Cryptography – Video cryptography – Copy protection or prevention
Reexamination Certificate
1999-03-16
2001-10-30
Trammell, James P. (Department: 2161)
Cryptography
Video cryptography
Copy protection or prevention
C713S176000, C705S057000
Reexamination Certificate
active
06310956
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to copy protection, particularly but not exclusively to an apparatus and method for protecting digital data from unauthorised copying and a digital data recording apparatus capable of preventing such unauthorised copying.
BACKGROUND OF THE INVENTION
Although digital media such as audio CDs and CD-ROMs allow perfect reproduction of digital data, the problems of controlling unauthorised reproduction are to some extent mitigated by the fact that these media are generally available in read-only form, so that the potential infringer needs specialist recording and CD-pressing equipment to make high quality copies.
However, the introduction of Digital Versatile Disk (DVD) technology, which aims to make low cost digital recorders widely available, has raised the need for sophisticated copy protection systems, to prevent extensive piracy. With the increasing provision of information, entertainment and other contents in digital form, for example digital video broadcasting (DVB) by satellite, cable television and digital terrestrial television (DVB-T) as well as through networks such as the Internet, DVD recorders, known as DVD-RAM recorders, have been developed to record such contents in digital form. Eventually, it is envisaged that such recorders will replace the various different forms of currently available storage equipment, including computer hard-disk drives and video cassette recorders.
The principles of DVD are well established, with DVD-RAM recorders such as the Hitachi GF-1000 series available on the market. Reference is directed to the substantial information on the Internet relating to DVD principles and products, including at <http://fp97.inet-images.com/dvd/index.html> and <http://www.videodiscovery.com/vdyweb/dvd/dvdfaq.html>, and to “DVD Demystified”, by Jim Taylor, published by McGraw-Hill.
Without any form of copy control, digital data received via television or over the Internet can be recorded by a DVD-RAM recorder or other digital recorder onto a digital recording medium such as a recordable DVD disk, from which it can be further copied numerous times onto other DVD disks, without any degradation in the copy quality.
A method that prevents unauthorised copying by embedding copy control signals in data prior to transmission, has been proposed by Nikkei Electronics, and is detailed on the Internet at http://www.dvcc.com/dhsg/CFP-v.10.rtf. This is a response to a Call for Proposals issued by the Data Hiding SubGroup of the Copy Protection Technical Working Group, Version 1.0, July 1997, at http://www.dvcc.com/dhsg.
The proposed method uses a copy control signal which may take one of four possible values: Copy-Free, indicating that the contents can be copied freely, Never-Copy indicating that the contents can never be copied, Copy-Once, indicating that the contents can be copied only once and No-More-Copy, indicating that the contents have already been copied once and that further copies cannot therefore be made.
The structure of the transmission apparatus
1
for the proposed method is shown in
FIG. 1. A
playback module
2
reads data from the medium
3
on which it is recorded and sends it to the copy control signal embedding module
4
. The embedding module
4
obtains the copy control signal to be embedded from the copy control information database
5
, embeds it into the data using a suitable technique, for example, by applying a digital watermark, and sends the data to the transmission module
6
. The transmission module
6
then transmits the data in a conventional way, for example broadcasting it via digital satellite, digital terrestrial television or digital cable television.
The structure of the recording apparatus
7
for the proposed method is shown in
FIG. 2. A
data enabling gate
8
lies between an input signal processing module
9
and a recording module
10
, the gate
8
only allowing data to pass to the recording module
10
in accordance with the copy control signal determined by the copy control signal detection module
11
. If data is allowed to pass to the recording module
10
, it is recorded to an appropriate recording medium
12
, such as a recordable DVD disk.
FIG. 3
is a flowchart showing the detailed operation of the recording apparatus
7
. The input signal processing module
9
reads data input to the recording apparatus
7
at step s
1
and sends it to the copy control signal detection module
11
, which detects the copy control signal embedded in the data at step s
2
. At step s
3
, the signal detection module
11
determines if the Copy-Free signal is present. If it is present, control proceeds to step s
4
at which a signal is sent to the data enabling gate
8
which in turn allows the data to pass to the recording module
10
. Control passes to step s
5
at which the data is recorded to the recording medium
12
. The sequence of recording apparatus operations stops at step s
6
.
If, on the other hand, the Copy-Free signal is not detected at step s
3
, step s
7
is executed at which the signal detection module
11
determines whether the Copy-Once signal is present. If the Copy-Once signal is not detected, the only possibilities remaining are that the copy control signal is set to Never-Copy or No-More-Copy. In either case, recording is not permitted, so control passes to terminating step s
6
. In this case, no enabling signal is sent to the data enabling gate
8
, so that the received data is unable to pass to the recording module
10
.
In the event that the Copy-Once signal is detected at step s
7
, control passes to step s
8
, at which an enabling signal is sent to the data enabling gate
8
which in turn allows the data to be sent to the recording module
10
. Control then passes to step s
9
, at which the recording module
10
changes the embedded Copy-Once signal to No-More-Copy, so that further recordings are prevented. Step s
5
follows, at which the recording module
10
records the data, including the new embedded copy control signal, onto the appropriate recording medium
12
.
As a result of the above operations, the data on the recorded medium
12
contains one of three possible copy control signals: Copy-Free, Never-Copy or No-More-Copy. The Copy-Once signal is eliminated, so that further recording is only permitted if the data was originally designated Copy-Free.
While this method of copy protection is suitable where all recording devices include copy control signal detection, a problem arises when data is recorded onto devices which do not have such detection facilities. For example, referring to
FIG. 4
, with the continual increase in the speed and storage capacity of personal computers, it is possible to use a conventional digital receiver
15
linked to a personal computer (PC)
16
to receive digital data marked as Copy-Once. The data can be stored on the computer's hard disk drive (HDD)
17
as received, namely with the Copy-Once signal still embedded. When the data stream from the hard disk
17
is subsequently sent through the PC
16
to the DVD-RAM recorder
18
, the recorder acts according to the appropriate branch of the flow chart in
FIG. 3
(s
3
-s
7
-s
8
-s
9
-s
5
), changing the Copy-Once signal to No-More-Copy and making a single recording of the data stream onto, for example, a recordable DVD-video disk
19
, from which no further copies can be made. However, since the original data is stored in Copy-Once format on the hard disk
17
, this recording process can be repeated many times to produce a large number of high quality copies on individual disks
19
.
SUMMARY OF THE INVENTION
The present invention aims to address the above problem.
According to a first aspect of the invention, there is provided copy protection apparatus comprising data transmission apparatus including means for associating information related to the transmission time of the data with the data to be transmitted, and data recording apparatus for recording data received from the transmission apparatus including means for comparing the transmission time information
Morito Hajime
Roe Michael
Yoshiura Hiroshi
E Elisca Pierre
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
Trammell James P.
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