  A semi-blind watermarking scheme is presented based on Singular Value
Decomposition (SVD), which makes essential use of the fact that, the SVD
subspace preserves significant amount of information of an image and is a one
way decomposition. The principal components are used, along with the
corresponding singular vectors of the watermark image to watermark the target
image. For further security, the semi-blind scheme is extended to an invisible
hash based watermarking scheme. The hash based scheme commits a watermark with
a key such that, it is incoherent with the actual watermark, and can only be
extracted using the key. Its security is analyzed in the random oracle model
and shown to be unforgeable, invisible and satisfying the property of
non-repudiation.
