United States Patent [19J
`Nardone et al.
`
`I lllll llllllll Ill lllll lllll lllll lllll lllll 111111111111111111111111111111111
`US005805700A
`[11] Patent Number:
`[ 45] Date of Patent:
`
`5,805,700
`Sep. 8, 1998
`
`[54] POLICY BASED SELECTIVE ENCRYPTION
`OF COMPRESSED VIDEO DATA
`
`[75]
`
`Inventors: Joseph M. Nardone, Portland, Oreg.;
`Keith L. Shippy, Tempe, Ariz.; David
`W. Aucsmith, Portland, Oreg.
`
`[73] Assignee: Intel Corporation, Santa Clara, Calif.
`
`[21] Appl. No.: 730,065
`
`[22] Filed:
`
`Oct. 15, 1996
`
`Int. Cl.6
`..................................................... H04N 7/167
`[51]
`[52] U.S. Cl .................................................. 380/10; 380/20
`[58] Field of Search .......................................... 380/20, 10
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,515,437
`5,594,492
`5,617,541
`
`5 /1996 Katta et al. .... ... ... ... ... .... ... ... ... .. 380/20
`1/1997 O'Callaghan et al.
`................... 380/20
`4/1997 Albanese et al. ......................... 380/42
`
`5,621,794
`5,621,799
`5,625,693
`5,684,876
`
`4/1997 Matsuda et al. .......................... 380/20
`4/1997 Katta et al. . ... ... ... .... ... ... ... ... ..... 380/20
`4/1997 Rohatgi et al. ........................... 380/23
`11/1997 Pinder et al.
`.. ... ... .... ... ... ... ... ..... 380/37
`
`Primary Examiner-Stephen C. Buczinski
`Attorney, Agent, or Firm-Blakely, Sokoloff, Taylor &
`Zafman
`
`[57]
`
`ABSTRACT
`
`Basic transfer units (BTUs) of compressed video data of
`video images are selectively encrypted in accordance with
`an encryption policy to degrade the video images to at least
`a virtually useless state, if the selectively encrypted com(cid:173)
`pressed video images were to be rendered without decryp(cid:173)
`tion. As a result, degradation that approximates the level
`provided by the total encryption approach is achieved, but
`requiring only a fraction of the processor cycle cost required
`by the total encryption approach, to decrypt and render the
`video images.
`
`19 Claims, 6 Drawing Sheets
`
`Video Frames 24
`\
`
`30
`
`32
`
`34
`
`32
`
`34
`
`32
`
`f_-Frame
`36
`
`~-Frame
`~-Frame
`36
`36
`
`BT Us
`
`Encrypt t
`\
`40
`
`I
`
`I \I 5SI
`t 1 38' 1 1
`
`I
`
`I
`t
`
`IPR2016-01710
`UNIFIED EX1018
`
`

`
`U.S. Patent
`
`Sep. 8, 1998
`
`Sheet 1 of 6
`
`5,805,700
`
`CVD
`
`11
`
`""'
`
`13
`Overlay Data
`~
`15
`
`CAD:1
`
`• •
`CADn •
`
`""'
`19
`"'--
`
`...
`...
`...
`...
`
`10
`
`/
`
`...._
`....
`
`{CVD+}
`\
`18
`
`Encryption Policy
`
`14
`J ..........
`
`,,
`
`Formatter
`
`...
