U.S. patent number RE40,468 [Application Number 11/288,023] was granted by the patent office on 2008-08-26 for video data bus communication system and method.
This patent grant is currently assigned to Sony Corporation. Invention is credited to Shinichi Fukushima, Koichi Goto, Junichi Tsukamoto.
United States Patent |
RE40,468 |
Tsukamoto , et al. |
August 26, 2008 |
Video data bus communication system and method
Abstract
A video data communication system and method are disclosed which
provides for the secure transmission of video data among devices
connected to a video data bus. The video data is transmitted with
address information corresponding to a particular device or,
alternatively, video data is encrypted and transmitted on the data
bus without address information.
Inventors: |
Tsukamoto; Junichi (Tokyo,
JP), Goto; Koichi (Kanagawa, JP),
Fukushima; Shinichi (Kanagawa, JP) |
Assignee: |
Sony Corporation (Tokyo,
JP)
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Family
ID: |
27316757 |
Appl.
No.: |
11/288,023 |
Filed: |
November 28, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10323357 |
Dec 19, 2002 |
Re. 38898 |
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09461136 |
Dec 14, 1999 |
Re. 38055 |
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Reissue of: |
08448254 |
May 23, 1995 |
05699426 |
Dec 16, 1997 |
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Foreign Application Priority Data
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May 24, 1994 [JP] |
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6-133813 |
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Current U.S.
Class: |
380/240;
348/E7.056; 348/E5.108; 375/E7.017; 380/242; 386/E5.002;
375/E7.019; 348/E5.004 |
Current CPC
Class: |
H04N
21/643 (20130101); H04N 21/426 (20130101); H04L
65/607 (20130101); H04N 5/4401 (20130101); H04N
21/4334 (20130101); H04L 12/403 (20130101); H04N
21/4367 (20130101); H04L 29/06027 (20130101); H04L
63/08 (20130101); H04N 7/1675 (20130101); H04N
5/765 (20130101); H04N 21/4325 (20130101); H04N
5/775 (20130101); H04L 63/04 (20130101) |
Current International
Class: |
H04N
7/167 (20060101) |
Field of
Search: |
;348/E5.004,E5.108,E7.056 ;386/E5.002 ;375/E7.017,E7.019
;380/200,210-242,255,268,277-286,30 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 506 435 |
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Mar 1992 |
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EP |
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0 505 302 |
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Sep 1992 |
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EP |
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58-85685 |
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May 1983 |
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JP |
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64-16143 |
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Jan 1989 |
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JP |
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1-246979 |
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Oct 1989 |
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JP |
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2-250439 |
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Aug 1990 |
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JP |
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4160940 |
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Jun 1992 |
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JP |
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6-132916 |
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Apr 1994 |
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JP |
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7-162832 |
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Jun 1995 |
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JP |
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Primary Examiner: Gregory; Bernarr E.
Attorney, Agent or Firm: Frommer Lawrence & Haug LLP
Frommer; William S.
Parent Case Text
.Iadd.More than one application has been filed to reissue U.S. Pat.
No. 5,699,426. This is a continuation of reissue U.S. Pat.
RE38,898, which is a continuation of reissue U.S. Pat. RE38,055,
which is a reissue of U.S. Pat. No. 5,699,426.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to and is a continuation
application of U.S. application Ser. No. 10/323,357, which was
filed on Dec. 19, 2002, now U.S. Pat. RE38,898, and which is a
continuation of U.S. application Ser. No. 09/461,136, which was
filed on Dec. 14, 1999, now U.S. Pat. RE38,055, which is a reissue
application of U.S. Pat. No. 5,699,426, issued Dec. 16, 1997. The
entire contents of the foregoing are incorporated herein by
reference..Iaddend.
Claims
What is claimed is:
.[.1. A method for communicating video data via a data bus between
a master device and a slave device which are each coupled to said
bus, comprising the steps of: transmitting from said master device
to said data bus a slave address of said slave device and a
command; generating, at said master device, a KEYCMD signal as a
function of said command and a master security key; receiving, at
said slave device from said data bus, said slave address and said
command and recognizing said slave address as corresponding to said
slave device; generating, at said slave device, an ACK signal as a
function of said command and a slave security key; transmitting
from said slave device to said data bus a master address of said
master device and said ACK signal; receiving, at said master device
from said data bus, said master address and said ACK signal and
recognizing said master address as corresponding to said master
device; comparing said KEYCMD signal generated by said master
device with said ACK signal received by said master device; and
executing a data transfer between said master device and said slave
device if said KEYCMD signal corresponds to said ACK signal..].
.[.2. The method, according to claim 1, further comprising the step
of: inhibiting a data transfer between said master device and said
slave device if said KEYCMD signal does not correspond to said ACK
signal..].
.[.3. The method, according to claim 2, wherein said data is
unencrypted and encoded and wherein said step of inhibiting a data
transfer comprises: transmitting said data from said slave device
to said data bus; and preventing said master device from decoding
said data from said data bus..].
.[.4. The method, according to claim 2, wherein said step of
inhibiting a data transfer comprises: preventing said master device
from transmitting said data to said data bus..].
.[.5. The method, according to claim 1, wherein said master device
is a receiver and said slave device is a peripheral device..].
.[.6. The method, according to claim 5, wherein said peripheral
device is a display device..].
.[.7. The method, according to claim 1, wherein said master device
is a peripheral device and said slave device is a receiver..].
.[.8. The method, according to claim 1, wherein said master device
is a first peripheral device and said slave device is a second
peripheral device..].
.[.9. The method, according to claim 1, wherein said slave device
comprises means for decoding an unencrypted coded data..].
.[.10. The method, according to claim 1, wherein said step of
executing a data transfer comprises: encrypting said data in said
master device according to an encryption key; and decrypting said
data in said slave device according to said encryption key..].
.[.11. The method, according to claim 10, wherein said step of
executing a data transfer further comprises: transmitting said
slave address and said encryption key from said master device to
said data bus; and receiving said encryption key and said slave
address at said slave device from said data bus and recognizing
said slave address as corresponding to said slave device..].
.[.12. The method, according to claim 10, further comprising the
step of: inhibiting a data transfer between said master device and
said slave device if said KEYCMD signal does not correspond to said
ACK signal..].
.[.13. The method, according to claim 12, wherein said step of
inhibiting a data transfer comprises: preventing said master device
from transmitting said data to said data bus..].
.[.14. The method, according to claim 10, wherein said master
device is a receiver and said slave device is a peripheral
device..].
.[.15. The method, according to claim 14, wherein said peripheral
device is a display device..].
.[.16. The method, according to claim 10, wherein said master
device is a peripheral device and said slave device is a
receiver..].
.[.17. The method, according to claim 10, wherein said master
device is a first peripheral device and said slave device is a
second peripheral device..].
.[.18. The method, according to claim 10, wherein said slave device
comprises means for decoding a decrypted coded data..].
.[.19. The method, according to claim 1, wherein said step of
executing a data transfer comprises: encrypting said data in said
slave device according to an encryption key; and decrypting said
data in said master device according to said encryption key..].
.[.20. The method, according to claim 19, wherein said step of
executing a data transfer further comprises: transmitting said
master address and said encryption key from said slave device to
said data bus; and receiving said master address and said
encryption key from said data bus at said master device and
recognizing said master address as corresponding to said master
device..].
.[.21. The method, according to claim 19, further comprising the
step of: inhibiting a data transfer between said master device and
said slave device if said KEYCMD signal does not correspond to said
ACK signal..].
.[.22. The method, according to claim 21, wherein said data is
encrypted and encoded and wherein said step of inhibiting a data
transfer comprises: transmitting said data from said slave device
to said data bus; and preventing said master device from decoding
said data from said data bus..].
.[.23. The method, according to claim 19, wherein said master
device is a receiver and said slave device is a peripheral
device..].
.[.24. The method, according to claim 23, wherein said peripheral
device is a display device..].
.[.25. The method, according to claim 19, wherein said master
device is a peripheral device and said slave device is a
receiver..].
.[.26. The method, according to claim 19, wherein said master
device is a first peripheral device and said slave device is a
second peripheral device..].
.[.27. The method, according to claim 19, wherein said slave device
comprises means for decoding a decrypted coded data..].
.[.28. A system for communicating video data comprising: at least
one master device having a master address; at least one slave
device having a slave address; a data bus, coupled to said master
device and to said slave device; said master device including:
means for transmitting to said data bus said slave address and a
command, means for generating a KEYCMD signal as a function of said
command and a master security key, means for receiving from said
data bus said master address and an ACK signal, means for
recognizing said master address as corresponding to said master
device, means for comparing said KEYCMD signal and said ACK signal,
and means for receiving said video data from said data bus if said
KEYCMD signal corresponds to said ACK signal; and said slave device
including: means for receiving from said data bus said slave
address and said command, means for recognizing said slave address
as corresponding to said slave device, means for generating said
ACK signal as a function of said command and a slave security key,
and means for transmitting to said data bus said master address,
said ACK signal, and said video data..].
.[.29. The system according to claim 28, wherein said master device
further comprises means for inhibiting reception of said video data
from said data bus if said KEYCMD signal does not correspond to
said ACK signal..].
.[.30. The system according to claim 29, wherein said means for
inhibiting includes a switch..].
.[.31. The system according to claim 28, wherein said master device
is a receiver and said slave device is a peripheral device..].
.[.32. The system according to claim 28, wherein said master device
is a peripheral device and said slave device is a receiver..].
.[.33. The system according to claim 28, wherein said master device
is a first peripheral device and said slave device is a second
peripheral device..].
