A novel chaos based optical image encryption using fractional Fourier transform and DNA sequence operation

•We propose a new method for optical image encryption using fractional Fourier transform.•Our algorithm is based on Shannon’s property of confusion and diffusion.•The confusion process is based on DNA encoding and on using DNA XOR to scramble the pixel values of the image. In this paper, we propose a new method for optical image encryption using fractional Fourier transform, DNA sequence operation and chaos theory. Random phase masks are generated using iterative Lorenz map and the plain image is transformed to a DNA matrix. This matrix is combined with the random phase mask and then transformed three times using the fractional Fourier transform. An Optical implementation of the encryption algorithm is proposed in our work. According to the experiment results and security analysis, we find that our algorithm has good encryption effect, larger secret key space and high sensitivity to the secret key. It can resist to most known attacks, such as statistical analysis and exhaustive attacks. All these features show that our encryption algorithm is very suitable for digital image encryption.