Title: Digital video recorder for encrypting/decrypting video programs in segments to facilitate trick play features
Abstract: A digital video recorder (DVR) is disclosed for storing a plaintext video program as an encrypted video program. The DVR comprises a random access storage (RAS) device for storing the encrypted video program in encrypted segments. The DVR further comprises a cryptography facility comprising an encoder for encrypting plaintext segments of the plaintext video program into the encrypted segments stored on the RAS device, and a decoder for randomly and independently decrypting the encrypted segments of the encrypted video program into plaintext segments during playback.
Patent Number: 6,851,055 Issued on 02/01/2005 to Boyle, et al.
| Inventors:
|
Boyle; William B. (Lake Forest, CA);
Rice; Alan P. (Santa Ana, CA)
|
| Assignee:
|
Keen Personal Technologies, Inc. (Lake Forest, CA);
Keen Personal Media, Inc. (Lake Forest, CA)
|
| Appl. No.:
|
676637 |
| Filed:
|
September 30, 2000 |
| Current U.S. Class: |
713/193; 713/187; 713/200; 713/201 |
| Intern'l Class: |
H04L 001/24 |
| Field of Search: |
713/193,187,200,201,165
|
References Cited [Referenced By]
U.S. Patent Documents
| 5488409 | Jan., 1996 | Yuen et al. | 725/41.
|
| 5592555 | Jan., 1997 | Stewart.
| |
| 5687237 | Nov., 1997 | Naclerio.
| |
| 5761607 | Jun., 1998 | Gudesen | 725/89.
|
| 5931947 | Aug., 1999 | Burns et al.
| |
| Foreign Patent Documents |
| WO 97-43761 | Nov., 1997 | WO.
| |
Other References
Bennet Yee, J.D. Tygar, "Secure Coprocessors in Electronic Commerce
Applications", First USENIX Workshop on Electronic Commerce, Jul. 11-12,
1995, 155-170.
Howard Gobioff, "Security for a High Performance Commodity Storage
Subsystem", School of Computer Science, Carnegie Mellon University,
CMU-CS-99-160, Jul. 1999, pp. 171-178.
Rodney Van Meter, Steve Hotz, Gregory Finn, "Derived Virtual Devices: A
Secure Distributed File System Mechanism", In Proceedings of the Fifth
NASA Goddard Space Flight Center Conference on Mass Storage Systems and
Technologies, Sep. 1996.
Garth A. Gibson, David F. Nagle, Khalil Amiri, Fay W. Chang, Howard
Gobioff, Erik Riedel, David Rochberg, and Jim Zelenka, "Filesystems for
Network-Attached Secure Disks", Jul. 1997, 1-18, CMU-CS-97-118, School of
Computer Science, Carnegie Mellon University, Pittsburgh, Pennsylvania.
Howard Gobioff, Garth Gibson, and Doug Tygar, "Security for Network
Attached Storage Devices", Oct. 23, 1997, 1-18 CMU-CS-97-185, School of
Computer Science, Carnegie Mellon University, Pittsburgh, PA 15213.
"Digital Transmission License Agreement", www.dtcp.com.
"Digital Transmission Content Protection Specification", vol. 1, Revision
1.0, Apr. 12, 1999, www.dtcp.com.
"5C Digital Transmission Content Protection White Paper", Revision 1.0,
Jul. 14, 1998, www.dtcp.com.
Steve Grossman, "Two-Chip Set Safeguards Digital Video Content", Electronic
Design, Jun. 12, 2000, pp. 68-72.
|
Primary Examiner: Peeso; Thomas R.
Attorney, Agent or Firm: Shara, Esq.; Milad G., Sheerin, Esq.; Howard H.
