Permutation-Substitution architecture based image encryption algorithm using middle square and RC4 PRNG

The growing importance of information security over recent years has prompted development of secure encryption algorithms. Most of the traditional algorithms such as AES and DES are computationally intensive. Hence, in this paper we propose a simple but secure symmetric key encryption algorithm. The image encryption approach makes use of two pseudorandom number generators to encrypt images. Middle Square Algorithm is used to swap the columns of the image followed by the swapping of the rows. This permutation step produces the intermediary cipher image. Subsequently, RC4 algorithm is used to produce a stream of pseudo-random numbers. These numbers are used to substitute the intensity of pixels of the intermediary cipher image, which gives the final encrypted image. Various analysis tests are performed on the quality of the encrypted image. The results of these tests prove that the proposed algorithm is secure and efficient.