Efficient watermarking technique for protection and authentication of document images

In this paper, a hashing based watermarking technique for the protection and authentication of document image is proposed. Message Digest 5 (MD5) hashing is applied on the cover document image to produce its hash value. This hash value is further translated to Unicode Zero Width Characters (ZWC) by using a lookup table. Watermark is also translated to ZWC prior to embedding in the input image. At the end of each sentence, both of these ZWC are inserted in the cover image. At the receiver end, this watermark is regenerated from its embedded ZWCs and used for the security purposes. The hash value of the cover image is used to detect tampering. The embedded data does not degrade the cover image as invisible Unicode white spaces are used in place of original watermark and hash value. The proposed technique’s effectiveness is demonstrated by comparison to existing state-of-the-art techniques.