how to write code in matlab to devise a highly fragile watermarking scheme

to devise a highly fragile watermarking scheme

[Walter Roberson]

What algorithm are you planning to use? We can give you some advice about implementation if you describe the algorithm. However, we will not suggest algorithms to you: algorithms are not questions about MATLAB.

http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer