateway DVR  100  also comprises an indexer  104 . The indexer parses through the incoming program stream and creates media stream blocks, each addressable by media stream indexes. The media stream indexes are provided to a security module  106  that generates a content key K cont  that is used to encrypt the media stream blocks using a seed key K seed  and content rights data. The security module  106  also monitors for events, and generates event indexes from the media stream indexes and the events. In one embodiment, the security module  106  accomplishes this based on incoming content rights data for any segment of the media content. Those events define media stream segments, which may comprise a plurality of media stream blocks. The event indexes and K seed  is used to generate a rights object  108 . While the gateway DVR could be a consumer device, it may also comprise an edge media server having a buffer for staging media before transmitting it to clients. The buffers used for this staging process are also considered LOD buffers. 
         [0031]      FIG. 2  is a diagram illustrating exemplary operations that can be used to securely store and retrieve live off-disk media programs. A media stream and content rights data is received, as shown in block  202 . This may be performed, for example, by receiver  102 . In the embodiment shown in  FIG. 2 , the content rights data and the media stream are be received within the same data stream, but this need not be the case. The content rights data may be provided in a separate data stream using the same transmission means as the media stream, or may be provided using a completely different communications system. For example, the media stream may be provided via wireless satellite transmission, while the content rights data may be provided via the Internet, or via a phone line via the public switched telephone network (PSTN). 
         [0032]    In block  204 , media stream indexes are generated from the received media stream, wherein each of the media indexes is associated with one of a plurality of media stream blocks. This operation is typically performed by the gateway DVR  100  as so that the incoming media stream can be stored and recalled when needed for playback. In one embodiment, the blocks 
         [0033]      FIG. 3  is a diagram illustrating the generation of indexes and media stream blocks. Media stream  302  typically comprises a plurality of frames  310 . Typically Such frames include index frames (I-frames) that utilize spatial compression, but not temporal compression. Hence, the images in I-frames can be reconstructed by decompression techniques that do not require reference to another one of the frames. The frames also include predictive frames (P-frames) that require reference at least one preceding frame for decompression, and bi-predictive (B-frames) that require reference to both preceding and following frames for decompression. Since I-frames represent milestones within the media stream that can be easily decompressed, each of the data blocks  304  is constructed from the media stream so that it includes, and in fact, begins with an I frame. The temporal length of the media stream blocks  304  of  FIG. 3  are depicted as constant over time, but that is generally not the case. Instead, the pictures between I-frames are commonly known as a group of pictures (GOP) and can comprise many more or many less frames than indicated. It is also possible to have more than one I frame within a media stream block, if desired, but if blocks are defined this way, trick play operations are more difficult to implement as the time resolution between I frames is reduced. 
         [0034]    Once the indexes (I 1 -I N ) are created, they can be used to reference back to any of the blocks  304  of the media stream. Accordingly, when the gateway DVR  100  receives the media stream, the frames  310  of the media stream are parsed into blocks beginning with I-frames, indexes (I 1 -I N ) are generated from the parsed media stream, and both the blocks and the an index file having the indexes (I 1 -I N ) is stored in a buffer such as a partition of the memory  112 . Similarly, when playback of the media stream is required, the index is used to find the media stream blocks corresponding to the desired temporal location in the media program, and those media stream blocks are retrieved from the buffer or memory  112  for presentation. 
         [0035]    The media stream arriving at the receiver  102  may be encrypted. Typically, the media stream is decrypted using decryptor  103  before indexing and storage, so that the media stream can be presented for display. However media content providers typically forbid storage of any significantly long portions of the decrypted media stream, hence, the media stream is usually re-encrypted before storage, even if such storage is only in a temporary LOD buffer. This is implemented by the generation of a content key K cont  that is supplied to the encryptor  110 . While a different content key can be defined for each media block or even each frame of the media stream, this would result in a large number of content keys that would need to be stored and managed. To minimize the number of required content keys while still providing different content keys when necessary, the gateway DVR  100  is configured to allow the generation of a new content encryption key in response an event that implicates the need for a new key. Exemplary events  306  are further described below, and can include a change in the content rights data. Such a change may occur if the media program manifested in the media stream changes, as would be the case if the user changes channels, or if the content provider begins transmitting a different program in the media stream as each may require a different content encryption key. To support this functionality, the security module  106  receives the generated media stream indexes from the indexer  104  as well as the content rights data (changes to which may signals an event) and may also receive information signaling other events which implicate the need for a new content key. Using this information the security module generates event indexes that delimit the media stream indexes that correspond to events during the reception of the media stream, as shown in bock  206  of  FIG. 2 . Media segments  308  are therefore defined between each event. In the example depicted in  FIG. 3 , events  306  E 1 , E 2  and E 3  occur at the indicated times in the media stream, signaling the security module to designate event indexes I 4 , I 8 , and I 14  as event indexes. Alternatively the event indexes may be generated and denoted without reference to the media block references (e.g. as EI 1 , EI 2  and EI 3 ), and may simply be generated directly from the media stream frames with the boundaries of the segments  308  defined by the frame associated with the temporal location of the events  306 . That the segments may be defined by events independent of the media blocks  304  and their indexing is denoted by the dashed line from the indexer  104  to the security module  106 . 
