Image analysis – Applications
Reexamination Certificate
2003-02-04
2004-06-01
Johns, Andrew W. (Department: 2621)
Image analysis
Applications
Reexamination Certificate
active
06744907
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to image capture devices that steganographically embed plural-bit auxiliary data within image data acquired thereby, and associated methods.
BACKGROUND AND SUMMARY OF THE INVENTION
“I would never put it in the power of any printer or publisher to suppress or alter a work of mine, by making him master of the copy”
Thomas Paine,
Rights of Man
, 1792.
“The printer dares not go beyond his licensed copy”
Milton,
Aeropagetica
, 1644.
Since time immemorial, unauthorized use and outright piracy of proprietary source material has been a source of lost revenue, confusion, and artistic corruption.
These historical problems have been compounded by the advent of digital technology. With it, the technology of copying materials and redistributing them in unauthorized manners has reached new heights of sophistication, and more importantly, omnipresence. Lacking objective means for comparing an alleged copy of material with the original, owners and possible litigation proceedings are left with a subjective opinion of whether the alleged copy is stolen, or has been used in an unauthorized manner. Furthermore, there is no simple means of tracing a path to an original purchaser of the material, something which can be valuable in tracing where a possible “leak” of the material first occurred.
A variety of methods for protecting commercial material have been attempted. One is to scramble signals via an encoding method prior to distribution, and descramble prior to use. This technique, however, requires that both the original and later descrambled signals never leave closed and controlled networks, lest they be intercepted and recorded. Furthermore, this arrangement is of little use in the broad field of mass marketing audio and visual material, where even a few dollars extra cost causes a major reduction in market, and where the signal must eventually be descrambled to be perceived, and thus can be easily recorded.
Another class of techniques relies on modification of source audio or video signals to include a subliminal identification signal, which can be sensed by electronic means. Examples of such systems are found in U.S. Pat. No. 4,972,471 and European patent publication EP 441,702, as well as in Komatsu et al, “Authentication System Using Concealed Image in Telematics,” Memoirs of the School of Science & Engineering, Waseda University, No. 52, p. 45-60 (1988) (Komatsu uses the term “digital watermark” for this technique). An elementary introduction to these methods is found in the article “Digital Signatures,” Byte Magazine, November, 1993, p. 309. These techniques have the common characteristic that deterministic signals with well defined patterns and sequences within the source material convey the identification information. For certain applications this is not a drawback. But in general, this is an inefficient form of embedding identification information for a variety of reasons: (a) the whole of the source material is not used; (b) deterministic patterns have a higher likelihood of being discovered and removed by a would-be pirate; and (c) the signals are not generally ‘holographic’ in that identifications may be difficult to make given only sections of the whole. (‘Holographic’ is used herein to refer to the property that the identification information is distributed globally throughout the coded signal, and can be fully discerned from an examination of even a fraction of the coded signal. Coding of this type is sometimes termed “distributed” herein.)
Among the cited references are descriptions of several programs which perform steganography—described in one document as “ . . . the ancient art of hiding information in some otherwise inconspicuous information.” These programs variously allow computer users to hide their own messages inside digital image files and digital audio files. All do so by toggling the least significant bit (the lowest order bit of a single data sample) of a given audio data stream or rasterized image. Some of these programs embed messages quite directly into the least significant bit, while other “pre-encrypt” or scramble a message first and then embed the encrypted data into the least significant bit.
Our current understanding of these programs is that they generally rely on error-free transmission of the of digital data in order to correctly transmit a given message in its entirety. Typically the message is passed only once, i.e., it is not repeated. These programs also seem to “take over” the least significant bit entirely, where actual data is obliterated and the message placed accordingly. This might mean that such codes could be easily erased by merely stripping off the least significant bit of all data values in a given image or audio file. It is these and other considerations which suggest that the only similarity between our invention and the established art of steganography is in the placement of information into data files with minimal perceptibility. The specifics of embedding and the uses of that buried information diverge from there.
Another cited reference is U.S. Pat. No. 5,325,167 to Melen. In the service of authenticating a given document, the high precision scanning of that document reveals patterns and “microscopic grain structure” which apparently is a kind of unique fingerprint for the underlying document media, such as paper itself or post-applied materials such as toner. Melen further teaches that scanning and storing this fingerprint can later be used in authentication by scanning a purported document and comparing it to the original fingerprint. Applicant is aware of a similar idea employed in the very high precision recording of credit card magnetic strips, as reported in the Wall Street Journal but which cannot presently be located, wherein very fine magnetic fluxuations tend to be unique from one card to the next, so that credit card authentication could be achieved through pre-recording these fluxuations later to be compared to the recordings of the purportedly same credit card.
Both of the foregoing techniques appear to rest on the same identification principles on which the mature science of fingerprint analysis rests: the innate uniqueness of some localized physical property. These methods then rely upon a single judgment and/or measurement of “similarity” or “correlation” between a suspect and a pre-recording master. Though fingerprint analysis has brought this to a high art, these methods are nevertheless open to a claim that preparations of the samples, and the “filtering” and “scanner specifications” of Melen's patent, unavoidably tend to bias the resulting judgment of similarity, and would create a need for more esoteric “expert testimony” to explain the confidence of a found match or mis-match. An object of the present invention is to avoid this reliance on expert testimony and to place the confidence in a match into simple “coin flip” vernacular, i.e., what are the odds you can call the correct coin flip 16 times in a row. Attempts to identify fragments of a fingerprint, document, or otherwise, exacerbate this issue of confidence in a judgment, where it is an object of the present invention to objectively apply the intuitive “coin flip” confidence to the smallest fragment possible. Also, storing unique fingerprints for each and every document or credit card magnetic strip, and having these fingerprints readily available for later cross-checking, should prove to be quite an economic undertaking. It is an object of this invention to allow for the “re-use” of noise codes and “snowy images” in the service of easing storage requirements.
U.S. Pat. No. 4,921,278 to Shiang et al. teaches a kind of spatial encryption technique wherein a signature or photograph is splayed out into what the untrained eye would refer to as noise, but which is actually a well defined structure referred to as Moire patterns. The similarities of the present invention to Shiang's system appear to be use of noise-like patterns which nevertheless carry information, and the use of this principl
Digimarc Corporation
Digimarc Corporation
Johns Andrew W.
LandOfFree
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