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Experiments have been implemented in Matlab 2010 release using the 16-bit double precision floating point real numbers radio map CYGUS A. The message size is 42976 bits, equal to the images capacity, that is maximum amount of data that can be embedded into the image map. The constant value d, according to which the WHD coefficient is shifted is experimentally chosen to be 0:0001. The proposed embedding algorithm is proved to be robust to FITS Liberator conversion into 16-bit depth, by only using the linear stretch function with white and black levels equal to the maximum and minimum values of the produced stego-fits image. As a consequence, all the dynamic range of the FITS image is exported into the TIF image and further image editing can be made with any image editing application, supporting 16-bit TIF format, with the advantage that information can be extracted from the image that in any other case would have been lost (eg. the flux of the source and the rms of the map). Experimental results show that embedding procedure makes no visual artifacts, so that the statistics remain unchanged and the good quality of the image is retained.

4 References

[1] Husrev Sencar, Mahalingam Ramkumar, Ali Akansu, ′Data Hiding Fundamentals and Applications′, Elsevier, 2004 [2] W. Bender, W. Butera, D. Gruhl, R. Hwang, F. J. Paiz, S. Pogreb, ′Applications for data hiding′, IBM Systems Journal, Volume 39 Issue 3-4, July 2000 [3] The ESA/ESO/NASA FITS Liberator v3 - ESA/Hubble http://www.spacetelescope.org/projects/fits−liberator/ [4] George J. Miao, Mark A. Clements, ′Digital Signal Processing and Statistical Classification′, Artech House, Inc. Norwood, MA, USA, 2002

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