I. Introduction
Face recognition can be used in various applications that range from consumer to professional or military level. A widely used example of face recognition technology for consumer-level applications is automatic or semi-automatic tagging of faces in a collection of digital photos. Such tagging helps user organize his/her photo collection and makes it easier to search for a particular photo. This capability is not only found in software installed in the user's machine, but is also be found in online applications such as Facebook. Another example is the application of face recognition technology to help identify suspects. Due to the increased mobility of people these days, a suspect can escape from one country to another country making it much more complicated for law enforcement agencies to apprehend them. In such situations, a face recognition system installed in airports can help law enforcement personals to identify a suspect before he/she escapes. Another emerging application is the use of face recognition system as a biometric authentication method for e-commerce applications. This method is designed to prevent fraud in electronic transactions over the internet. The use of face recognition in the last two applications (i.e., suspect identification and biometric authentication) is highly preferred, since it is considered to be the least intrusive method while retaining high accuracy [1].