Note: Descriptions are shown in the official language in which they were submitted.
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RECORDED MEDIUM FOR VIDEO CONTROL SYSTEM
s RELATED COPENDING APPLICATIONS
U.S. Patent Application Ser. No. 07/501,684, now U.S. Pat. No. 4,991,208,
issued Feb. 5, 1991, filed the same date as this, for Video Control System
Having
Session Encryption Key is concerned with video control systems having a
session
to encryption key.
U.S. Patent Application Ser. No. 07/501,682, now U.S. Pat. No. 5,046,092,
issued Sept. 3, 1991, filed the same date as this, for Video Control System
For
t5 Transmitted Programs is concerned with video control systems wherein the
video
program is transmitted to a terminal.
BACKGROUND OF THE INVENTION
2o This invention is concerned with video control systems and more
particularly
is concerned with such systems concerned with recorded media for such systems.
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It is desirable to provide a video control system which decrypts encrypted
broadcasts or recorded copies of video material such that the subsequent
viewing is
controlled. This allows the owner to either forbid viewing, or collect revenue
at his or
her discretion.
In the prior art, a software distribution system is known wherein a computer
program is downloaded once, followed by an access key to allow use of it on
each
subsequent use. This system uses a dynamic key that constantly changes, and is
directly related to an user's decoder box, both by ID and an internal dynamic
counter.
Also known is a video system that autonomously controls the viewing of a
recording for either 24 hours or once only. It does not have the power of
control
desired.
is SUMMARY OF THE INVENTION
Briefly, a video recording medium storing a video program includes a series
of television fields including a first field containing both a random digital
code
encrypted according to a code encryption key and program identification data,
and a
second field containing an unintelligible video signal previously transformed
from an
2o intelligible video signal according to the random digital code.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a video system embodying the invention; and
FIG. 2 shows an encryption arrangement according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
Reference is made to FIG. 1 which is a block diagram of a video system 10
embodying the invention. The video system comprises a central facility 1 l, a
terminal
12, and a duplex communication link 13 between central facility 11 and
terminal 12.
3o An overview of the system is first given.
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Terminal 12 is provided with a video program including a series of television
fields including first field containing both a random digital code encrypted
according
to a code encryption key and program identification data, and a second field
containing an unintelligible video signal previously transformed from an
intelligible
video signal according to the random digital code.
The video program may be transmitted by broadcast, cable, satellite, fiber, or
any other transmission medium 14. Alternative the video program may be stored
on a
video recording medium 15 such as magnetic tape or video disk and played by
player
to 16. The unintelligible video signal may be either analog or digital.
A second field containing both a random digital code encrypted according to a
code encryption key and program identification data, and is followed according
to a
third field containing an unintelligible video signal previously transformed
from an
is intelligible video signal according to the random digital code of the
second field.
Terminal 12 includes means 17 to store terminal identification data and means
to send to the central facility I I the terminal identification data and the
program
identification data over link 13.
Central facility 11 includes a data base 19 for storing and retrieving at
least
one code encryption key corresponding to the program identification data,
means 20
for sending the code encryption key from the central facility 11 to the
terminal 12,
and means 21 for generating billing data based on both terminal identification
data
and program identification data.
Terminal 12 further including means 22 for receiving the code encryption key
from central facility 1 l, decrypting means 23 for decrypting the encrypted
random
digital code of the first frame in accordance with the code encryption key,
and means
24 for transforming the unintelligible video signal of the second frame to the
intelligible video signal using the decrypted random digital code.
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Each terminal 12 may have a terminal specific encryption key and means 18
to send to the central facility the program identification data and the
terminal 11
identification data encrypted according to the terminal specific encryption
key. The
central facility 11 has means for storing a duplicate of the terminal specific
encryption key, means for encrypting the code encryption key according to the
terminal specific encryption key; and means for sending the encrypted code
encryption key from central facility 11 to terminal 12.
t o Terminal 12 further includes means 22 for receiving the encrypted code
encryption key from central facility 11, decryption means 23 for decrypting
the code
encryption key according to the terminal specific encryption key, and
decrypting the
encrypted random digital code of the first frame in accordance with the code
encryption key, and means 24 for transforming the unintelligible video signal
of the
is second frame to the intelligible video signal using the decrypted random
digital code.
