On the Security of “A Steganographic Scheme for Secure Communications Based on the Chaos and the Euler Theorem”

This paper contains a security analysis of the construction of a public key steganographic system based on chaos theory and the Euler theorem (PKS-CE) as proposed by Lou and Sung in a previous issue of this transactions. Our analysis results in attack strategies on two different layers: first, we identify weaknesses of the embedding function, which allow a passive warden to tell steganographic images from clean carriers apart. Second, we show that the allegedly asymmetric trap-door function in fact can be efficiently inverted solely with the knowledge of its public parameters, thus revealing the secret message as plain text to a passive adversary. Experimental results from a re-implementation further indicate that the claimed robustness of the embedded message against transformations of the carrier medium was far too optimistic. Finally, we demonstrate that a secure alternative system can easily be constructed from standard primitives if the strong assumptions made in PKS-CE for the mutual key exchange can actually be fulfilled.