Claims
We claim:
1. A digital video recorder for storing a plaintext video program as an
encrypted video program, the digital video recorder comprising:
(a) a random access storage (RAS) device for storing the encrypted video
program in encrypted segments;
(b) a cryptography facility comprising:
an encoder for encrypting plaintext segments of the plaintext video program
into the encrypted segments stored on the RAS device; and
a decoder for randomly and independently decrypting each encrypted segment
of the encrypted video program into a plaintext segment during playback.
2. The digital video recorder as recited in claim 1, wherein the
cryptography facility further comprises a pseudo-random sequence generator
for generating a pseudo-random sequence.
3. The digital video recorder as recited in claim 2, wherein:
(a) the pseudo-random sequence generator is initialized with segment seed
values corresponding to the plaintext segments of the plaintext video
program; and
(b) the encoder combines the pseudo-random sequence generated for each
segment seed, value with the plaintext segments of the plaintext video
program to generate the encrypted segments of the encrypted video program
stored on the RAS device.
4. The digital video recorder as recited in claim 2, wherein:
(a) the pseudo-random sequence generator is initialized with segment seed
values corresponding to the encrypted segments of the encrypted video
program; and
(b) the decoder combines the pseudo-random sequence generated for each
segment seed value with the encrypted segments of the encrypted video
program to generate the plaintext segments of the plaintext video program
during playback.
5. The digital video recorder as recited in claim 2, wherein:
(a) the pseudo-random sequence generator comprises a linear feedback shift
register (LFSR); and
(b) the LFSR is initialized with segment seed values corresponding to the
plaintext segments of the plaintext video program during encoding, and
with segment seed values corresponding to the encrypted segments of the
encrypted video program during decoding.
6. The digital video recorder as recited in claim 5, further comprising a
seed value generator for generating the segment seed values from an
initial value.
7. The digital video recorder as recited in claim 1, wherein:
(a) the RAS device comprises a hard disk drive (HDD) comprising a disk;
(b) the disk comprises a plurality of data tracks;
(c) ach track comprises a plurality of data sectors; and
(d) each data sector stores an encrypted segment of the encrypted video
program.
8. A method for processing a video program in a digital video recorder
comprising a random access storage (RAS) device, the method comprising the
steps of:
(a) encrypting plaintext segments of a plaintext video program into
encrypted segments;
(b) storing the encrypted segments on the RAS device;
(c) randomly reading the encrypted segments from the RAS device; and
(d) independently decrypting each encrypted segment into a plaintext
segment.
9. The method for processing a video program as recited in claim 8, further
comprising the step of generating a pseudo-random sequence using a
pseudo-random sequence generator.
10. The method for processing a video program as recited in claim 9,
further comprising the steps of:
(a) initializing the pseudo-random sequence generator with segment seed
values corresponding to the plaintext segments of the plaintext video
program; and
(b) combining the pseudo-random sequence generated for each segment seed
value with the plaintext segments of the plaintext video program to
generate the encrypted segments of the encrypted video program stored on
the RAS device.
11. The method for processing a video program as recited in claim 9,
further comprising the step of:
(a) initializing the pseudo-random sequence generator with segment seed
values corresponding to the encrypted segments of the encrypted video
program; and
(b) combining the pseudo-random sequence generated for each segment seed
value with the encrypted segments of the encrypted video program to
generate the plaintext segments of the plaintext video program.
12. The method for processing a video program as recited in claim 9,
wherein:
(a) the pseudo-random sequence generator comprises a linear feedback shift
register (LFSR); and
(b) the LFSR is initialized with segment seed values corresponding to the
plaintext segments of the plaintext video program during encoding, and
with segment seed values corresponding to the encrypted segments of the
encrypted video program during decoding.
13. The method for processing a video program as recited in claim 12,
further comprising the step of generating the segment seed values from an
initial value.
14. The method for processing a video program as recited in claim 8,
wherein:
(a) the RAS device comprises a hard disk drive (HDD) comprising a disk;
(b) the disk comprises a plurality of data tracks;
(c) each track comprises a plurality of data sectors; and each data sector
stores an encrypted segment of the encrypted video program.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to digital video recorders. More
particularly, the present invention relates to a digital video recorder
for encrypting/decrypting video programs in segments to facilitate trick
play features.
2. Description of the Prior Art
Digital video recorders (DVRs) typically store video programs on a random
access storage (RAS) device, such as on a conventional hard disk drive
(HDD), which enables certain "trick play" features, such as skipping ahead
in a program. The trick play features are enabled by processing frame
headers which are recorded in arbitrary length frames of the video
program. Due to the arbitrary frame lengths, the video programs are
typically processed in unencrypted form in order to detect frame headers
which identify frame boundaries. Thus, prior art DVRs typically store
copyrighted video programs in unencrypted form so that the DVR can
randomly access individual frames during playback. This design, however,
subjects the copyrighted material to unauthorized reproduction, for
example, by eavesdropping while the copyrighted content is transferred
from the DVR host circuitry to the RAS device.
Prior art DVRs typically employ a conventional hard disk drive (HDD), such
as an IDE hard disk drive, as the RAS device since HDDs have sufficient
capacity to store video content and are relatively inexpensive due to
their prevalent use in personal computers (PCs). Rather than design and
manufacture a customized HDD for the DVR market, DVRs are constructed
similar to a PC, including DVR host circuitry for interfacing with a
commodity HDD which reduces the cost of the DVR. Using a conventional HDD,
however, has rendered the DVR more susceptible to unauthorized copying of
video programs since the HDD can be removed and installed in another DVR
or in a PC.
There is, therefore, a need to protect against unauthorized reproduction of
copyrighted video programs in a DVR employing a cost effective, commodity
HDD, while supporting trick play features.
SUMMARY OF THE INVENTION
The present invention may be regarded as a digital video recorder (DVR) for
storing a plaintext video program as an encrypted video program. The DVR
comprises a random access storage (RAS) device for storing the encrypted
video program in encrypted segments. The DVR further comprises a
cryptography facility comprising an encoder for encrypting plaintext
segments of the plaintext video program into the encrypted segments stored
on the RAS device, and a decoder for randomly and independently decrypting
the encrypted segments of the encrypted video program into plaintext
segments during playback.
In one embodiment the cryptography facility comprises a pseudo-random
sequence generator for generating a pseudo-random sequence. In one
embodiment, the pseudo-random sequence generator is initialized with
segment seed values corresponding to the plaintext segments of the
plaintext video program, and the encoder combines the pseudo-random
sequence generated for each segment seed value with the plaintext segments
of the plaintext video program to generate the encrypted segments of the
encrypted video program stored on the RAS device. During playback, the
pseudo-random sequence generator is initialized with segment seed values
corresponding to the encrypted segments of the encrypted video program,
and the decoder combines the pseudo-random sequence generated for each
segment seed value with the encrypted segments of the encrypted video
program to generate the plaintext segments of the plaintext video program.
In an alternative embodiment, the RAS device comprises a hard disk drive
(DD) comprising a disk, the disk comprises a plurality of data tracks,
each track comprises a plurality of data sectors, and each data sector
stores an encrypted segment of the encrypted video program.
The present invention may also be regarded as a method for processing a
video program in a digital video recorder comprising a random access
storage (RAS) device. Plaintext segments of a plaintext video program are
encrypted into encrypted segments. The encrypted segments are stored on
the RAS device and, during playback, randomly read from the RAS device.
Each encrypted segment is then independently decrypted into a plaintext
segment
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a digital video recorder according to an embodiment of the
present invention wherein a video program is encrypted in segments, and
the encrypted segments stored on a random access storage device.
FIG. 2 shows a digital video recorder according to an alternative
embodiment of the present invention wherein video programs are stored in
encrypted form on a hard disk drive (HDD) using plaintext keys which are
also encrypted using a pseudo-random sequence generated from a unique ID
and stored in encrypted file system entries on the HDD.