         [0036]    As described in block  208 , a content key is generated for each defined media segment according to the content rights data and the key seed, K seed . In one embodiment, the key seed is a key derived from a identifier of the content of the media stream. Such identifier can be a name of the content asset (e.g. the name of a movie) or combination of a name of the program, the channel the media stream embodying the program is transmitted on, or other information. 
         [0037]    The content key is then used to encrypt each media segment  308 , as shown in block  210 . This is accomplished, for example, by encryptor  110 . The security module  106  then generates a media rights data that comprises the event index for each defined media segment  308  as well as the key seed, as shown in block  214 . The encrypted media segments, indexes, and media program rights data are then stored or buffered as shown in block  216 . This can be accomplished by memory  112 , or in other gateway DVR  100  memory (for example, the security module  106  may include its own buffer memory for purposes of storing media program rights data). 
         [0038]    The operations illustrated  FIG. 2  can be on going, and performed while the data stream is received. Hence, the media stream is separated into indexed blocks, and segments identified as events occur with media program rights data generated for each segment, and the resulting segments encrypted using content keys generated from content rights and a key seed, with the encrypted content and the information needed to retrieve and decrypt it buffered for retrieval and use when required. As described above, if this information is stored in a LOD buffer, several hours worth of media streams may be recorded, which may comprise more than one media program (e.g. television show or movie) or portion of a media program. Further, if not designated for permanent storage, the contents of the LOD buffer will eventually be overwritten with other data. Consequently, if the user wishes to store media programs temporarily stored in the LOD buffer on a permanent basis, the user provides a command to do so. Such a command may be provided while the media program desired for permanent storage is being received, or after the media program has been received, but has not been overwritten (at least not entirely so) by other data into the LOD buffer. 
         [0039]      FIG. 4  is a diagram illustrating exemplary operations performed when the user wishes designate at least a portion of a media program stored in the LOD buffer for long term storage. The term “long term” rather than “permanent” is used herein to acknowledge the fact that no storage is permanent, as the user may decide to later delete the stored object or the gateway DVR may fail. Items may also be stored for “long term,” yet still be designated for erasure at some point in the future (e.g. because the gateway DVR has been set to erase programs older than a designated time frame). For purpose of this disclosure, “long term” generally refers to storage greater than that which is possible using the LOD buffer alone and specifically storage for an order of magnitude or more longer than the LOD buffer permits. 
         [0040]    A command designating at least a portion of a media program comprising one or more of the buffered media segments for long term storage is received, as shown in block  402 . In response to this command, the security module identifies the media segments  308  that together comprise the selected at least a portion of the media program, assembles the identified media segments into a media program object and assembles the media program rights associated with the identified media segments into a media program rights object, as shown in blocks  404 - 406 . In block  408 , the media program object and the media program rights object are stored in long term storage. 
         [0041]    Identifying media segments that together comprise the selected media program (or portion thereof) can be accomplished in a number of different ways. For example, the index (I 1 -I N ) for each block  304  or segment  308  of the media stream may include or be mapped to a media program (e.g. content) identifier. In which case, searching for the relevant segments comprises matter of searching for blocks  304  (or segments  308 ) that include the media program identifier associated with the selected media program. 
         [0042]      FIG. 5  is a diagram illustrating the foregoing process of moving media program from buffered storage  112 A into long term storage  112 B. In this embodiment, it is assumed that all data is stored in memory  112 , but as described above, the encrypted media segments E[S], the media block indexes (I) and the rights data object (RDO) can be stored in partitioned memory, or in separate memory devices. For example, the security module may use a different memory device (other than memory  112 ) to store the rights data such as the event indexes or the key seed. As illustrated, in response to the receipt of the command to store the media program stored in the LOD buffer  112 A, the security module  106  retrieves the rights data from the buffer  112 A. This rights data includes the event index and key seed for each of the segments that together comprise the requested media program. Once the segments are identified, the media program object (MO) is generated from the identified segments, and a rights data object (RDO) is generated from the rights data object (RDO) elements associated with the identified media segments. The result is then stored in long term storage  112 B. 
