Multimedia information security: Cryptography and steganography

Information security has traditionally been ensured with data encryption techniques. Different generic data encryption standards, such as DES, RSA, AES, have been developed. These encryption standards provide high level of security to the encrypted data. However, they are not very efficient in the encryption of multimedia contents due to the large volume of digital image/video data. In order to address this issue, different image/video encryption methodologies have been developed. These methodologies encrypt only the key parameters of image/video data instead of encrypting it as a bitstream. Joint compressionencryption is a very promising direction for image/video encryption. Nowadays, researchers start to utilize information hiding techniques to enhance the security level of data encryption methodologies. Information hiding conceals not only the content of the secret message, but also its very existence. In terms of the amount of data to be embedded, information hiding methodologies can be classified into low bitrate and high bitrate algorithms. In terms of the domain for embedding, they can be classified into spatial domain and transform domain algorithms. In this chapter, we have reviewed various data encryption standards, image/video encryption algorithms, and joint compression-encryption methodologies. Besides, we have also presented different categories of information hiding methodologies as well as data embedding strategies for digital image/video contents. This chapter is organized as following: in Section-1, we give a brief introduction to data encryption system as well as the state-of-the-art encryption standards; Section-2 presents a review of representative image encryption algorithms; Section-3 first gives a brief introduction of lossless compression and then moves to joint compression-encryption algorithms; Section-4 presents different video encryption methodologies; Section-5 gives a brief introduction to information hiding techniques; Section-6 presents different categories of low bitrate information algorithms; Section-7 presents different categories of high bitrate information algorithms; Section-8 discusses the embedding strategies within digital video contents; this chapter is summarized in Section-9