A Complexity Approach for Steganalysis

Robustness and security are two major concerns in information hiding. These two concerns have been defined in [6] as follows. “Robust watermarking is a mechanism to create a communication channel that is multiplexed into original content [...]. It is required that, firstly, the perceptual degradation of the marked content [...] is minimal and, secondly, that the capacity of the watermark channel degrades as a smooth function of the degradation of the marked content. [...]. Watermarking security refers to the inability by unauthorized users to have access to the raw watermarking channel. [...] to remove, detect and estimate, write or modify the raw watermarking bits.” In the framework of watermarking and steganography, security has seen several important developments since the last decade [1, 4, 7]. The first fundamental work in security was made by Cachin in the context of steganography [2]. Cachin interprets the attempts of an attacker to distinguish between an innocent image and a stego-content as a hypothesis testing problem. In this document, the basic properties of a stegosystem are defined using the notions of entropy, mutual information, and relative entropy. Mittelholzer, inspired by the work of Cachin, proposed the first theoretical framework for analyzing the security of a watermarking scheme [8]. These efforts to bring a theoretical framework for security in steganography and watermarking have been followed up by Kalker, who tries to clarify the concepts (robustness vs. security), and the classifications of watermarking attacks [6]. This work has been deepened by Furon et al., who have translated Kerckhoffs’ principle (Alice and Bob shall only rely on some previously shared secret for privacy), from cryptography to data hiding [5]. They used Diffie and Hellman methodology, and Shannon’s cryptographic framework [10], to classify the watermarking attacks into categories, according to the type of information Eve has access to [4, 9], namely : Watermarked Only Attack (WOA), Known