         [0043]      FIG. 6  is a diagram illustrating exemplary operations by which a media program stored as described above may be transmitted to a requesting client and thereafter played back. In block  602 , a request is accepted from a client to provide the at least a portion of the media program stored in long term storage  112 B as described above. In response to this request, the gateway DVR  100  retrieves the stored media program object (MO) and media program rights data object (RDO), as shown in block  604 . In one embodiment, this process is be managed by the security module  106 . The data within the media program rights data object (RDO) is transmitted to the client device, as shown in block  606 . 
         [0044]    The event indexes and key seed contained within the media program rights data object (RDO) may be transmitted together to the client device  700 , but in the embodiment illustrated in  FIG. 6 , the event indexes are transmitted in a different transmission than the key seed. In this embodiment, the security module  106  retrieves the media program rights data object (RDO), extracts the key seed, and transmits the key seed to the device  700  via a secure communications channel, and the gateway DVR  100  transmits the event indexes to the client device  700  via a different (and potentially non-secure communication path). 
         [0045]    Returning to  FIG. 6 , the media program object is then streamed to the client device  700 . This may comprise streaming the media program in blocks  304  along with the media program block indexes (I 1 -I N ) to the blocks  305 , streaming the media program in segments  308  along with the event indexes  306 . 
         [0046]      FIG. 7  is a drawing illustrating the gateway DVR  110  transmitting a media program to a client playback device  700 . In the embodiment shown in  FIG. 7 , the event indexes and media program object comprising the encrypted media segments  308  embodying the selected media program are transmitted to the client device  700  together, and are separated using the parser  714 . The parser  704  then provides the event indexes to the security module and the encrypted media program segments to decryptor  712 , which decrypts the media segments  308  to reverse the encryption operation applied by encryptor  110 . In the illustrated embodiment, the same content key is used to encrypt the media program segments  308  as is used to decrypt them. This is known as symmetric encryption via a shared secret. However, other encryption techniques may be employed, including asymmetric cryptography, utilizing public/private key techniques. Also, the encryption can be implemented by use of a shared secret algorithm rather than a secret key. 
         [0047]    The client device  700  comprises an associated security module  702  that receives the key seed securely transmitted by the security module  106  of the gateway DVR  100 , and using the key seed and the event indexes received by the client device  700  (e.g. the parser  704 ), regenerates the content key for each media segment  308 . This operation is shown in block  612 . The security module then generates a temporary rights object  716  that includes the rights objects provided in the media program rights data object (RDO) received from the gateway DVR  100 . This temporary rights object  716  will be used by the security module  702  to store and retrieve information required to generate the content keys for each of the media segments using the event indexes. The security module  702  then regenerates the content key using the key seed and the event indexes, and forwards the key to the decryptor  712 . In one embodiment, the content key is securely provided to the decryptor  712  via a key proxy  710  to prevent exposure of they key. The decryptor  712  then decrypts each media program segment according to the received content key as shown in block  614 . The decrypted media program segment is then provided for display on a suitable device, as shown in block  616 . 
         [0048]    Although the foregoing operations are described with respect to a gateway DVR  100  streaming a media program to a client device  700 , the client device  700  operations may instead be performed by the gateway DVR  100  for playback. In such case, a single security module can be shared for both operations, and a secure communications channel between the security modules is no longer required. Further, the transmission of the event indexes and encrypted segments may be performed without using a streaming protocol, with the segments instead simply being identified by the event indexes, recalled from the long term memory  112 , and played back using operations analogous to those above. Further, playback of programs within the LOD buffer  112 A may also be performed while other data is being stored in the LOD buffer  112 A, whether by the client device  700  or a gateway DVR performing analogous functions using the same operations described above. 
       Application to IPRM and HTTP Live Streaming 
       [0049]    Advantageously, the foregoing storage and playback paradigm dovetails well with media streams handled using the HLS protocols and secured using IPRM. In the HLS protocol, an incoming media stream is broken into media stream blocks known as “chunks.” 
         [0050]      FIG. 8  is a diagram depicting the indexing of the media stream using an HLS streaming protocol. Each chunk  804  is made available by the gateway DVR  100  at an address provided in a structure known as an index file, (.m3u8) playlist, or manifest. If a media stream was comprises of only three 10 second chunks, the playlist may appear as follows:
       #EXT-X-VERSION:3   #EXTM3U   #EXT-X-TARGETDURATION:10   #EXT-X-MEDIA-SEQUENCE:1   #EXTINF:10.0,   http://media.example.com/chunk1.ts   #EXTINF:9.5,   http://media.example.com/chunk2.ts   #EXTINF:9.0,   http://media.example.com/chunk3.ts   #EXT-X-ENDLIST
 
