Secure Image encryption through key hashing and wavelet transform techniques

To provide security of the images in the multimedia environment encryption plays an important role. The traditional cryptographic algorithm such as AES, DES, TDES, RSA, IDEA, etc. are not so effective for image encryption because of their slow processing speed, inherent features of image data like bulk data capacity, high redundancy and ineffectiveness in removing the correlations of the adjacent pixels of the image[1],[2]. In order to cope with this problem a noble technique of digital image encryption is proposed. In this technique the symmetric key is used for image encryption. The hash value (SHA1) of the key file is generated and stored as text file [4],[5]. The SHA test is converted to binary string. The key hash value is now expanded to match with the image dimension. For creating confusion the image to be encrypted is wavelet transform is first calculated and then converted into binary string and the hash of the secret key value (SHA1) is finally bitxored to create the encrypted image. The experimental results, correlation analysis of adjacent pixels of encrypted image in the horizontally, vertically and diagonally spaced pixels, histogram analysis and Structural Similarity Index Measure (SSIM), tests have been carried out and results are found to be quite satisfactory in terms of security and performance. Keywords-Cipher text, Encryption, Decryption, SHA, symmetric key, image histogram, Correlation coefficient, Structural Similarity Index Measure (SSIM)