1.  Field
The field of the present invention relates to processing digital data.  More particularly, the field of the present invention relates to identifying, reporting and/or protecting digital works from unauthorized transmission and/or copying, such as over networks or network segments connected to the Internet. 
2.  Background
Technological developments such as peer to peer file sharing have revolutionized the exchange of information over digital networks such as the Internet.  The result has been a virtual explosion of copyright violations, as intellectual property is transmitted to individuals not licensed to receive and use it.  Once copyrighted content is available on the Internet, that content is exposed to piracy.  The unlicensed use of digital copyrighted works online is a growing, major concern to the owners of these properties.  Current peer-to-peer file sharing technology facilitates widespread copyright infringement of various works including songs, images, and movies.  At the same time, security measures placed into widespread use have been defeated.  For example, DVD encryption was “hacked” by mid-2000, resulting in the digital copying and distribution of movies without regard for copyright.  As a result of the widespread availability of digital works on computer networks, artists and companies affiliated with them receive no payment for distribution of copyrighted works on an unprecedented scale. 
In response to the growing copyright infringement problem tied to unregulated peer-to-peer file sharing, copyright owners have sought and obtained legal relief, including injunctive relief, against peer-to-peer facilitators such as Napster.  Some copyright owners have further requested that network operators, including colleges and universities, block access to peer-to-peer sites to prevent further copyright infringement.  At the same time, however, there exist substantial non-infringing uses for peer-to-peer file sharing, including exchange of creative works that exist in the public domain (such as may exist through expiration or abandonment of copyrights, for example) and/or uses that have been expressly permitted.  If aggrieved copyright owners prevail in their legal battles against peer-to-peer facilitators, then such facilitators may be forced to stop operating irrespective of the content they provide. 
The injunction entered against Napster in March 2000 by a federal judge in San Francisco, Calif. has ordered the company to remove copyrighted sound recordings from its system.  The recording industry has been given the duty to provide lists containing the titles, names of artists, file names, and ownership rights of recordings, and Napster, shortly after receiving such identification, is responsible for blocking those materials from its system.  Yet compliance with this name-based regime has already proven difficult, since there exists no file-naming standard and file names can be easily manipulated with known method presently in use.  The inclusion of metadata (data about data, usually constituting text embedded in an audio file or stream to represent information such as artist name, album name, track name, etc.)  in selected audio works may aid in identifying works even if file names are changed.  However, metadata is only present on newer works, and essentially amounts to a more sophisticated extension of file naming technology that is subject to manipulation and hacking. 
A potential alternative to relying on file naming technology for identifying digital works on computer networks is an identification technology known as watermarking.  A watermark is digital information that is embedded into a file in such a way that it does not affect human perception of the content but is easily detectable by machines.  One advantage offered by watermarking is its easy recognition.  However, drawbacks of watermarking technology include its inability to protect the huge amount of previously released audio content, and its susceptibility to hacking.  Once a watermark is disabled or removed from a creative work by a hacker, the resulting product is unprotected. 
A different identification technology known as content-based identification (“CBID”), relying on the content of creative works, represents yet another alternative to file naming technology.  For example, when applied to audio works, CBID analyzes acoustic qualities.  Various CBID techniques may be used to characterize the qualities of sound perceived by a listener.  A typical approach is to analyze the spectrum of a sound, such as by measuring the loudness of each frequency contained in a multi-frequency sound. 
A more compact CBID technology involves creation of a “fingerprint” from a creative work that is compact from a data perspective, yet preserves distinguishing characteristics that may be used to positively identify a unique audio file.  Many simple fingerprinting methods have been developed, such as spectral averaging, for example.  In using these simpler methods, however, a substantial amount of information about the audio work is lost.  Great care must be taken in applying a particular CBID method for a number of reasons: not only to ensure only accurate identification, but also to ensure that compressed versions of an audio file can be identified, and to avoid known evasion techniques such as adding a small segment to the beginning of an audio file.  A more sophisticated CBID technology would be appropriate to address these concerns. 
One structural application of a sophisticated CBID fingerprinting method for audio data is found in U.S. Pat.  No.  5,918,223, issued to Blum et al.,  the disclosure of which is hereby incorporated by reference as if fully set forth herein.  The patent provides a system and method for performing analysis and comparison of audio data files based upon the content of the data files.  However, U.S. Pat.  No.  5,918,223 by itself does not address a comprehensive solution to regulating distribution of digital copyrighted works.  Moreover, U.S. Pat.  No.  5,918,223 expressly relates to audio information, and does not address the similar but distinct problems with regulating online distribution of copyrighted works such as motion pictures, still images, games, software, and other media. 
Regarding movies, the transformation taking place in the motion picture industry from VHS video to digital DVD format has led to the spread of illegally shared copies of movies online.  While a universal DVD encryption system has been adopted by the motion picture industry to block the online trade of illegal DVD content, as mentioned previously, decryption software such as De-Content Scrambling System (DeCSS) is readily available online.  Moreover, technologies such as DivX allows users to take the decoded movie and copy the material onto a CD-ROM for home use through a standard Internet connection.  The Motion Picture Association of America (MPAA) has moved aggressively to stop the illicit trade of movies online.  The MPAA has sued online sites and chat rooms that offer pirated movies, as well as sites offering shared movie files, under the recently adopted Digital Millennium Copyright Act. 
With regard to images, photo communities are quickly becoming a favorite new tool of online users, as such communities allow users to post, print, and share their photos online with other subscribers.  The explosive growth in digital camera use has greatly expanded the popularity of these photo communities.  While many sites promote their usefulness in sharing family moments and other important events online, some estimates provide that, in reality, half of all images posted on these sites are copyright-protected images, and are being posted, printed and shared illegally. 
In summary, peer-to-peer file sharing technology offers unprecedented ease in exchanging information over digital networks.  Unfortunately, this technology also permits intellectual property rights to be infringed on a widespread scale.  Without a comprehensive protection system in place to prevent further infringement of intellectual property rights, if intellectual property owners prevail in their ongoing legal battles against peer-to-peer providers, then the benefits of peer-to-peer file sharing may be lost to everyone.  In light of all of the considerations discussed above, it would be desirable to provide a reliable and secure system for enabling intellectual property owners to distribute digital materials while preventing infringement of intellectual property rights.  Preferably, such a system would permit intellectual property owners to choose whether distribution of particular works should be unrestricted, restricted, or disallowed entirely.