| 摘要 |
<p>A system provides improved security in a streaming media decoder includes decryption of encoded media information at the media layer, within a decoder component of a playback device 100. A content source, such as an MPEG-4 media stream from a network, or a file on a local storage device, etc. that contains packetized content, and supplies encrypted and encoded media information 110. A reassembler component 120 is used to initiate decryption of a nominal amount of information needed to perform further processing at the QuickTime player. Encrypted access units are sent from the reassembler 120 to the decoder 140, where the decoder 140 causes decryption of the access unit information. This approach prevents decrypted, encoded information from being transferred from the reassembler 120 to the decoder 140. Such decrypted and encoded information is especially susceptible to copying. Instead, the information transferred from the reassembler 120 to the decoder 140 is largely still encrypted. In a preferred embodiment, an Internet Protocol rights management system (IPRM) 150 is used to perform the decryption processing. The reassembler 120 makes requests of the IPRM process 150 to open a decryption session and decrypts selected packets to identify the window rendering size. The decoder 140 makes requests of the IPRM process 150 to decrypt access units within the same decryption session and to close the decryption session. Because content is encrypted on packet boundaries, and when called upon by the decoder 140, the IPRM component 150 must recreate the packet boundaries from the access unit before decryption is possible. The IPRM system component 150 is able to do so because the encrypted packets contain an IPRM header that is used by the IPRM system 150 to calculate the packet length. After decrypting all the packets, the IPRM system component 150 reconstructs the decrypted access unit and returns decrypted content to the decoder 140.</p> |
