International Journal of Advance Foundation and Research in Computer (IJAFRC) Volume 2, Issue 12, December - 2015. ISSN 2348 – 4853, Impact Factor – 1.317 A Comprehensive Study of Cryptography & Content Hiding Techniques for Security of Digital Videos Mr.Chaitanya Vijaykumar Mahamuni. PG Research Scholar in Electronics & Telecommunication Engineering, University of Mumbai.
[email protected] ABSTRACT A multimedia system is a system which is used to process the multimedia data and the applications of it. The multimedia database usually comprises of the data in the form of text, images, audio and graphic objects. A video consists of moving images with the presence of audio i.e. sound in it because of which the information can be conveyed effectively through it. Thus the digital videos have formed a very important place in most of the digital information systems. The two fundamental considerations in the transmission of a digital video are security and authentication of the data. Hence, use of cryptography and steganography or watermarking techniques for transmission of digital videos in multimedia systems play an important role. This paper presents a comprehensive study of cryptography and data hiding techniques i.e. both steganography and watermarking techniques in digital videos to develop a smart and secure multimedia based application. The purpose of cryptography is to hide the content of the message while the steganography aims to hide the existence of the message itself to prevent its unauthorized access, hence also known as covered writing. The watermarking techniques also do the same thing but the objective of using them is to maintain the unique identity of owner and authenticate the file. Thus if we use both cryptographic schemes and the tools or methods for hiding the existence of data, then it will enhance the level of security in terms of prevention of illegal/fraud access, protection of right of the ownership of the file. Therefore, both the aspects should be simultaneously taken into consideration so far the development of security systems for digital videos is concerned is suggested in the paper. Index Terms: Multimedia, video, cryptography, steganography, watermarking, and security. I. INTRODUCTION A video can be defined as visual multimedia source in which a series of images are combined together in the form of a moving picture. The video can be of two types- analog video and digital video. The analog video is a video that represents the motion of the visual images with analog signal whereas in the digital video, the images in the form of encoded digital data are set in motion. The digital bitmap images those are orthogonal in the form of series when played sequentially at a fast speed with a constant rate make a digital video. The rate at which these images i.e. frame in case of a video is called as Frames per Second (FpS). Every color corresponds to a fixed set of bits. We can vary the color by changing the number of bits associated with it which is known as Color Depth (CD). The width and height of the frame are W and H. The two most important parameters of a digital video are its size and bit-rate which are calculated as follows: 1. Bit-rate = W*H*CD*FpS 2. Video size = Bit-rate*T The applications of the digital video include digital television broadcasts, cinemas, playback from DVD, video-streaming and conferencing over wired or wireless internet. A multimedia system basically involves processing of the multimedia files. Besides the other functions like storing, producing, manipulating and retaining the multimedia information are related to it. The digital videos are widely used in the multimedia based applications because they can effectively convey the information in the audio visual form. However, the transmission of video files through a wired or wireless network is a challenging task. The security and authentication of content present in the video files is a sensitive issue. This goal can be 46 | © 2015, IJAFRC All Rights Reserved www.ijfarc.org International Journal of Advance Foundation and Research in Computer (IJAFRC) Volume 2, Issue 12, December - 2015. ISSN 2348 – 4853, Impact Factor – 1.317 accomplished by use of cryptography and steganography for transmission of digital videos. The next section covers a detailed study of cryptography and steganography in digital videos for multimedia based applications. II.CRYPTOGRAPHY IN DIGITAL VIDEOS If we explore the digital videos, then the important factors that cause a major concern to us will basically include the following: 1. Use of efficient coding techniques. 2. High networking speed. 3. Low cost storage mechanisms. 4. Good quality of cam-recorders. It is expected that in near future, almost all the data in the digital form will be stored in the form of video and rich media. Some of the systems where the use of cryptographic methods is needed in the videos are listed below: 1. Interactive Television. 2. Training and learning through distance education. 3. Video on Demand (VOD). 4. Movie on Demand (MOD). 