The importance of protecting personal information is increasing day by day due to invasion of privacy, and data encryption is the most effective way to eliminate it. However, current data encryption methods tend to having problems for applying in practical fields because of critical issues such as low performances and frequent changes of applications. In order to find proper solutions for data security, this paper reviews data encryption technologies and experiments on performance of encrypted data in Oracle Database. On top of that, this paper analyses a data encryption technique not only efficiency of performance but also minimization of application changes.