  The Least Significant Bit (LSB) substitution is an old and simple data hiding
method that could almost effortlessly be implemented in spatial or transform
domain over any digital media. This method can be attacked by several
steganalysis methods, because it detectably changes statistical and perceptual
characteristics of the cover signal. A typical method for steganalysis of the
LSB substitution is the histogram attack that attempts to diagnose anomalies in
the cover image's histogram. A well-known method to stand the histogram attack
is the LSB+ steganography that intentionally embeds some extra bits to make the
histogram look natural. However, the LSB+ method still affects the perceptual
and statistical characteristics of the cover signal. In this paper, we propose
a new method for image steganography, called LSB++, which improves over the
LSB+ image steganography by decreasing the amount of changes made to the
perceptual and statistical attributes of the cover image. We identify some
sensitive pixels affecting the signal characteristics, and then lock and keep
them from the extra bit embedding process of the LSB+ method, by introducing a
new embedding key. Evaluation results show that, without reducing the embedding
capacity, our method can decrease potentially detectable changes caused by the
embedding process.
