Digital images

Digital images

Digital images are sensitive images that must be secured against intruders through network channel transmission. Different imaging techniques are used to encrypt images using symmetrical asymmetric and encryption algorithms. Many of the image algorithms support only either symmetrical encryption and decryption or asymmetric encryption and Decryption. Thus we have researched three different hybrid methods for the implementation of image encryption such as Hill Cipher Elliptic Curve Cryptography (ECC), Advanced Encryption Standard (AES) ECC, and Double Playfair Cipher ElGamal. Test cases performed with a set of greyscale and colored images and performance metrics are measured. When calculating all the parameters such as Encryption Time, Decryption Time, Entropy, Squared Error in Decrypted Image, PSNR, NPCR, UACI, we can infer which algorithm is better suited to the needs of the user. The result shows effectiveness with lesser the value of encryption and decryption time. The proposed hybrid algorithm Entropy Value obtained is closure to 8 which is better than existing algorithms. We obtain the lesser value for Squared Error in the Decrypted image which proves better than other algorithms. However, the value of the Peak Signal to Noise Ratio (PSNR) is higher by the metric scales and higher the value of Number of Pixel Change Rate (NPCR) better the algorithm is, and higher value of Unified Average Changing Intensity (UACI) indicates it is more secured from attacks. Based on the time taken for encryption and decryption, we can recognize that ECC with AES is computationally intensive and not feasible for applications involving the protection of large image databases. ECC with AES appears to be good for remote or private communications with smaller image sizes. To conclude the ECC and Hill Cipher turn out to be a good overall alternative for image encryption algorithms.