Abstract: Disclosed herein is a communication method between a set-top box and a smart card and interface module used for the same. In the communication method of the present invention, a Set-Top Box (STB) communicates with a smart card through a Recommended Standard (RS)-232C serial interface when providing information to the smart card and receiving an encryption key (Control Word: CW) from the smart card so as to descramble a scrambled Transport Stream (TS) after receiving the scrambled TS, in a case where a broadcast is received using the STB. The interface module of the present invention includes a smart card connector, a signal converter, a clock provider and a power/reset unit. The smart card connector accommodates the smart card, and transmits and receives signals to and from the smart card.