.[.34. The system according to claim 28, wherein said video data is
unencrypted and encoded and wherein said slave device comprises
means for decoding said video data..].
.[.35. The system according to claim 28, wherein: said master
device further includes means for decrypting said video data
according to an encryption key; and said slave device further
includes means for encrypting said video data according to said
encryption key..].
.[.36. The system according to claim 35, wherein: said master
device further includes means for receiving said encryption key
from said data bus; and said slave device further includes means
for transmitting said encryption key to said data bus..].
.[.37. A system for communicating video data comprising: at least
one master device having a master address; at least one slave
device having a slave address; a data bus, coupled to said master
device and to said slave device; said master device including:
means for transmitting to said data bus said slave address and a
command, means for generating a KEYCMD signal as a function of said
command and a master security key, means for receiving from said
data bus said master address and an ACK signal, means for
recognizing said master address as corresponding to said master
device, means for comparing said KEYCMD signal and said ACK signal,
and means for transmitting to said data bus said video data if said
KEYCMD signal corresponds to said ACK signal; and said slave device
including: means for receiving from said data bus said slave
address, said command and said video data, means for recognizing
said slave address as corresponding to said slave device, means for
generating said ACK signal as a function of said command and a
slave security key; and means for transmitting to said data bus
said master address and said ACK signal..].
.[.38. The system according to claim 37, wherein said master device
further includes means for inhibiting transmission of said video
data to said data bus if said KEYCMD signal does not correspond to
said ACK signal..].
.[.39. The system according to claim 37, wherein: said master
device further includes means for encrypting said video data
according to an encryption key; and said slave device further
includes means for decrypting said video data according to said
encryption key..].
.[.40. The system according to claim 39, wherein: said master
device further includes means for transmitting said encryption key
to said data bus; and said slave device further includes means for
receiving said encryption key from said data bus..].
.Iadd.41. A display apparatus for displaying a video image,
comprising: a display device; a communication interface locally
connected to an external device for receiving encrypted digital
video data; a decryptor for decrypting said received encrypted
digital video data; a controller for executing an authentication
procedure between said display apparatus and said external device
and for controlling said decryptor; and a switch for selecting
either said digital video data received from said external device
or another video signal to result in a display of a video image by
said display device corresponding to the selection; wherein said
controller controls said decryptor to initiate said decrypting of
said received encrypted digital video data if said received digital
video data is selected for display and if said authentication
procedure is successfully executed..Iaddend.
.Iadd.42. The display apparatus according to claim 41, wherein said
received encrypted digital video data is digital video data which
is reproduced from a recording medium and encrypted in said
external device..Iaddend.
.Iadd.43. The display apparatus according to claim 41, wherein said
other video signal is an output from a television
tuner..Iaddend.
.Iadd.44. The display apparatus according to claim 43, wherein said
television tuner receives a digital television broadcast
signal..Iaddend.
.Iadd.45. The display apparatus according to claim 43, wherein said
television tuner receives an analog television broadcast
signal..Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a video data communication system and
method in which video data is transmitted between devices connected
to a data bus according to a protocol which ensures the security of
the transmitted video data.
2. Description of the Related Art
Video data devices are connected to a common data bus to facilitate
the communication of video data among the devices. Such devices
include video signal receivers, video signal decoders, video signal
recorders, video signal processing devices, video signal display
devices, and video signal reproducing or playback devices. The data
bus architecture has the advantage of being easy to implement,
modify, and expand.
A video data bus system which conveys digital video data signals
has the added advantage of substantially preserving the integrity
of digital video signals transmitted on the bus. Such a system may
transmit video data at great speeds without degrading the quality
of the transmitted signal. Such a system is particularly useful for
reproducing and disseminating copyrighted video data.
To preserve the value of copyrighted video data, a data bus
communication system is needed that can selectively prevent certain
devices connected to the bus from accessing certain video data but
allowing such devices to access other video data. Also, a flexible
communication protocol is needed to facilitate the secure and
organized flow of video data through a video data bus system.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the present invention is to provide a communication
system in which the security of video data transmitted on a data
bus is maintained.
Another object of the present invention is to prevent the
unauthorized retrieval, reproduction, or display of video data
transmitted on a video data bus.
Yet another object of the present invention is to provide a method
for securely communicating video data among particular devices
connected to a common video data bus.
A further object of the invention is to provide a communication
system in which a device connected to a common video bus is able to
address particular other devices for the transfer of video data
thereamong.
A still further object of the invention is to provide a
communication system in which devices connected to a common data
bus can issue control signals to other devices to initiate specific
types of video data transfers.
Another object of the present invention is to provide a
communication system in which video data signals are transmitted on
a video data bus without specifically included address signals.
In accordance with one aspect of the present invention, a method
for communicating video data via a data bus between a master device
and a slave device which are each coupled to the bus, comprises the
steps of transmitting a slave address of the slave device and a
command from the said master device to said data bus, generating,
at said master device, a KEYCMD signal as a function of said
command and a master security key, receiving, at said slave device
from said data bus, said slave address and said command and
recognizing said slave address as corresponding to said slave
device, generating, at said slave device, an ACK signal as a
function of said command and a slave security key, transmitting
from said slave device to said data bus a master address of said
master device and said ACK signal, receiving, at said master device
from said data bus, said master address and said ACK signal and
recognizing said master address as corresponding to said master
device, comparing said KEYCMD signal generated by said master
device which said ACK signal received by said master device, and
executing a data transfer between said master device and said slave
device if said KEYCMD signal corresponds to said ACK signal.
In accordance with another aspect of the present invention, in a
system for communicating video data between at least one master
device having a master address and at least one slave device having
a slave address by way of a data bus coupled to said master device
and to said slave device; said master device includes means for
transmitting to said data bus said slave address and a command,
means for generating a KEYCMD signal as a function of said command
and a master security key, means for receiving from said data bus
said master address and an ACK signal, means for recognizing said
master address as corresponding to said master device, means for
comparing said KEYCMD signal, and means for receiving said video
data from said data bus if said KEYCMD signal corresponds to said
ACK signal; and said slave device includes means for receiving from
said data bus said slave address and said command, means for
recognizing said slave address as corresponding to said slave
device, means for generating said ACK signal as a function of said
command and a slave security key, and means for transmitting to
said data bus said master address, said ACK signal, and said video
data.
In accordance with still another aspect of this invention, in a
system for communicating video data between at least one master
device having a master address and at least one slave device having
a slave address by way of a data bus coupled to said master device
and to said slave device; and said master device includes means for
transmitting to said data bus said slave address and a command,
means for generating a KEYCMD signal as a function of said command
and a master security key, means for receiving from said data bus
said master address and an ACK signal, means for recognizing said
master address as corresponding to said master device, means for
comparing said KEYCMD signal and said ACK signal, and means for
transmitting to said data bus said video data if said KEYCMD signal
corresponds to said ACK signal; and said slave device includes
means for receiving from said data bus said slave address, said
command and said video data, means for recognizing said slave
address as corresponding to said slave device, means for generating
said ACK signal as a function of said command and a slave security
key, and means for transmitting to said data bus said master
address and said ACK signal.
In accordance with a feature of this invention, in executing a data
transfer, the data in said master device is encrypted according to
an encryption key and the data in said slave device is decrypted
according to said encryption key, and said slave address and said
encryption key are transmitted from said master device to said data
bus and said encryption key and said slave address are received at
said slave device from said data bus with said slave address being
recognized as corresponding to said slave device. Alternatively, is
executing a data transfer, the data in said slave device is
encrypted according to an encryption key and said data in said
master device is decrypted according to said encryption key, said
master address and said encryption key are transmitted from said
slave device to said data bus and said master address and said
encryption key are received from said data bus at said master
device with said master address being recognized as corresponding
to said master device.
The above, and other objects, features and advantages of the
present invention will become apparent from the following detailed
description of illustrative embodiments when read in conjunction
with the accompanying drawings in which the same components are
identified by the same reference numerals.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of a video data communication system
according to a first embodiment of the present invention;
FIGS. 2(a)-(d) are process timing diagrams to which reference will
be made in explaining the operation of the video data communication
system of FIG. 1;
FIGS. 3(a)-(d) are additional process timing diagrams to which
reference will be made in explaining the operation of the video
data communication system of FIG. 1;
FIG. 4 is a flow diagram to which reference will be made in
explaining the general sequence of communication and processing
conducted by the video data communication system of FIG. 1;
FIG. 5 is a schematic diagram of a video data communication system
according to a second embodiment of the present invention;
FIGS. 6(a)-(d) are process timing diagrams to which reference will
be made in explaining the operation of the video data communication
system of FIG. 5;
FIGS. 7(a)-(d) are additional process timing diagrams to which
reference will be made in explaining the operation of the video
data communication system of FIG. 5;
FIG. 8 is a flow diagram to which reference will be made in
explaining the general sequence of communication and processing
conducted by the video data communication system of FIG. 5;
FIG. 9 is a schematic diagram of a display device compatible with
the video data communication system of FIG. 1;
FIG. 10 is a schematic diagram of a decoding device compatible with
the video data communication system of FIG. 1;
FIG. 11 is a schematic diagram of a display device compatible with
the video data communication system of FIG. 5; and
FIG. 12 is a schematic diagram of a decoding device compatible with
the video data communication system of FIG. 5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A first embodiment of the video data communication system according
to the present invention is illustrated in FIG. 1. As explained in
the following, it is preferred that the video data communication
system be specifically adapted to receive, process, and transmit
digital video data. Nevertheless, it should be appreciated that
this system can be modified to accommodate other digital data or
analog signals without departing from the scope of the invention.