`
`'-...._
`17
`
`\
`\
`12
`
`Navigation Control
`
`Figure 1
`
`

`
`U.S. Patent
`
`Sep. 8, 1998
`
`Sheet 2 of 6
`
`5,805,700
`
`r - - - - - - - - - - , 14'
`Encryption Policy
`
`(CVD+)
`
`16
`
`Encryption
`Module
`
`12'
`
`Figure 5
`
`10a
`
`/
`
`{CVD+}
`
`18
`
`{CVD+} 18
`\
`Video Data
`Unit (VDU)
`
`VDU
`
`20
`
`20
`
`2 I
`
`VDU
`\
`20
`
`Figure 2
`
`

`
`U.S. Patent
`
`Sep. 8, 1998
`
`Sheet 3 of 6
`
`5,805,700
`
`VDU
`
`2~
`
`38
`
`BTU
`
`Navigation Info
`
`Video Frames
`
`Audio Frames
`
`Overlay Data Frames
`
`Video Frames
`
`• •
`•
`
`Figure 3
`
`'
`
`""" 2 2
`
`'~
`2 4
`
`'"" 2 6
`
`'~
`2 8
`
`'""'
`
`2 4
`
`Video Frames 24
`\
`
`30
`
`32
`
`34
`
`32
`
`34
`
`32
`
`I-Frame ~~rame
`
`BT Us
`
`I I
`Encrypt t
`\
`40
`
`I
`
`I \I 5}1
`t 1 38' 1 1
`
`I
`
`I
`t
`
`Figure 4
`
`

`
`U.S. Patent
`
`Sep. 8, 1998
`
`Sheet 4 of 6
`
`5,805,700
`
`.---------------., 42
`User Interface
`
`.--------'--------, 14'
`Encryption Policy
`
`10b
`I
`
`(CVD+)
`
`16
`
`Encryption
`Module
`
`{CVD+} ~
`\
`18
`
`12'
`
`Figure 6
`
`. - - - - - - - - - - 42
`User Interface
`
`10c
`I
`
`Analyzer
`
`Encryption Policy
`
`44
`
`(CVD+)
`\
`16
`
`Encryption
`Module
`
`{CVD+} ~
`\
`18
`
`12'
`
`Figure 7
`
`

`
`U.S. Patent
`
`Sep. 8, 1998
`
`Sheet 5 of 6
`
`5,805,700
`
`16
`
`(CVD+)
`
`[CVD+]
`
`46
`
`User Interface
`
`42
`
`Selection Policy
`
`10d
`I
`
`Selector
`
`{CVD+}.,
`\
`18
`
`12"
`Figure 8
`
`User Interface
`
`42
`
`10e
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`
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`
`Analyzer
`
`Selection Policy
`
`Figure 9
`
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`Formatter/
`
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`
`Encryption/
`
`100
`
`104
`
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`
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`
`I
`
`114
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`
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`
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`
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`
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`
`Figure 10
`
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`
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`
`Memory
`
`

`
`5,805,700
`
`1
`POLICY BASED SELECTIVE ENCRYPTION
`OF COMPRESSED VIDEO DATA
`
`BACKGROUND OF THE INVENTION
`
`5
`
`2
`FIG. 2 illustrates a formatted stream of compressed video
`data in further details;
`FIG. 3 illustrates one embodiment of a video data unit in
`further details;
`FIG. 4 illustrates a group of pictures in a video object unit
`in further details;
`FIGS. 5-9 are block diagrams illustrating various
`embodiments of the present invention; and
`FIG. 10 illustrates one embodiment of a computer system
`10 suitable for practicing a software implementation of the
`present invention.
`
`1. Field of the Invention
`This invention relates to the art of data encryption, and in
`particular, to the art of encrypting video data for subsequent
`rendering on processor-based video systems.
`2. Background of the Invention
`There is substantial interest in the computer and enter(cid:173)
`tainment industries in incorporating video data into multi(cid:173)
`media and related applications for use on processor-based
`video systems. Potential growth in this area has been 15
`enabled by the development of video compression schemes
`that reduce the amount of video data required to display high
`quality video images, and by the development of storage
`media, such as digital video discs (DVDs), which can
`accommodate data (in compressed form) for an entire movie 20
`on a single compact disc.
`With the compressed data of an entire movie readily
`available in a single compact disc, naturally content provid(cid:173)
`ers are extremely concerned with the unauthorized copying
`of the content. Thus, content providers are planning to 25
`encrypt the compressed data. As a result, the video data must
`be decrypted before they can be decompressed for rendering.
`The present practice is to encrypt the entire content.