FIG. 3A shows a programmable file system (FS) polynomial implemented using
a linear feedback shift register (LFSR) for generating the pseudo-random
sequence of FIG. 2, wherein a seed value is generated for the LFSR from
the unique ID.
FIG. 3B shows a programmable FS polynomial implemented using a LFSR for
generating the pseudo-random sequence of FIG. 2, wherein coefficient
values are generated for the LFSR from the unique ID.
FIG. 4A shows an LFSR for generating a pseudo-random sequence for
encrypting a plaintext video program using a plaintext key as a seed value
for the LFSR.
FIG. 4B shows an LFSR for generating a pseudo-random sequence for
encrypting a plaintext video program using a plaintext key, wherein a seed
value is generated from the plaintext key. In an alternative embodiment, a
plurality of segment seed values are generated from the plaintext key
wherein each segment seed value is used to encrypt a corresponding segment
of the plaintext video program.
FIG. 4C shows an LFSR for generating a pseudo-random sequence for
encrypting a plaintext video program using a plaintext key, wherein
coefficient values are generated from the plaintext key. In an alternative
embodiment, sets of coefficient values are generated from the plaintext
key wherein each set of coefficient values is used to encrypt a
corresponding segment of the plaintext video program.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a digital video recorder (DVR) 1 for storing a plaintext video
program as an encrypted video program according to an embodiment of the
present invention. The DVR 1 comprises a random access storage (RAS)
device 3 for storing the encrypted video program in encrypted segments 5.
The DVR 1 further comprises a cryptography facility 14 comprising an
encoder 24 for encrypting plaintext segments 7A of the plaintext video
program into the encrypted segments 5 stored on the RAS device 3, and a
decoder 26 for randomly and independently decrypting the encrypted
segments 5 of the encrypted video program into plaintext segments 7B
during playback.
The DVR 1 of FIG. 1 further comprises a video controller 28 for receiving
video data 30 from an external entity (e.g., a cable or satellite) and for
providing video data 34 to a display device during playback. The video
controller 28 processes the headers in the video frames of the video data
30 in order to implement trick play features. Certain trick play features,
such as skip ahead or behind, require that the video program be accessed
randomly rather than in a consecutive sequence of frames. The DVR 1 of
FIG. 1 facilitates this feature by decrypting the video program in
segments. When the video controller 28 requires access to a particular
segment of the video program, it initializes the decoder 26 with an
appropriate segment key for decrypting the video-segment as it is read
from the RAS device 3.
FIG. 2 shows a DVR 2 according to an embodiment of the present invention
wherein the RAS device 3 of FIG. 1 is implemented as a hard disk drive
(HDD) 6. The HDD 6 stores a plurality of encrypted video programs 8 and an
encrypted file system, the encrypted file system comprising a plurality of
encrypted file system entries 10 for decrypting the plurality of encrypted
video programs 8. The DVR 2 further comprises host circuitry 12 for
interfacing with the HDD 6, the host circuitry 12 comprising the
cryptography facility 14 for encrypting plaintext file system entries 16A
into the encrypted file system entries 10 stored on the HDD 6, and for
decrypting the encrypted file system entries 10 read from the HDD 6 into
plaintext file system entries 16B. The cryptography facility 14 comprises
a pseudo-random sequence generator 20, responsive to the unique ID 4, for
generating a pseudo-random sequence 22. The cryptography facility 14
further comprises an encoder 24 for combining the pseudo-random sequence
22 with the plaintext file system entries 16A to generate the encrypted
file system entries 10 stored on the HDD 6, and a decoder 26 for combining
the pseudo-random sequence 22 with the encrypted file system entries 10
read from the HDD 6 to generate the plaintext file system entries 16B.