As it is understood that the system can easily be implemented to
accommodate other types of data, the following is specifically
directed towards a digital video data communication system to
simplify explanation of the invention.
The video data communication system is generally comprised of a
receiver 21, a data bus 24, and one or more peripheral devices. The
peripheral devices, depending on their particular configurations,
may transmit and/or receive control signals and/or video data
through data bus 24. Two such peripheral devices are illustrated in
FIG. 1, specifically, a recording/reproducing device 22 and a
recording/reproducing device 23. Each of receiver 21, device 22,
and device 23 are connected to data bus 24 and are capable of
transmitting and receiving control signals and video data through
data bus 24.
Receiver 21 is suited for receiving, descrambling, and decoding an
input digital video signal. Specifically, receiver 21 is comprised
of a tuner 30, a descrambler 31, a switch 32, an input/output port
33, a controller 34, a memory 35, a switch 36, and a decoder 37.
Preferably, the input digital video signal is a satellite broadcast
digital video signal acquired by a satellite antenna system.
Alternatively, the input digital video signal is acquired from any
of a number of other transmission media, such as a land-based
broadcast system, a cable television system, or a fiber optic
network.
Tuner 30 receives an input digital video signal (not shown) and
selects a particular digital video signal or channel therefrom.
Preferably, tuner 30 can be controlled by a user to select among a
number of different video signals. Tuner 30 is coupled to
descrambler 31, and provides a selected digital video signal
thereto.
Descrambler 31 descrambles a scrambled digital video signal. As is
well known in the art, transmitted video signals are commonly
scrambled or coded by a signal provider to prevent unauthorized
reception of the video signal. Descrambler 31 descrambles, as
needed, the selected digital video signal provided by tuner 30 and
provides an unscrambled version of the digital video signal to
switch 32. In an alternate embodiment, a direct connection (not
shown) between descrambler 31 and decoder 37 is provided to carry
the unscrambled signal directly to decoder 37.
Switch 32 is coupled to descrambler 31, controller 34, and
input/output (I/O) port 33. In accordance with a switch signal
provided by controller 34, switch 32 closes to connect descrambler
31 with I/O port 33. Switch 36 is connected to decoder 37,
controller 34, and I/O port 33. In accordance with another switch
signal provided by controller 34, switch 36 closes to connect
decoder 37 with I/O port 33. I/O port 33 is further coupled to data
bus 24 and controller 34.
Through closed switch 36, decoder 37 receives a coded digital video
signal from I/O port 33. As is well known in the art, video signals
are commonly compressed or otherwise coded to facilitate their
transmission through a transmission medium. Decoder 37 decodes, as
needed, a coded digital video signal to produce an uncoded digital
video signal. Decoder 37 provides the uncoded digital video signal
to a video display device (not shown) for display to a user. It is
preferred that decoder 37 is adapted to decode digital video
signals encoded in accordance with the Moving Picture Image Coding
Experts Group (MPEG) standard.
Memory 35 is a storage device for storing one or more security
keys. Memory 35 is coupled to controller 34 and stores or provides
security keys and other data as required by controller 34. In
response to commands provided by a user, or according to a
pre-stored set of instructions, controller 34 transmits or receives
address, control and data signals, through I/O port 33, to or from
data bus 24. By manipulating switch signals provided to switches 32
and 36, controller 34 controls the flow of digital video data
through I/O port 33. In an alternate embodiment, controller 34
further controls the operation of I/O port 33 directly with I/O
port control signals and monitors data flowing through I/O port
33.
Recording/reproducing device 22 is comprised of an I/O port 40A, a
switch 41A, a recording/reproducing section 42A, a switch 43A, a
controller 44A, and a card port 45A. I/O port 40A is coupled to
data bus 24, controller 44A, switch 41A, and switch 43A. I/O port
40A routes address, control, and data signals to and from data bus
24 and controller 44A. I/O port 40A routes data signals to switch
41A and routes data signals from switch 43A. In an alternate
embodiment, address and control signals are also routed through I/O
port 40A to or from switches 41A and 43A. Switch 41A is further
coupled to controller 44A and section 42A. Similarly, switch 43A is
further coupled to controller 44A and section 42A.
According to switch commands from controller 44A, switch 41A closes
to connect I/O port 40A and section 42A. Also, according to switch
commands from controller 44A, switch 43A closes to connect section
42A and I/O port 40A. Alternatively, switches 41A and 43A may be
replaced with a single bi-directional switch (not shown) controlled
by controller 44A and connecting I/O port 40A and section 42A.
Recording/reproducing section 42A records data supplied through
switch 41A. Section 42A reproduces prerecorded data and supplies
the reproduced data to switch 43A. Preferably, section 42A is a
digital video tape recording/reproducing device (VTR).
Card port 45A is adapted to mechanically, electronically, or
otherwise engage a key card 48 and to obtain security key data or
other information therefrom. Key card 48, which is shown engaged in
device 23 in FIG. 1, comprises an active or passive device, as is
well known in the art. Card port 45A is coupled to controller 44A
and facilitates the communication of signals between controller 44A
and an engaged key card. While a key card is not installed in card
port 45A, card port 45A responds to signals from controller 44A by
returning a signal that is not a valid security key.
In response to commands provided by a user, or according to a
pre-stored set of instructions controller 44A transmits to or
receives from data bus 24, through I/O port 40A, address, control
and data signals. By manipulating switch signals provided to
switches 41A and 43A, controller 44A controls the flow of digital
video data through I/O port 40A. In an alternate embodiment,
controller 44A may control the operation of I/O port 40A directly
with I/O port control signals and monitor data flowing through I/O
port 40A.
As illustrated, device 23 is substantially the same as device 22,
like elements being denoted by like reference numerals with the
exception of the terminating letter A and B. Key card 48, shown
attached to card port 45B of device 23, stores a valid security key
corresponding to a security key stored in memory 35.
Operation of the first embodiment of the video data communication
system will be described below. One of the most important features
of this first embodiment is that each signal transmitted via data
bus 24 is accompanied by an address signal corresponding to an
address of a particular device, each device attached to data bus 24
having at least one address. Communication of signals between
selected devices includes communication of an address of the device
intended as the recipient of the transmitted signal. Each device
connected to data bus 24 reads or writes, as appropriate, signals
on data bus 24 when the device detects its own address on the bus.
Signals accompanying addresses for other devices are ignored. In
this manner, data are securely transferred between a transmitting
device and a selected destination device.
This communication protocol allows for many different sequences of
signal transfer between devices connected to data bus 24. Examples
of these signal transfer sequences, implemented in different modes
of operation of the present invention, will be described in detail
below. In one mode of operation, broadcast digital video data
signals are received by receiver 21 and transmitted to data bus 24
for display by a display device (not shown), for recording by a
recording device, or for other signal processing. In another mode,
prerecorded video data are reproduced by a peripheral device and
transmitted to a decoding device for decoding and subsequent
display. In still another mode, prerecorded video data are
reproduced by one peripheral device and transmitted to another
peripheral device which records the video data.
In a first broadcast display mode, receiver 21 receives a broadcast
signal and suitably processes it for display by a video display
(not shown). Tuner 30 selectively receives a broadcast signal and
supplies the signal to descrambler 31. Descrambler 31 descrambles
the broadcast signal and provides a descrambler version of the
signal to switch 32. Controller 34 outputs switch signals that
cause switches 32 and 36 to close and outputs I/O port control
signals to cause I/O port 33 to couple switches 32 and 36 together.
The descrambled video signal propagates through switch 32, I/O port
33, and switch 36, to decoder 37. Decoder 37 decodes the
descrambled video signal and supplies the decoded signal to a video
display (not shown). When a direct connection between descrambler
31 and decoder 37 is provided, the descrambled signal is supplied
directly to decoder 37, bypassing switch 32, switch 36, and I/O
port 33.
In a second broadcast display mode, receiver 21 receives a
broadcast video signal and supplies the broadcast signal to a
display device (not shown) connected to data bus 24. An example of
such a display device is illustrated in FIG. 9 and will be
described in detail in a later section. As in the first broadcast
display mode, tuner 30 selectively receives a broadcast signal and
provides the signal to descrambler 31. Descrambler 31 descrambles
the broadcast video signal to produce a descrambled video signal.
Controller 34 issues an address signal corresponding to a selected
display device and a display command, and appropriately manipulates
I/O port 33 to route the address signal and display command to data
bus 24.
The display device (not shown in FIG. 1) reads the address on data
bus 24, recognizes the address as its own, and reads the
accompanying display command from data bus 24. The display device
processes the display command to generate an ACK signal and
transmits an address of receiver 21 along with the ACK signal to
data bus 24. The address and ACK signal supplied by the display
device are received by controller 34 via I/O port 33.
Controller 34 retrieves a security key from memory 35 and generates
a KEYCMD signal as a function of the display command and the
retrieved security key. The KEYCMD signal is then compared to the
received ACK signal. If the ACK address is equal to the KEYCMD
signal, then controller 34 transmits an address corresponding to
the display device to data bus 24. Controller 34 also issues a
switch command to switch 32, causing it to close, and an I/O port
control signal to I/O port 33, causing it to couple switch 32 with
data bus 24. Descrambled video signal transmitted from descrambler
31 propagates through switch 32 and I/O port 33 to data bus 24.
The address signal on data bus 24 is recognized by the display
device and the subsequently transmitted video data are received,
processed, and displayed. Other peripheral devices connected to
data bus 24 do not read the video data present on the bus if the
address signal does not correspond to one of their own respective
addresses.