`However, the present practice has the disadvantage of sig(cid:173)
`nificantly burdening the processor during the decryption and 30
`decompression phase. Experience has shown that the
`decryption and decompression of a fully encrypted MPEG
`compressed movie can consume as much as over 30% of the
`available processor cycles, even with the latest high perfor(cid:173)
`mance processors. Thus, a less burdening approach to pre- 35
`venting unauthorized copying of MPEG compressed video
`data is desirable.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`In the following description, various aspects of the
`present invention will be described. However, it will be
`apparent to those skilled in the art that the present invention
`may be practiced with only some or all aspects of the present
`invention. For purposes of explanation, specific numbers,
`materials and configurations are set forth in order to provide
`a thorough understanding of the present invention. However,
`it will also be apparent to one skilled in the art that the
`present invention may be practiced without the specific
`details. In other instances, well known features are omitted
`or simplified in order not to obscure the present invention.
`Parts of the description will be presented in terms of
`operations performed by a computer system, using terms
`such as data, flags, bits, values, characters, strings, numbers
`and the like, consistent with the manner commonly
`employed by those skilled in the art to convey the substance
`of their work to others skilled in the art. As well understood
`by those skilled in the art, these quantities take the form of
`electrical, magnetic, or optical signals capable of being
`stored, transferred, combined, and otherwise manipulated
`through mechanical and electrical components of the com(cid:173)
`puter system; and the term computer system include general
`purpose as well as special purpose data processing
`machines, systems, and the like, that are standalone, adjunct
`or embedded.
`Referring now to FIG. 1, wherein a block diagram illus-
`trating the present invention is shown. As illustrated, for(cid:173)
`matter 12 of the present invention generates a formatted and
`partially encrypted stream of compressed video and related
`data { CVD+} 18 by selectively encrypting the basic transfer
`45 units (BTUs) of the compressed video and related data in
`accordance with an encryption policy 14. The BTUs are
`formed using compressed video data (CVD) 11, overlay data
`13, e.g. closed captions, compressed audio data (CADl ...
`CADn) 15, and navigation control 17. As will be readily
`50 apparent from the description to follow, the video images of
`{ CVD+} 18 are degraded to a level that approximates the
`degradation achieved by a total encryption approach, but
`requiring only a fraction of the processor cycle cost required
`by the total encryption approach to decrypt and render the
`55 video images.
`In one embodiment, video images are compressed in
`accordance with one of the standards promulgated by the
`Moving Pictures Expert Group (MPEG, group ISO-IEC(cid:173)
`JTCl SC29/WG11) and the Joint Photographic Experts
`60 Group (JPEG, ISO/IEC International Standard 10918-1).
`The amount of spatial and temporal redundancy in the video
`data is reduced by application of lossy data transformations.
`Hereafter, MPEG is used to refer to MPEG-1 (ISO standard
`11172), MPEG-2 (ISO standard 13818ISO), and JPEG com-
`65 pliant compression processes. Audio data are dolby AC3 or
`MPEG audio (MPEGl or MPEG2). The selected BTUs are
`encrypted employing a stream cipher technique.
`
`SUMMARY OF THE INVENTION
`Basic transfer units (BTUs) of compressed video data of 40
`video images are selectively encrypted in accordance with
`an encryption policy to degrade the video images to at least
`a virtually useless state, if the selectively encrypted com(cid:173)
`pressed video images were to be rendered without decryp(cid:173)
`tion. As a result, degradation that approximates the level
`provided by the total encryption approach is achieved, but
`requiring only a fraction of the processor cycle cost required
`by the total encryption approach, to decrypt and render the
`video images.
`In some embodiments, the encryption policy is
`predetermined, while in others, it is dynamically adjusted. In
`one embodiment, where the video images are MPEG
`compressed, all BTUs containing either the start code for a
`group of pictures or the start code for a particular frame are
`encrypted, to prevent recovery of the video frames. In an
`alternate embodiment, a fraction of the BTUs of an I-frame,
`and a fraction of the BTUs of a P-frame are encrypted, to
`destroy data references by future frames.
