Secure steganography based on embedding capacity

Abstract

Mostly the embedding capacity of steganography methods is assessed in non-zero DCT coefficients. Due to unequal distribution of non-zero DCT coefficients in images with different contents, images with the same number of non-zero DCT coefficients may have different actual embedding capacities. This paper introduces embedding capacity as a property of images in the presence of multiple steganalyzers, and discusses a method for computing embedding capacity of cover images. Using the capacity constraint, embedding can be done more secure than the state when the embedder does not know how much data can be hidden securely in an image. In our proposed approach, an ensemble system that uses different steganalyzer units determines the security limits for embedding in cover images. In this system, each steganalyzer unit is formed by a combination of multiple steganalyzers from the same type, which are sensitive to different payloads. The confidence of each steganalyzer on an image leads us to determine the upper bound of embedding rate for the image. Considering embedding capacity, the steganographer can minimize the risk of detection by selecting a proper cover image that is secure for a certain payload. Moreover, we analyzed the relation between complexity and embedding capacity of images. Experimental results showed the effectiveness of the proposed approach in enhancing the security of stego images.