Text document authentication by integrating inter character and word spaces watermarking

A method for watermarking on text document images to authenticate the owner or authorized user is proposed. The proposed method makes use of the integrated inter character and word spaces for watermark embedding. An overlapping component which is of size three is utilized, whereby the relationship of the left and right spaces of the character is employed for the watermark embedding. The integrity of the document can be ensured by comparing the hash value of the character components of the document before and after watermark embedding, which can be applied to other line shifting and word-shifting methods as well. While the authenticity of the document can be ensured by generating the Gold-like sequence, which takes the secret key of the authorized user/owner as the seed value, and it is subsequently XORed with hash value of the character components of the document to generate the content-based watermark. The capacity of the watermark has increased compared with conventional line shifting and word shifting methods. Retrieval of the watermark does not require the presence of the original text document image. Discussions on the cons and pros of the method are also provided. Experimental results are given to validate the arguments.