In a recording mode of operation, receiver 21 receives a broadcast
signal and transmits the broadcast signal via data bus 24 to a
particular peripheral device which records the signal. Controller
34 configures I/O port 33 to couple controller 34 with data bus 24
and then transmits an address of a particular recording device
along with a record command to data bus 24. Assuming, for example,
that the address transmitted corresponds to an address of device
22, controller 44A, through I/O port 40A, reads the address on data
bus 24, recognizes the address as its own, and reads the
accompanying record command from data bus 24. Controller 44A
processes the record command to generate an acknowledge (ACK)
signal.
Specifically, controller 44A polls card port 45A for a security key
and generates an ACK signal as a function of the received record
command and the signal returned by card port 45A. Controller 44A
then transmits an address of receiver 21 and the ACK signal via I/O
port 40A to data bus 24. The address and ACK signal supplied by
device 22 are received by controller 34 via I/O port 33.
Controller 34 retrieves a security key from memory 35 and generates
a KEYCMD signal as a function of the record command and the
retrieved security key. The KEYCMD signal is then compared to the
received ACK signal. If the ACK signal is equal to the KEYCMD
signal, then controller 34 transmits an address signal of the
particular recording device to data bus 24 through I/O port 33 and
configures switch 32 and I/O port 33 for the transmission of
descrambled video data from descrambler 31 to data bus 24 to
initiate the transfer of video data. If the ACK signal is not equal
to the KEYCMD signal, then controller 34 issues a switch command
signal, causing switch 32 to open, to prevent the flow of
descrambled broadcast video data to data bus 24.
Since, as illustrated in FIG. 1, card port 45A of device 22 is not
coupled to a card key containing a correct security key, controller
44A will generate an ACK signal which is not equal to the KEYCMD
signal produced by controller 34 and no video data transfer will
occur. Thus, the supply of descrambled broadcast video data to a
particular recording device depends upon the installation of an
appropriate key card in the card port of the particular device.
When device 23 is selected to record broadcast video data,
controller 34 outputs an address of device 23 to data bus 24
through I/O port 33 along with a record command. Controller 44B,
through I/O port 40B, reads the address on data bus 24, recognizes
the address signal as its own and reads the accompanying record
command. Controller 44B retrieves a security key from key card 48
via card port 45B. Controller 44B generates an ACK signal as a
function of the received record command and the retrieved security
key. Controller 44B transmits an address of receiver 21 and the ACK
signal to data bus 24 through I/O port 40B.
As above, controller 34 reads the address signal and the ACK
signal, generates a KEYCMD signal, and compares the ACK and KEYCMD
signals. If the security key contained in key card 48 corresponds
to the security key contained in memory 35, the ACK signal and the
KEYCMD signal are equal. Meanwhile, controller 44B supplies a
switch control signal to switch 41B, causing it to close, thereby
connecting I/O port 40B with recording/reproducing section 42B.
Further, I/O port 40B is configured to route video data from data
bus 24 to section 42B. After verifying that the two security keys
correspond, controller 34 facilitates the transmission of an
address of device 23 and descrambled broadcast video data to device
23.
Controller 44B, through I/O port 40B, reads the address on data bus
24 and recognizes the address signal as its own. The accompanying
descrambled video data on data bus 24 is retrieved and passed
through I/O port 40B and switch 41B to section 42B for recording.
As a result, recording devices having the selected address and
provided with a key card 48 having the correct security key
retrieve and record video data supplied by receiver 21.
In a playback mode of operation, receiver 21 initiates the playback
of prerecorded video data from a peripheral device. Controller 34
transmits an address signal, corresponding to an address of a
particular peripheral device, along with a playback command to data
bus 24 through I/O port 33. Assuming, for example, that the address
signal corresponds to an address of device 22, controller 44A,
through I/O port 40A, reads the address on data bus 24, recognizes
the address as its own, and reads the accompanying playback command
from data bus 24. As described previously, controller 44A generates
an ACK signal as a function of the playback command and a signal
provided by card port 45A. Controller 44A then transmits an address
of receiver 21 and this ACK signal via I/O port 40A to data bus 24.
Controller 44A also issues a switch control signal to switch 43A,
causing it to close, and configures I/O port 40A to connect data
bus 24 and switch 43A.
Controller 34, through I/O port 33, reads the address on data bus
24, recognizes the address as its own, and reads the accompanying
ACK signal. Controller 34 retrieves a security key from memory 35
and generates a KEYCMD signal as a function of the playback command
and the retrieved security key. The received ACK signal is compared
to the KEYCMD signal and, if they are equal, controller 34 issues a
switch control signal to switch 36, causing it to close, and issues
an I/O port control signal to I/O port 33, causing it to route
signals from data bus 24 to switch 36. However, if the ACK signal
does not equal the KEYCMD signal, then controller 34 issues a
switch control signal which causes switch 36 to open.
Since device 22, as shown in FIG. 1, is not engaged with a key card
having a correct security key, the ACK signal it produces will not
be equivalent to the KEYCMD signal produced by controller 34. Even
though recording/reproducing section 42A may output prerecorded
video data to data bus 24 via switch 43A and I/O port 40A, the data
will not reach decoder 37, since switch 36 will have been
opened.
In the case where controller 34 initially issues an address
corresponding to device 23, controller 44B reads and recognizes the
address, reads the accompanying playback command, and polls card
port 45B. Key card 48, having a security key corresponding to that
stored in memory 35, supplies the security key to controller 44B
through card port 45B. Controller 44B generates an ACK signal as a
function of the received playback command and the security key
received from key card 48. The ACK signal and the address of
receiver 21 are transmitted via data bus 24 to controller 34 and
switch 43B is closed. Controller 34 reads and recognizes the
address, reads the accompanying ACK signal, and generates a KEYCMD
signal as a function of the playback command and a security key
obtained from memory 35. In this instance, the ACK signal and the
KEYCMD signal are equal, and accordingly, controller 34 causes
switch 36 to close.
Controller 44B outputs an address of receiver 21 and
recording/reproducing section 42B outputs a prerecorded video data
signal to data bus 24. Controller 34 reads and recognizes the
address. The accompanying video data signal is retrieved from data
bus 24 and supplied through I/O port 33 and switch 36 to decoder
37. Decoder 37 decodes the prerecorded video data signal and
supplies the decoded signal to a video display device (not shown).
Receiver 21 thus decodes data reproduced by a peripheral device in
which a key card having a correct security key is installed.
The signal processing and exchange of messages in
receiver-initiated data transfers is summarized in FIGS. 2(a)-(d).
In each of FIGS. 2(a)-(d), the time axis runs positive in the
direction indicated by the arrow. Although not explicitly mentioned
in the following discussion, it should be understood that each
communication between devices includes an address of the device to
which the communication is being sent.
FIG. 2(a) illustrates the interaction between receiver 21 and
device 22 of FIG. 1 when receiver 21 initiates video data
recording. In FIG. 2(a) receiver 21 first issues a record command
to device 22. Receiver 21 then processes the record command in
conjunction with a security key retrieved from memory 35 to produce
a KEYCMD signal. Device 22 receives the record command and
similarly processes it in conjunction with a security key retrieved
from card port 45A to produce an ACK signal. Device 22 then
transmits the ACK signal to receiver 21. Receiver 21 compares the
received ACK signal with the KEYCMD signal to determine if they are
equal. Since a key card having a correct security key is not
installed in device 22, the KEYCMD signal and the ACK signal are
not equal. As a result, receiver 21 determines that the ACK signal
is "no good" (NG) and no data is output by receiver 21.
In FIG. 2(b), receiver 21 transmits a record command to device 23.
As in the manner previously described, both receiver 21 and device
23 process the recording command to produce, respectively, a KEYCMD
signal and an ACK signal. Device 23 transmits the ACK signal to
receiver 21. Receiver 21 compares the KEYCMD signal and the
received ACK signal. Since device 23 is engaged with a key card
having a correct security key, the ACK signal and the KEYCMD are
equal. Receiver 21 determines that the ACK signal is thus "OK" and
initiates the transmission of video data to device 23. Device 23
records the video data it receives.
FIGS. 2(c) and 2(d) illustrate the sequence of steps which occur
when receiver 21 issues a playback command to a peripheral device.
In FIG. 2(c), receiver 21 transmits a playback command to device
22. Receiver 21 processes the playback command in conjunction with
a security key retrieved from memory 35 to produce a KEYCMD signal.
Device 22 processes the received playback command in conjunction
with a security key retrieved from card port 45A to produce an ACK
signal. Device 22 transmits the ACK signal to receiver 21. Receiver
21 compares the KEYCMD signal with the received ACK signal to
determine if they are equal. Since a key card containing a correct
security key is not installed in device 22, the ACK signal is not
equal to the KEYCMD signal. Accordingly, receiver 21 determines
that the ACK signal is "no good" (NG). Nonetheless, device 22
reproduces a prerecorded video signal and transmits the reproduced
video data to receiver 21. Receiver 21 rejects the video data.
In FIG. 2(d), receiver 21 transmits a playback command to device
23. Receiver 21 process the playback command, as before, to produce
a KEYCMD signal. Device 23 processes the received playback command
in conjunction with a security key retrieved from card port 45B to
produce an ACK signal. Device 23 transmits this ACK signal to
receiver 21. Receiver 21 compares the KEYCMD signal to the received
ACK signal to determine if they are equal. Since key card 48 is
engaged in device 23 and key card 48 contains a valid security key,
the ACK signal and the KEYCMD signal are equal. Accordingly,
receiver 21 determines that the ACK signal is "OK". Device 23
reproduces a prerecorded video signal and transmits the reproduced
video data to receiver 21. Receiver 21 accepts the video data from
device 23 and decodes it, as described with reference to FIG.
