A Review of Text Watermarking: Theory, Methods, and Applications <s> A. LOGICAL EMBEDDING <s> Copyright protection of digital contents is very necessary in today’s digital world with efficient communication mediums as internet. Text is the dominant part of the internet contents and there are very limited techniques available for text protection. This paper presents a novel algorithm for protection of plain text, which embeds the logo image of the copyright owner in the text and this logo can be extracted from the text later to prove ownership. The algorithm is robust against content-preserving modifications and at the same time, is capable of detecting malicious tampering. Experimental results demonstrate the effectiveness of the algorithm against tampering attacks by calculating normalized hamming distances. The results are also compared with a recent work in this domain <s> BIB001 </s> A Review of Text Watermarking: Theory, Methods, and Applications <s> A. LOGICAL EMBEDDING <s> This paper addresses the problems and threats associated with verification of integrity, proof of authenticity, tamper detection, and copyright protection for digital-text content. Such issues were largely addressed in the literature for images, audio, and video, with only a few papers addressing the challenge of sensitive plain-text media under known constraints. Specifically, with text as the predominant online communication medium, it becomes crucial that techniques are deployed to protect such information. A number of digital-signature, hashing, and watermarking schemes have been proposed that essentially bind source data or embed invisible data in a cover media to achieve its goal. While many such complex schemes with resource redundancies are sufficient in offline and less-sensitive texts, this paper proposes a hybrid approach based on zero-watermarking and digital-signature-like manipulations for sensitive text documents in order to achieve content originality and integrity verification without physically modifying the cover text in anyway. The proposed algorithm was implemented and shown to be robust against undetected content modifications and is capable of confirming proof of originality whilst detecting and locating deliberate/nondeliberate tampering. Additionally, enhancements in resource utilisation and reduced redundancies were achieved in comparison to traditional encryption-based approaches. Finally, analysis and remarks are made about the current state of the art, and future research issues are discussed under the given constraints. <s> BIB002
Logical embedding is a completely invisible or imperceptible text watermarking method. It is a case of data hiding where the embedded data is completely invisible to the viewer due to the fact that it is not done on the text. This unique method entails embedding the watermark digitally into the text, without physically applying the watermark inside the text BIB001 , BIB002 . This is achieved by generating the watermark data from the text. While the watermarked data are kept secret and ready for verification, the original texts are distributed to the public. In order to verify the authenticity of the attacked data, the watermarked information is gathered from the data and compared with the original watermarked data. As the method of logical embedding is not done on the text, the image, structural or feature characteristics of the text are analyzed and certain embedding characteristics are gathered to obtain the watermark information. The information is kept safe with certification authority and is used for future authentication purposes. This process proves to be highly robust and is imperceptible, since the data distributed to the public do not contain the secret information. However, it has some drawbacks that deserve to be highlighted. Although it is safe from format-based attack or content-based attack, a potential attacker may easily change or alter a major part of the text so that the watermark information cannot be detected anymore. If the watermark is hard to be detected, the text information can be misused. Most of the proposed logical embedding process techniques use the term zero-watermarking approach. In this work, we analyze some of the studies on the logical embedding method. The analysis of the methods in relation to the attacks and performance are summarized in Table 1 .