Image Encryption Algorithm Research And Implementation Based On Fractional Fourier Transform

As the rapid development of computer networks and communication technology, multimedia information is more widely used. Because digital information is easy to be stolen and tampered, the encryption and protection of digital information has become an important issue in information security field. Meanwhile, fractional Fourier transform is hot research topic both in optics and informatics, it is also a research direction in image processing. This paper studied the nature of fractional Fourier transform and its applications in signal processing, image analysis and image encryption. The application in modern image encryption of chaotic technology was studied. An image encryption algorithm was proposed after the analyzing the characteristics of the chaotic scrambling encryption technology and transform domain encryption technology.This paper also discussed the detection, parameter estimation and separation about the single and multi-component chirp signal, and the filtering of LMF signal with noise based on fractional Fourier transform. Simulation results demonstrated that fractional Fourier transform can separate the multi-component chirp signal well compared with Wigner-Ville or Short-time Fourier transform, also, the single component chrip signal with additive noise still has a better filtering effect even though the SNR was low. This paper proposed and simulated an image encryption algorithm based on fractional Fourier transform by using its coefficient's sensitivity and diversity to initial value. This algorithm has good robustness and better ability to against statistical properties'attacks. An encryption algorithm based on chaotic scrambling was proposed and simulated, the algorithm has larger key space and better safty, but it seldom prevent clipping or noise, its robustness is poor in addition. An improved image encryption algorithm was present after analyzing the results of chaotic scrambling image encryption algorithm and fractional Fourier image encryption algorithm simulation experiment in this paper. The result show that the histogram of cryptograph became more flatter, the MSE and relativity was sensitived to the key. At last, the paper realized encryption algorithm on DSK6711. The result shows that the space and frequency information of original image were hidden perfectly.