A new watermarking algorithm for scanned grey PDF files using DWT and hash function

This paper deals with the development and assessment of a watermarking technique which is suitable for scanned PDF documents. The watermark will serve two purposes. The first one is to protect the copyright ownership. This watermark is a logo which can be extracted even if the document has gone through slight image manipulations. The second one is to authenticate the document. A slight editing in the document will change the second watermark and indicate forgery. The algorithm was tested successfully on a variety of scanned documents and the performances of the algorithm were assessed.