`
`BRIEF DESCRIPTION OF DRAWINGS
`
`The present invention will be described by way of exem(cid:173)
`plary embodiments, but not limitations, illustrated in the
`accompanying drawings in which like references denote
`similar elements, and in which:
`FIG. 1 is a block diagram illustrating the present inven(cid:173)
`tion;
`
`

`
`5,805,700
`
`10
`
`3
`FIG. 2 illustrates the formatted and partially encrypted
`{ CVD+} 18 in further details. As shown, { CVD+} 18 are
`formatted into video data units (VDUs) 20. In an embodi(cid:173)
`ment where the compressed video data are organized in
`accordance with a DVD scheme, VDUs 20 are video object 5
`units (VOBUs). FIG. 3 illustrates one embodiment of a VDU
`20, more specifically, a VOBU corresponding to a group of
`pictures, in further details. As shown, a VDU 20 or VOBU
`includes navigation information 22, multiple series of com(cid:173)
`pressed video frames 24 interleaved with series of com-
`pressed audio frames 26 and series of compressed overlay
`data frames 28, spanning a number of BTUs 38. The
`constitution of a BTU 38 is application dependent. An
`example of a BTU 38 is a data packet. In a DVD application,
`each BTU 38 corresponds to a data packet for a disk sector, 15
`in the order of 2 k bytes. In a digital satellite service (DSS)
`application, each BTU 38 corresponds to a transmission
`packet.
`FIG. 4 illustrates a series of compressed video frames 24
`in a VOBU in further details. As shown, a series of com- 20
`pressed video frames 24 include a compressed I-frame 30, a
`number of compressed B-frames 32, and a number of
`compressed P-frames 34, spanning the BTUs 38'. Note that
`neither I-frame 30, B-frames 32, nor P-frames 34 are bound(cid:173)
`ary aligned with BTUs 38'. Each ofl-frame 30, B-frames 32, 25
`and P-frames 34 includes a start code 36. Each VOBU, that
`is, each group of pictures, also includes a start code (not
`shown).
`Compressed I-frame 30 is generated in reference to itself,
`and is used as a reference frame for reconstituting the group 30
`of pictures during decompression. Compressed I-frame 30
`includes almost exclusively "motionless" macroblocks.
`Compressed B-frames 32 are generated using motion com(cid:173)
`pensated predictions referencing preceding as well as sub(cid:173)
`sequent I-frames and P-frames. Compressed B-frames 32 35
`include mostly backward as well as forward motion vectors.
`Compressed P-frames 34 are generated using motion com(cid:173)
`pensated predictions referencing preceding I-frames and
`P-frames. Compressed P-frames 34 include mostly forward
`motion vectors, and a small amount of motionless macrob- 40
`locks. The manner in which compressed I-frame 30,
`B-frames 32 and P-frames 34 may be generated is well
`known in the art.
`FIG. 4 also illustrates one embodiment of an encryption
`policy 40. As shown, in accordance with the illustrated
`embodiment of encryption policy 40, each BTU 38' con(cid:173)
`taining the start code of either a group of pictures, an I-frame
`30, one of the B-frames 32 or one of the P-frames 34 is
`encrypted. As will be appreciated by those skilled in the art,
`by encrypting each of the BTUs 38' containing the start code
`of a group of pictures or the start code of a frame, frames 30,
`32 and 34 are unrecoverable, that is effectively "destroyed",
`if the video images of partially encrypted { CVD+} 18 are
`rendered without decryption. As will be also appreciated by
`those skilled in the art, the number of BTUs 38' containing 55
`start codes for the various groups of pictures and the start
`codes of I, B and P-frame 30, 32 and 34 is a very small
`percentage of all BTUs 38'. In other words, only a few
`percent of the processor cycles required by the total encryp(cid:173)
`tion approach for decryption will be required to decrypt and
`render the partially encrypted { CVD+} 18, and yet the video
`images of partially encrypted { CVD+} 18 are degraded to
`the same level (that is, total "destruction") as the degradation
`achieved by the total encryption approach.
`In an alternate embodiment, a fraction of the BTUs of
`either the I-frames 30 or the P-frames 34 are encrypted, to
`destroy data references for future frames. For example,
`
`4
`every 3 of 4 BTUs 38' of an I-frame 30 within a VOBU, and
`every fourth BTU 38' of an P-frame 34 within the VOBU are
`encrypted, to destroy data references for future frames. None
`of the BTUs 38' of B-frames 32 within a VOBU are
`encrypted. Experience has shown that the number of BTUs
`38' encrypted is a small percentage of all BTUs 38'. In other
`words, only a few percent of the processor cycles required
`by the total encryption approach for decryption will be
`required to decrypt and render the partially encrypted
`{ CVD+} 18, and yet the video images of partially encrypted
`{ CVD+} 18 are degraded to a level that is virtually useless,
`approximating the degradation achieved by the total encryp(cid:173)
`tion approach.
`FIGS. 5-9 illustrates various embodiments of the present
`invention. FIG. 5 illustrates embodiment lOa wherein "for(cid:173)
`matter" 12 of FIG. 1 is replaced with encryption module 12'.
`Encryption module 12' performs the selective encryption
`based on encryption policy 14' as described earlier.
`However, encryption module 12' receives a formatted
`"clear" (that is, unencrypted) stream of compressed video
`and related data (CVD+) as input instead. FIG. 6 illustrates
`embodiment lOb wherein the present invention further
`includes user interface 42 for specifying encryption policy
`14' for encryption modules 12'. FIG. 7 illustrates embodi(cid:173)
`ment lOc wherein the present invention further includes
`analyzer 44 for analyzing the video images of CVD 16 to
`dynamically adjust encryption policy 14'. For examples,
`analyzer 44 may adjust encryption policy 14' based on
`certain frame statistics maintained for the video images of
`CVD 16. Alternatively, analyzer 44 may adjust encryption
`policy 14' based on the detection of a number constant or
`"slow" changing "landmarks", e.g. a mountain scene. Ana-
`lyzer 44 may provide the analysis results to a user through
`user interface 42, who in turn will adjust encryption policy
`14' through user interface 42. Alternatively, analyzer 44 may
`apply the analysis results directly to adjust encryption policy
`14'. Statistical analysis of video images, as well as detection
`for "static" imagery in video images may be performed
`using any one of a number of these analysis techniques
`known in the art. Similarly, for both embodiments lOa and
`lOb, encryption module 12' may encrypt a selected BTU 38
`using any number of encryption techniques known in the art.
`FIG. 8 illustrates embodiment lOd, which is similar to
`embodiment lOb, except "encryption" module 12" is imple(cid:173)
`mented with a selector, and "encryption policy" 14" is
`45 implemented with a selection policy. "Encryption" or selec(cid:173)
`tor module 12" is provided with fully encrypted video
`images of CVD+ 16, that is [CVD+] 46, as well as CVD+
`16. Whenever a BTU 38 is selected for encryption, instead
`of encrypting the selected BTU 38 on the fly, selector 12"
`50 simply selects and outputs the corresponding portion of
`[CVD+] 46. FIG. 9 illustrates embodiment lOe, which is
`similar to embodiment lOc, except "encryption" module 12"
`is implemented with a selector, and "encryption policy" 14"
`is implemented with a selection policy, as described earlier.
`Encryption module 12' as well as "encryption" or selector
`module 12" may be implemented in hardware or software.
`FIG. 10 illustrates one embodiment of a computer system
`suitable for practicing a software implementation of the
`present invention. As shown, for the illustrated embodiment,
`60 computer system 100 includes processor 102, memory 104,
`system bus 106, mass storage 108, input devices 110, display
`adapter 112 and display 114 coupled to each other as shown.
`Except for the manner they are used to practice the present
`invention, each of these elements 102-114 performs its
`65 corresponding conventional function known in the art, and
`each of these elements 102-114 is intended to represent a
`broad category of similar elements known in the art.
`
`

`
`5,805,700
`
`10
`
`5
`In particular, memory 104 is used to store a working copy
`each of formatter/encryption/selector module 12 and
`encryption/selection policy 14. Memory 104 may also be
`used to store a working copy each of end user interface 42
`and analyzer 44. Mass storage 108 is used to store a working 5
`copy of CVD 11, CVD+16, {CVD+} 18, and/or [CVD+] 46.
`Alternatively, for systems with large memory or for small
`amount of video data, CVD 11, CVD+ 16, { CVD+} 18
`and/or [CVD+] 46 may also be stored in memory 104.
`Finally, mass storage 108 may also be used to store a
`permanent copy of formatter/encryption/selector module 12
`and encryption/selection policy 14, as well as end user
`interface 42 and analyzer 44.
`While the present invention has been described in terms
`of the above illustrated embodiments, those skilled in the art
`will recognize that the invention is not limited to the 15
`embodiments described. The present invention may be prac(cid:173)
`ticed with modification and alteration within the spirit and
`scope of the appended claims. The description is thus to be
`regarded as illustrative instead of restrictive on the present
`invention.
