Decryption method of encryption broadcasting using ic chip performed by mobile and the mobile thereof

A portable terminal for decoding encrypted broadcast by using an IC chip and a method thereof are provided to enable a user to view a pay broadcast according to a CAS(Conditional Access System) without setting an additional authentication key even though the portable terminal is replaced with new one. A broadcast receiver(110) receives broadcast data corresponding to a selected channel. A main controller(150) transmits a control command to an IC chip if the broadcast data are encrypted. The control command is used to obtain authentication information corresponding to the channel or present broadcast of the channel. A CAS(conditional access system) module(130) compares control information of the broadcast data and the authentication information to perform an authentication process. The CAS module(130) decodes the encrypted broadcast data if the authentication is successively completed.