Schneier on Security

Peter G. • December 28, 2006 12:12 AM

What follows are some comments I wrote up for an email list I’m on.

I’ll skip the summaries and start with the introduction.

Gutmann writes:

“This document looks purely at the
cost of the technical portions of Vista’s
content protection.”

He should have said “complexity” because almost nothing he describes has a direct or necessary relationship with cost. There are complexities involved, but they’re pretty much insignificant especially by comparison with Gutmann’s hype.

“However, one important point that
must be kept in mind when reading this
document is that in order to work,
Vista’s content protection must be able
to violate the laws of physics,
something that’s unlikely to happen no
matter how much the content industry
wishes it were possible.”

This point sounds important but he never backs it up, so I’ll skip it too.

“Since S/PDIF doesn’t provide any content
protection, Vista requires that it be
disabled when playing protected content.”

I believe this is wrong. I’m pretty sure Microsoft and the content creators aren’t going to prevent people from playing high-quality audio over USB speakers and Bluetooth headsets. I’m pretty sure that digital audio may be transmitted at CD quality levels (stereo, 44.1 KHz, 16-bit samples).

“For example PC voice communications rely on
automatic echo cancellation (AEC) in order
to work. …”

This is a very interesting point. If it’s okay to get the downsampled CD-quality audio, AEC should still work just as well. If not, people may just have to give up on doing full-duplex voice communications while simultaneously using the PC to play protected high-def content. I think perhaps this is not a big problem.

“Alongside the all-or-nothing approach of
disabling output, Vista requires that
any interface that provides high-quality
output degrade the signal quality
that passes through it.”

This is grossly overstated because it implies this happens all the time. It’s true only when the content is protected and the selected output is inherently insecure.

In practice, once secure hardware gets out there, most end users will never see this problem.

In the meantime, yeah, Microsoft and the hardware guys shouldn’t claim to support protected HD content if they don’t have a complete solution.

“For example the field of medical imaging
either bans outright or strongly frowns on
any form of lossy compression because
artifacts introduced by the compression
process can cause mis-diagnoses and in
extreme cases even become life-threatening.”

This is grossly irresponsible and tantamount to invoking Godwin’s Law. No medical-imaging system in the world is ever going to use the kind of content protection that Microsoft and the MPAA care about, and no medical technician would ever overlook the sudden downsampling-and-supersampling of medical imagery. Nobody’s going to die.

“Elimination of Open-source Hardware Support”

“Elimination of Unified Drivers”

These sections are ridiculous. The only thing the open-source software movement won’t get is enough information to let them violate the intellectual-property rights of the hardware vendors and content creators.

Users will be able to get closed-source drivers where there’s enough demand. Nobody has the right to expect anything more than that.

“This means that a report of a compromise of a
particular driver or device will cause all
support for that device worldwide
to be turned off until a fix can be found.”

This is a clumsy lie. The only thing that has to be denied in the event of a crack is the ability of the compromised device to violate intellectual-property rights.

The truth hiding behind the lie is that this repudiation process could make enemies if it’s invoked clumsily, inappropriately, or too often. This might happen, or it might not. If it does happen, the eventual result will be the relaxation of the content-protection requirements in order to protect the revenue stream.

“For example if there are unusual voltage
fluctuations, maybe some jitter on bus
signals, a slightly funny return code from
a function call, a device register that
doesn’t contain quite the value that was
expected, or anything similar, a tilt bit
gets set.”

Another clumsy lie. Nobody’s building graphics cards with super-sensitive voltage comparators on the power-supply lines or bus signals. It’s likely there will be software tell-tales. If these are badly implemented or exploited by malware, they’ll be removed.

“‘Cannot go to market until it works to
specification… potentially more respins
of hardware’ — ATI.”

How is this different than any other generation of hardware? Sheesh.

“Apart from the massive headache that this
poses to device manufacturers, it also
imposes additional increased costs beyond
the ones incurred simply by having to lay
out board designs in a suboptimal manner.”

Nonsense. This is like the old arguments against clean-burning engines. It turns out it’s cheaper and easier in the long run to do it the right way. Plus, signals that can easily be intercepted have to carry encrypted data anyway. The only places that unprotected digital video could be intercepted are inside chips.

“Increased Cost due to Requirement to License
Unnecessary Third-party IP”

This section is also nonsense. There are hundreds of chips in the world that contain unlicensed IP– because the functionality is disabled. At least as a first-order effect, the only chip costs due to IP licensing will be for chips that actually expose the licensed functionality.

“Unnecessary CPU Resource Consumption”

Completely false. The only thing that really matters here is the effort required to decrypt pre-authored content. Apart from a stopgap solution here or there, this will always be done in hardware. Gutmann goes on to admit as much in the very next section, too. Every graphics-chip vendor is putting 100% of the HD-DVD/Blu-Ray processing stack into hardware. CPU utilization will go DOWN with these implementations– almost to zero, in fact– not up.

Most of this section is just heartburn over the fact that marginal codecs aren’t mainstream codecs. Oh, well. Better skill next time.

“Final Thoughts”

Well, that’s pretentious. He never STARTED thinking clearly about the issue. It’s all just knee-jerk mumbo-jumbo.

“In July 2006, Cory Doctorow published an
analysis of the anti-competitive nature of
Apple’s iTunes copy-restriction system.”

One thoughtless crank referencing another. Brilliant.

. png