In post globalization era of computer networks and communication, image and video plays a significance role; rather the fashion of text based systems will be replaced by the image based system. The associated threats and challenges related to image security and its authentication is an active research issues. In order to ensure a full proof security mechanism for image the notion of message authentication code for data authentication and notion of encryption for preserving confidentiality need to be combined. In this paper a complete frame work of crypto-system has been proposed, where the parameterization of hash value of encrypted image is done in such a way that it should be exactly same with zero difference error of hash value that of the parent unencrypted original image. It will have enormous scope into various medical imaging systems where privacy preservation is an important issue. Designing parametric hashing algorithm, which is invariant to encryption only by accepting small part of statistical signature of the original unencrypted image to emerge despite the encryption process is a non trivial task. The proposed work formulates authentication of encrypted data by using notion of authentication code and a novel but yet simple hashing algorithm which are usable with encrypted image s. The implementation results of various images, where the hash value is being computed without the decryption of the original input image, thus validates the authentication without compromising the privacy information. Since the hash value is computed without decrypting the original data, one can prove authenticity without actually revealing the information.

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