Re: Saving Screen Capture
- From: Joseph M. Newcomer <newcomer@xxxxxxxxxxxx>
- Date: Wed, 25 Mar 2009 02:44:07 -0500
Unless you have complete physical security and network, you cannot protect a computer. You
cannot effectively protect the pixels on the screen. You can pretty much assume that if
someone tells you how you can, they will be wrong. You can make it somewhat clumsy for a
casual non-technical user (such as my mother, who is 89) but you will not stop a serious
attack, nor will you be able to stop even the most casual user who knows how to search the
Internet and download programs.
The DRM people forced Microsoft to require signed drivers for the 64-bit OS; it isn't
there for security; it is there so if I download a driver and use it to "steal" what I've
already paid for, the driver can be traced back to its creator, who can then be prosecuted
under the DMCA (Disney Must Conquer All, otherwise known as the Digital Millenium
Copyright Act). So it is not technically possible to prevent the data from being
captured, only possible to prosecute someone using a highly questionable law which is
internally inconsistent ("fair use" demands that I be able to crack security!). And only
if I'm caught can the legal remedy be applied; I can code-sign my own driver on my own
machine using my own code-signing certificate and use it to capture whatever I want.
In the TCB (Trusted Computing Base) this issue presents a number of problems. The only
way this can be effectively protected is by building capabilities into the graphics card
so that pixels placed on the screen by the trusted core cannot be seen, captured, etc.,
EVEN if the attacker has created a device driver that goes after the raw hardware buffers!
Note that it is not possible to run ordinary apps in the trusted core, because it is not
Windows.
TCB requires hardware-encrypted disk drives, special DMA chips (to prevent data snarfing
using DMA), keyboards that send encrypted packets for each keystroke, and video
controllers that can be controlled from the trusted core in a way that makes the trusted
part of the buffer inaccessible.
I spent a couple years working on TCB technology a few years ago, but cannot say anything
at all about who I was working for, what I worked on, or anything about the code internals
of the project (it was the strongest NDA I ever signed!) But it is kind of cool to know
that millions of instances of my code are out there running somewhere (and I can't say
where)
joe
On Tue, 24 Mar 2009 15:41:33 -0500, "AliR \(VC++ MVP\)" <AliR@xxxxxxxxxxxxx> wrote:
Maybe his program is really top secret, government stuff. Who knows.Joseph M. Newcomer [MVP]
AliR.
"Goran" <goran.pusic@xxxxxxxxx> wrote in message
news:222155a9-c00f-427e-81a1-89e4f15c4409@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Please, don't try to do that!
First, why on Earth do you think your program is so important or
"secret" or whatever, that it should prevent it's user from doing what
he can do with countless other programs!?
Second, AFAIK, Joe is right and you will fail ;-).
Raymond Chen rightly ridicules inflated feeling of self-importance of
certain programs. Don't make more of them.
Goran.
email: newcomer@xxxxxxxxxxxx
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm
.
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