In one embodiment, the encoder 24 of FIG. 2 performs the encryption
operation by XORing each element (e.g., byte) of the plaintext file system
entry 16A with a corresponding element (e.g., byte) of the pseudo-random
sequence 22. Similarly, the decoder 26 performs the decryption operation
by XORing each element (e.g., byte) of the encrypted file system entry 10
with a corresponding element (e.g., byte) of the pseudo-random sequence 22
to generate the plaintext file system entry 16B.
The video controller 28 generates control signals 32 for controlling the
operation of the cryptography facility 14 when recording an encrypted
video program 8, together with the encrypted file system entry 10 for
decrypting the encrypted video program 8. The video controller also
processes the decrypted file system entries 16B so that the encrypted
video programs 8 can be decrypted and output as video data 34 to a display
device. Because the file system entries 10 are stored in encrypted form
relative to the unique ID 4 assigned to the DVR 2, the encrypted video
programs 8 stored on the HDD 6 cannot be decrypted by connecting the HDD 6
to another DVR or to a PC. In effect, the HDD 6 is married to the host
circuitry 12 of the DVR 2 through the unique ID 4 which protects against
unauthorized copying. In addition, the encrypted file system entries 10
are transparent to the operation of the HDD 6 so that any conventional HDD
6 may be employed without modification.
In one embodiment, the plaintext file system entry 16A comprises a
plaintext key for encrypting a plaintext video program into an encrypted
video program 8 stored on the HDD 6. The cryptography facility 14 encrypts
the plaintext video program into an encrypted video program 8 stored on
the HDD 6, and encrypts the plaintext key into an encrypted key stored on
the HDD 6 in an encrypted file system entry 10. In one embodiment, the
encoder 24 combines the pseudo-random sequence 22 with the plaintext video
program to generate the encrypted video program 8 stored on the HDD 6.
In another embodiment, the encrypted file system entry 10 comprises an
encrypted key for decrypting an encrypted video program 8 read from the
HDD 6 into a plaintext video program. The cryptography facility 14
decrypts the encrypted key read from encrypted file system entry 10 into a
plaintext key, and decrypts the encrypted video program 8 read from the
HDD 6 using the plaintext key. In one embodiment, the decoder 26 combines
the pseudo-random sequence 22 with the encrypted video program 8 read from
the HDD 6 to generate the plaintext video program.
In one embodiment, the pseudo-random sequence generator 20 comprises a
programmable file system (FS) polynomial for generating the pseudo-random
sequence 22. In one embodiment, the programmable FS polynomial is
programmed with coefficients which, in one embodiment, are generated by a
coefficient generator responsive to the unique ID 4. In another
embodiment, the programmable FS polynomial is programmed with a seed value
which, in one embodiment, is generated by a seed value generator
responsive to the unique ID 4.
FIG. 3A shows an embodiment of the present invention wherein the FS
polynomial is implemented using a suitable linear feedback register (LFSR)
36. An LFSR may be implemented using a number of different configurations.
The LFSR 36 of FIG. 3A comprises a shift register 38 comprising N storage
elements which are initialized with a seed value 40 generated by a seed
value generator 50 from the unique ID 4. A number of taps 42A-42E connect
a corresponding number of the storage elements to an adder 44 for adding
the values stored in the storage elements. The resulting sum 44 is fed
back 46 to an input of the LFSR 36. The LFSR 36 is shifted from left to
right, and the right most storage element 48 outputs each value of the
pseudo-random sequence 22.
FIG. 3B shows an alternative embodiment of the present invention wherein
the FS polynomial is implemented using an LFSR 52 comprising programmable
coefficients 54.sub.0 -54.sub.N. A coefficient generator 56 generates
coefficient values 58 for programming each of the programmable
coefficients 54.sub.0 -54.sub.N. In the embodiment shown in FIG. 3B, the
coefficients are binary valued and the programmable coefficients 54.sub.0
-54.sub.N are implemented as switches.
In yet another embodiment of the present invention, the FS polynomial is
implemented using an LFSR comprising both a programmable seed value and
programmable coefficients values which are generated from the unique ID 4.
