US Patent 7639812 Digital content encrypting apparatus and operating method thereof

The invention is directed to a source device and a method for encrypting digital contents at the source device. According to an embodiment, the method includes receiving digital content from an external device, the digital content being encrypted using a first encryption algorithm in the external device; decrypting the received digital content; performing an addition operation by using a first source internal key and an identifier (ID), the ID being associated with at least one of a target device and a storage medium of the target device; generating a source encryption key based on an output of the addition operation and a second source internal key by using a second encryption algorithm; re-encrypting the decrypted digital content using the source encryption key; and transmitting the re-encrypted digital content without the source encryption key to the target device.