1.
The signal processing and exchange of messages in peripheral
device-initiated data transfers is summarized in FIGS. 3(a)-(d). In
each of FIGS. 3(a)-(d), the time axis runs positive in the
direction indicated by the arrow. Each communication between the
devices includes an address of the device to which the
communication is being sent.
FIGS. 3(a) and 3(c) illustrate the interaction between device 22
and receiver 21 of FIG. 1 when device 22 initiates the transfer of
video data. In FIG. 3(a), device 22 first issues a send data
command to receiver 21. Device 22 then processes the send data
command in conjunction with a security key retrieved from card port
45A to produced a KEYCMD signal. Receiver 21 receives the send data
command and similarly processes it in conjunction with a security
key retrieved from memory 35 to produce an ACK signal. Receiver 21
then transmits the ACK signal to device 22. Device 22 compares the
received ACK signal with the KEYCMD signal to determine if they are
equal. Since a key card having a correct security key is not
installed in device 22, the KEYCMD signal and the ACK signal are
not equal. As a result, device 22 determines that the ACK signal is
"no good" (NG). Nonetheless, receiver 21 attempts to transmit
broadcast video data to device 22. Device 22 rejects the video
data.
In FIG. 3(c), device 22 first transmits a receive data command to
receiver 21. Device 22 then processes the receive data command in
conjunctions with a security key retrieved from card port 45A to
produce a KEYCMD signal. Receiver 21 receives the receive data
command and similarly processes it in conjunction with a security
key retrieved from memory 35 to produce an ACK signal. Receiver 21
then transmits the ACK signal to device 22. Device 22 compares the
received ACK signal with the KEYCMD signal to determine if they are
equal. Since a key card having a correct security key is not
installed in device 22, the KEYCMD signal and the ACK signal are
not equal. As a result, device 22 determines that the ACK signal is
"no good" (NG) and no data is output by device 22.
FIGS. 3(b) and 3(d) each illustrate the sequence of operations that
occur when device 23 issues a command to receiver 21. In FIG. 3(b),
device 23 first transmits a send data command to receiver 21.
Device 23 processes the send data command in conjunction with a
security key retrieved from card port 45B to produce a KEYCMD
signal. Receiver 21 processes the send data command in conjunction
with a security key retrieved from memory 35 to produce an ACK
signal. Receiver 21 then transmits the ACK signal to device 23.
Device 23 compares the KEYCMD signal with the received ACK signal
to determine if they are equal. Since key card 48 is engaged in
device 23 and key card 48 contains a valid security key, the ACK
signal and the KEYCMD signal are equal. Accordingly, device 23
determines that the ACK signal is "OK". Receiver 21 transmits video
data to device 23 which records the video data.
In FIG. 3(d), device 23 first transmits a receive data command to
receiver 21. Device 23 processes the receive data command in
conjunction with a security key retrieved from card port 45B to
produce a KEYCMD signal. Receiver 21 processes the receive data
command in conjunction with a security key retrieved from memory 35
to produce an ACK signal Receiver 21 then transmits the ACK signal
to device 23. Device 23 compares the KEYCMD signal with the
received ACK signal to determine if they are equal. Since key card
48 is engaged in device 23 and key card 48 contains a valid
security key, the ACK signal and the KEYCMD signal are equal.
Accordingly, device 23 determines that the ACK signal is "OK".
Device 23 reproduces a prerecorded video signal and transmits the
reproduced video data to receiver 21. Receiver 21 accepts the video
data from device 23 and processes it, as described above.
In a dubbing mode, two peripheral devices, each installed with a
key card having the same security key, reproduce and record,
respectively, prerecorded video data. A master peripheral device
initiates a video data transfer by transmitting to data bus 24 an
address of a slave peripheral device along with a record command or
a playback command. As described in the preceding, the slave device
reads and recognizes the address, configures itself according to
the command, and returns an address and an ACK signal. As also
described in the preceding, the master device reads and recognizes
the address and processes the ACK signal to determine its validity.
If the ACK signal is "OK" then a data transfer according to the
command is executed; otherwise, no data transfer occurs.
The communication protocol of the apparatus of FIG. 1 is summarized
in the flow diagram of FIG. 4. For ease of explanation, the term
"Master" is employed to indicate the device which initiates a data
transfer. The term "Slave" is employed to indicate the device which
is addressed by the Master.
In step S1, the Master transmits an address of the Slave and a
command to data bus 24. In step S2, the Slave receives the command
and the Master and the Slave, separately process the command in
accordance with security key data obtained locally. The Master
produces a KEYCMD signal as a function of the command and its
security key. The Slave produces an ACK signal as a function of the
received command and its security key.
In step S3, the Slave transmits an address of the Master and the
ACK signal to data bus 24. In step S4, the Master receives the ACK
signal and determines whether the ACK signal is equal to the KEYCMD
signal. If the two signals are not equal, then processing follows
step S5; otherwise, processing follows step S6. In step S5, the
Master inhibits or simply does not execute a video data transfer
between the Master and the Slave. In step S6, the Master executes a
video data transfer by transmitting an address of the Slave and
video data to the Slave, or by receiving and recognizing its own
address and receiving video data transmitted by the Slave.
A second embodiment of the video data communication system
according to the present invention is illustrated in FIG. 5. Such
video data communication system is comprised of a receiver 25, a
data bus 24, and one or more peripheral devices. The peripheral
devices may transmit and/or receive control signals and/or video
data through data bus 24. Two such peripheral devices are
illustrated in FIG. 5, specifically, a recording/reproducing device
26 and a recording/reproducing device 27. Each of receiver 25,
device 26, and device 27 is connected to data bus 24 and is capable
of transmitting and receiving control signal and video data through
data bus 24.
Receiver 25 is suited for receiving, descrambling, enciphering,
deciphering, and decoding an input digital video signal.
Specifically, receiver 25 is comprised of a tuner 30, a descrambler
31, a switch 32, an I/O port 33, a controller 134, a memory 35, a
switch 36, an encipherer 38, a decipherer 39, and a decoder 37.
Elements of FIG. 5 having the same structure and function as the
corresponding elements of FIG. 1 are indicated by the same
reference numeral used in FIG. 1. Tuner 30 is coupled to
descrambler 31. Descrambler 31 descrambles, as needed, the selected
digital video signal provided by tuner 30 and provides an
unscrambled version of the digital video signal to encipherer
38.
Encipherer 38 is coupled to descrambler 31, controller 134, and
switch 32. Utilizing an encryption key provided by controller 134,
encipherer 38 encrypts the descrambled video signal provided by
descrambler 31. The encrypted video signal is provided to switch
32.
Switch 32 is further connected to controller 134 and I/O port 33.
Switch 36 is coupled to controller 134, decipherer 39 and I/O port
33. I/O port 33 is further connected to data bus 24 and to
controller 134.
Decipherer 39 is coupled to controller 134 and decoder 37.
Decipherer 39 receives an encryption key from controller 134 to
decrypt video data provided from switch 36. Decipherer 39 supplies
decrypted video data to decoder 37. Decoder 37 provides uncoded
digital video signal data to a video display device (not
shown).
Controller 134 is coupled to memory 35. In response to commands
provided by a user, or according to a prestored set of
instructions, controller 134 transmits to or receives from data bus
24, through I/O port 33, address, control and data signals. By
manipulating switch signals provided to switches 32 and 36,
controller 134 controls the flow of digital video data through I/O
port 33. In an alternate embodiment (not shown), controller 134
directly controls the operation of I/O port 33 with I/O port
control signals and monitors data flowing through I/O port 33.
Controller 134 additionally controls the encryption and decryption
of video data by receiver 25. Controller 134 provides an encryption
key to encipherer 38 for the encryption of descrambled video data.
Similarly, controller 134 provides an encryption key to decipherer
39 to decrypt the video data supplied through switch 36. As
detailed below, the encryption key is either retrieved from memory
35 or from data bus 24.
Recording/reproducing device 26 is comprised of an I/O port 40A, a
switch 41A, a recording/reproducing section 42A, a switch 43A, a
controller 144A, a card port 45A, a decipherer 46A, and an
encipherer 47A. I/O port 40A is coupled to data bus 24, controller
144A, switch 41A, and switch 43A. I/O port 40A routes address,
control and data signals to and from data bus 24 and controller
144A. Switch 41A is further coupled to controller 144A and
decipherer 46A. Switch 43A is further coupled to controller 144A
and encipherer 47A. Controller 144A is coupled to card port 45A,
decipherer 46A and encipherer 47A. Recording/reproducing section
42A is coupled to decipherer 46A and encipherer 47A.
Decipherer 46A receives an encryption key from controller 144A and
encrypted video data from switch 41A. Decipherer 46A decrypts the
encrypted data according to the encryption key and provides
decrypted data to section 42A. Encipherer 47A receives an
encryption key from controller 144A and video data from section
42A. Encipherer 47A encrypts the video data according to the
encryption key and provides the encrypted video data to switch
43A.
In response to commands provided by a user or according to a
prestored set of instructions, and in dependence upon signals
supplied by card port 45A, controller 144A transmits to or receives
from data bus 24, through I/O port 40A, address, control and data
signals. By manipulating switch signals provided to switches 41A
and 43A, controller 144A controls the flow of digital video data
through I/O port 40A. In an alternate embodiment (not shown),
controller 144A further directly controls the operation of I/O port
40A with I/O port control signals and monitors data flowing through
I/O port 40A.