In one embodiment, the seed value generator 50 implements a function f(x),
such as a polynomial, with the unique ID 4 as the input argument x and the
seed value 40 the result. In another embodiment, the seed value generator
50 comprises a programmable algorithm for computing the seed value 40 from
the unique ID 4. This embodiment allows a DVR manufacture to select the
function f(x) for implementing a line of DVRs. This embodiment also allows
an external entity to update the programmable algorithm to protect against
system compromise. For example, in one embodiment the DVR 2 of FIG. 2
comprises network circuitry for connecting to a network (e.g., through a
cable or satellite), and a system administrator on the network
periodically changes the programmable algorithm in a random manner. Thus,
if an attacker discovers the algorithm used by the seed value generator 50
to generate the seed value 40, the compromise is only temporary until the
system administrator updates the algorithm.
In another embodiment, the coefficient value generator 56 implements a
plurality of functions f(x), such as a plurality of polynomials, with the
unique ID as the input argument x and the coefficient values 58 the result
of each function f(x). The coefficient value generator 56 may also
implement a programmable algorithm for computing the coefficient values 58
to facilitate different DVR manufactures and to protect against system
compromise as described above.
In another embodiment of the present invention, the seed value generator 50
comprises a seed table comprising a plurality of table entries, each table
entry comprising a seed value. An index generator, responsive to the
unique ID 4, generates an index into the seed table. In yet another
embodiment, the coefficient value generator 56 comprises a coefficient
table comprising a plurality of table entries, each table entry comprising
coefficient values. An index generator, responsive to the unique ID 4,
generates an index into the coefficient table.
FIG. 4A shows an alternative embodiment of the present invention as
comprising a programmable LFSR 59 for generating a pseudo-random sequence
22 used to encrypt a plaintext video program into an encrypted video
program 8 stored on the HDD 6. A plaintext key 18 is used as a seed value
for the LFSR 59, where the plaintext key 18 is associated with the
plaintext video program. In one embodiment, the plaintext key is derived
from the filename or other attribute of the video program. In another
embodiment, the plaintext key is generated randomly using any suitable
method, for example, by reading a system clock value just prior to
encrypting the plaintext video.
FIG. 4B shows an alternative embodiment of the present invention as
comprising a programmable LFSR 60 for generating a pseudo-random sequence
22 used to encrypt a plaintext video program into an encrypted video
program 8 stored on the HDD 6. A seed value generator 62 generates a seed
value 64 used to initialize the shift register 38. The seed value 64 is
generated from the plaintext key 18 used to encrypt the plaintext video
program. In one embodiment, the plaintext video program is encrypted in
segments, and the seed value generator 62 generates a distinct seed value
64 for each segment number 66. Each segment seed value 64 is essentially a
distinct key for use in encrypting a corresponding segment of the
plaintext video program. In this manner, compromise of a single key
enables successful decrypting of only a segment of the encrypted video
program. Further, encrypting the video program in segments facilitates
trick play features during playback as described above.
In one embodiment, the plaintext key 18 comprises a plurality of segment
keys for encrypting each segment of the plaintext video program, and the
seed value generator 62 generates a corresponding seed value 64 for each
segment key. In another embodiment, the segment keys are computed from the
plaintext key 18, and the seed value generator 62 generates a
corresponding seed value 64 for each computed segment key. In one
embodiment, the seed value generator 62 comprises a function F(x,y) for
computing the segment seed values 64 wherein the plaintext key 18 and
segment number 66 are the input arguments x and y, and the segment seed
value 64 is the result. Lookup tables may also be employed for generating
the segment keys, and the algorithm for computing the segment keys may be
programmably updated to facilitate different DVR manufactures and to
protect against system compromise as described above.
