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Re: Separate trusted computing designs

From: Michal Suchanek
Subject: Re: Separate trusted computing designs
Date: Wed, 30 Aug 2006 21:14:30 +0200

On 8/30/06, Christian Stüble <address@hidden> wrote:
> > > I asked for use cases that have a clear benefit for the public as a
> > > whole or the free software community.
> >
> > I personally would like to be able to enforce my privacy rules even on
> > platforms that have another owner.
> If you can enforce a property about a system, then it is not owned
> exclusively by another party.  That's a contradiction in terms.
Maybe this depends on your definition of "owned" or that you have not read my
text carefully. I said that I want to enforce "my rules", not "my
properties". If the platform has certain properties that I accept (and that
imply that the platform owner cannot bypass security mechanisms enforced by
my agent), my agent will execute. Else it will not.

You confuse two cases

a) I want to buy a service, and to ensure that the service is provided
in the way I requested I rely on TPM verification. I run my software
on somebody else's hardware.

b) I want to buy a service, and the provider requests that it runs on
certain hardware/OS/PC color/whatever. Today I have the choice to
access the service in any way I want. TPM would forbid it.

The problem is that service providers are in the position to enforce
conditions on the consumers. TPM could be used either to get a better
balance if used for the benefit of the consumer or to reinforce the
strong position of the service provider if  it is used to its benefit.
Since the provider is in the position to dictate conditions to the
consumers TPM is going to be used to reinforce it position.

If a program requires a specific amount of memory (or a specific vga adapter)
for execution, does this mean that the platform is not owned exclusively? In
my scenario, the owner can define any security policy it would like to. I
will never be able to change this technically. But I can decide whether my
agent will be executed in this environment or not.

But without TPM I am free to emulate the required hardware in any way
I see fit. The program may break but if I emulate it well wnough it
will work. TPM forbids this.

> What you can do is to engage in a contract with somebody else, where
> this other party will, for the purpose of the contract (ie, the
> implementation of a common will), alienate his ownership of the
> machine so that it can be used for the duration and purpose of the
> contract.  The contract may have provisions that guarantee your
> privacy for the use of it.
> But, the crucial issue is that for the duration the contract is
> engaged under such terms, the other party will *not* be the owner of
> the machine.
Is the owner of a house not the owner, because s/he is not allowed to
open the electric meter? If you sign the contract with the power supplier,
you accept not to open it. And it becomes a part of your house. Now,
you are not the house owner any more? Sorry, but I do not understand why a
platform owner alienates his ownership by accepting a contract not to
access the internal state of an application.

You provide an example that appears to be similar on the surface but
has different implications.

The meter
- is not actively used by you, it is in fact used by the service
provider, you only use the electricity which is in no way impeded by
the meter (as opposed to poorly developed application that you use to
access content)
- will work equally well if placed outside your house, except
somebody may steal electricity from you  (but it will provide the
service for the supplier - as opposed to an appliaction that you
cannot execute outside of your computer)

> > > > If there
> > > > are two
> > > > comparable open operating systems - one providing these features and
> > > > one that
> > > > does not, I would select the one that does. I do not want to discuss
> > > > the
> > > > opinion of the government or the industry. And I don't want to
> > > > discuss
> > > > whether people are intelligent enough to use privacy-protecting
> > > > features or
> > > > not. If other people do not want to use them, they don't have to. My
> > > > requirement is that they have the chance to decide (explicitly or by
> > > > defining, or using a predefined, privacy policy enforced by the
> > > > system).
> > >
> > > I am always impressed how easily some fall to the fallacy that the use
> > > of this technology is voluntarily for the people.  It is not.  First,
> > > the use of the technology will be required to access the content.  And
> > > people will need to access the content, to be able to participate in
> > > our culture and society.  All the major cultural distribution channels
> > > are completely owned by the big industry, exactly because this allows
> > > these industries to have a grip-hold over our culture.  There is an
> > > option for popular struggle against this, but it will require a huge
> > > effort, and success is by no means guaranteed.
> >
> > I did not talk about TC in general, but about the "privacy-protecting
> > agent".
> I am not sure what you mean by that term.  The crucial point here is
> that TC removes the choice from the people which software to run.
I never said that I think that the users will have the free choice to use TC
technology or not. Different circumstances may force him to use it,
e.g., his employer, or that s/he prefers an operating system that does not
allow to disable TC support.

I suggested a use case that uses TC in a meaningful sense (at least in my
opinion), and as a response people are asking me whether users will be able
to use this technology. My statement was that I would like to have such a
system and that I am currently not interested in opinions of the industry or
the government, or whether other people need this feature.

But your system will not run in a vacuum. There will be government and
the industry around, and their actions may severly impact the
usefulness of your system.

I beleive the question what purpose your system serves is an important
one. You probably had something in mind but I haven't followed the
development of your system and do not understand how it is meaningful.
I would really like to know.

