A wireless power transmitter includes a power converter configured to transfer wireless power to a wireless power receiver, and a controller configured to communicate with the wireless power receiver to control transmission of the wireless power. The controller is configured to receive, from the wireless power receiver, an authentication request message for authentication of the wireless power transmitter, and transmit, to the wireless power receiver, a data stream including a plurality of auxiliary data transport (ADT) data packets in which at least a part of an authentication response message is divided. The data stream includes at a beginning an auxiliary data control packet informing a start of the data stream.