Medical data play an essential role in our daily life. They are usually recorded in electronic formats in databases, which are so-called electronic medical records (EMRs). EMRs are more convenient for the reuse of medical records than handwritten records, especially as a reference when people need medical treatment. However, most medical records are maintained through centralized systems which in many cases may lead to problems that adversely effects the use of EMRs, especially when sharing with others. The main problems can be recognized as medical data security, sharing efficiency, and ownership of medical data. This research is intended to design novel methods to address the aforementioned issues to realize secure, high-efficiency, and patient-centric medical data sharing.