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Method for isolating bus signals for content protection over a user-accessible bus

IP.com Disclosure Number: IPCOM000029801D
Publication Date: 2004-Jul-13
Document File: 6 page(s) / 617K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for isolating bus signals for content protection over a user-accessible bus. Benefits include improved functionality, improved performance and lower system cost.

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Method for isolating bus signals for content protection over a user-accessible bus

Disclosed is a method for isolating bus signals for content protection over a user-accessible bus.  Benefits include improved functionality, improved performance and lower system cost.

Background

              Various content protection technology license agreements require the device manufacturers to abide by robustness rules published in their license agreements. The main purpose of these rules is to ensure that the platform design includes the security features required to thwart the attempts of most hackers from the illegal interception and distribution of premium content.

              One important goal is to prevent the interception of unencrypted premium audio and video content flowing between the semiconductor devices that are processing this content when processing cannot be limited to the circuits physically located on the same die. One possible method for safeguarding the unencrypted data is to use ball-grid array (BGA) packages for the devices and bury the interconnects in the internal layers of the printed circuit board (PCB). The interconnects become limited to point-to-point connections between dedicated pins on the devices. However, conventional digital electronics uses common busses that are shared by multiple devices to build a flexible, modular system and reduce pin count to reduce cost. In set top boxes (STBs), user accessible buses, such as the peripheral component interconnect (PCI) bus, may host devices that receive unencrypted content and devices that are not exchanging unencrypted audio visual data. Moreover, the PCI bus may have connectors hosting removable modules, such as wireless adapters, which provide easy access to the bus signals.

              The requirement for a slot to provide the flexibility of add-in cards makes the PCI bus vulnerable to content interception and directly conflicts with robustness rules. One possible solution is the removal of all add-in card connectors on the PCI bus. Additionally, the traces of the PCI bus may be hidden in inner layers of the board. Lastly, where feasible, all the devices that connect to the PCI bus may be of BGA package type to prevent tapping into pins that may carry signals containing the premium content.

              Another example is when a shared expansion bus for connecting external non-volatile memory to the CPU chip typically drives other interfaces or removable security modules. When the systems operate, the shared bus makes the ROM data available on the user-accessible point of deployment (POD) connector. As a result, the system is vulnerable to hacking.

              A possible solution is to implement separate buses, and not send any premium content or sensitive data to the bus that is exposed on connectors. However, when the buses are wide, the typical pin count associated with the bus may be 20-50 or more. The cost associated with extra pins is too high.

              Another solution i...