To ensure the security and reliability of the transmission of digital images in the network,an image encryption algorithm was proposed based on the sequences of Logistic map and DES (Data Encryption Standard) combined with scrambling and diffusion.Firstly,two modified chaotic sequences of Logistic maps were generated and applied to encryption processes such as iteration and bit encryption;secondly,pixels were scrambled according to the sorted order of the chaotic sequences;finally,the encrypted image was generated with more effective diffusion and more random scrambling,as the initial scrambling and cryptographic function of DES were modified.After the encryption system was analyzed in terms of entropy,correlation and key space,the result shows that this image encryption method is able to cover up plaintext effectively and safely with huge key space,high speed,good anti-attack capability.

For the problem that BP neural network is easy to fall into the local minimum,the metropolis acceptance criteria in the mechanism of simulated annealing algorithm and the taboo list in the taboo searching algorithm are introduced in the system to escape from the local minimum,and the values of minima were recorded and compared in the taboo list,which is more efficient in dealing with multiple local minima and accurate system. The modified algorithm is applied to the BP network to construct a neural network which is easier to jump off from local minima. At last, the modified neural network algorithm is used for image compression and reconstruction. The experimental results show the higher efficiency and accuracy of the modified neural network.