  Steganography (literally meaning covered writing) is the art and science of
embedding secret message into seemingly harmless message. Stenography is
practice from olden days where in ancient Greece people used wooden blocks to
inscribe secret data and cover the date with wax and write normal message on
it. Today stenography is used in various field like multimedia, networks,
medical, military etc. With increasing technology trends steganography is
becoming more and more advanced where people not only interested on hiding
messages in multimedia data (cover data) but also at the receiving end they are
willing to obtain original cover data without any distortion after extracting
secret message. This paper will discuss few irreversible data hiding techniques
and also, some recently proposed reversible data hiding approach using images.