Terminal 12 includes means to encrypt the terminal identification data
according to the terminal specific encryption key, means to send unencrypted
terminal identification data and encrypted terminal identification data to the
central
2o facility, which in turn includes means to compare unencrypted and encrypted
terminal identification data to verify terminal identity.
A plurality of code encryption keys may be used for one program wherein a
desired code encryption key is selected from the plurality of code encryption
keys in
2s accordance with code encryption key identification data corresponding to
the random
digital code encrypted with the desired code encryption key or a session
encryption
key.
Various features of the system are now discussed in more detail.
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System 10 controls the viewing of video programs, by which is meant any
video material, either transmitted or recorded, in television format
consisting of a
series of fields of lines. Two interlaced field make up a television frame.
Video programs are rendered unintelligible, e.g. scrambled, by any analog or
digital method, and are made intelligible, e.g. descrambled, using random
digital
codes located in fields. The random digital keys are themselves encrypted, and
decrypted by a one or more key obtained from a database located at the central
facility, along with user-specific information at the time of viewing. The
system does
t o not stop copying, it controls viewing, while protecting revenues. As such,
it can
encourage copying, which could ease the distribution issue by controlling the
playback such that revenue can be collected each time.
Preferably duplex communication link 13 is a continuous data channel
is between a terminal and a central facility such as an ISDN D-channel or by
modem a
regular phone line.
The video program is encrypted, and needs a decrypter in the terminal for
viewing. The decrypter uses data embedded in the video program along with a
data
2o access to correctly perform the decryption, so the process is completely
controlled.
The embedded data and key transfer from the remote database may be protected
with
public domain encryption techniques, providing high level security before
first
viewing.
2s The video program may be recorded as is, but it is still unviewable. To
view
it, the decrypter is used, along with the encrypted embedded data, and an
access to a
secure database, to perform the decryption. Recordings may be freely copied,
but
remain unviewable unless used with the decrypter.
3o To view the programs requires access to the database using encrypted data
transfer. This process yields the control of the video program, whether
recording or
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transmission. The decrypter requires one or more keys that arrives from the
database.
To get the key, information from the video program as well as terminal
identification
is sent to the database.
s A direct Electronic funds Transfer (EFT) debit can be performed using the
information. If the program is a video store copy, the EFT could include the
store fee
and the copyright fee. Note that the video distribution to video stores
becomes trivial,
as they are encouraged to take a direct recording with a video store key,
along with
their authorized converter box, and make as many copies as they like. The
revenue
o control takes place at viewing time. This encourages a shareware type of
distribution.
A passkey can be sent to the database, to allow viewing of questionable taste
films by adults, controlling access by minors.
i s On the first access, the database will capture a signature derived from
the
user's equipment and the recording, and store it for subsequent tracking. As
there is a
compelled database access in this process, data on usage may be collected.
This same
process may be used for revenue collection.
2o The system preferably uses at least one downloadable key, a encrypted video
program that uses the key for decryption, and data stored a field of the video
program. It may be implemented in an all digital, analog or mixed
analog/digital
environment.
2s The video programs are encrypted, with data relating to the programs, e.g.
where and when, who transmitted it. The data may also contain part of the
decryption
key. This information would be extracted from the signal, and used to access a
database, maintained by the program's owners, to obtain an encrypted key for
the
decrypter. After a subscriber andlor a credit check is successfully completed,
the one
30 or more keys would be transmitted. At this time the owner has obtained
usage data,
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with a specific user's ID, and has the option of billing him. If it is a free
program, at
least the viewer data is available.
If a user records a transmission or another recording, he captures the
s encrypted signal, along with embedded data, as described above. This
accomplishes
the signature part of the process. A recording created by this method may be
on a
regular VCR, but is encrypted and individually marked. Copying a recording
does not
affect the system, as the rerecording is only usable with the correct keys.
Potentially,
the first few minutes of a program might be viewable without the need of a
key, to
to allow the user to see what the contents of the program are, as well as to
allow time
for the database access and key synchronization process.
To play a recording back, it is necessary to re-obtain the one or more keys.
The combination of data stored in a field is used to access the database.
Before the
~ s keys are made available, there is a check that the terminal identification
and the
embedded data match.
