Novel Blind Colour Image Watermarking Technique Using Cholesky Decomposition

In today's electronic distribution environment, it is really necessary to protect the copyrights of digital products. Robust watermarking is one of the effective solutions to protect the ownership of digital images through information embedded in the images. In this paper, the classical Cholesky decomposition (LL<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sup>) is applied in image watermarking techniques for the first time. We divide the host image into 2×2 image blocks, and then apply the Cholesky transform on each block. Elements L21 and L<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> of lower triangular matrix L are selected to embed the watermark bits. In the extracting stage, to reduce the execution time, we calculate elements L21 and L<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> instead of applying the Cholesky decomposition. The experimental results show that our proposed method provides better quality for the watermarked image and it can effectively extract the watermark information under several attacks.