This book provides hybrid robust watermarking algorithms using content based features of an image, various image transforms such as DCT, DWT, SVD are used and the d-sequence acts as a key which gives security to the system. Four distinct blind and non-blind watermarking algorithms are developed. The analysis of results should help shed some light on this new concept adopted in developing the watermarking algorithms, and should be particularly useful to professionals in publishing industries, broadcast monitoring, medical applications, data security or anyone else who may be considering the field of data security /authentication.