A content transmission device has a first encryption process means that encrypts, by a digital communication interface, a digital content for transmission to a content reception device and encrypts a low-resolution content by a first encryption process; a second encryption process that encrypts a high-resolution content by a second encryption process; and a down-conversion means that down-converts the high-resolution content to the low-resolution content. The content transmission device receives, from a digital reception device, information related to an encryption process of the digital reception device. Then, if the digital reception device supports the second encryption process, the content transmission device transmits the high-resolution content as encrypted by the second encryption process. If the digital reception device does not support the second encryption process, the content transmission device down-converts the high-resolution content and encrypts, by the first encryption process, the down-converted content for transmission.