> On 11/16/2014 11:18 AM, David Li wrote:
> >
> > A Perhaps related topic that I often find people asking is:  "How
> > do you
> > trust the TPM itself given today's global economy?". There is one
> > school
> > of thought that regards the TPM as totally untrustworthy. Another
> > thinks
> > it's trusted to some degree. The debate seems never ending without
> > a
> > clear answer.
> >
> > I am curious about what experts on this list think of this issue.
> 
> Since we're engineers, can you provide references for the "totally
> untrustworthy" research?  I've seen some papers on errors in the old
> 1.1b TPMs, before there were good test suites.  I've also seen some
> research attacking the infrastructure, generally hardware attacks
> that
> the TCG doesn't claim to protect against.
> 
> I haven't seem any research at all concluding that the TPM is totally
> untrustworthy.
> 

I think this question is not about TPM itself but more about the entire root of 
trust. Essentially, do you trust your board manufacturer? Can you be sure that 
it is not putting backdoor code in the BIOS that can intentionally exclude some 
attributes to be excluded from hash? Can you trust the chip manufacturer? Can 
you be sure that TPM chip is not a altered replica coming from a third party?

I think the technology itself is secure enough but it is only a part of the 
equation. If one wants to be absolutely sure that root of trust is not 
compromised then he or she would need to follow security protocols that would 
include supervising of the entire manufacturing process of both TPM chips and 
boards and verifying every bit of the BIOS code (which is proprietary in most 
cases). In the real world all these measures are eithr too costly to implement 
or totally unrealistic. This implies that TPM based security is as trustworthy 
as Asian manufacturer that supplies your boards.

As with any security related application it is all about trade-off between 
value of assets you are protecting and cost of the security overhead. But I'm 
pretty sure that cost of subverting properly implemented TPM based security 
would be  very high and this is good enough for substantial number of 
applications.

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