A private cloud provides organizations a secure environment to run business process. It provides a flexible way to extend the working environment. While user mobility has become

an important feature for many systems, technologies that provide users a lower cost and flexible way in joining a secure private cloud are in a strong demand. This paper exploits

the extension of IPSec to have secured tunnels with private cloud for users who might move around dynamically without carrying the same machine. A strong authentication with a key agreement scheme is proposed to establish the secure tunnel. Besides, several related security properties of the proposed mechanism are presented.