Disclosed is a system for transmitting encrypted broadcast signals to different transmitters on a single frequency network (SFN) in a digital broadcasting system. The system for transmitting encrypted broadcast signals on the SFN includes: a main broadcasting system for transmitting encrypted broadcast signals including data streams and transmitter identification information (TII) through a main broadcasting network; a repeating system for amplifying encrypted broadcast signals of the main broadcasting network and transmitting the amplified broadcast signals, or modulating and amplifying streams input by the main broadcasting system through a private line and repeating broadcast signals of the main broadcasting system through a repeating network; and a decrypting key provider for receiving a decrypting key value from the main broadcasting or repeating system and transmitting a user authentication and decrypting key to a charged subscriber terminal through a mobile communication network.