Cryptographic measures in information hiding

Recent information hiding schemes are scrutinized in terms of their cryptographic performance. We establish conditions under which the key equivocation function is optimal for the studied schemes, and show that, under a reasonable key generation model, the perfect secrecy property is nearly satisfied, limited by a mutual information measure that decreases exponentially with the block length. The novelty of the work is to extend classical cryptographic analysis results to schemes involving cover signals, a component absent from standard cryptography. The schemes show unexpectedly good cryptographic security, although we observe that information embedding with robustness has steganographic weaknesses.