methods, which are also called private watermarking schemes, both the host image and embedded watermark contents are required to extract the watermark. It is clear that the non-blind methods offer better robustness compared to blind methods, but in the case when it is hard to get the original cover and watermark image forwatermark extraction, the blind methods are more desired. The watermarking schemes can alsobe categorized as spatial domain or frequency domain techniques depending on embedding of watermark
CHAPTER # 1: LITERATURE REVIEW Gardnerj et al (1956) investigated citric acid production by mutants of Aspergillus niger. The strain of Aspergillus niger was improved by X-rays and ultraviolet irradiations and found that as compared to wild, the mutated strain give more yield of citric acid. They concluded that 80 % of the sugar fermented was obtained in aerated culture, whereas only 21 % was obtained with the parent strain. Banik et al