  ...The steganography scheme makes it possible to hide the medical image in
different bit locations of host media without inviting suspicion. The Secret
file is embedded in a cover media with a key. At the receiving end the key can
be derived by all the classes which are higher in the hierarchy using symmetric
polynomial and the medical image file can be retrieved. The system is
implemented and found to be secure, fast and scalable. Simulation results show
that the system is dynamic in nature and allows any type of hierarchy. The
proposed approach performs better even during frequent member joins and leaves.
The computation cost is reduced as the same algorithm is used for key
computation and descendant key derivation. Steganographic technique used in
this paper does not use the conventional LSB's and uses two bit positions and
the hidden data occurs only from a frame which is dictated by the key that is
used. Hence the quality of stego data is improved.