5. Conferencing Services. Most of the video content transmitted via streaming protocols such as MMS, RTSP is not secure. Such types of files are highly prone to get passively attacked while transmitted over the network. Suppose that there is an online video conversation between two officers or conversation between two people, one in national administrative control unit and another military person in his headquarters, there is wide possibility of unauthorized access of the data by network attackers due to which a threat to security of commercial and military information. A. NEED OF CRYPTOGRAPHY IN DIGITAL VIDEOS The image and video encryption becomes important in the multimedia applications due to the following reasons: 1. To avoid a third party or any other unwanted person from tapping and extracting the content of transmitted video. 2. The private messages can be prevented from getting exchanged when transmitted over the wired or wireless networks. 3. The transmission of secure videos will improve QoS attributes of video services like Video on Demand (VOD), e-learning through videos, video conferencing etc. 4. The videos of medical diagnosis of patient may contain some confidential information related to patient’s health which is prone to be accessed by malicious users; it can be prevented by using robust encryption of the video file. 5. The security of the transmitted data is major factor that influence the QoS of any of the digital multimedia system and it can be taken care of by use of effective cryptographic methods. B. APPROCHES AND METHODS OF VIDEO ENCRYPTION [1] The plain text or a video stream can be done in two ways i.e. private key encryption and public key encryption. In single key encryption, only one key is used for both encryption and decryption. This key is secret between sender and receiver. The level of security depends on how properly and safely the key is used by the two. The DES, Double DES, Triple DES, AES. In public key encryption, there is a public key which is known by all the senders used for encryption while the receiver only has the knowledge of public key. 47 | © 2015, IJAFRC All Rights Reserved www.ijfarc.org International Journal of Advance Foundation and Research in Computer (IJAFRC) Volume 2, Issue 12, December - 2015. ISSN 2348 – 4853, Impact Factor – 1.317 The examples of public key cryptography schemes are RSA, DH Key Exchange. These methods are also known as symmetric key and asymmetric key methods. The comparison of symmetric and asymmetric methods is below: Table no.1: Comparison of symmetric and asymmetric methods. The two approaches followed for the video encryption are full encryption and selective encryption. The full encryption is a type of encryption in which the entire video bit-stream undergoes encryption while in the other type selected bytes from video frame are encrypted. The various methods for encryption of a video are as explained below: 1. Native Method: In this method, all the bit-streams from a MPEG video are encrypted using a standard algorithm like AES or DES. 2. Permutation based algorithms: The permutation function is used to scramble the bytes present in the MPEG video bit-stream. The permutation can be either pure permutation or zigzag type of permutation. The zigzag permutation maps a block into a vector by using random permutation which gives a better encryption result. 3. Forming-deforming algorithm: It is a full encryption method in which encryption is achieved based on the key image. The video encryption is a result of the I-frame encryption. Ith frame is computed by using a specific mathematical process. 4. Video Encryption Algorithm (VEA): The original video-stream will be divided into parts i.e. even parts and odd parts. The even part will be encrypted and the encrypted part will be XOR with even part that gives the resultant cipher text. The comparison of the video encryption methods is shown in the following table: Table no.2: Comparison of video encryption methods 48 | © 2015, IJAFRC All Rights Reserved www.ijfarc.org International Journal of Advance Foundation and Research in Computer (IJAFRC) Volume 2, Issue 12, December - 2015. ISSN 2348 – 4853, Impact Factor – 1.317 C. LITERATURE REVIEW The paper [2] gives a detailed history of video encryption. Onwards mid of 1990’s, several efforts have been made to develop algorithms specifically for the encryption of the video. Fuhrt and Kirovski in 2004 gave detailed information through study of all the early algorithms for encryption of a video. Fumen Liu and Harmut in 2010 showed classification of video encryption schemes related to the compression of a video. The computational complexity is reduced by the encryption of DCT coefficients. The next i.e. REVA can sustain the plain text but inability to counter the perceptual attack. Perceptual MPEG video encryption algorithm selectively encrypts the FLC’s under the control of intra DC co-efficient, non-intra DC co-efficient, sign bits and residuals of motion vectors. Each will have different visual quality. Cheng and Li in 2000 proposed a scheme for partial encryption of images; it was further extended for videos. The method was used for encryption of I-frame, residual error code of bit stream and motion vectors. Wen et al in 2002 generalized the concept of selective bit-stream encryption into a new method called as format compliant configurable encryption. Zeing and Lei in the same year proposed the algorithm for scrambling the bytes in the bit-stream of a video. Wu and Kuo in the years 2000 and 2005 respectively put forward Multiple Huffman Table (HMT) encryption scheme and Multiple State Indicies (MSI). The