A content transfer system for transferring content between a source device transmitting the content in accordance with digital content transmission protection - internet protocol (DTCP-IP) specification and a sink device receiving the content comprising: content specifying means for specifying the content to be transferred between the source device and the sink device; authentication means for performing an authentication exchange key process between the source device and the sink device; content transfer means for performing a content transfer process by encrypting and transferring the content specified by the content specifying means from the source device to the sink device using a key dedicated to the content and exchanged by the authentication means on a per content basis; and content transfer finalizing means for performing a content transfer finalizing process by invalidating the original content at the source device in response to a first move finalizing command transmitted by the sink device and indicating the end of the content transfer process performed by the content transfer means and validating the content at the sink device in response to a first move finalizing response transmitted by the source device after invalidating the original content the content thus being moved from the source device to the sink device. - internet protocol (DTCP-IP) specification and a sink device receiving the content comprising: content specifying means for specifying the content to be transferred between the source device and the sink device; authentication means for performing an authentication exchange key process between the source device and the sink device; content transfer means for performing a content transfer process by encrypting and transferring the content specified by the content specifying means from the source device to the sink device using a key dedicated to the content and exchanged by the authentication means on a per content basis; and content transfer finalizing means for performing a content transfer finalizing process by invalidating the original content at the source device in response to a first move finalizing command transmitted by the sink device and indicating the end of the content transfer process performed by the content transfer means and validating the content at the sink device in response to a first move finalizing response transmitted by the source device after invalidating the original content the content thus being moved from the source device to the sink device. content specifying means for specifying the content to be transferred between the source device and the sink device; authentication means for performing an authentication exchange key process between the source device and the sink device; content transfer means for performing a content transfer process by encrypting and transferring the content specified by the content specifying means from the source device to the sink device using a key dedicated to the content and exchanged by the authentication means on a per content basis; and content transfer finalizing means for performing a content transfer finalizing process by invalidating the original content at the source device in response to a first move finalizing command transmitted by the sink device and indicating the end of the content transfer process performed by the content transfer means and validating the content at the sink device in response to a first move finalizing response transmitted by the source device after invalidating the original content the content thus being moved from the source device to the sink device.