MS Patent for DRM OS

[Anthony Naggs]

In message <20011213145708.E51502@colon.colondot.net>, Matthew Byng-
Maddick <ukcrypto@lists.colondot.net> wrote
>
>I also note the idea that it gets the time off a "trusted" time server,
>what will the "trust" be based on, and how will it cope if not networked.

Not a "time server", a clock.

>Surely this doesn't imply that I have to be on a live, internet-connected
>network, to run software?

The trusted clock would tick at a fast rate, but probably slower than
the processor clock.  The purpose would be to detect the operation of
debugging tools in the vein of Numega's SoftIce.  If a debugger was
active then the code would take longer to execute.

The trusted clock would have to be part of a hardened core to the host
platform.  Perhaps incorporated in the microprocessor.  The timers in
Pentium class CPUs may be sufficient for this purpose.

Applying this rapidly becomes much harder in an environment such as a
PC, where the processor is frequently interrupted by hardware requiring
supervision.  Allowing for some time to be used by genuine interrupts
loosens the time constraint that can be applied, possibly allowing
debugging tools to probe the DRM code.


Regards,
       Tony