Electrical computers and digital processing systems: support – Multiple computer communication using cryptography – Particular communication authentication technique
Reexamination Certificate
1998-04-30
2004-06-22
Smithers, Matthew (Department: 2132)
Electrical computers and digital processing systems: support
Multiple computer communication using cryptography
Particular communication authentication technique
Reexamination Certificate
active
06754822
ABSTRACT:
CROSS REFERENCE TO RELATED PATENT APPLICATIONS
This application has the same Detailed Description as Jian Zhao and E. Koch, Digital Authentication with Analog Documents, assigned to Mediasec LLP and filed on even date with this application.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to digital representations of images and other information and more specifically to techniques for protecting the security of digital representations and of analog forms produced from them.
2. Description of the Prior Art
Nowadays, the easiest way to work with pictures or sounds is often to make digital representations of them. Once the digital representation is made, anyone with a computer can copy the digital representation without degradation, can manipulate it, and can send it virtually instantaneously to anywhere in the world. The Internet, finally, has made it possible for anyone to distribute any digital representation from anywhere in the world From the point of view of the owners of the digital representations, there is one problem with all of this: pirates, too, have computers, and they can use them to copy, manipulate, and distribute digital representations as easily as the legitimate owners and users can. If the owners of the original digital representations are to be properly compensated for making or publishing them, the digital representations must be protected from pirates. There are a number of different approaches that can be used:
the digital representation may be rendered unreadable except by its intended recipients; this is done with encryption techniques;
the digital representation may be marked to indicate its authenticity; this is done with digital signatures;
the digital representation may contain information from which it may be determined whether it has been tampered with in transit; this information is termed a digest and the digital signature often includes a digest;
the digital representation may contain a watermark, an invisible indication of ownership which cannot be removed from the digital representation and may even be detected in an analog copy made from the digital representation; and
the above techniques can be employed in systems that not only protect the digital representations, but also meter their use and/or detect illegal use.
For an example of a system that uses encryption to protect digital representations, see U.S. Pat. No. 5,646,999, Saito, Data Copyright Management Method, issued Jul. 8, 1997, for a general discussion of digital watermarking, see Jian Zhao, “Look, It's Not There”, in:
BYTE Magazine,
January, 1997. Detailed discussions of particular techniques for digital watermarking may be found in E. Koch and J. Zhao, “Towards Robust and Hidden Image Copyright Labeling”, in:
Proc. Of
1995
IEEE Workshop on Nonlinear Signal and Image Processing,
Jun. 20-22, 1995, and in U.S. Pat. No. 5,710,834, Rhoads, Method and Apparatus Responsive to a Code Signal Conveyed through a Graphic Image, issued Jan. 20, 1998. For an example of a commercial watermarking system that uses the digital watermarking techniques disclosed in the Rhoads patent, see Digimarc Watermarking Guide, Digimarc Corporation, 1997, available at in March, 1998 at http://www.digimarc.com.
FIG. 1
shows a prior-art system
101
which employs the above protection techniques. A number of digital representation clients
105
, of which only one, digital representation client
105
(
j
) is shown, are connected via a network
103
such as the Internet to a digital representation server
129
which receives digital representations from clients
105
and distributes them to clients
105
. Server
129
includes a data storage device
133
which contains copied digital representations
135
for distribution and a management data base
139
. Server
129
further includes a program for managing the digital representations
135
, a program for reading and writing watermarks
109
, a program for authenticating a digital representation and confirming that a digital representation is authentic
111
, and a program for encrypting and decrypting digital representations
113
. Programs
109
,
111
, and
113
together make up security programs
107
.
Client
105
has its own versions of security programs
107
, it further has editor/viewer program
115
which lets the user of client
105
edit and/or view digital representations that it receives via network
103
or that are stored in storage device
117
. Storage device
117
as shown contains an original digital representation
119
which was made by a user of client
105
and a copied digital representation
121
that was received from DR Server
129
. Of course, the user may have made original representation
119
by modifying a copied digital representation. Editor/viewer program
115
, finally, permits the user to output digital representations to analog output devices
123
. Included among these devices are a display
123
, upon which an analog image
124
made from a digital representation may be displayed and a printer
127
upon which an analog image
126
made from the digital representation may be printed. A loudspeaker may also be included in analog output devices
123
. The output of the analog output device will be termed herein an analog form of the digital representation. For example, if the output device is a printer, the analog form is printed sheet
126
; if it is a display device, it is display
124
.
When client
105
(
j
) wishes to receive a digital representation from server
129
, it sends a message requesting the the digital representation to server
129
. The message includes at least an identification of the desired digital representation and an identification of the user. Manager
131
responds to the request by locating the digital representation in CDRs
135
, consulting management data base
139
to determine the conditions under which the digital representation may be distributed and the status of the user of client
105
as a customer. If the information in data base
139
indicates to manager
131
that the transaction should go forward, manager
131
sends client
105
(
j
) a copy of the selected digital representation. In the course of sending the copy, manager
131
may use watermark reader/writer
109
to add a watermark to the digital representation, use authenticator/confirmer
111
to add authentication information, and encrypter/decrypter
113
to encrypt the digital representation in such a fashion that it can only be decrypted in DR client
105
(
j
).
When client
105
(
j
) receives the digital representation, it decrypts it using program
113
, confirms that the digital representation is authentic using program
111
, and editor/viewer
115
may use program
109
to display the watermark. The user of client
105
(
j
) may save the encrypted or unencrypted digital representation in storage
117
. The user of client
105
(
j
) may finally employ editor/viewer
115
to decode the digital representation and output the results of the decoding to an analog output device
123
. Analog output device
123
may be a display device
125
, a printer
127
, or in the case of digital representations of audio, a loudspeaker.
It should be pointed out that when the digital representation is displayed or printed in analog form, the only remaining protection against copying is watermark
128
, which cannot be perceived in the analog form by the human observer, but which can be detected by scanning the analog form and using a computer to find watermark
128
. Watermark
128
thus provides a backup to encryption: if a digital representation is pirated, either because someone has broken the encryption, or more likely because someone with legitimate access to the digital representation has made illegitimate copies, the watermark at least makes it possible to determine the owner of the original digital representation and given that evidence, to pursue the pirate for copyright infringement and/or violation of a confidentiality agreement.
If the user of client
105
(
j
) wishes to send an
Fraunhofer-Gesellschaft zur Forderung der angewandten forshung e
Meislahn Douglas J.
Nelson Gordon E.
Smithers Matthew
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