Modified and Efficient Image Encryption Algorithm Based on Chaos Theory, DNA Complementary Rules and SHA-256

Abstract: The emerging topic, symmetric encryption technique for digital imagesusing chaotic function and DNA bases has recently drawn a lot ofattentions from the research community. The use of voice and visualmaterial as an addition to textual data has become more widespread.Multimedia content, the core of which is the digital image, has becomean earth-shaking element in prospective information transmission. Thismeans that multimedia contents such as audio, video and images haveto be transmitted over communication channels securely using newencryption techniques.Chaos theory is a widely studied topic in non-linear dynamics becauseof features like periodicity, sensitivity to initial conditions and controlparameters. The lower dimensional discrete chaotic functions are simpleand efficient to generate a pseudo-random sequence for encryption.However, DNA cryptography is an additional weapon in thecryptographer’s armoury. Characteristics such as of vast parallelism andlarge storage capacity make it a very promising field. The algorithmsbased on DNA and discrete chaotic functions use the advantages of bothfields to provide image protection in an effective way.Traditional digital cryptosystems like DES, AES and RSA are designedprimarily for textual data, which does not fit the multimedia streambecause of the essential structures of image data such as large size, solidpixel correlation and high redundancy, which incurs significantoverhead. Also, in conventional cryptographic techniques, thedecrypted data is exactly the same as plaintext data.To solve this problem, symmetric encryption aims to provide sufficientsecurity with an important gain in computational complexity anddelays, thereby making the cipher suitable for real time applications.This study uses an encryption approach by adding adjacent rows andcolumns of plain text after converting into DNA bases in order to reducethe encryption overhead. To improve the use of DNA complementary rules in a better and moredynamic way, and to incorporate DNA diffusion prior to the encryptionalgorithm, a complete set of DNA complementary rules is employed inthe encryption and decryption process. The selection of DNA rules foreach block is made depending on the chaotic sequence. The initialconditions and control parameters of the chaotic maps are madedepending on the 256-bits hash value which is generated from a plainimage to avoid chosen plaintext attacks.