A novel image encryption algorithm based on the extracted map of overlapping paths from the secret key

In the digital era, most types of transmitted data over the Internet are images. These images may carry secret information. So, it became necessary to have an effective encryption system to hide information inside these images. The use of random and large-sized key represents the main factors that give the encryption system the required strength and give encrypted data more protection. This paper presents a non-traditional encryption algorithm that uses a large key size (256 bytes) = 2048 bits, to achieve a high degree of protection for the image. First, the algorithm represents the source image as a set of two-dimensional blocks of size 16 × 16 bytes and the secret key as a two-dimensional block of size 16 × 16 bytes. Second, transposition and substitution operations are implemented within each block of the image based on the extracted map of overlapped paths from the secret key block. Successive different keys are generated by using another way of implementation of the substitution and transposition operations in the secret key block. The recorded performance results, from the evaluation tests, have been compared with some well-known encryption algorithms and they proved that the proposed algorithm can be used effectively to protect images.