Steganography is the art of hiding data in a medium without making it apparent that the medium contains a message. Various techniques for Steganography have been proposed in different mediums by researchers. The most commonly used form of Steganography is the LSB (Least Significant Bit) Steganography in which the Least Significant Bit of a byte is changed. Here, we propose a variable higher bit approach to Steganography with audio as our medium of choice. We present an algorithm which uses either of 2 consecutive higher order bits to hide data. In this approach, instead of simply setting or resetting the relevant bit, the whole byte is modified so that it retains the data while being nearest to the original byte value. Since the LSB itself is not used in this method, an additional bit of data can also be hidden if need be.

It is shown that the sign detection technique for binary signeddigit number system reported by Srikanthan, Lam and Suman [1] cannot work correctly. The root cause of the problem is detected and some modifications are proposed. The proposed modifications are found to be significant.

In this article, it is shown that although the reverse conversion scheme for binary signed-digit number system proposed by Choo et. al. can not support full parallelism; the rules on which it is based are correct. In this connection, a mathematical induction technique is used to validate the decomposition rules. Accordingly, it can be inferred that the reverse conversion scheme for binary signed-digit number system proposed by Veeramachaneni et. al. works correctly and performs reverse conversion in Ω (log n) time, where, n is the input size. As a consequence, the scheme by Veeramachaneni et. al. need to be considered as a potential contender of the more recent schemes for the same.

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