[jlokier]

Yes it does, because it's not a random third party.

It's the device manufacturer.

Everyone is already dependent on some level of integrity by the device manufacturer, whether they're happy with this or not, because there is no other option.

That integrity might be checked. The manufacturer may be audited. Their processes and people may be background checked. Their hiring practices subject to a standard. Some of their devices may be selected at random, scrutinised, picked apart, checked by third parties, just to be sure. It's not done much, but perhaps it should be. Anyway, if that's done there is some higher level of justification in trusting the manufacturer's integrity, even if it remains a weak point.

If we already have to trust the device manufacturer and/or their auditors, that makes them owning the software trust root a very different proposition compared with anyone else owning it.

[tpxl]

>That integrity might be checked

It might also be broken and they don't care for you and you're screwed.

Also, as was shown many a time, the manufacturer will prevent you from doing whatever you please with your own hardware, if you chose to do so. In that case, their integrity is broken by design.

[jlokier]

That's all true, but the context here is things like payment terminals, ticket machines and energy charging meters, and whether it makes sense for third parties to easily modify the software running on them.

That hardware is not "your own". It is deployed to facilitate and protect a transaction between you and someone else.

The certainly exists a possibility that the manufacturer of those devices doesn't care about protecting them, with the result that you the user get over-charged, have your card details stolen etc.

But it's hard to see how making it easy for "anyone" to modify the software on those kinds of devices in an unconstrained way doesn't pose strictly greater risks of the above kind to you the user (being over-charged etc).

Surely you would rather have to trust just a few entities in control of the device, who have some kind of quality control legal obligation through the usual network of contracts and liabilities, than trust the 100s of entities that have had some contact at some point with the device, any of whom could have modified the software on it?

Any ideas on how to solve this problem which don't involve trusted roots?

[tpxl]

I see there was a misunderstanding. The owner of the payment terminal has to be the trusted root, not the manufacturer.