
This work considers digital images as covers and fondation is
spatial least significant-bit (LSB) replacement.
I this data hiding scheme a subset of all the LSB of the cover image is modified 
with a secret bit stream depending on to a key, the cover, and the message to embed.
This well studied steganographic approach  never decreases (resp. increases)
pixel with even value (resp. odd value) and may break structural symetry.
These structural modification can be detected  by statistical approaches 
and thus by steganalysis methods~\cite{DBLP:journals/tsp/DumitrescuWW03,DBLP:conf/mmsec/FridrichGD01,Dumitrescu:2005:LSB:1073170.1073176}

This drawback is avoided in LSB matching (LSBM) where
the $+1$ or $-1$ is randomly added to the cover pixel LSB value 
only if this one does not match the secret bit.
Since probabilities of increasing or decreasing pixel value are the same, statistical approaches 
cannot be applied there to discover stego-images in LSBM.
The most accurate detectors for this matching are universal steganalysers such as~\cite{LHS08,DBLP:conf/ih/2005,FK12}
which classify images thanks to extracted features from neighboring elements of noise residual.  

LSB matching revisited (LSBMR)~\cite{Mielikainen06} have been recently introduced. 
For a given pair of pixels, in which the LSB
of the first pixel carries one bit of secret message, and the relationship
(odd–even combination) of the two pixel values carries
another bit of secret message. 



In such a way, the modification
rate of pixels can decrease from 0.5 to 0.375 bits/pixel
(bpp) in the case of a maximum embedding rate, meaning fewer
changes to the cover image at the same payload compared to
LSB replacement and LSBM. It is also shown that such a new
scheme can avoid the LSB replacement style asymmetry, and
thus it should make the detection slightly more difficult than the
LSBM approach based on our experiments

random LSB selection: coarse, easily tractable, easilly detactable



feature-based : precise but time consuming 

security need : message has to be encrypted before beeing introduced. Using efficient and secured cryptographic approach

LSBR: to coarse (apply hugo breaker on it)
