Research On Image Encryption Method Based On Chaos And Fractional Fourier Transform

With the rapid development of the network and the information technology, theinformation security and confidentiality of digital image has drawn more and moreattention. So image encryption technology has become a hot research. Chaos hasbecome a important encryption method for its good properties such as beingsensitive to the initial condition and randomness. Encryption based on chaos whichdoes transform in the image space domain has a drawback. If the encrypted imageloses some information, the decrypted image is equiva lent to lose the sameinformation. So the robustness of encryption method based on chaos isn’t very good.As a new tool of encryption, the fractional Fourier transform(FRFT)has been paid agreat deal of attention. This FRFT does image encryption in the transform domain.When the encryption image lost some information during the transmission, thedecryption image still contain most of the original image information. So therobustness of encryption method based on this FRFT is very good. Thus, researchon encryption algorithm combining FRFT and chaos has great significance.Firstly, this paper introduced the chaotic theory and the theory of FRFT, andfocused on the multi-parameter fractional Fourier transform(MPFRFT). Secondly,this paper propose a new image encryption method based on a three-dimensionhyperchaotic system and this MPFRFT. In the proposed algorithm, the keys includethe order of the fractional Fourier transform and four free parameters besidescoefficients of chaos and the initia l conditions. The key space becomes larger.Finally, digital simulations are illustrated to verify the security of the algorithm,which include the key space, key sensitive, histogram, relativity and robustness.This encryption algorithm use not only the extremely strong sensitivity to the keybased on chaos, but also the very good robustness based on the fractional Fouriertransform. Without any increase of the computational complexity, the encryptionmethod has stronger resistance for the exhaustion attack, count attack, and large keyspace, considerable robustness, and it is of high security.