`Thus, a method and apparatus for policy based selective
`encryption of compressed video data has been described.
`What is claimed is:
`1. An apparatus comprising a formatter module for selec(cid:173)
`tively encrypting basic transfer units (BTUs) of a stream of 25
`MPEG compressed video and related data in accordance
`with an encryption policy, the stream of MPEG compressed
`video and related data being organized into multiple video
`object units (VOBUs), with each VOBU being further
`organized into a plurality of BTUs, wherein the encryption 30
`policy prescribes for encryption of each BTU containing a
`start code of either a group of pictures, an I-frame, a B-frame
`or a P-frame.
`2. An apparatus comprising a formatter module for selec(cid:173)
`tively encrypting basic transfer units (BTUs) of a stream of 35
`MPEG compressed video and related data in accordance
`with an encryption policy, the stream of MPEG compressed
`video and related data being organized into multiple video
`object units (VOBUs), with each VOBU being further
`organized into a plurality of BTUs, wherein the encryption 40
`policy prescribes for encryption of a fraction of the BTUs of
`an I-frame within a VOBU.
`3. The apparatus as set forth in claim 2, wherein
`the encryption policy prescribes for encryption of three of
`every four BTUs of an I-frame within a VOBU.
`4. An apparatus comprising a formatter module for selec(cid:173)
`tively encrypting basic transfer units (BTUs) of a stream of
`MPEG compressed video and related data in accordance
`with an encryption policy, the stream of MPEG compressed
`video and related data being organized into multiple video
`object units (VOBUs), with each VOBU being further
`organized into a plurality of BTUs, wherein the encryption
`policy prescribes for encryption of a fraction of the BTUs of
`a P-frame within a VOBU.
`5. The apparatus as set forth in claim 4, wherein
`the encryption policy prescribes for encryption of every
`fourth BTU of a P-frame within a VOBU.
`6. An apparatus comprising an encryption module for
`selectively encrypting basic transfer units (BTUs) of a
`stream of MPEG compressed video data in accordance with
`an encryption policy, the stream of MPEG compressed video
`data being organized into multiple video object units
`(VOBUs), with each VOBU being further organized into a
`plurality of BTUs, wherein the encryption policy prescribes
`for encryption of each BTU containing a start code of either
`a group of pictures, an I-frame, a B-frame or a P-frame
`within a VOBU.
`
`6
`7. An apparatus comprising an encryption module for
`selectively encrypting basic transfer units (BTUs) of a
`stream of MPEG compressed video data in accordance with
`an encryption policy, the stream of MPEG compressed video
`data being organized into multiple video object units
`(VOBUs), with each VOBU being further organized into a
`plurality of BTUs, wherein the encryption policy prescribes
`for encryption of a fraction of the BTUs of an I-frame within
`a VOBU.
`8. The apparatus as set forth in claim 7, wherein
`the encryption policy prescribes for encryption of three of
`every four BTUs of an I-frame, within a VOBU.
`9. An apparatus comprising an encryption module for
`selectively encrypting basic transfer units (BTUs) of a
`stream of MPEG compressed video data in accordance with
`an encryption policy, the stream of MPEG compressed video
`data being organized into multiple video object units
`(VOBUs), with each VOBU being further organized into a
`plurality of BTUs, wherein the encryption policy prescribes
`20 for encryption of a fraction of the BTUs of a P-frame within
`a VOBU.
`10. The apparatus as set forth in claim 9, wherein
`the encryption policy prescribes for encryption of every
`fourth BTU of a P-frame within a VOBU.
`11. An apparatus comprising a selector module for gen(cid:173)
`erating a partially encrypted stream of MPEG compressed
`video data by selectively outputting basic transfer units
`(BTUs) of a formatted (but unencrypted) stream of MPEG
`compressed video data and BTUs of a formatted and
`encrypted stream of MPEG compressed video data, in
`accordance with a selection policy, each of the formatted
`unencrypted and encrypted streams of MPEG compressed
`video data being organized in multiple video object units
`(VOBUs), with each VOBU being further organized into a
`plurality of BTUs, wherein the selection policy prescribes
`for selection of each BTU containing a start code of either
`a group of pictures, an I-frame, a B-frame or a P-frame
`within a VOBU from the formatted encrypted stream of
`MPEG compressed video data.
