Cryptography – Video cryptography – Copy protection or prevention
Reexamination Certificate
1999-02-24
2002-12-03
Darrow, Justin T. (Department: 2132)
Cryptography
Video cryptography
Copy protection or prevention
C380S054000, C380S201000, C705S051000, C705S057000, C713S165000, C713S176000, C713S178000, C713S179000
Reexamination Certificate
active
06490355
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to a system for protecting content. Specifically, the present invention pertains to utilizing a ticket, a watermark, and a time reference to indicate the copy protection status of content.
BACKGROUND OF THE INVENTION
The ability to transmit digital information securely is increasingly important. Owners of content want to be able to provide the content to authorize users without having the content utilized by unauthorized users. However, one problem with digital content is that an exact copy can be made without any degradation in the quality of the copy. Therefore, the copying of digital content is very attractive to pirating operations or attackers.
There are several different levels of attackers. Each type of attacker has a different level of sophistication, motivation, and means (software and hardware) needed to defeat a copy protection method. There are four typical types of attackers, a casual attacker, a hacker, a small-scale pirate, and a commercial pirate.
A casual attacker is an ordinary consumer that is motivated to copy content for later use (time shifting) or for distribution to friends and relatives. The level sophistication of a casual attacker is low. The casual attacker will typically only use consumer equipment in an unmodified form. A more aggressive casual attack may be mounted if a relatively inexpensive modification to consumer equipment is available. This may take the form of a hardware device such as the equipment used to defeat the Macrovision system. Typically, a casual attacker will not open a product to access the internal connections.
A hacker is usually motivated to copy protected content just to see if it can be done. The content may then be distributed widely in avoidance or in spite of copy protection laws. An attacker of this type is often highly skilled and may go to great lengths to acquire content. The financial resources of such an attacker are limited but the time resources can be high. Once the content is acquired, the content may be distributed to friends and relatives. In addition, the Internet may also provide an anonymous method for distributing the illegally copied content.
Both small-scale and commercial pirates are interested in defeating copy-protected content in order to produce and sell illegal copies of the content. By avoiding payments to the rightful owner of the copy-protected content, the pirates may reap large profits. Typically, the pirate may take advantage of the difference in release windows in order access high value content and distribute it.
For instance, in the movie industry, release windows are utilized to maximize profit from content. The essence of these release windows is to first release the content to a premium service such as a pay-per-view service or a video on demand service. Thereafter, the content may be released on a lower price service such as a home-box-office service. At this time, the content may also be available to a consumer through a purchased storage medium such as a Digital Video Disc (DVD).
Pirates however, frustrate the use of these release windows by pirating the content that is available through the premium service and then releasing pirated versions of the content to the public. This may cause substantial financial losses to the rightful owners of the content. Accordingly, a successful copy protection scheme should at least frustrate a pirates attempt for a sufficient period of time till the legitimate owner of the content may reap their rightful profits.
As a class, pirates are assumed to have information not readily available to the consumer including a direct knowledge and understanding of the circuitry within a product. Additionally, the pirate is willing to open the cover of the device to gain access to internal connections. These connections can be easily accessible or may take some amount of specialized tooling to locate or tap. A pirate may have the ability to reverse engineer a product sufficiently to determine the location of clear digital signals. A pirate may also have detailed information about internal circuitry of consumer electronics devices that would allow for the tapping of clear digital signals before or after compression. The pirate typically has the understanding needed to use expensive custom hardware that is designed to break cryptographic keys. Finally, the pirate is assumed to have knowledge of the algorithms and protocols used within the copy protection system and some ability to attempt to defeat them. The systems used to defeat copy protection may include a PC, a group of PCs, or custom-built equipment assembled for the sole purpose of defeating copy protection.
Beyond some level of attacker, the expense of defeating the attacker exceeds a reasonable limit whereby the device must be priced beyond what consumer is willing to pay. Thus, a copy protection solution must be cost effective but secure against a large number of attackers.
A cost-effective method of copy protection is discussed in detail by Jean-Paul Linnartz et al., in Philips Electronics Response to Call for Proposals Issued by the Data Hiding Subgroup Copy Protection Technical Working Group, July 1997 (“Linnartz”), which is incorporated herein by reference. Within a digital transmission, such as an MPEG transport stream, additional data may be embedded within the transport stream to set the copy protection status of content contained within the digital transmission. For instance, the desired copy protection status may be “copy-once”, “no-more-copy”, “copy-never”, and “copy-freely”. Content that has a status of copy-once may be played and copied. During copying, the copy-once content is altered such that the content is in the no-more-copy state. Copy-never content is content that may only be played and may not be copied. Copy-freely content may be played and copied without restriction.
The additional data may take the form of a digital watermark. The watermark may be embedded directly into the content so that removal of the watermark will degrade the quality of the content. The watermark may be utilized as part of the copy protection scheme. As an example, the copy-freely state may be designated by the lack of a watermark within the content.
In operation, a transmission, such as a digital transmission, is sent from a source device and received by a receiving device. A source device is a device that is writing content onto a data bus, initiating a broadcast transmission, initiating a terrestrial transmission, etc. A sink device is a device that reads content from the data bus, etc.
FIG. 1
shows a typical system for the transmission of content. In
FIG. 1
, the source device is a broadcast initiator
101
that utilizes a transmitting antenna
102
to transmit content. The sink device is a broadcast receiver, such as a set-top-box (STB)
104
that utilizes a receiving antenna
103
for receiving the transmitted content. The STB
104
is shown connected to a display device
105
, a player
106
, and a player/recorder
107
, through a bus
108
. The term bus is utilized herein to refer to any system for connecting one device to another device. The bus may be a hard wired system such as a coaxial wire, an IEEE 1553 bus, etc., or the bus may be a wireless system such as an infra-red or broadcast system. Several of the devices shown in
FIG. 1
may at one time act as a source device and at another time act as a sink device. The STB
104
may be a sink for the broadcast transmission and be a source for a transmission on the bus
108
. The player/recorder
107
may be a source/sink of a transmission to/from, respectively, the bus
108
.
In the copy protection scheme discussed by Linnartz, a watermark (W) is embedded within transmitted content. A ticket is transmitted along with the transmitted content. The embedded watermark and the ticket together are utilized to determine the copy protection status of the transmitted content. The watermark may be embedded into the content by at least two known methods. One method embeds the watermark (W) in the MPEG c
Darrow Justin T.
Goodman Edward W.
Koninklijke Philips Electronics , N.V.
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