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. Index Terms — Information hiding; wet paper coding; key equivocation; message equivocation; perfect secrecy. 1.

the secure embedding scheme (see Section II), it is hard to generate a watermarked version of c which has a low correlation with k0. An estimation attack usually yields a watermarked object that still correlates well with k0; a judge will reject the accusation on such an object, as it can only originate from a malicious seller (k0 is only available to the seller). • Finally, can attempt to cheat in step 6 by submitting the customer a wrongly encrypted watermark EK (nkw 8 k). However, this is detected by the client in step 7 by checking the integrity of the transaction number contained therein. IV. CONCLUSION In this correspondence, we proposed a buyer–seller protocol that utilizes the concepts of secure watermark embedding. In contrast to the known solutions, which use homomorphic public-key encryption on the content and impose unpractical constraints on computational resources and transmission bandwidth, our protocol is efficient due to the use of recent secure embedding algorithms.

Abstract — This paper proposes a practical successive decoding scheme with finite levels for the finite-state Markov channels where there is no a priori state information at the transmitter or the receiver. The design employs either a random interleaver or a deterministic interleaver with an irregular pattern and an optional iterative estimation and decoding procedure within each level. The interleaver design criteria may be the achievable rate or the extrinsic information transfer (EXIT) chart, depending on the receiver type. For random interleavers, the optimization problem is solved efficiently using a pilot-utility function, while for deterministic interleavers, a good construction is given using empirical rules. Simulation results demonstrate that the new successive decoding scheme combined with irregular low-density parity-check codes can approach the identically and uniformly distributed (i.u.d.) input capacity on the Markov-fading channel using only a few levels. Index Terms — Capacity, decision feedback, fading channel, finite-state Markov channel, low-density parity-check (LDPC) codes, Markov channel, multistage decoding, mutual information, successive decoding. I.