Complete complementary code-based digital watermarking with embedding region reduction

Complete complementary code (CCC)-based digital watermarking proposed by Horii, Kojima, et. al. allows multiple watermarks to be embedded in a single image with complete orthogonally under relative shifts. The DCT embedding region size grows as the maximum number of interference-free watermarks increases. In previous methods, each CCC-based watermark was embedded as a cyclically shifted zero-inserted sequence. An alternative embedding method is proposed where the zeros are removed, leading to a significant reduction of the embedding region size without affecting the performance.