As illustrated, device 27 is substantially the same as device 26,
like elements being denoted by like reference numerals with the
exception of the terminating letter A and B. Key card 48, which is
shown attached to card port 45B of device 27, stores a valid
security key corresponding to a security key stored in memory
35.
Operation of the second embodiment of the video data communication
system will be described below. One of the most important features
of this second embodiment is that each signal, except video data
signals, transmitted via data bus 24 is accompanied by an address
signal corresponding to an address of a particular device. As in
the first embodiment, each device attached to data bus 24 is
assigned a particular address. Video data is transmitted to data
bus 24 in an encrypted form but without an address. Each device
connected to data bus 24 and capable of receiving data therefrom
has access to encrypted data on data bus 24. However, only devices
having a correct encryption key can decrypt the encrypted video
data. In this manner, encrypted video data is provided to devices
connected to data bus 24 but only devices having a correct
encryption key can decrypt and utilize the video data. The
encryption key may be stored in each decrypting device or provided
by the device supplying the encrypted data.
This communication protocol allows for many different sequences of
signal transfer between devices connected to data bus 24. Examples
of these signal transfer sequences, implemented in different modes
of operation of the present invention, will be described in detail
below. In one mode of operation, broadcast digital video data
signals are received by receiver 25, encrypted, and transmitted to
data bus 24 for receipt by a peripheral device which decrypts the
signals and displays, records, or otherwise processes the decrypted
data. In another mode, prerecorded video data are reproduced,
encrypted, and transmitted by a peripheral device to a decoding
device for decryption, decoding, and subsequent display. In still
another mode, prerecorded video data are reproduced, encrypted, and
transmitted by one peripheral device to another peripheral device
which decrypts and records the video data.
In a broadcast encrypt/decrypt display mode, receiver 25 receives a
broadcast video signal and supplies the broadcast signal to a
decryption display device (not shown on FIG. 5) connected to data
bus 24. An example of such a decryption display device is
illustrated in FIG. 11 and will be described in detail in a later
section. Tuner 30 selectively receives a broadcast signal and
provides the data to descrambler 31. Descrambler 31 descrambles the
broadcast video signal and provides a descrambled version of the
signal to encipherer 38.
Controller 134 configures I/O port 33 to couple controller 134 with
data bus 24 and then transmits an address of a particular display
device along with a display command to data bus 24. The display
device (not shown in FIG. 5) reads the address on data bus 24,
recognizes the address as its own, and reads the accompanying
display command from data bus 24. The display device processes the
display command to generate an ACK signal and transmits an address
of receiver 25 along with the ACK signal to data bus 24. The
address and ACK signal supplied by the display device are received
by controller 134 via I/O port 33.
Controller 134 retrieves a security key from memory 35 and
generates a KEYCMD signal as a function of the display command and
the retrieved security key. The KEYCMD signal is then compared to
the received ACK signal. If the ACK signal is equal to the KEYCMD
signal, then controller 134 transmits an address signal,
corresponding to the selected display device, along with an
encryption key, and appropriately manipulates I/O port 33 to route
the address signal and the encryption key to data bus 24.
Controller 134 provides the encryption key to encipherer 38.
Encipherer 38 encrypts the descrambled signal according to the
encryption key and provides an encrypted signal to switch 32.
Controller 134 also issues a switch command to switch 32, causing
it to close, and an I/O port control signal to I/O port 33, causing
it to couple switch 32 with data bus 24.
The encrypted video signal transmitted from encipherer 38
propagates through switch 32 and I/O port 33 to data bus 24. The
address signal on data bus 24 is recognized by the display device
and the subsequently transmitted encryption key is received and
stored. Encrypted video signal is retrieved from data bus 24 and is
decrypted according to the received encryption key, processed, and
displayed. Other peripheral devices connected to data bus 24 read
the video data present on data bus 24, however, only a device which
possesses a correct encryption key can decrypt the data.
In an alternate embodiment, the receiver does not transmit an
address along with the encryption key to the data bus and instead
the encryption key is prestored in the display device. The
encrypted data is still transmitted to data bus 24 without an
address.
In an encrypt/decrypt recording mode of operation, receiver 25
receives a broadcast signal, encrypts the signal according to an
encryption key, and transmits the key and the encrypted signal via
data bus 24 to a particular peripheral device which records the
signal. Specifically, controller 134 configures I/O port 33 to
couple controller 134 with data bus 24 and then transmits an
address of a particular recording device along with a record
command to data bus 24. Assuming, for example, that the address
transmitted corresponds to an address of device 26, controller
144A, through I/O port 40A, reads the address on data bus 24,
recognizes the address as its own, and reads the accompanying
record command from data bus 24. Controller 144A processes the
record command to generate an ACK signal.
Specifically, controller 144A polls card port 45A for a security
key and generates an ACK signal as a function of the received
record command and the signal returned by card port 45A. Controller
144A then transmits an address of receiver 25 and the ACK signal
via I/O port 40A to data bus 24. The address and ACK signal
supplied by device 26 is received by controller 134 via I/O port
33.
Controller 134 retrieves a security key from memory 35 and
generates a KEYCMD signal as a function of the record command and
the retrieved security key. The KEYCMD signal is then compared to
the received ACK signal. If the ACK signal is equal to the KEYCMD
signal, then controller 134 transmits an address signal of the
particular recording device along with the encryption key to data
bus 24 through I/O port 33 and configures switch 32 and I/O port 33
for the transmission of encrypted video data from encipherer 38 to
data bus 24 to initiate the transfer of video data. If the ACK
signal is not equal to the KEYCMD signal, then controller 134
issues a switch command signal, causing switch 32 to open, to
prevent the flow of encrypted broadcast video data to data bus
24.
Since, as illustrated in FIG. 5, card port 45A of device 26 is not
coupled to a card key containing a correct security key, controller
144A will, in that case, generate an ACK signal which is not equal
to the KEYCMD signal produced by controller 134 and no video data
transfer will occur. Thus, the supply of encrypted broadcast video
data to a particular recording device depends upon the installation
of an appropriate key card in the card port of the particular
device.
When device 27 is selected to record broadcast video data,
controller 134 outputs an address of device 27 along with a record
command to data bus 24 through I/O port 33. Controller 144B,
through I/O port 40B reads the address on data bus 24, recognizes
the address signal as its own, and reads the accompanying record
command. Controller 144B retrieves a security key from key card 48
via card port 45B. Controller 144B generates an ACK signal as a
function of the received record command and the retrieved security
key. Controller 144B transmits an address of receiver 25 and the
ACK signal to data bus 24 through I/O port 40B.
As above, controller 134 reads the address signal and the ACK
signal, generates a KEYCMD signal, and compares the ACK and KEYCMD
signals. If the security key contained in key card 48 corresponds
to the security key contained in memory 35, the ACK signal and the
KEYCMD signal are equal. Meanwhile, controller 144B supplies a
switch control signal to switch 41B, causing it to close, thereby
connecting I/O port 40B with decipherer 46B. Further, I/O port 40B
is configured to route video data from data bus 24 to decipherer
46B. After verifying that the two security keys correspond,
controller 134 facilitates the transmission to device 27 of an
address of device 27 along with an encryption key followed by
encrypted video data without an address.
Controller 144B, through I/O port 40B, reads the address on data
bus 24, recognizes the address as its own, and reads the
accompanying encryption key from data bus 24. Controller 144B
supplies the encryption key to decipherer 46B. Encrypted video data
on data bus 24 is retrieved and passed through I/O port 40B and
switch 41B to decipherer 46B for deciphering according to the
retrieved encryption key. Decipherer 46B supplies decrypted video
data to section 42B for recording. As a result, recording devices
having the selected address and provided with a key card 48 having
a correct security key retrieve, decrypt, and record encrypted
video data supplied by receiver 25.
In a playback mode of operation, receiver 25 initiates the playback
of prerecorded data from a peripheral device. Controller 134
transmits an address signal, corresponding to an address of a
particular peripheral device, along with a playback command to data
bus 24 through I/O port 33. Assuming, for example, that the address
signal corresponds to an address of device 26, controller 144A,
through I/O port 40A, reads the address on data bus 24, recognizes
the address as its own, and reads the accompanying playback command
from data bus 24. As described previously, controller 144A
generates an ACK signal as a function of the playback command and a
signal provided by card port 45A. Controller 144A then transmits an
address of receiver 25 and this ACK signal via I/O port 40A to data
bus 24. Controller 144A also issues a switch control signal to
switch 43A, causing it to close and configures I/O port 40A to
connect data bus 24 and switch 43A.
Controller 134, through I/O port 33, reads the address on data bus
24, recognizes the address as its own, and reads the accompanying
ACK signal. Controller 134 retrieves a security key from memory 35
and generates a KEYCMD signal as a function of the playback command
and the retrieved security key. The received ACK signal is compared
to the KEYCMD signal and, if they are equal, controller 134 issues
a switch control signal to switch 36, causing it to close, and
issues an I/O port control signal to I/O port 33, causing it to
route signals from data bus 24 to switch 36. However, if the ACK
signal does not equal the KEYCMD signal, then controller 134 issues
a switch control signal which causes switch 36 to open.
Since a key card having a correct security key is not installed in
device 26, the ACK signal produced by device 26 will not be
equivalent to the KEYCMD signal produced by controller 134. Even
though recording/reproducing section 42A may output encrypted
prerecorded video data to data bus 24 via switch 43A and I/O port
40A, the data will not reach decoder 37, since switch 36 will have
been opened.
