In recent years， respiratory infectious diseases break out in crowded places frequently. How to restore transmission path of the virus between people has become a key issue in epidemic prevention and control. However， the existing methods have problems such as the difficulty in describing the crowd movement trajectory in crowded places and the difficulty in simulating spread of the virus caused by contact between people. To this end， a virus transmission’s visual analysis system of Agent-Based Modeling （ABM） was proposed to simulate dynamically and visualize the virus transmission process as well as show individual contact relationships and transmission paths. Firstly， a multi-head rapidly-exploring random tree algorithm was combined with movement statistical data to generate crowd movement trajectories conforming to actual laws. Secondly， by refining the contact rules of people and the virus transmission mechanism， a transmission model based on ABM was constructed to simulate the impact of crowd interaction on virus transmission. Case analysis shows that the virus transmission’s visual analysis system restores the contact relationship between people and the process of virus transmission between people， the transmission chain simulated by the system is highly similar to the actual chain， the number of simulated cases is basically consistent with the actual number of cases， and the multi-head rapidly-exploring random tree algorithm can generate highly realistic trajectories efficiently. The case verifies the decision support value of the system in the optimization of epidemic prevention and control strategies.

The privacy policy document declares the privacy information that an application needs to obtain， but it cannot guarantee that it clearly and fully discloses the types of privacy information that the application obtains. Currently， there are still deficiencies in the analysis of the consistency between actual sensitive behaviors of applications and privacy policies. To address the above issues， a method for analyzing the consistency between sensitive behaviors and privacy policies of Android applications was proposed. In the privacy policy analysis stage， a Bi-GRU-CRF （Bi-directional Gated Recurrent Unit Conditional Random Field） neural network was used and the model was incrementally trained by adding a custom annotation library to extract key information from the privacy policy declaration. In the sensitive behavior analysis stage， IFDS （Interprocedural， Finite， Distributive， Subset） algorithm was optimized by classifying sensitive API （Application Programming Interface） calls， deleting already analyzed sensitive API calls from the input sensitive source list， and marking already extracted sensitive paths. It ensured that the analysis results of sensitive behaviors matched the language granularity of the privacy policy description， reduced the redundancy of the analysis results and improved the efficiency of analysis. In the consistency analysis stage， the semantic relationships between ontologies were classified into equivalence， subordination， and approximation relationships， and a formal model for consistency between sensitive behaviors and privacy policies was defined based on these relationships. The consistency situations between sensitive behaviors and privacy policies were classified into clear expression and ambiguous expression， and inconsistency situations were classified into omitted expression， incorrect expression， and ambiguous expression. Finally， based on the proposed semantic similarity-based consistency analysis algorithm， the consistency between sensitive behaviors and privacy policies was analyzed. Experimental results show that， by analyzing 928 applications， with the privacy policy analysis accuracy of 97.34%， 51.4% of Android applications are found to have inconsistencies between the actual sensitive behaviors and the privacy policy declaration.

With the development of mobile Internet technology， the scale of image data is getting larger and larger， and the large-scale image retrieval task has become an urgent problem. Due to the fast retrieval speed and very low storage consumption， the hashing algorithm has received extensive attention from researchers. Deep learning based hashing algorithms need a certain amount of high-quality training data to train the model to improve the retrieval performance. However， the existing hashing methods usually ignore the problem of imbalance of data categories in the dataset， which may reduce the retrieval performance. Aiming at this problem， a deep hashing retrieval algorithm based on meta-learning network was proposed， which can automatically learn the weighting function directly from the data. The weighting function is a Multi-Layer Perceptron （MLP） with only one hidden layer. Under the guidance of a small amount of unbiased meta data， the parameters of the weighting function were able to be optimized and updated simultaneously with the parameters during model training process. The updating equations of the meta-learning network parameters were able to be explained as： increasing the weights of samples which are consistent with the meta-learning data， and reducing the weights of samples which are not consistent with the meta-learning data. The impact of imbalanced data on image retrieval was able to be effectively reduced and the robustness of the model was able to be improved through the deep hashing retrieval algorithm based on meta-learning network. A large number of experiments were conducted on widely used benchmark datasets such as CIFAR-10. The results show that the mean Average Precision （mAP） of the hashing algorithm based on meta-learning network is the highest with large imbalanced rate；especially， under the condition of imbalanced ratio=200， the mAP of the proposed algorithm is 0.54 percentage points，30.93 percentage points and 48.43 percentage points higher than those of central similarity quantization algorithm， Asymmetric Deep Supervised Hashing （ADSH） algorithm and Fast Scalable Supervised Hashing （FSSH） algorithm.

Aiming at the problems of low computational efficiency and insufficient accuracy in the privacy-preserving neural network based on homomorphic encryption， an efficient Homomorphic Neural Network （HNN） under three-party collaborative supporting privacy-preserving training was proposed. Firstly， in order to reduce the computational cost of ciphertext-ciphertext multiplication in homomorphic encryption， the idea of secret sharing was combined to design a secure fast multiplication protocol to convert the ciphertext-ciphertext multiplication into plaintext-ciphertext multiplication with low complexity. Then， in order to avoid multiple iterations of ciphertext polynomials generated during the construction of HNN and improve the nonlinear calculation accuracy， a secure nonlinear calculation method was studied， which executed the corresponding nonlinear operator for the confused plaintext message with random mask. Finally， the security， correctness and efficiency of the proposed protocols were analyzed theoretically， and the effectiveness and superiority of HNN were verified by experiments. Experimental results show that compared with the dual server scheme PPML （Privacy Protection Machine Learning）， HNN has the training efficiency improved by 18.9 times and the model accuracy improved by 1.4 percentage points.