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Does psnr of stego image for LSB after AES algorithm and LSB after RC4 algorithm have any difference?
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Image Analyst on 15 Aug 2015
Try it and see. There is a psnr() function in the Image Processing Toolbox.
Walter Roberson on 15 Aug 2015
Encryption is most useful when its output is statistically identical to random, so that you cannot perform correlation attacks on the output.
There are two possibilities: either the two encryption schemes have different random statistics or they have the same random statistics. If they have different random statistics then clearly psnr would have to be different. If they have the same random statistics then the question becomes equivalent to asking whether the psnr measurements of two different random samples are going to be the same. And the answer to that is "probably they will be different". If you flip a coin 20 times in a row and record the number of "heads", and then flip again 20 times in a row and record the number of "heads" for that, the number is probably going to be different.