Method and apparatus for use of a time-dependent watermark for the purpose of copy protection

DETAILED DESCRIPTION These and other objects of the present invention are achieved by a copy protection system for protecting content wherein a ticket and a watermark are utilized to indicate the copy protection status of the content.
In accordance with the present invention, the ticket and watermark are created utilizing a first time reference (TD) and a one-way function.
The system utilizes a source device to produce the ticket and watermark.
The watermark is then embedded into the content in such a way that the watermark can not be removed from the content without largely degrading the content.
The ticket is then transmitted, along with the first time reference (TD), the embedded watermark, and the content, to a receiver device.
Prior to playing, recording, etc, the receiver device verifies the ticket and watermark utilizing the first time reference, and thereby, determines the copy protection status of the content.
During authorized creation of a medium such as a CD_ROM containing content, a physical mark is placed on the CD-ROM that is not accessible by typical user equipment.
The data for the physical mark may be calculated by processing (e.
g.
, performing a hashing function) seed data.
Seed data is determined utilizing randomly occurring phenomena such as natural physical phenomena (e.
g.
, the number of gamma ray emissions from the sun in a determined period of time).
The methods for determining suitable seed data are known by a person of ordinary skill in the art.
The seed data is selected such that there is a negligibly small chance that a party would guess the seed data.
At the source device (e.
g.
, a broadcasting device), in a preferred embodiment, a one-way function, such as a hashing function, is performed on the physical mark data to produce a ticket (T).
The ticket (T) is combined with the first time reference (TD), utilizing for instance a concatenation function, to produce a result (T.
TD).
A hashing function is performed on the result (T.
TD) to produce a ticket (T').
The ticket (T') is combined with the first time reference to produce a result (T'