In the case where controller 134 initially issues an address
corresponding to device 27, controller 144B reads and recognizes
the address, reads the accompanying playback command, and polls
card port 45B. Key card 48, having a security key corresponding to
that stored in memory 35, supplies the security key to controller
144B through card port 45B. Controller 144B generates an ACK signal
as a function of the received playback command and the security key
received from key card 48. The ACK signal and the address of
receiver 25 are transmitted via data bus 24 to controller 134 and
switch 43B is closed. Controller 134 reads and recognizes the
address, reads the accompanying ACK signal, and generates a KEYCMD
signal as a function of the playback command and a security key
obtained from memory 35. In this instance, the ACK signal and the
KEYCMD signal are equal, and accordingly, controller 134 causes
switch 36 to close.
Controller 144B outputs an address of receiver 25 along with an
encryption key to data bus 24. Recording/reproducing section 42B
outputs a prerecorded video data signal to encipherer 47B which
encrypts the signal according to the encryption key. Encipherer 47B
outputs an encrypted data signal to data bus 24 via switch 43B and
I/O port 40B.
Controller 134 reads and recognizes the address and retrieves the
accompanying encryption key. Controller 134 provides the encryption
key to decipherer 39. The encrypted video data signal is retrieved
from data bus 24 and supplied through I/O port 33 and switch 36 to
decipherer 39. Decipherer 39 decrypts the encrypted signal
according to the encryption key and supplies a decrypted video
signal to decoder 37. Decoder 37 decodes the prerecorded video data
signal and supplies the decoded signal to a video display (not
shown). Receiver 25 thus decrypts and decodes video data reproduced
by a peripheral device in which a key card having a correct
security key is installed.
In each of the above modes, it is alternately contemplated that one
or more of the I/O ports has a fixed and inflexible structure which
prevents its manipulation by a connected controller. In each of the
above modes, it is further alternately contemplated that an address
and the encryption key are not transmitted prior to the
transmission of encrypted video data, but rather that the
encryption key is prestored in the device which retrieves the
encrypted video data.
The signal processing and interchange of messages in
receiver-initiated data transfers according to the embodiment of
the invention shown in FIG. 5 are diagrammatically represented in
FIGS. 6(a)-(d). In each of FIGS. 6(a)-(d), the time axis runs
positive in the direction indicated by the arrow. Although not
explicitly mentioned in the following discussion, it should be
understood that each communication between devices, with the
exception of encrypted video data, includes an address of the
device to which the communication is being sent.
FIG. 6(a) illustrates the interaction between receiver 25 and
device 26 of FIG. 5 when receiver 25 initiates video data
recording. In FIG. 6(a) receiver 25 first issues a record command
to device 26. Receiver 25 then processes the record command in
conjunction with a security key retrieved from memory 35 to produce
a KEYCMD signal. Device 26 receives the record command and
similarly processes it in conjunction with a security key retrieved
from card port 45A to produce an ACK signal. Device 26 then
transmits the ACK signal to receiver 25. Receiver 25 compares the
received ACK signal with the KEYCMD signal to determine if they are
equal. Since a key card having a correct security key is not
installed in device 26, the KEYCMD signal and the ACK signal are
not equal. As a result, receiver 25 determines that the ACK signal
is "no good" (NG) and no data is output by receiver 25.
In FIG. 6(b), receiver 25 transmits a record command to device 27.
As in the manner previously described, both receiver 25 and device
27 process the recording command to produce, respectively, a KEYCMD
signal and an ACK signal. Device 27 transmits the ACK signal to
receiver 25. Receiver 25 compares the KEYCMD signal and the
received ACK signal. Since device 27 is engaged with a key card
having a correct security key, the ACK signal and the KEYCMD are
equal. Receiver 25 determines that the ACK signal is thus "OK" and
transmits an encryption key to device 27. Receiver 25 also sends
encrypted video data to data bus 24. Device 27 retrieves, decrypts,
and records the encrypted video data.
FIGS. 6(c) and 6(d) illustrate the sequence of steps which occur
when receiver 25 issues a playback command to a peripheral device.
In FIG. 6(c), receiver 25 transmits a playback command to device
26. Receiver 25 processes the playback command in conjunction with
a security key retrieved from memory 35 to produce a KEYCMD signal.
Device 26 processes the received playback command in conjunction
with a security key retrieved from card port 45A to produce an ACK
signal. Device 26 transmits the ACK signal to receiver 25. Receiver
25 compares the KEYCMD signal with the received ACK signal to
determine if they are equal. Since a key card containing a correct
security key is not installed in device 26, the ACK signal is not
equal to the KEYCMD signal. Accordingly, receiver 25 determines
that the ACK signal is "no good" (NG). Nonetheless, device 26
attempts to send an encryption key and encrypted reproduced video
signal data to receiver 25 via data bus 24, but receiver 25 does
not retrieve the key and the video data.
In FIG. 6(d), receiver 25 transmits a playback command to device
27. Receiver 25 process the playback command, as before, to produce
a KEYCMD signal. Device 27 processes the received playback command
in conjunction with a security key retrieved from card port 45B to
produce an ACK signal. Device 27 transmits this ACK signal to
receiver 25. Receiver 25 compares the KEYCMD signal to the received
ACK signal to determine if they are equal. Since key card 48 is
engaged in device 27 and key card 48 contains a valid security key,
the ACK signal and the KEYCMD signal are equal. Accordingly,
receiver 25 determines that the ACK signal is "OK". Device 27
reproduces a prerecorded video signal and transmits an encryption
key and encrypted reproduced video data to receiver 25. Receiver 25
accepts the encryption key and retrieves the encrypted video
data.
The signal processing and interchange of messaging in
device-initiated data transfers according to the second embodiment
of the invention are diagrammatically represented in FIGS.
7(a)-(d). In each of FIGS. 7(a)-(d), the time axis runs positive in
the direction indicated by the arrow. Although not explicitly
mentioned in the following discussion, it should be understood that
each communication between devices, with the exception of encrypted
video data, includes an address of the device to which the
communication is being sent.
FIGS. 7(a) and 7(c) illustrate the interaction between device 26
and receiver 25 of FIG. 1 when device 26 initiates the transfer of
video data. In FIG. 7(a), device 26 first issues a send data
command to receiver 25. Device 26 then processes the send data
command in conjunction with a security key retrieved from card port
45A to produced a KEYCMD signal. Receiver 25 receives the send data
command and similarly processes it in conjunction with a security
key retrieved from memory 35 to produce an ACK signal. Receiver 25
then transmits the ACK signal to device 26. Device 26 compares the
received ACK signal with the KEYCMD signal to determine if they are
equal. Since a key card having a correct security key is not
installed in device 26, the KEYCMD signal and the ACK signal are
not equal. As a result, device 26 determines that the ACK signal is
"no good" (NG). Nonetheless, receiver 25 attempts to transmit an
encryption key and encrypted broadcast video data to device 26 via
data bus 24, but device 26 does not retrieve the encryption key nor
the video data.
In FIG. 7(c), device 26 first transmits a receive data command to
receive 25. Device 26 then processes the receive data command in
conjunction with a security key retrieved from card port 45A to
produce a KEYCMD signal. Receiver 25 receives the receive data
command and similarly processes it in conjunction with a security
key retrieved from memory 35 to produce an ACK signal. Receiver 25
then transmits the ACK signal to device 26. Device 26 compares the
received ACK signal with the KEYCMD signal to determine if they are
equal. Since a key card having a correct security key is not
installed in device 26, the KEYCMD signal and the ACK signal are
not equal. As a result, device 26 determines that the ACK signal is
"no good" (NG) and no data is output by device 26.
Each of FIGS. 7(b) and 7(d) illustrates the sequence of operations
that occur when device 27 issues a command to receiver 25. In FIG.
7(b), device 27 first transmits a send data command to receiver 25.
Device 27 processes the send data command in conjunction with a
security key retrieved from card port 45B to produce a KEYCMD
signal. Receiver 25 processes the send data command in conjunction
with a security key retrieved from memory 35 to produce an ACK
signal. Receiver 25 then transmits the ACK signal to device 27.
Device 27 compares the KEYCMD signal with the received ACK signal
to determine if they are equal. Since key card 48 is engaged in
device 27 and key card 48 contains a correct security key, the ACK
signal and the KEYCMD signal are equal. Accordingly, device 27
determines that the ACK signal is "OK". Receiver 25 transmits an
encryption key and encrypted video data to device 27 which decrypts
and records the video data.
In FIG. 7(d), device 27 first transmits a receive data command to
receiver 25. Device 27 processes the receive data command in
conjunction with a security key retrieved from card port 45B to
produce a KEYCMD signal. Receiver 25 processes the receive data
command in conjunction with a security key retrieved from memory 35
to produce an ACK signal. Receiver 25 transmits the ACK signal to
device 27. Device 27 compares the KEYCMD signal with the received
ACK signal to determine if they are equal. Since key card 48 is
engaged in device 27 and key card 48 contains a correct security
key, the ACK signal and the KEYCMD signal are equal. Accordingly,
device 27 determines that the ACK signal is "OK". Device 27
reproduces and encrypts a prerecorded video signal and transmits
the encryption key and the encrypted reproduced video data to
receiver 25. Receiver 25 accepts, decrypts, and further processes
the video data as described above.
