A Review of Text Watermarking: Theory, Methods, and Applications <s> I. INTRODUCTION <s> Information-hiding techniques have recently become important in a number of application areas. Digital audio, video, and pictures are increasingly furnished with distinguishing but imperceptible marks, which may contain a hidden copyright notice or serial number or even help to prevent unauthorized copying directly. Military communications systems make increasing use of traffic security techniques which, rather than merely concealing the content of a message using encryption, seek to conceal its sender, its receiver, or its very existence. Similar techniques are used in some mobile phone systems and schemes proposed for digital elections. Criminals try to use whatever traffic security properties are provided intentionally or otherwise in the available communications systems, and police forces try to restrict their use. However, many of the techniques proposed in this young and rapidly evolving field can trace their history back to antiquity, and many of them are surprisingly easy to circumvent. In this article, we try to give an overview of the field, of what we know, what works, what does not, and what are the interesting topics for research. <s> BIB001 </s> A Review of Text Watermarking: Theory, Methods, and Applications <s> I. INTRODUCTION <s> Security issues of text watermarking are greatly different from those of other multimedia watermarking, in terms of its specific requirements and characteristics of text watermarking. The security theory of text watermarking is proposed in this paper, and the following security topics are discussed: (i) the classification and application of text watermarking; (ii) the classification and analysis of attacks; (iii) the watermarking model and security countermeasures. Other open issues and further challenges related to text watermarking are also addressed. <s> BIB002 </s> A Review of Text Watermarking: Theory, Methods, and Applications <s> I. INTRODUCTION <s> The expansion of the Internet has frequently increased the availability of digital data such as audio, images and videos to the public. Digital watermarking is a technology being developed to ensure and facilitate data authentication, security and copyright protection of digital media. This paper incorporate the detail study watermarking definition, concept and the main contributions in this field such as categories of watermarking process that tell which watermarking method should be used. It starts with overview, classification, features, framework, techniques, application, challenges, limitations and performance metric of watermarking and a comparative analysis of some major watermarking techniques. In the survey our prime concern is image only. <s> BIB003 </s> A Review of Text Watermarking: Theory, Methods, and Applications <s> I. INTRODUCTION <s> Targeted attacks consist of sophisticated malware developed by attackers having the resources and motivation to research targets in depth. Although rare, such attacks are particularly difficult to defend against and can be extremely harmful. We show in this work that data relating to the profiles of organisations and individuals subject to targeted attacks is amenable to study using epidemiological techniques. Considering the taxonomy of Standard Industry Classification (SIC) codes, the organization sizes and the public profiles of individuals as potential risk factors, we design case-control studies to calculate odds ratios reflecting the degree of association between the identified risk factors and the receipt of targeted attack. We perform an experimental validation with a large corpus of targeted attacks blocked by a large security company’s mail scanning service during 2013–2014, revealing that certain industry sectors and larger organizations –as well as specific individual profiles – are statistically at elevated risk compared with others. Considering targeted attacks as akin to a public health issue and adapting techniques from epidemiology may allow the proactive identification of those at increased risk of attack. Our approach is a first step towards developing a predictive framework for the analysis of targeted threats, and may be leveraged for the development of cyber insurance schemes based on accurate risk assessments. <s> BIB004 </s> A Review of Text Watermarking: Theory, Methods, and Applications <s> I. INTRODUCTION <s> Digital steganography is the art and science of hiding communications; a steganographic system thus embeds secret data in public cover media so as not to arouse an eavesdropper's suspicion. A steganographic system has two main aspects: steganographic capacity and imperceptibility. However, these two characteristics are at odds with each other. Furthermore, it is quite difficult to increase the steganographic capacity and simultaneously maintain the imperceptibility of a steganographic system. Additionally, there are still very limited methods of Steganography to be used with communication protocols, which represent unconventional but promising Steganography mediums. Digital image Steganography, as a method of secret communication, aims to convey a large amount of secret data, relatively to the size of cover image, between communicating parties. Additionally, it aims to avoid the suspicion of non-communicating parties to this kind of communication. Thus, this research addresses and proposes some methods to improve these fundamental aspects of digital image Steganography. Hence, some characteristics and properties of digital images have been employed to increase the steganographic capacity and enhance the stego image quality (imperceptibility). Here, the research aim is identified based on the established definition of the research problem and motivations. Unlike encryption, Steganography hides the very existence of secret information rather than hiding its meaning only. Image based Steganography is the most common system used since digital images are widely used over the Internet and Web. However, the capacity is mostly limited and restricted by the size of cover images. In addition, there is a tradeoff between both steganographic capacity and stego image quality. Therefore, increasing steganographic capacity and enhancing stego image quality are still challenges, and this is exactly our research main aim. To get a high steganographic capacity, novel Steganography methods were proposed. The first method was based on using 8x8 non-overlapping blocks and quantization table for DCT with compression. Second method incorporates the DWT technique, with quality of any stego images as enhanced to get correct hidden image. And last LSB as to store images with Key type security built in. <s> BIB005 </s> A Review