Steganography is the process used hide the existence of information during transmission. Cover mediums like text, image, audio, and video protocols are used to hide the secret information. This process helps to provide secret communication between two parties. As data is unknown, it is challenging to attract the attention of any third parties. Therefore, steganography becomes the best and most secure method for data transmission. Digital images are the most common cover media or carriers in steganographic processes, where the secret payload is embedded into images. Several techniques are coming under image steganography, and there includes a different method to ensure the secrecy of messages. This chapter gives an overview of the different commonly used techniques in this area and the latest existing image steganography methods and the comparison of techniques.
TopIntroduction
Technology and internet usage have entirely changed in every social field. Social evolution is growing each and every day and affects our daily life also. Without the internet and technologies, a day will not pass (Hossen et al., 2020). As the internet revolution is increasing higher, the main challenge is to provide information security. People give more importance to privacy in life. Hidden communication is a difficult thing in this internet era. It is important to keep information secure from hackers or cyber-thieves so that a proactive security system is necessary (Kalaichelvi V et al., 2020). In such situations, security methods like cryptography, watermarking etc., gain attention. In this chapter, such a security strategy named Steganography and its latest existing methods are briefly discussed.
Steganography is an art of communication that provides a healthy means of security to information transmission and reception. It hides the existence of the information, which is the main factor which differ steganography from other hiding methods (Al-Sanjary O I et al., 2020). Steganography is a way of inserting a secret message in text/ image/ audio/ video or protocol. The main concept of steganography is illustrated in Figure 1.
Figure 1. shows the basic concept of steganography, the term cover file indicates the carrier like image, text, video or audio etc. The secret message is embedding in the cover file with the help of stego-key. Stego key is an optional key that uses in both the embedding and extraction process. After embedding, the output is obtained as a stego object or stego file containing the secret information in the cover file. At the extraction process, the secret message is extracting from stego object with the provided stego key. That stego key must be the same which used for embedding (Pramanik S et al., 2020).
Image steganography, text steganography, audio Steganography, video steganography or protocol steganography etc. are disparate kinds of steganographic means (Anusha M et al., 2020). Just as the cover file changes the method of Steganography will be different.
In the image steganography, a cover file that hides the secret message is an image. And stego-object becomes stego-image, which is the output image that contains a secret message (Kaur et al., 2020). The hiding process will not affect the physical properties of the carrier image. Therefore, it doesn't attract any attention of outside parties other than the sender and recipient. The basic concept of image steganography is shown in Figure 2.
Figure 2. Concept of Image Steganography
The hierarchical tree diagram of image steganography is given in Figure 3. to obtain a brief idea about basic technologies (Dhawan S & Gupta R., 2021).
Figure 3. General hierarchical tree diagram of image steganography
The Figure 4. shows the percentage of general image steganographic techniques in total percentage of surveyed papers. Out of 52 research papers, the half percentage is spatial domain techniques i.e., 50%. And 24% is transform domain techniques, 26% shows of other techniques.
Figure 4. General Pie-chart of all methods
Out of total 50% of spatial techniques, 76% is Least significant bit insertion method because of the easiness. And the second most commonly used method is Pixel value differentiation scheme which is as 24% of total. The pie-diagram is shown in Figure 5.
Figure 5.
Pie-chart of Spatial domain techniques