Hacking the Xbox

Chapter 13 - Onward! 203
Palladium’s requirement for cooperation between chipset vendors, OEMs
and Microsoft is a potentially large flaw. There isn’t enough margin in the
commodity PC hardware industry today to support the overhead of an
extensive cryptographic security overhaul. Too, many chipset vendors do
not have any experience with implementing secure systems. On top of the
language barrier faced by many overseas chipset vendors, chipsets are
usually developed on a short fuse and with a keen eye on the pocketbook.
Can chipsets developed under these conditions be expected to protect
sensitive secrets?
The Xbox is an example of what can go wrong when security policies are
defined by one body and implemented by another very different organization.
Microsoft wrote a specification for a trustable piece of hardware,
namely, the Xbox. Strong cryptographic algorithms are used liberally in the
Xbox, and the master key for the system is locked deep inside a complex
piece of silicon. However, experience has demonstrated that the Xbox’s
security system can be bypassed using a combination of an unsecured debug
port, a flaw in the hardware initialization scheme, and a bug in the handling
of a boundary case of the instruction pointer in the CPU. These three minor
oversights, committed by three independent parties (the assembly contractor,
the Xbox firmware designer, and Intel), conspire to provide a
convenient method for defeating Xbox security.
Each of these oversights on their own does not represent a significant
security problem. This leads to the disconcerting question of how many
security breaches in a particular Palladium implementation will be caused by
the stacking of multiple benign flaws. Every complex consumer electronics
system has minor bugs or design oversights, especially when systems are
composed of components built by multiple independent entities whose
primary interest is in turning a profit.
In the consumer electronics industry, one can either ship a perfect
product, or one can make money. Products that don’t make money are
quickly cancelled. Thus, it is very rare to find a consumer product that is
technically perfect in all respects. As a result, the only practical way to
guarantee the security of consumer electronics system as complex as
Palladium is to throw it into the wild, and let the hackers have their way
with it for many years until all of the big security holes have been
discovered and plugged.
On the other hand, the TCPA’s TPM is a device created to solve a certain
set of problems that is smaller in scope than Palladium’s. Thus, the TPM
is not as exciting from a market perspective, but it may be more practical
and serviceable for its intended purpose. Both the TPM and Palladium
are weak to hardware attacks, but the TPM doesn’t attempt to extend
security requirements as far into third-party system design territory. The
TPM is primarily a secured key management module that can detect most
modifications and intrusions to the host system. The software layers built
on top of this substrate do the rest of the heavy lifting, caveat emptor.