On Sunday 02 June 2002 08:24 pm, Joseph Ashwood wrote: >> > The MPAA has not asked that all ADCs be forced to comply, only that those > in a position to be used for video/audio be controlled by a cop-chip. While > the initial concept for this is certainly to bloat the ADC to include the > watermark detection on chip, there are alternatives, and at least one that > is much simpler to create, as well as more benficial for most involved > (although not for the MPAA). Since I'm writing this in text I cannot supply > a wonderful diagram, but I will attempt anyway. The idea looks somewhat > like this: > > analog source ------>ADC------>CopGate----->digital > > Where the ADC is the same ADC that many of us have seen in undergrad > electrical engineering, or any suitable replacement. The CopGate is the new > part, and will not be normally as much of a commodity as the ADC. The > purpose of the CopGate is to search for watermarks, and if found, disable > the bus that the information is flowing across, this bus disabling is again > something that is commonly seen in undergrad EE courses, the complexity is > in the watermark detection itself. > > The simplest design for the copgate looks somewhat like this (again bad > diagram): > > in----|---------------buffergates----out > ----CopChip-----| > > Where the buffer gates are simply standard buffer gates. > > This overall design is beneficial for the manufacturer because the ADC does > not require redesign, and may already include the buffergates. In the event > that the buffer needs to be offchip the gate design is well understood and > commodity parts are already available that are suitable. For the consumer > there are two advantages to this design; 1) the device will be cheaper, 2) > the CopChip can be disabled easily. In fact disabling the CopChip can be > done by simply removing the chip itself, and tying the output bit to either > PWR or GND. As an added bonus for manufacturing this leaves only a very > small deviation in the production lines for inside and outside the US. This > seems to be a reasonable way to design to fit the requirements, without > allowing for software disablement (since it is purely hardware). > Joe
Bzzzzztttt! Wrong Answer ! How do you prevent some hacker/pirate (digital rights freedom fighter) from disabling the "CopGate" (by either removing the CopChip, finding a way to bypass it, or figure out how to make it think it's in, "Government Snoop" mode ) ? Then the watermark can be removed. Remember it only requires ONE high-quality non-watermarked analog to digital copy to make it on the net and it's all over. -- Neil Johnson, N0SFH http://www.iowatelecom.net/~njohnsn http://www.njohnsn.com/ PGP key available on request.