> > > > This is (except of the elementary security properties provided by the
> > > > underlying virtualization layer, e.g., a microkernel) an
> > > > implementation
> > > > detail of the appropriate service. There may be implementations
> > > > enforcing
> > > > strong isolation between compartments and others that do not. That't
> > > > basic
> > > > idea behind our high-level design how to provide multilateral
> > > > security: The
> > > > system enforces the user-defined security policy with one exception:
> > > > Applications can decide themselves whether they want to continue
> > > > execution
> > > > based on the (integer) information they get (e.g., whether the GUI
> > > > enforces
> > > > isolation or not). But this requires that users cannot access the
> > > > applications's internal state.
> > >
> > > That's incompatible with my ideas on user freedom and protection the
> > > user from the malicious influences of applications.
> >
> > I know. But this is IMO a basic requirement to be able to provide some
> > kind of multilateral security. A negotiation of policies 'before' the
> > application is executed.
> It's not a requirement to provide multilateral security, it is only a
> requirement for an attempt to enforce multilateral security by
> technological means.  Issues of multilateral security exists since the
> first time people engaged into contracts with each other.

> The problem with negotiation of policies is that balanced policies as
> they exist in our society are not representable in a computer,
Of course not. And nobody wants to replace the judge by the computer.
But if rights can be enforced technically, I prefer this solution over
good-will of the software vendor or the judges. Moreover, I think that
we often have to prove that a better solution exists to convice judges
to "ban" the not-so-good solutions. In the real world, even the bad
solutions solve some problems.

But DRM will represent exactly the good-will of the software vendors,
and it will technologically prevent any override by judges or anybody

> and
> that the distribution of power today will often do away with
> negotiation altogether.
> I think it is very important to understand what "balanced policies"
> means in our society.  For example, if an employer asks in a job
> interview if the job applicant is pregnant or wants a child in the
> near future, the applicant is allowed to consciously lie.
Good example. In one of our papers we suggested to encrypt the PCR values,
and/or to allow users to lie about their values, and allow a decryption
only in the context of a conflict, e.g., at a judge.

This means that there must exist some sort of 'judge-key' which is
administered by somebody.
So in this case the benefit of using systems with TPM over TPM-free
systems is not obvious.

> Similarly,
> shrink-wrap licenses often contain unenforcable provisions.  However,
> one does not need to negotiate the provisions, one can simply "accept"
> them and then violate them without violating the law.  Our social
> structure allows for bending of the rules in all sort of places,
> including situations which involve an imbalance of power (as the above
> examples), emergencies, customary law, and cases where simply no one
> cares.
This is exactly the main motivation behind our work.
It is exactly what I do not understand: how this motivation affects
any TPM-based system.

> Thus, it is completely illusorical to expect that a balanced policy
> can be defined in the terms of a computing machine, and that it is the
> result of _prior_ negotiation.  Life is much more complicated than
> that.
It is. But in my opinion computing machines can do better than today.
But TPM is going to be deployed (or at lest attempted) on todays machines.

> Thus, "Trusted computing" and the assumptions underlying its
> security model are a large-scale assault on our social fabric if
> deployed in a socially significant scope.
A unlogic conclusion, since TC does not aim to solve the problems discussed
It was developed at least partly to enforce otherwise unenforcable provisions.

> > > It is also incompatible with the free software principles.
I am sure TC is not. But some implementations based on it may be.

> >
> > What exactly is in your opinion incompatible with the free software
> > principles?
> From the current GPLv3 draft:
> "Some computers are designed to deny users access to install or run
> modified versions of the software inside them. This is fundamentally
> incompatible with the purpose of the GPL, which is to protect users'
> freedom to change the software. Therefore, the GPL ensures that the
> software it covers will not be restricted in this way."
No problem, my "privacy agent" does not prevent users from installing
or running modified versions of software. And the underlying TCB does
not, too.

But what about a Linux user that is not allowed to install software? This can
be configured by root. Is Linux incompatible to GPL-v3? Or only certain

The problem is that you can implement everything on a platfrom without TC that
the GPL-v3 wants to prevent. Most often, it is only a configuration option.
But does the GPL-v3 restrict users regarding the allowed configurations?

It allows to install software to at least one user: the owner/administrator.

TiVo does not allow installing software at all. It runs Linux, you get
the sources, modify to your liking, but unless you install software
signed by the manufacturer it won't run.

> The views of the FSF on DRM and TC are well-published, and easily
> available.  For example, search for "TiVo-ization".
> What is incompatible with the free software principles is exactly
> this: I am only free to run the software that I want to run, with my
> modifications, if the hardware obeys my command.  If the hardware puts
> somebody else's security policy over mine, I lose my freedom to run
> modified versions of the software.  This is why any attempt to enforce
> the security policy of the author or distributor of a free software
> work is in direct conflict with the rights given by the free software
> license to the recipient of the work.
What does the view say about a user that freely accepts a policy? I _never_
talked about a system that "puts somebody else's security policy over mine".

I guess the discussion went way off.

The original question was what useful uses do you (or anybody) see for TPM.

Not how bad it is. We all know it has flaws, and that hey will be
probably abused if it is allowed to spread.



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