A zero-watermarking algorithm based on merging features of sentences for Chinese text

A robust zero-watermarking algorithm is proposed based on merging features of sentences for Chinese text document authentication. In the scheme, a text is first segmented into sets of sentences, where a semantic code for every word can be obtained. Then the sentence entropy is calculated by the frequency of semantic codes, and the sentence relevance is calculated by the semantic similarity between words through the tree structure of words in Tongyici Cilin. By employing the sentence entropy, the sentence relevance, and the sentence length, a weighting function is used to obtain the final weight of each sentence. The nouns and verbs of the high weight sentences are selected to construct a watermark, which is encrypted and registered with a trusted third party called Certificate Authority (CA). To resolve disputes, the similarity between the watermark generated from the suspicious text and the watermark from CA is calculated. The experimental results show that the proposed algorithm offers better performance in terms of imperceptibility and robustness than other available algorithms.