In an encrypt/decrypt dubbing mode, encrypted data is communicated
between two peripheral devices, such as the devices 26 and 27, each
installed with a key card having the same security key. A master of
such peripheral devices initiates a video data transfer by
transmitting to data bus 24 an address of a slave among the
peripheral devices along with a record command or a playback
command. As described in the preceding, the slave device reads and
recognizes the address, configures itself according to the command,
and returns an address and an ACK signal.
As also described in the preceding, the master device reads and
recognizes the address and processes the ACK signal to determine
its validity. If the ACK signal is "OK" then a data transfer
according to the command is executed; otherwise, no data transfer
occurs. As part of a data transfer, the transmitting device
reproduces and encrypts, according to an encryption key,
prerecorded data. The encryption key is sent with the address of
the receiving peripheral device to data bus 24. The other receiving
peripheral device reads and recognizes the address and retrieves
the encryption key. The transmitting device sends the encrypted
data to data bus 24 and the receiving device retrieves, decrypts,
and records the encrypted data.
The communication protocol of the apparatus of FIG. 5 is summarized
in the flow diagram of FIG. 8. For ease of explanation, the term
"Master" is employed to indicate the device which initiates a data
transfer. The term "Slave" is employed to indicate the device which
is addressed by the Master.
In step S7, the Master transmits an address of the Slave and a
command to data bus 24. In step S8, the Slave receives the command
and the Master and the Slave separately process the command in
accordance with security key data obtained locally. The Master
device produces a KEYCMD signal as a function of the command and
its security key. The Slave produces an ACK signal as a function of
the received command and its security key.
In step S9, the Slave transmits an address of the Master and the
ACK signal to data bus 24. In step S10, the Master receives the ACK
signal and determines whether the ACK signal is equal to the KEYCMD
signal. If the two signals are not equal, then processing follows
step S11; otherwise, processing follows step S12. In step S11, the
Master inhibits or simply does not execute a video data transfer
between the Master and the Slave. In step S12, the Master executes
a video data transfer by transmitting an encryption key and
encrypted video data to the Slave, or by receiving and retrieving
an encryption key and encrypted video data transmitted by the
Slave.
FIG. 9 illustrates a display device 28-1 suitable for connection to
data bus 24 of the first embodiment of the invention described
above with reference to FIG. 1. Display device 28-1 is comprised of
a cathode-ray tube (CRT) 60, a signal processor 59, a decoder 58, a
descrambler 57, a memory 56, a controller 55A, a switch 54, a tuner
53, a digital tuner 52, a switch 51, and an I/O port 59. CRT 60 and
signal processor 59 are conventional devices which together
comprise a conventional display apparatus. Tuner 53 is a
conventional broadcast tuner which receives an unscrambled video
signal. Tuner 52 is a satellite digital signal tuner which receives
scrambled video data signals. Tuner 53, tuner 52 and switch 51 are
coupled to inputs of switch 54 and each provides a respective video
signal thereto.
I/O port 50 is coupled to data bus 24 (not shown), switch 51, and
controller 55A. I/O port 50 routes data signals to switch 51 and
routes address, control and data signals to controller 55A.
Controller 55A is further coupled to switch 51, memory 56, switch
54, descrambler 57 and decoder 58. Memory 56 stores one or more
security keys which controller 55A retrieves as needed. Controller
55A controls the state of switches 54 and 51 with switch control
signals. Controller 55A can also enable or disable the operations
of decoder 58 and descrambler 57.
Descrambler 57 is further coupled to the output of switch 54 and
the input of decoder 58. When enabled by controller 55A,
descrambler 57 descrambles video data and supplies unscrambled
video data to decoder 58. When disabled by controller 55A,
descrambler 57 passes video signals from switch 54 to decoder
58.
Decoder 58 is further coupled to the input of signal processor 59.
When enabled by controller 55A, decoder 58 decodes video data and
supplies decoded video data to signal processor 59. When disabled
by controller 55A, decoder 58 passes video signals from descrambler
57 to signal processor 59.
Display device 28-1 has three modes of operation. In the first
mode, controller 55A causes switch 54 to link tuner 53 with
descrambler 57. Controller 55A disables descrambler 57 and decoder
58, allowing signal processor 59 and CRT 60 to display ordinary
video data received by tuner 53.
In the second mode, controller 55A causes switch 54 to link tuner
52 with descrambler 57. Controller 57 enables descrambler 57 and
decoder 58. Descrambler 57 descrambles a scrambled and coded video
signal supplied by tuner 52 and supplies an unscrambled, though
still coded, video signal to decoder 58. Decoder 58 decodes the
coded signal and provides an uncoded video signal to signal
processor 59 for display.
In the third mode, controller 55A reads an address signal on data
bus 24 through I/O port 50. If the address corresponds to an
address previously assigned to device 28-1, then controller 55A
recognizes the address as such and processing proceeds as follows.
Controller 55A retrieves a display command from data bus 24.
Controller 55A generates an ACK signal as a function of the display
command and a security key retrieved from memory 56. Controller
transmits an address of the device which sent the display command
along with the ACK signal to data bus 24 through I/O port 50.
Controller 55A also causes switch 51 to close, connecting I/O port
50 with switch 54, and causes switch 54 to connect switch 51 with
descrambler 57. Controller 55A also enables descrambler 57 and
decoder 58.
Controller 55A monitors data bus 24 for another address signal
corresponding to device 28-1. Upon receipt of such an address,
video data is then retrieved from data bus 24 and supplied through
I/O port 50, switch 51, and switch 54 to descrambler 57.
Descrambler 57 descrambles, as needed, the retrieved video data and
provides an unscrambled video signal to decoder 58. Decoder 58
decodes the signal and supplies an uncoded video signal to signal
processor 59 for display on CRT 60.
FIG. 10 illustrates a decoding device 29-1 suitable for connection
to data bus 24 of the first embodiment of the invention in place of
the receiver 21. Decoding device 29-1 is comprised of a memory 72,
a controller 71A, an I/O port 70, a switch 73, and a decoder 74.
Decoder 74 and switch 73 have the same structure and function as
their counterparts decoder 37 and switch 36 of receiver 21.
Controller 71A is coupled to memory 72, I/O port 70, and switch 73.
Switch 73 is further connected to decoder 74 and I/O port 70. I/O
port 70 is further coupled to data bus 24.
As in the processing described above, controller 71A monitors data
bus 24 for an address signal of device 29-1. Upon recognizing such
an address signal, controller 71A retrieves a display command from
data bus 24 and generates an ACK signal as a function of the
display command and a security key retrieved from memory 72. The
ACK signal is transmitted with the appropriate address to data bus
24. Video data accompanied by an address of device 29-1 is
retrieved and routed through I/O port 70 and switch 73 to decoder
74. Decoder 74 decodes the video signal and provides an uncoded
video signal to a display (not shown).
As earlier noted, FIG. 11 illustrates a display device 28-2
suitable for connection to data bus 24 of the second embodiment of
the invention. Display device 28-2 is comprised of the elements
described above in connection with the display device 28-1, and
which are interconnected and function in the same manner as in
display device 28-1 except as described in the following. Unlike
display device 28-1, display device 28-2 includes a decipherer 61
interposed between switch 51 and switch 54 and controller 55A is
replaced by controller 55B. Controller 55B is additionally coupled
to decipherer 61 and supplies an encryption key thereto. Decipherer
61 decrypts encrypted video data supplied from switch 51 and
supplies decrypted video data to switch 54.
In accordance with the protocol of the second embodiment,
controller 55B monitors data bus 24 for an address of device 28-2
and an accompanying display command. An ACK signal is generated as
a function of the retrieved display command a security key
retrieved from memory 56. Controller 55B then transmits an
appropriate address and the ACK signal to data bus 24. Controller
55B monitors data bus 24 for the address of device 28-2 and an
accompanying encryption key. Upon receipt, decipherer 51 is
supplied with the encryption key, and I/O port 50 and switch 51 are
configured to route encrypted data through to decipherer 61.
Decipherer 61 decrypts the video data and supplies a decrypted
signal suitable for subsequent processing as described with respect
to device 28-1.
FIG. 12 illustrates a decoding device 29-2 suitable for connection
to data bus 24 in place of the receiver 25 in the second embodiment
of the invention. Decoding device 29-2 is comprised of the same
elements as decoding device 29-1, and such elements are
interconnected and function in the same manner as in decoding
device 29-1 except as described in the following. Unlike decoding
device 29-1, decoding device 29-2 includes a decipherer 76
interposed between switch 73 and decoder 74, and controller 71A is
replaced by controller 71B. Controller 71B is additionally coupled
to decipherer 76 and supplies an encryption key thereto. Decipherer
76 decrypts encrypted video data supplied from switch 73 and
supplies decrypted video data to decoder 74.
As described in the process above, controller 71B monitors data bus
24 for an address signal of device 29-2. Upon recognizing such an
address signal, controller 71B retrieves a display command from
data bus 24 and generates an ACK signal as a function of the
display command and a security key retrieved from memory 72. The
ACK signal is transmitted with the appropriate address to data bus
24. An encryption key accompanied by an address of device 29-2 is
retrieved by controller 71B from data bus 24. Encrypted video data
supplied from data bus 24 is routed through I/O port 70 and switch
73 to decipherer 76. Decipherer 76 decrypts the encrypted video
data and provides a decrypted video signal to decoder 74. Decoder
74 decodes the decrypted video signal and provides an uncoded video
signal to a display (not shown).
Although illustrative embodiments of the present invention and
modifications thereof have been described in detail herein, it is
to be understood that this invention is not limited to these
precise embodiments and modifications, and that other modifications
and variations may be effected therein by one skilled in the art
without departing from the scope and spirit of the invention as
defined by the appended claims.
* * * * *