`12. An apparatus comprising a selector module for gen-
`erating a partially encrypted stream of MPEG compressed
`video data by selectively outputting basic transfer units
`(BTUs) of a formatted (but unencrypted) stream of MPEG
`compressed video data and BTUs of a formatted and
`45 encrypted stream of MPEG compressed video data, in
`accordance with a selection policy, each of the formatted
`unencrypted and encrypted streams of MPEG compressed
`video data being organized in multiple video object units
`(VOBUs), with each VOBU being further organized into a
`50 plurality of BTUs, wherein the selection policy prescribes
`for selection of a fraction of the BTUs of an I-frame within
`a VOBU from the formatted encrypted stream of MPEG
`compressed video data.
`13. The apparatus as set forth in claim 12, wherein pl the
`55 selection policy prescribes for selection of three of every
`four BTUs of an I-frame, within a VOBU, from the format(cid:173)
`ted encrypted stream of MPEG compressed video data.
`14. An apparatus comprising a selector module for gen(cid:173)
`erating a partially encrypted stream of MPEG compressed
`60 video data by selectively outputting basic transfer units
`(BTUs) of a formatted (but unencrypted) stream of MPEG
`compressed video data and BTUs of a formatted and
`encrypted stream of MPEG compressed video data, in
`accordance with a selection policy, each of the formatted
`65 unencrypted and encrypted streams of MPEG compressed
`video data being organized in multiple video object units
`(VOBUs), with each VOBU being further organized into a
`
`

`
`5,805,700
`
`7
`plurality of BTUs, wherein the selection policy prescribes
`for selection of a fraction of the BTUs of a P-frame within
`a VOBU from the formatted encrypted streams of the MPEG
`compressed video data.
`15. The apparatus as set forth in claim 14, wherein
`the selection policy prescribes for encryption of every
`fourth BTU of a P-frame within a VOBU from the
`formatted encrypted stream of MPEG compressed
`video data.
`16. An apparatus comprising
`a storage medium having stored therein a plurality of
`programming instructions for implementing an encryp(cid:173)
`tion function for selectively encrypting basic transfer
`units (BTUs) of MPEG compressed video data, in
`accordance with an encryption policy, the MPEG com-
`pressed video data being organized into multiple video
`object units (VOBUs), with each VOBU being further
`organized into a plurality of BTUs, wherein the encryp(cid:173)
`tion policy prescribes for encryption of each BTU
`containing a start code of a group of pictures or a start
`code of a frame within a VOBU; and
`an execution unit coupled to the storage medium for
`executing the plurality of programming instructions
`during operation.
`17. The apparatus as set forth in claim 16, wherein
`the encryption policy prescribes for encryption of a frac(cid:173)
`tion of the BTUs of an I-frame or a P-frame within a
`VOBU.
`
`5
`
`10
`
`15
`
`20
`
`25
`
`8
`18. An apparatus comprising
`a storage medium having stored therein a plurality of
`programming instructions for implementing a selection
`function for generating a partially encrypted stream of
`MPEG compressed video data by selectively outputting
`basic transfer units (BTUs) of an unencrypted stream of
`MPEG compressed video data and BTUs of an
`encrypted stream of MPEG compressed video data, in
`accordance with a selection policy, each of the unen(cid:173)
`crypted and encrypted streams of MPEG compressed
`video data being organized into multiple video object
`units (VOBUs), with each VOBU further being orga(cid:173)
`nized into a plurality of BTUs, wherein, the selection
`policy prescribes for selection of each BTU containing
`a start code a group of pictures or a start code of a frame
`within a VOBU, from the encrypted stream of com(cid:173)
`pressed video data;
`an execution unit coupled to the storage medium for
`executing the plurality of programming instructions
`during operation.
`19. The apparatus as set forth in claim 18, wherein
`the selection policy prescribes for selection of a fraction
`of the BTUs of either an I-frame or a P-frame within a
`VOBU, from the encrypted streams of the MPEG
`compressed video data.
`
`* * * * *