5 December 2001 Use of amplitude and position modulation to augment the payload of 1-bit watermarking
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So far, only a limited attention has been paid to the distinction between readable and detectable watermarking. A drawback with detectable watermarking is that the embedded code can convey only 1 bit of information. Actually, if one could look for all possible watermarks, then the detection of one such watermark would convey log2N information bits. Unfortunately, such an approach is not computationally feasible, since the number of possible watermarks is usually very high. In this work we explore two alternative strategies to build a readable watermark by starting from a detectable one. According to the first strategy (position encoding), information bits are encoded in the position of M known pseudo-random sequences, embedded within the host document by relying on a generic detectable watermarking algorithm. In the second case (amplitude encoding), the pseudo-random sequence is split into a set of sub-sequences, and each sub-sequence is modulated by multiplying it by +1 or -1. To compare the two different approaches, we focus on image watermarking achieved through a well-known, frequency-domain watermarking algorithm previously proposed by the authors. The two alternative strategies are compared both from the point of view of bit error probability and watermark presence assessment.
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Mauro Barni, Riccardo Baitello, Franco Bartolini, "Use of amplitude and position modulation to augment the payload of 1-bit watermarking", Proc. SPIE 4475, Mathematics of Data/Image Coding, Compression, and Encryption IV, with Applications, (5 December 2001); doi: 10.1117/12.449584; https://doi.org/10.1117/12.449584

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