COPY-PROTECTION BY ALTERATION OF CONTROL SIGNALS

摘要

A method and system modifies one or more control signals that are associated with the transmission or reception of copy-protected material. By modifying the control signals, most communication devices that rely on the protocol will prevent the transmission of the message, or will prevent or inhibit the subsequent processing or relaying of a received message. For example, if a cyclic-redundancy-code (CRC) is modified, a conventional network device that uses the received-but-modified CRC will likely reject the received material, thereby preventing it from being processed or transmitted further through the network. Select devices are configured to recognize and undo the modification, thereby allowing the material to be further processed. If the material is to be relayed, the modification is reapplied. Preferably, only local-area network devices are configured to undo the modification, while devices that provide wide-area network access are not configured to undo the modification. In this manner, protected content material with modified control signals is likely to be prevented from wide-area network distribution.