The Internet and the information technology are evolving rapidly. Consequently, people are using interactive media extensively in communication. The images occupy a vast portion of multimedia and play a significant role in communication, e.g., military, national security agencies, diplomatic affairs and social. Since, an image may contain highly confidential information and when people want to transfer an image over insecure a network, then it is necessary to provide sublime protection. Mainly, an image needs protection against tampering and breaching confidentiality by illegal parties.
The primary purpose of keeping the image secured is to maintain the confidentiality, ...view middle of the document...
However, the public key and the private (secret) key are different, but mathematically are connected. Apart from that, Hashing ensures authenticity of the retrieved image due to having the one way property.
There are diverse algorithms to encrypt data, specifically, RSA, DES, and AES and are paramount to encrypt the text data; however these algorithms are less effective for the image encryption . Since, the images have intrinsic features such as redundancy of pixels and high correlation between two adjacent pixels . Consequently, it is effortless to infer the value of neighbors of a pixel. Therefore, the images need effective security technique to insure the absolute security.
Primarily, the image encryption techniques are based on three methods. (1) Pixel permutation based  : the encryption technique disperses the pixels (2) Pixel substitution based  : the encryption technique modifies the pixel value (3) Visual transformation based  .
Mainly, an excellent encryption technique qualifies these following salient security parameters: (1) large key space: large key space is necessary to thwart the brute force attack . An encryption technique must have adequate large key space. (2) Key sensitivity: It ensures that system generate entirely different consequence in spite of a whit change in key . Thus an encryption technique must be key sensitive. (3) Uniform Image histogram: Histogram provides information about the frequency distribution of continuous pixels and density estimation  . So a cipher image must have a uniform histogram to be secure from known plaintext attack . (4) Information entropy: It defines the degree of uncertainty and uniform distribution in the system . Thus an encryption technique must show randomness and uniform distribution in the encryption process. (5) Correlation analysis: It assesses the correlation between two adjacent pixels of the plain-image and the cipher image . A cipher image must have low correlation between two adjacent pixels. (6) Differential analysis: NPCR and UACI compute the strength against to differential attacks of image . NPCR determines the change rate of number of pixels in the cipher image after modification in one pixel of the plain-image  , consequently, high NPCR value is effective. Furthermore, UACI computes the variation in intensity of the corresponding pixel of the plain-image and the cipher image .
Apart from these techniques, Artificial neural network also an approach which provides security to an image. Artificial neural network (ANN) is effective duo to its non linear and one way properties . In ANN it is easy to produce output while to retrieve input from output is a difficult task and without information of weights and bias, it is almost impossible to retrieve input from output back .
Furthermore, compression is another technique to encrypt an image by...