SECURE SPREAD-SPECTRUM WATERMARKING FOR MULTIMEDIA

This paper presents a secure (tamper-resistant) algorithm for watermar king images, and a methodology for digital watermarking that may be ge neralized to audio, video, and multimedia data, We advocate that a wat ermark should be constructed as an independent and identically distrib uted (i.i.d.) Gaussian random vector that is imperceptibly inserted in a spread-spectrum-like fashion into the perceptually most significant spectral components of the data, We argue that insertion of a waterma rk under this regime makes the watermark robust to signal processing o perations (such as lossy compression, filtering, digital-analog and an alog-digital conversion, requantization, etc.), and common geometric t ransformations (such as cropping, scaling, translation, and rotation) provided that the original image is available and that it can be succe sfully registered against the transformed watermarked image, In these cases, the watermark detector unambiguously identifies the owner, Furt her, the use of Gaussian noise, ensures strong resilience to multiple- document, or collusional, attacks. Experimental results are provided t o support these claims, along with an exposition of pending open probl ems.