where “chunk1.ts,” “chunk2.ts,” and “chunk3.ts” refer to the chunks available at the addresses indicated by the URLs in the playlist. The playlist of chunks  804  is provided to the client playback device  700 , and the client playback device  700  uses this playlist to request one chunk  804  after the other. Barring trick play, such chunks  804  are requested in the order they are presented on the playlist, but with trick play commands, the client device  700  may request any of the chunks  804  in the playlist in any order. These chunks are substantially analogous to the media program blocks  304  depicted in  FIG. 3 , and the indexes I 1 -I N  also shown in  FIG. 3  are analogous to the chunk address entries that are in the playlist (e.g. http://media.example.com/chunk1.ts,” http://media.example.com/chunk2.ts, and http://media.example.com/chunk3.ts). Although the media stream blocks depicted in  FIG. 3  typically begin with an I frame and extend to the next I-frame, chunks may include no I frames or more than one I frame.
       
 
         [0062]    Further, each of the media block indexes I 1 -I N  shown in  FIG. 3  are each analogous to the http address entries in the playlist above, and are indicated by H 1 -H N  in  FIG. 8 . The HLS playlist is therefore analogous to a list of H 1 -H N  in sequential order of presentation. IPRM is a content rights management system for streaming applications that uses two parameters to derive the content encryption key. Those two parameters include (1) a key seed or subkey and (2) content key identifying data (CKID). 
         [0063]    The key seed can be derived from a content ID identifying the media program embodied in the media stream or a randomly generated seed. The content ide can comprise the name of the asset (media program) or a combination of channel and program names) 
         [0064]    The CKID is a collection of copy control data which may include copy control information (CCI). The CCI of IPRM is analogous to the content rights data depicted in  FIG. 3 , and may be received as a part of the data stream received by the receiver  102  or by other means. 
         [0065]      FIG. 9  is a diagram illustrating elements analogous to those of  FIG. 7 , in an HLS and IPRM context. A data stream is received by the receiver  102  and decrypted (if encrypted), and CCI data and a media program stream is parsed from the data stream. The CCI data is provided to the security module  106 , and the media program stream is provided to the indexer  104 . The indexer  104  performs the indexing operations to separate the media stream into chunks as described above with respect to  FIG. 8 , producing chunks C and the playlist H 1 -H N . The chunks are provided to the encryptor  110  and the playlist may be provided to the security module  106 . The security module  106  generates media program rights data from the CCI, events and the key seed for each segment, as triggered by events, as described above. This data is later compiled into a media program rights data object (RDO)  108  or IPRM rights data file. The media program rights data object (RDO)  108  operates as a license for the segments that together comprise the object, and include, for example, the IPRM content ID used to derive the key seed, the key seed itself, and data regarding each segment, including the CCI data associated with the segment, an index of the segment, and a time stamp associated with the segment. The IPRM content ID may be the channel number, the program name (as obtained for example, from an electronic program guide), or an asset name designated by the user when converting to long term storage. 
         [0066]    The security module  106  also generates a content key identifier (content key ID) from the CCI as well as other data. The CKID can later be used to identify and regenerate content key using the key seed. In one embodiment, the CKID is generated from the CCI data by encoding the data described in Table I below in base  64  encoding. 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Field 
                 Size (bytes) 
                 bit # 
               
