In this digital era, with the advent of technology like 4G network and VOIP, video calling is the most cost effective and cutting-edge communication technique. Simultaneously, video sharing through social networking sites is very popular, as it can reach a wider public domain in seconds. This enormous use of video motivates the fact that as digital medium video can be effectively utilized for secret sharing. Using video steganography, any kind of secret data like text, image, audio, even a short video can be hidden inside another video object, which can be securely transmitted to the recipient over the internet. In this chapter, an effort has been made to relate various techniques of video steganography under a single header to identify future scope of research. Also, all possible quality metrics for videos and for measuring robustness have been studied, and different steganalysis attacks on video have been analyzed. The broad mission of this chapter is to be a quick reference to future researchers of video steganography.
TopIntroduction To Video Steganography
In this era of internet, communication through postal mail or through PSTN are out dated. In near future, talking over cellular phone or sending e-mail may become obsolete, as VOIP call and video chats are developing into cheapest and most innovative communication channel. In recent times, one of the trendy way of communication is video sharing in social networking sites, through which within a minute, it is possible to reach a wider domain of public. Those videos are created for literally all kind of subjects like movies, songs, animations, advertisements, recipes, lectures, handcrafts etc., and can be easily shared through social networking sites like YouTube, Facebook, Twitter, Instagram, LinkedIn, Reddit etc. As per recent press release of the most popular video sharing website YouTube, they have over 1,300,000,000 users and each day those users watch a billion hours of video; In every minute, approximately 300 hours of videos are uploaded to YouTube. All these facts reveal that video is grabbing almost 80% of digital data now-a-days.
As communication using video becomes prevalent, it turns into necessary to protect video communication from tampering. Video can also be used as carrier of secret data, which can be transmitted over the globe to the intended recipient without any obstacles from the network administrator or the intruder, as no one can anticipate existence of secret data, hidden inside video. Steganography is very primeval technique of data hiding where except sender and intended recipient, no one is aware of presence of hidden data even beyond their presumption. With the arrival of internet, digital steganography replaces the primitive ways of steganography. In steganography, there are three objects –
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Cover: The object where the secret data would be hidden
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Secret: The object to be hidden
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Stego: The object created after data hiding is completed
Gupta Banik, B., & Bandyopadhyay, S. K. (2015) have shown that in digital steganography, the cover and secret can be any digital objects like text, image, audio, and video. The stego object is similar to cover object in format and up to human perception.
In Video Steganography, cover object is chosen as video, where secret data is hidden. A video is collection of frames and a frame is similar to a still image. If motion is created by arranging sequential frames one after another, then video is generated. Since the size of the video is bigger than any other digital cover media (like image, text, audio etc.), hence it is possible to hide large amount of data in a video. With the advent of computer technology, there are plenty of video compression techniques available (like MPEG-7 or H.264/AVC), which reduces the overall video size keeping duration of the video intact. Even such compressed videos can also be used as carrier of secret data. The general block diagram of video steganography to create stego video has been shown in Figure 1.
Figure 1. Stego video creation technique in video steganography
In this article, various techniques of video steganography are studied along with their quality metrices and different steganalysis attacks on video have been performed, using which the robustness of the steganography method can be determined. At last, the discussed approaches are compared to unveil the future prospect of video steganography.
TopIntroduction To Video
A sequence of images used to compose a moving picture is called video, whereas those individual images are known as frames. Therefore, to hide any secret, at first video needs to be broken into frames. Then by Scene Change Detection process, one/few particular frames are selected where secret data can be hidden.
The frequency at which frames are displayed known as frame rate. Read, P., & Meyer, M.-P. (2000) states generally human visual system can process 10-15 frames per second. Videos are saved in compressed format otherwise it could have taken bulk memory space. There are different formats available in Video, among those, MPEG format is most popular; hence it has been discussed here.