A Review of Text Watermarking: Theory, Methods, and Applications <s> 1) HE et al. (2009) <s> Zero-watermarking technology without modifying the carrier's data, resolved the imperceptibility of watermarking. Since natural language is lack of embedding space, zero-watermarking is suitable. Without modifying carrier text passive attack does not works, and only active attack may destroy the zero-watermarking. In this paper, we proposed a novel text zero-watermarking algorithm. Words, which are corresponding to one special POS tag sub-sequence pattern, were extracted as candidate for zero-watermarking. Again, words were chose under the control of chaotic function. Since there are so many possible permutation of POS tags sub-sequence and chaotic function has sensitive dependence on initial conditions or the key, the robustness was guaranteed. Experiments results show that it is almost impossible destroyed the zero-watermarking by stochastic synonym substitution and sentence transform and the results also show the robustness is better than other text zero-watermarking algorithms. <s> BIB001 </s> A Review of Text Watermarking: Theory, Methods, and Applications <s> 1) HE et al. (2009) <s> In order to promote the Chinese digital text's copyright protection technology, this paper proposes a Chinese Text Zero-Watermark scenario based on Sentence's Entropy. This scenario calculates the entropies of sentences based on wordfrequency and makes crucial sentence selection based on entropy. After that, watermark is constructed with the order of crucial sentences. Furthermore, to prove its effectiveness, the scenario is validated by simulation and it has shown fine robust and ability of anti-attack. <s> BIB002
The authors proposed a novel text zero watermarking algorithm which use words that correspond to one special partof-speech (POS) tag subsequence pattern. Part-of-speech is a category of words that have similar grammatical properties. The sequences were extracted using the chaotic function to develop the watermark without modifying the cover data, which resolves the problem of imperceptibility. This method offers good security since any attacker does not know the sequence of the selected POS tag while the chaotic function has unpredictable properties. Robustness is also assured and includes protection against reformatting and converting document type, synonym substitution, and sentence transformation attack with a very low success percentage BIB001 . The team discussed a method where the watermark key is calculated based on the sentence entropy. Entropy is the average expected value of the information contained in each message. The entropy of the sentence is calculated based on word frequency and crucial selections, where the VOLUME 6, 2018 watermark is constructed based on the order of the crucial sentences. Given the complexity of Chinese text semantics, a sentence with a high word frequency possesses bigger entropy. This method is tested for some known attacks which includes 'adding and deleting' attacks and synonym substitution attacks. Tests have shown that this method is robust and withstands this kind of attacks which shows very low success rate. This method offers imperceptibility and security where the watermark key is registered with the authority BIB002 .