               
                   
                   
               
             
             
               
                   
                 Index 
                 1 
                   
               
               
                   
                 Time Stamp 
                 4 
               
               
                   
                 Copy Control Data 
                 1 
               
               
                   
                 CCI 
                   
                 0-1 
               
               
                   
                 APS 
                   
                 2-3 
               
               
                   
                 CIT 
                   
                 4 
               
               
                   
                 RCT 
                   
                 5 
               
               
                   
                 Reserved 
                   
                 6-7 
               
               
                   
                 Copy Control Enhance 
                 1 
               
               
                   
                 Domain Copy 
                   
                 0 
               
               
                   
                 Analog Disable 
                   
                 1 
               
               
                   
                 Analog Sunset 
                   
                 2 
               
               
                   
                 Digital Comp/Disable 
                   
                 3 
               
               
                   
                 RemoteAccessEnable 
                   
                 4 
               
               
                   
                 HDMIDisable 
                   
                 5 
               
               
                   
                 Airplay Enable 
                   
                 6 
               
               
                   
                 Reserved 
                   
                 7 
               
               
                   
                   
               
             
          
         
       
     
         [0067]    This would result in a CKID of 010A4589BF01A. The CKID can be appended to the KeyTag (*EXT-X-KEY) in the playlist. For example, the following entry may be included in the HLS playlist: lprm://gateway/channel-1?CKID=010A4589BF01A. Since a new CKID is generated when the CCI changes or another event occurs, the CKID functions as the event index described above. 
         [0068]    Returning to  FIG. 9 , the media stream chunks are provided from the indexer to encryptor  110 , which encrypts the one or more chunks that make up a segment using the content key to produce a series of encrypted segments E[S], which are stored in LOD buffer  112 A. The playlist P indexing the media program chunks  804  may also be stored in the LOD buffer  112 A or elsewhere in the gateway DVR  100 , as well as the rights data generated by the security module  106 . 
         [0069]    The security module  106  responds to channel changing event  306  (for example, the user switching from one cable channel to another, thus changing the CCI data and media program stream) by calling an application program interface (API) to create a rights data file or object. This can be implemented by an API to create a data rights file or object. This API accepts the channel ID and CCI data as an input, and generates an output CKID, as well as a content key generated from the CKID and the key seed. The content key is used to encrypt the media chunk that begins at the channel change. The output CKID is appended to a key tag and added to the playlist. Hence, upon an event changing from channel-1 to channel-2, the value of a key tag (#EXT-X-KEY) generated by the security module  106  and added to the playlist may change as follows:
       lprm://gateway/Channel-1_Live?CKID=af2398bc3   lprm://gateway/Channel-2_Live?CKID=edc2398b2       
 
