The present invention is relative to a data transmission method for transmitting data such as encrypted content data. A device which is to be a destination of transmission is authenticated and, if the device has not been authenticated, encrypted data read out from a storage unit is decrypted to give decoded data, which then is re-encrypted, based on innate key data acquired from the device which is to be the destination of transmission, to give re-encrypted data. The re-encrypted data is then transmitted to the device which is to be a destination of transmission.  
본 발명은 암호화된 콘텐츠데이터등의 데이터의 송신을 행하는 데이터송신방법이고, 송신처가 되는 장치의 인증을 행하고, 송신처가 되는 장치의 인증이 행하여진 때에는 기억부에서 독출된 암호화된 데이터를 해독하고, 해독한 데이터에 송신처가 되는 장치에서 취득한 고유키데이터에 의거해서 재암호화처리를 시행하여 송신처가 되는 장치에 송신한다. 