In the case wherein a recording is rented from a video store, a code may
identify the store. The database recognizes the recording as a rental copy,
and charge
2o either the user or the video store a fee. If the recording is viewed a
second time, the
charge is repeated. In the event a copy is made, when it is played, the
database will
identify the originating video store, but not the actual copier. However, if
validation
is performed at rental time, there would be some measure of control. If the
entire
charging process were to be reversed, such that the viewer carries all the
liability for
2s charges, then copying is encouraged, as per shareware, and the distribution
problem
is minimized, while revenues are maintained on a usage basis.
The program's owner has the responsibility to get a secured copy to whoever
deals with the distribution of the programs. The programs are encrypted, and
require
3o a database update to enable viewers to make use of the program. The viewer
has a
terminal including a decrypter, linked to the central facility's database via
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automatic dial-up, that, when enabled, decrypts the video program. As
appropriate,
there can be credit checks and billing from the database, as well as
statistics
collection.
The encryption has two levels, one for protection of video decryption codes
on the program, and one for protection of messages between the terminal and
the
central facility. Both may use the NBS Data Encryption Standard (DES).
DES encryption and decryption may be implemented with a commercial
~o Motorola 6859 Data Security Device or similar product at the terminal and
at the
central faci 1 ity.
The decryption code itself is protected by being DES-encrypted. The
decryption key is not on the video program but is retained in the database at
the
is central facility. A program identification number and a decryption key
number allow
the central facility to recover the decryption key itself and send it to the
terminal for
decrypting the decryption codes.
A different DES decryption key is not required for every field. One key can
2o span several fields. DES key requests and acknowledgements from the
terminal may
also act as keep-alive messages to the central facility.
DES decryption keys are transmitted from the central facility to the terminal
protected by a higher-level DES "session" key terminal requests for new keys
as the
2s tape progresses are also protected by the DES session key. This key is
generated by
the central facility at the beginning of the session and remains valid for the
duration
of the session. The terminal begins the session using a terminal-unique DES
key
stored in a ROM.
3o Frame contents are transferred from the Analog Subsystem to the DCSS and
the decrypted decryption code from the DCSS to the Analog Subsystem over the
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analog interface shown in the Figure. Transfer of data between the subsystems
may
be coordinated by means of the vertical and horizontal blanking signals and
their
derivative interrupts.
s All messages between terminal and central facility use Cyclic Redundancy
Code (CRC) checking to verify message integrity. The CRC-CCITT generating
polynomial generates two block check characters (BCC) for each message. If the
terminal receives a message that is not verified by the BCC, it sends a
request (ARQ)
to the central facility to retransmit the last message. The central facility
does not
to attempt to ARQ garbled messages. It discards them and waits for a terminal
to send
again.
Message exchange in the VCS is by a positive acknowledgment scheme in
which a response of some kind is expected for every message sent. For example,
a
is terminal expects a DES decryption key message after it sends a request for
the same;
the central facility expects a key receipt acknowledge after it sends the key
message.
When a user begins to play a protected program, the terminal initiates a
session by sending a "session start" message (STS) to the central facility
containing
2o user and program identifications. The message contains message type, user
number
and CRC code in the clear, but the balance of the message is DES-encrypted
with the
initial DES session key stored in the terminal ROM. (The user identification
is also
stored in ROM.) The central facility uses the unencrypted data to access its
database
and find the user DES value for decrypting the remainder of the message.
The central facility authenticates the message by comparing clear and
decrypted user numbers. If the user numbers are identical, the central
facility then
confirms that the program serial number is valid. The central facility may
also check
user credit. If all is well, the central facility accepts the session and
generates a new
(and random) DES key that is unique for that session. It encrypts this using
the initial
user value in the database and sends it to the terminal, which decrypts the
message
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and stores the new value in its database (MCU RAM) as the session key for the
remainder of the session.
The central facility then uses the tape and decryption key number in the STS
message to recover a set of DES decryption keys for the program from the
database.
These are encrypted with the session key and sent to the terminal at the start
of a
session or during the course of a session.
The terminal generates session start, key acknowledgement, and ARQ
to messages. The central facility responds in kind. Both the central facility
and the
terminal generate and verify block check characters.
The preferred embodiment and best mode of practicing the invention have
been described. Alternatives now will be apparent to those skilled in the art
in light of
is these teachings. Accordingly the invention is to be defined by the
following claims
and not by the particular examples given.
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