         [0072]    Similarly on an event requesting a particular media program (program-A) to be recorded, the security module  106  may call an IPRM API to create data rights. This API also accepts the channel ID and CCI as input, and generates an output CKID and a content key generated from the CKID and the key seed. The security module  106  also appends the value of the CKID to a key tag and adds the result to the playlist. The value of the key tag generated by the security module  106  and added to the playlist may change due to the recording request as follows:
       lprm://gateway/Channel-1_Live?CKID=af2398bc3   lprm://gateway/Program-A?CKID=4c43398b2       
 
         [0075]    On an event wherein the CCI data itself changes (indicating a change in rights), the security module  106  calls an IPRM API to extend the data rights. This API accepts the CCI as input, and outputs an output CKID and a content key generated from the CKID and the key seed. The value of the key tag generated by the security module  106  and added to the playlist may change as follows:
       lprm://gateway/Channel-1_Program-A?CKID=12f2398bc3   lprm://gateway/Channel-1_Program-A?CKID=ecec2398b2       
 
         [0078]    When the gateway DVR  100  accepts a command designating at least a portion of the media program that comprises one or more of the buffered media program segments  308  for long term storage, the security module  702  calls an API to clone the buffered data rights file for use in the long term storage of the buffered media program segments  308 . The input to this API include the channel ID, the asset name (to derive the content ID), and the starting and ending CKID for the media selected at least a portion of the media program. In one embodiment, the gateway DVR  100  maintains a table relating timestamps and CKIDs for all segments in the LOD buffer  112 . The gateway DVR uses the time stamp to look up the starting and ending CKIDs required by the API that clones the buffered data rights. Using the CKID data, the security module  106  identifies the media segments that together comprise the requested media program, assembles the identified media segments and CKIDs to generate the media file object and the media file rights object, and places these objects in long term storage for later retrieval. 
         [0079]    As described in the analogous operations described in  FIG. 6 , the media program segments  308  in buffered or long term  112 B storage can be recalled for playback. After accepting a request from the client device  700  to provide at least a portion of the media program object, the security module  106  retrieves the stored media program object and the media program rights object needed to decrypt and play the stored media program object. As described above with respect to  FIG. 6 , the CKIDs and key seed of the media program rights object can be transmitted to the client device together, but in the embodiment shown in  FIG. 9 , the CKIDs are transmitted to the client device  700  in a different transmission than the key seed. In this embodiment, the security module  106  retrieves the media program rights data object (RDO), extracts the key seed, and transmits the key seed to the device via a secure communications channel, and the gateway DVR  100  transmits the CKIDs to the client device  700  via a different (and potentially non secure communications path). In the HLS embodiment, the CKIDs are transmitted to the client device  700  appended to the playlist(s) that are used to identify the media chunks in the order they are to be played, as described above. Parser  704  parses through the playlist to find the CKIDs, and provides them to the client device security module  702 . Using the key received via the secure communication path and the CKIDs received from the parser  704 , the client device security module  702  generates the content key, and provides it to the decryptor  712 , optionally through a key proxy  710  as described above. The decryptor accepts the encrypted media segments E[S] that were encrypted using the key seed, decrypts the segments, and provides the decrypted segments for playback, as shown in block  714 . The client device security module  702  may also generate a temporary rights object for playback purposes. 
       Hardware Environment 
       [0080]      FIG. 10  is a diagram illustrating an exemplary computer system  1000  that could be used to implement elements of the present invention, including elements of the gateway DVR  100  and client playback device  700 . The computer system  1000  includes a processing device such as a computer  1002 , which comprises a general purpose hardware processor  1004 A and/or a special purpose hardware processor  1004 B (hereinafter alternatively collectively referred to as processor  1004 ) and a memory  1006 , such as random access memory (RAM). The computer  1002  may be coupled to other devices, including input/output (I/O) devices such as a keyboard  1014 , a mouse device  1016  and a printer  1028 . 
         [0081]    In one embodiment, the computer  1002  operates by the general purpose processor  1004 A performing instructions defined by the computer program  1010  under control of an operating system  1008 . The computer program  1010  and/or the operating system  1008  may be stored in the memory  1006  and may interface with the user and/or other devices to accept input and commands and, based on such input and commands and the instructions defined by the computer program  1010  and operating system  1008  to provide output and results. 
