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Sharing medical data can benefit many aspects of biomedical research studies. However, medical data usually contains sensitive patient information, which cannot be shared directly. Summary statistics, like histogram, are widely used in medical research which serves as a sanitized synopsis of the raw health dataset such as Electrical Health Records (EHR). Such synopsized representation is then be used to support advanced operations over health dataset such as counting queries and learning based tasks. While privacy becomes an increasingly important issue for generating and publishing health data based histograms. Previous solutions show promise on securely generating histogram via differential privacy, however such methods only consider a centralized solution and the accuracy is still a limitation for real world applications. In this paper, we propose a novel hybrid solution to combine two rigorous theoretical models (homomorphic encryption and differential privacy) for securely generating synthetic V-optimal histograms over distributed datasets. Our results demonstrated accuracy improvement over previous study over real medical datasets.

We developed an online multimedia event detection (MED) system. However, there are a secure access control issue and a large scale robust representation issue when we want to integrate traditional event detection algorithms into the online environment. For the first issue, we proposed a tree proxy-based and service-oriented access control (TPSAC) model based on the traditional role based access control model. Verification experiments were conducted on the CloudSim simulation platform, and the results showed that the TPSAC model is suitable for the access control of dynamic online environments. For the second issue, inspired by the object-bank scene descriptor, we proposed a 1000-object-bank (1000OBK) event descriptor. Feature vectors of the 1000OBK were extracted from response pyramids of 1000 generic object detectors which were trained on standard annotated image datasets, such as the ImageNet dataset. A spatial bag of words tiling approach was then adopted to encode these feature vectors for bridging the gap between the objects and events. Furthermore, we performed experiments in the context of event classification on the challenging TRECVID MED 2012 dataset, and the results showed that the robust 1000OBK event descriptor outperforms the state-of-the-art approaches.