encryption was done during the entropy coding The chaotic maps [3] are used for encrypting an image or video. In case of chaotic maps, the encryption process fully depends on arithmetic coding and so it is called as Chaotic Arithmetic Coding (CAC). In this method, a large number of chaotic maps are employed to achieve the goal of attaining Shanon Optimal Performance. The key utilized will determine which map should be used. The method allows encryption of video without any trading the coding efficiency. The paper [4] presents a new method to encode VLC multimedia bit-streams. The diffusion of the codeword and the techniques for shuffling the content can be together employed to enhance the security of multimedia files. A random code generator based on chaotic maps and a block with lower level of complexity for shuffling procedures. The content of the file to be encrypted will be divided into a random number of blocks with arbitrary size; some bits in each block will be altered so that correlation amongst the codeword gets diffused. The blocks will be now randomly shuffled. The AES algorithm i.e. Advanced Encryption Standard in [5] emerged as one of the popular schemes for encryption of a video. This algorithm offers flexibility of combining the data with key size varying as 128, 192 and 256 bits. The 128 bit data is usually divided into four parts where each part can be called as a state. This algorithm is one of the efficient schemes for video encryption. The encryption schemes can be effectively used with an upper limit of no of frames that determine the run time of the video. The encryption of live videos or larger size multimedia files is difficult task. The 49 | © 2015, IJAFRC All Rights Reserved www.ijfarc.org International Journal of Advance Foundation and Research in Computer (IJAFRC) Volume 2, Issue 12, December - 2015. ISSN 2348 – 4853, Impact Factor – 1.317 development of new schemes and algorithms that can enhance the security of the file by improving the metrics for evaluation of the performance is one of the major research challenges. III. TECHNIQUES FOR CONTENT HIDING IN DIGITAL VIDEOS There are two ways of hiding the information namely: 1. Steganography 2. Watermarking In watermarking, the purpose of hiding the data is either authentication of data or to demonstrate the intellectual property rights whereas steganography aims to hide the data to prevent the access of the data to the third party. Steganography and cryptography both are used to make the data confidential but the major difference between the two is cryptography secures the message while steganography makes the message hidden. Preventing the creation of unauthorized versions of the data and maintaining authentication of owner of file can be achieved by using watermarking. If the actual message is embedded within a cover file then message becomes locked because of which accessing the file becomes highly difficult. The technique of hiding the data which is embedded using redundant cover that may be either an image, audio, document or a movie. The text steganography is the simplest form but the problem is that it has limited capacity. The confidentiality of secure message in the text steganography however cannot be measured. The image based steganography however shows an improved capacity. The steganography techniques can be equivalently used in the applications digital audio, sensitive text documents, images of different types like images conveying medical data, some text being transmitted in the form of images or the series of images displayed in rapid succession. The different ways of hiding data in a video file [6] are explained below 1. Exploitation of YCbCr color space based steganography: YCbCr space is a space that eliminates the correlation amongst R, G and B in the given image. Since the amount of correlation between the colors is very less, the distortion is highly negligible. This method largely focuses on human video images i.e. the tone of the skin and color for hiding the data. It can be used to detect forged documents, ID card etc. 2. Embedding in transform domain: This is one of the difficult methods of hiding the information within an image. Different algorithms and transformations are used for it. The DCT transform used in the JPEG compression scheme will transform 8*8 pixel matrix resulting into 64 DCT coefficients. The division of image into two distinct parts or spectral sub-bands of varying significance w.r.t the visual quality of image is done. The drawback of this method is that since most of the DCT coefficients out of 64 are zero and more the frequency of changing the zeros to non-zero values , cause an ambiguity in the compression rate. Thus the number of bits that one can put in the transform domain using DCT is less than LSB technique which is discussed next. 3. Insertion of bit in LSB position: This method is one of the simplest techniques for steganography. It is known as LSB technique since the LSB bit of one byte is used for storing the secret data. The change after insertion of data in the stego-bit is not identifiable to human eye. Lossless image compression techniques must be used. The use of lossy techniques may result into loss of hidden information. 