FIG. 4C shows an alternative embodiment of the present invention as
comprising a programmable LFSR 68 for generating a pseudo-random sequence
22 used to encode a plaintext video program into an encrypted video
program 8 stored on the HDD 6. A coefficient value generator 70 generates
a coefficient values 72 used to initialize the coefficients of the LFSR
68. The coefficient values 72 are generated from the plaintext key 18 used
to encrypt the plaintext video program. In one embodiment, the plaintext
video program is encrypted in segments, and the coefficient value
generator 70 generates distinct coefficient values 72 for each segment
number 66. Similar to the embodiment of FIG. 4B, each set of coefficient
values 72 is essentially a distinct key for use in encrypting a
corresponding segment of the plaintext video program so that compromise of
a single key enables successful decrypting of only a segment of the
encrypted video program. Further, decrypting the video program in segments
facilitates trick lay features during playback as described above.
In one embodiment, the plaintext key 18 comprises a plurality of segment
keys for encrypting each segment of the plaintext video program, and the
coefficient value generator 70 generates a set of coefficient values 72
for each segment key. In another embodiment, the segment keys are computed
from the plaintext key 18, and the coefficient value generator 70
generates a corresponding set of coefficient values 72 for each computed
segment key. In one embodiment, the coefficient value generator 70
comprises a function f(x,y) for computing the segment coefficient values
72 wherein the plaintext key 18 and segment number 66 are the input
arguments x and y, and the segment coefficient values 72 are the result.
Lookup tables may also be employed for generating the segment keys, and
the algorithm for computing the segment keys may be programmably updated
to facilitate different DVR manufactures and to protect against system
compromise as described above.
In another embodiment, the LFSR 60 of FIG. 4B or the LFSR 68 of FIG. 4C is
used to decrypt an encrypted video program 8 in segments using the segment
keys. In one embodiment, the plaintext key 18 comprises a plurality of
segment keys which are encrypted and stored as an encrypted file system
entry 10 for use in decrypting the encrypted video program 8 during
playback. In another embodiment, the plaintext key 18 is encrypted and
stored as an encrypted file system entry 10. During playback, the
encrypted key is decrypted into the plaintext key 18, and the plaintext
key 18 is used to generate the segment keys for use in decrypting the
encrypted video program 8 in segments.
In one embodiment, the HDD 6 comprises a disk having a plurality of data
tracks, where each data track comprises a plurality of data sectors. In
the embodiments of FIGS. 4B and 4C, a segment of a video program
corresponds to a data sector. This simplifies the design since data is
typically written to and read from a conventional HDD 6 in sector blocks.
In one embodiment, the encrypted key for use in decrypting a corresponding
sector is stored in the sector.
In another embodiment of the present invention, the unique ID 4 is
implemented using tamper and inspection resistant circuitry to protect
against discovery. In one embodiment, the host circuitry 12 and unique ID
4 are implemented within an integrated circuit (IC), and the unique ID 4
is buried, scattered or otherwise concealed within the IC using any
suitable method. In yet another embodiment, at least part of the
cryptography facility 14 (e.g., the seed value generator 62 of FIG. 4B or
the coefficient value generator 70 of FIG. 4C) is implemented using tamper
and inspection resistant circuitry to protect against discovery. An
example of tamper and inspection resistant circuitry is disclosed in
Tygar, J. D. and Yee, B. S., "Secure Coprocessors in Electronic Commerce
Applications," Proceedings 1995 USENIX Electronic Commerce Workshop, 1995,
New York, which is incorporated herein by reference.
The embodiments of the present invention may be implemented in circuitry or
software or both. The circuitry and/or software may be static or field
programmable as described above. Software embodiments comprise code
segments embodied on a computer readable medium, such as a hard disk,
floppy disk, compact disk (CD), digital video disk (DVD), or programmable
memory (e.g., an EEPROM). The code segments may be embodied on the
computer readable medium in any suitable form, such as source code
segments, assembly code segments, or executable code segments.
*
