Digital watermarking is a technique for inserting information (the watermark) into digital multimedia

which can be later extracted or detected for a variety of purposes including identification or authentication purposes.Based on analysis of the past fragile watermark techniques

three new efficient fragile watermark techniques are proposed

benefiting from the good properties of chaos

including the ease of their generation

their sensitive dependence on their initial condition and noise like

thus a same image sub block can embed different information at the same location and resist Holliman's attack.The scheme can detect any modification made to the image and indicate the specific locations that have been modified

because any modification would be reflected in a corresponding error in the extracted watermark.