A CMOS APS image sensor with watermarking.

摘要

A novel idea is proposed for integrating digital watermarking capabilities into complementary metal-oxide semiconductor (CMOS) image sensors. The background of watermarking and previous hardware implementation is given and a simple digital watermarking scheme, ideal for implementation in a CMOS image sensor, is outlined.; The watermarking algorithm was analyzed in terms of the effect on image quality, the statistics for successful watermark detection, and its susceptibility to attack. It was found that image quality could be high if less than three watermark bits were added to an image. A trend was also discovered that if the inequality 2delta MN ≥ 2048 is satisfied, where M and N are the dimensions of the image, in pixels, and delta is the number of bits used for the watermark values, successful detection statistics will be obtained. It was also demonstrated that removing a watermark placed with this particular algorithm is relatively easy using low-pass filters; however, extracting the watermark from a watermarked image for insertion into an unauthorized image was accomplished and represents a greater threat.; A device prototype was designed and fabricated and the results are discussed. The design of key components is highlighted in the context of the larger system. The operation of the chip in terms of signals and timing is given. Successful fabrication turned out to be an elusive goal and the difficulties encountered provide valuable information to the next phase of the project, recently submitted for fabrication.; Finally, the noise data show conclusively that fixed pattern noise (FPN) is a useful source for key generation. It allows for the unique identification of sensors through the key generation process; however, small changes in the input data can affect the key, if the length of the key is large enough. Keys should be stored in non-volatile memory on the image sensor in order to speed up the image capture process.; In summary, a complete system from sensor to key generation to embedding and detection of digital watermarks has been created, and can help provide a much needed boost to image veracity in target applications.