         [0082]    Output/results may be presented on the display  1022  or provided to another device for presentation or further processing or action. In one embodiment, the display  1022  comprises a liquid crystal display (LCD) having a plurality of separately addressable pixels formed by liquid crystals. Each pixel of the display  1022  changes to an opaque or translucent state to form a part of the image on the display in response to the data or information generated by the processor  1004  from the application of the instructions of the computer program  1010  and/or operating system  1008  to the input and commands. Other display  1022  types also include picture elements that change state in order to create the image presented on the display  1022 . The image may be provided through a graphical user interface (GUI) module  1018 A. Although the GUI module  1018 A is depicted as a separate module, the instructions performing the GUI functions can be resident or distributed in the operating system  1008 , the computer program  1010 , or implemented with special purpose memory and processors. 
         [0083]    Some or all of the operations performed by the computer  1002  according to the computer program  1010  instructions may be implemented in a special purpose processor  1004 B. In this embodiment, some or all of the computer program  1010  instructions may be implemented via firmware instructions stored in a read only memory (ROM), a programmable read only memory (PROM) or flash memory within the special purpose processor  1004 B or in memory  1006 . The special purpose processor  1004 B may also be hardwired through circuit design to perform some or all of the operations to implement the present invention. Further, the special purpose processor  1004 B may be a hybrid processor, which includes dedicated circuitry for performing a subset of functions, and other circuits for performing more general functions such as responding to computer program instructions. In one embodiment, the special purpose processor is an application specific integrated circuit (ASIC). 
         [0084]    The computer  1002  may also implement a compiler  1012  which allows an application program  1010  written in a programming language such as COBOL, C++, FORTRAN, or other language to be translated into processor  1004  readable code. After completion, the application or computer program  1010  accesses and manipulates data accepted from I/O devices and stored in the memory  1006  of the computer  1002  using the relationships and logic that was generated using the compiler  1012 . 
         [0085]    The computer  1002  also optionally comprises an external communication device such as a modem, satellite link, Ethernet card, or other device for accepting input from and providing output to other computers. 
         [0086]    In one embodiment, instructions implementing the operating system  1008 , the computer program  1010 , and/or the compiler  1012  are tangibly embodied in a computer-readable medium, e.g., data storage device, which could include an internal storage device  1020  or external storage device  1024  in the form of one or more fixed or removable data storage devices, such as a zip drive, floppy disc drive, hard drive, CD-ROM drive, tape drive, or a flash drive. Further, the operating system  1008  and the computer program  1010  are comprised of computer program instructions which, when accessed, read and executed by the computer  1002 , causes the computer  1002  to perform the steps necessary to implement and/or use the present invention or to load the program of instructions into a memory, thus creating a special purpose data structure causing the computer to operate as a specially programmed computer executing the method steps described herein. Computer program  1010  and/or operating instructions may also be tangibly embodied in memory  1006  and/or data communications devices  1030 , thereby making a computer program product or article of manufacture according to the invention. As such, the terms “article of manufacture,” “program storage device” and “computer program product” or “computer readable storage device” as used herein are intended to encompass a computer program accessible from any computer readable device or media. 
         [0087]    Of course, those skilled in the art will recognize that any combination of the above components, or any number of different components, peripherals, and other devices, may be used with the computer  1002 . 
         [0088]    Although the term “computer” is referred to herein, it is understood that the computer may include portable devices such as cellphones, portable MP3 players, video game consoles, notebook computers, pocket computers, or any other device with suitable processing, communication, and input/output capability. 
       CONCLUSION 
       [0089]    This concludes the description of the preferred embodiments of the present invention. The foregoing description of the preferred embodiment of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. 
         [0090]    It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto. The above specification, examples and data provide a complete description of the manufacture and use of the apparatus and method of the invention. Since many embodiments of the invention can be made without departing from the scope of the invention, the invention resides in the claims hereinafter appended.