of Text Watermarking: Theory, Methods, and Applications <s> I. INTRODUCTION <s> Data protection from malicious attacks and misuse has become a crucial issue. Various types of data, including images, videos, audio and text documents, have given cause for the development of different methods for their protection. Cryptography, digital signatures and steganography are the most well known technologies used to protect data. During the last decade, digital watermarking technology has also been utilized as an alternative to prevent media forgery and tampering or falsification to ensure both copyright and authentication. Much work has been done to protect images, videos and audio but only a few algorithms have been considered for text document protection with digital watermarking. However, our survey observed that available text watermarking algorithms are neither robust nor imperceptible and as such remain unsecured methods of protection. Hence, research to improve the performance of text watermarking algorithms is required. This paper reviews current watermarking algorithms for text documents and categorizes text watermarking methods based on the way the text was treated during the watermarking process. It also discusses merits and demerits of available methods as well as recent proposed methods for evaluating text watermarking systems and the need for further research on digital text watermarking. <s> BIB006
The rapid developments currently observable in the field of information technology in the form of storage devices, digital content and communications has created a vast electronic environment with the ability to transmit, duplicate, copy and distribute information through digital media without any loss of quality. Nevertheless, this technological revolution in the online propagation of digital multimedia also suggests that such data are vulnerable to attacks, unauthorized access, and other threats BIB004 . Hence the study of information security which includes not just encryption but also traffic security whose essence lies in hiding data are increasing in demand BIB001 . Digital watermarking belongs to the branch of information hiding methods. It involves the idea of using an algorithm to hide copyright information by embedding it in the digital data. This copyright information can be in the form of text, image or logo chosen by the owner. Digital watermarking seems to be the most suitable application to protect intellectual property rights, identify ownership, keep track of digital media content, and ensure authentication and security [3] , BIB003 . Watermarking aims at protecting the rights of the owners of digital media. Even if an unauthorized copy is made or minor modifications are made to the watermarked file, the owner can still prove his original ownership. The goal of watermarking is to protect the cover file itself BIB005 . As of to date, digital data have come to invade almost all types of public media, be they in the form of audio, video, image and text. Among the media of digital content, text is the least discussed topic when it comes to information hiding. A digital text consists of any type of textual content in the form of monographs, articles, and webpages. These uploaded texts are prone to all kinds of attacks and copying, which in turn makes their security and protection a crucial matter. The protection of digital text has become difficult considering the lack of available techniques in handling the security of digital content BIB002 . Thus, it is very crucial to take control of the intellectual copyright over the text content, by first analyzing its nature of implementation and the theory behind it. Differences in text watermarking methods also contribute to the level of effectiveness in the protection of digital text BIB006 . FIGURE 1. Top 10 languages in the Internet in millions of users  . The rate of information accessible over the Internet is staggering. Of a considerable challenge posed to researchers and practitioners is that this growth rate exceeds their ability to design appropriate text watermarking techniques in order to protect the text based on the language used. It is crucial to preserve the integrity of the data content and at the same time ensure the confidentiality and availability of information. The rise of the Internet has resulted in an outgrowth of many languages including English, Chinese, Spanish, and Arabic  (see Fig. 1 ). However, the one method of text watermarking that's applicable for text of any languages has yet to be studied thoroughly and in depth. Many of the proposed text watermarking focused on certain types of language due to the differences in the nature and properties of its text. More general text watermarking techniques that can be applied to any types of text needs to be developed and tested in order to overcome the difficulty and vulnerability in information transfer and information hiding due to language barrier. Thus, the goal of this study is to carry out a comprehensive investigation of the current status of the development of text watermarking, which includes its theory, methods and applications. This comprises of the discussion on the text watermarking definition, embedding and extraction processes, requirements, approaches, and applications based on the languages used in the watermarking methods. This article also reviews in detail the new classification of text watermarking; which is according to the embedding process. Also discussed is the relationship between the embedding process against its related attacks and language applicability. Furthermore, open research challenges that require substantial research efforts are investigated, with focus on information integrity, information availability, originality preservation, information confidentiality, protection of sensitive information, document transformation, cryptography application, and language flexibility. The remainder of this paper is organized as follows. Section 2 presents the definition, overview and process of embedding and extracting the watermark. Section 3 outlines the currently available approaches of text watermarking. The requirements and measurements for text watermarking are presented in Section 4. Section 5 presents the main findings related to the logical and physical embedding process. The applications of text watermarking based on the three most widely used languages are discussed in Section 6. Section 7 summarizes the classifications done in the form of taxonomy. Several issues and research challenges are discussed in Section 8 followed by the conclusions of this research in Section 9. but needs the presence of X' and W (see Fig. 4 ). Semi-blind watermarking is used to see whether the watermark can be detected  .