Abstract: Image watermarking has become an important tool for
intellectual property protection and authentication. In this paper a
watermarking technique is suggested that incorporates two
watermarks in a host image for improved protection and robustness.
A watermark, in form of a PN sequence (will be called the secondary
watermark), is embedded in the wavelet domain of a primary
watermark before being embedded in the host image. The technique
has been tested using Lena image as a host and the camera man as
the primary watermark. The embedded PN sequence was detectable
through correlation among other five sequences where a PSNR of
44.1065 dB was measured. Furthermore, to test the robustness of the
technique, the watermarked image was exposed to four types of
attacks, namely compression, low pass filtering, salt and pepper noise
and luminance change. In all cases the secondary watermark was
easy to detect even when the primary one is severely distorted.
Abstract: Image watermarking has proven to be quite an
efficient tool for the purpose of copyright protection and
authentication over the last few years. In this paper, a novel image
watermarking technique in the wavelet domain is suggested and
tested. To achieve more security and robustness, the proposed
techniques relies on using two nested watermarks that are embedded
into the image to be watermarked. A primary watermark in form of a
PN sequence is first embedded into an image (the secondary
watermark) before being embedded into the host image. The
technique is implemented using Daubechies mother wavelets where
an arbitrary embedding factor α is introduced to improve the
invisibility and robustness. The proposed technique has been applied
on several gray scale images where a PSNR of about 60 dB was
achieved.