My research interest is in the theoretical foundation of computer science and in applying fundamental tools to various areas. To understand the structure of the objects to be manipulated computationally, to classify the resources needed for various computational problems and to find more efficient algorithms interest me the most. In the application area, I am interested in information privacy, security and medical informatics. Lately, I have also been involved in information privacy protection mechanism design and the development of privacy regulations in medical research. The goal is to clarify the privacy protection problem and to design and constr uct a practical protection mechanism so that information can be shared efficiently and personal privacy can be protected at the same time. Over the past few years, we developed a prototype system CellSecu to safe guard personal privacy. The system will check if datasets to be released leak too much personal information. We discovered appropriate logic model for the problem and quantified the privacy leakage with information theory and economic models. Secure Multiparty Protocol can be applied to tackle the problem that some important information can be computed while the data owners do not have to reveal their data. Although there are beautiful theoretical solutions, they are not suitable for problems involving large dataset. We try to quantify the information leakage in this setting with an information theoretical framework, so that tradeoff between the computational resources needed and the level of privacy protection achieved becomes possible.