Embedded system, authentication system comprising the same, method of authenticating the system

Provided are an authentication method and a portable terminal. The authentication method includes the steps of: performing a first authentication which determines whether or not an access system is authenticated by a first authentication agent; performing a second authentication which determines whether or not the access system is authenticated by a second authentication agent different from the first authentication agent, and receiving the result; and approving the access of the access system to the second authentication agent when the first and the second authentication are completed.