4. Representation of video as distinct images: Every single frame of the video is represented as distinct image in which the information is supposed to be hidden. This is an advantageous method as the algorithm for image can be equivalently used for video also. However, a large amount of computation is required. 50 | © 2015, IJAFRC All Rights Reserved www.ijfarc.org International Journal of Advance Foundation and Research in Computer (IJAFRC) Volume 2, Issue 12, December - 2015. ISSN 2348 – 4853, Impact Factor – 1.317 5. Real time video steganography: In this method, we hide the information generated by any device like advertisement billboard. Each frame shown on the device is essentially considered to be an image and then converted into blocks. If the block colors are same, then they are changed so that data hiding is possible. 6. Another aspect of data hiding i.e. watermarking in videos: The term watermarking means inserting some other data in the form of watermark (usually a watermark image) into the original file. The watermark can be either visible or invisible. A combination of various image transforms like DCT, DWT and feature extraction algorithms like PCA, ICA etc can be used to achieve it. The purpose of inserting a watermark is protecting the right of the owner of the file. If someone gets an authorized access to the file and steals it, shows it as his or her data, the presence of watermark will be able to detect the cheating and preserve the ownership rights. A comparison is shown below Table no.3: Comparison of cryptography, steganography and watermarking. IV. CONCLUSION The use of digital videos for data storage in multimedia systems and applications has been increasing. Hence the security of the content of the video when it is transmitted over the network plays an important role. The various aspects related to the security systems for the digital videos include cryptography, steganography and watermarking. The purpose of cryptography is third party not being able to reveal the content of message while steganography aims inability of attacker to identify that the message is transmitted over the network and it exists there. A complete study of the various methods of encryption of a video, detailed literature survey and their comparative analysis was done. The different of hiding the data in the video file were listed and discussed. Although the ultimate use of cryptography, steganography and watermarking is for the same purpose, the three things are different aspects or directions for development of security systems. Thus, in order to develop a smart robust and highly efficient security system, the combination of cryptography and data hiding techniques i.e. either steganography or watermarking should be integrated together in right way. V. REFERENCES [1] Negi, Yogita. "A Survey on Video Encryption Techniques." International Journal of Emerging Technology and Advanced Engineering 3.4 (2013). [2] Hooda, Darshana, and Parvinder Singh. "A comprehensive survey of video encryption algorithms." IJCA. Vol. 59. No. 1. 2012. 51 | © 2015, IJAFRC All Rights Reserved www.ijfarc.org International Journal of Advance Foundation and Research in Computer (IJAFRC) Volume 2, Issue 12, December - 2015. ISSN 2348 – 4853, Impact Factor – 1.317 [3] Amit Pande, Prasant Mohapatra, Joseph Zambreno,” Using Chaotic Maps for Encrypting Image and Video Content”, 2011 IEEE International Symposium on Multimedia [4] Sufyan T. Faraj Al-Janabi, Khalida Shaaban Rijab, Ali Makki Sagheer,” Video Encryption Based on Special Huffman Coding and Rabbit Stream Cipher”, 2011 Developments in E- systems Engineering. [5] Mayank Arya Chandra, Dr. Ravindra Purwar, Dr. Navin Rajpal ,”A Novel Approach of Digital Video Encryption”, International Journal of Computer Applications (0975 – 8887) Volume 49– No.4, July 2012. [6] Al-Frajat, A. K., et al. "Hiding data in video file: An overview." J. Appl. Sci10.15 (2010): 1644-1649. [7] Swanson, Mitchell D., Bin Zhu, and Ahmed H. Tewfik. "Data hiding for video-in-video." Image Processing, 1997. Proceedings, International Conference on. Vol. 2. IEEE, 1997. [8] Bender, Walter, et al. "Techniques for data hiding." IBM systems journal 35.3.4 (1996): 313-336. [9] Potdar, Vidyasagar M., Song Han, and Elizabeth Chang. "A survey of digital image watermarking techniques." Industrial Informatics, 2005. INDIN'05. 2005 3rd IEEE International Conference on. IEEE, 2005. [10] Petitcolas, Fabien AP, Ross J. Anderson, and Markus G. Kuhn. "Information hiding-a survey" .Proceedings of the IEEE 87.7 (1999): 1062-1078. AUTHORS BIOGRAPHY Mr. Chaitanya Vijaykumar Mahamuni was born on 6th Oct, 1991 at Gadhinglaj in Kolhapur district in state of Maharashtra. He has completed the graduation in Electronics & Telecommunication Engineering from University of Mumbai in 2013. Presently he pursues Masters in Electronics & Telecommunication Engineering. He has published and presented altogether seven papers in refereed international journals and conferences. His research work till date is related to use of cryptographic schemes and content hiding techniques, feature extraction methods and wavelets in development of algorithms for security of digital videos, study of metamaterials and plasmonics in microwave & millimeter-wave wireless systems, miniaturization of antennas, smart nano-micro systems, coverage enhancement by effective sleep scheduling in wireless sensor networks. 52 | © 2015, IJAFRC All Rights Reserved www.ijfarc.org