Research On 3d Invertible Map Based Image Encryption Algorithm Of Satelite Image

Some satellite images are related to state security, military affairs security or company benefit. Protecting those satellite images becomes an important issue for avoiding that they are viewed or tampered by those who are not authorized. But traditional encryption algorithms have some flaws, such as low speed, small key space and weak to some attacks. As a result, it is necessary to study novel and practical digital satellite image encryption algorithm.In this paper, a 3D invertible map based image encryption scheme is studied using the idea of chaotic stretch and fold map. In order to increase the efficiency of permutation and diffusion, this paper uses a 3D bit matrix to depict digital image, and then proposes transformation, stretch and fold algorithm, which can constitute a invertible map set. The security key is carefully designed, and image encryption can be realized by a sequence of iterations of transformation, permutation and substitution according to the security key. Since image has large data quality, if the deduced formulas are used for encryption/decryption, there will be large amount of calculation and long encryption/decryption time. In order to solve this problem, an optimized algorithm is proposed. This paper carried out image encryption/decryption simulations, and also analyzed security performance indexes, which shows that proposed scheme has big key space and high level of security, et al.Aiming at enhancing cryptosystem's sensitivity to security key and plain image, this paper studies an image encryption scheme based on 3D discrete chaotic sequence. Firstly, the chaotic system's characteristics of strong inner pseudorandom, sensitivity to initial conditions and paremeters are utilized to design pseudorandom sequence generator. Randomness test result shows that the generated pseudorandom sequence passed the tests, which means that it can be used in image encryption scheme to guarantee the security of encrypted image. The proposed image encryption scheme is very related to security key and plain image, and they are used to update the selected pseudorandom sequence during encryption process, which can improve the scheme's sensitivity to plain image. In the end, simulations are carried out to test the proposed scheme's security level, and the test results show that the scheme has good diffusion performance, and also very sensitivity to security key and plain image.Digital chaotic system has the inner-defect of dynamical degeneracy, in order to avoid this flaw and increase cryptosystem's practical applicability, this paper studies an image encryption scheme based on synchronization of multi-chaotic systems. The synchronization of Chua's circuit and Lorenz system are studied respectively by using P-C method, and their corresponding hardware circuits are designed. In the transmitter, the plain image are transformed to bit sequence, and the chaotic states of master Chua circuit and Lorenz system are discretized to bit key sequence by applying sampling pulse and threshold control method. Then the bit key sequences are used to encrypt the bit stream of plain image to cipher stream, and the synchronization drive signals are applied to mask and transmit the cipher stream. In the receiver, the cipher stream can be extract from the synchronizing signals, and then decrypted by the same key sequence achieved from the slave chaotic system. Experimental results and security anlysis show that the proposed image encryption system can effectly avoid the dynamical degeneracy, and also has high level of security and practical applicability.For the sake of saving memory space, encryption and transmission time, an image encryption scheme based on contourlet transformation is studied. Wavelet based Contourlet transformation (WBCT) is studied and used to transform the original image to low and high frequency sub-bands, and the low frequency sub-band contain basic information of the original image. Based on this characteristic, a WBCT based partial image encryption scheme is proposed, in which only the lowest frequency sub-band and the sign of all transform coefficients are encrypted to increase the encryption efficieny. Meanwhile, multi-croll chaotic system is used to construct a pseudorandom sequence generator, and the generated sequence is applied to encrypt the lowest frequency sub-band and the sign of transform coefficients. In the end, SPIHT algorithm is utilized to realize compression. Wireless image monitoring system is also designed in this paper, and the proposed image encryption is implemented in this monitoting system to guarantee the security of the monitored images.