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Comment by pjc50 | Hacker News Reader

"Hiding peripherals and memory from the non-secure world is a key feature of TrustZone"

Whenever anyone says "secure", you must ask what is being secured, and against whom. The purpose of the secure world is to run a small operating system with privileged access to hardware that the outside world has no access to. It is the ultimate in nonfree software: it cannot be inspected at all, even on the binary level, and its loading can be governed by hardware keys. I believe it's also secure against JTAG inspection although this article doesn't mention that.

To use a device with TrustZone is to place total trust in the author of the software inside the trust zone. If they want to put Superfish-style malware in there, there's nothing you can do about it.

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Indeed. This requires to explicitly talk about who owns a given computer. There's a good case for trusted computing in your car, or on an airplane, or in a power plant. But if you want to use it in consumer equipment, we need to fight the urge of companies to be the owners of computers. You also have entertainment industry that wants to own your computer.

That's what the whole War over General-Purpose Computing is about. And I fear that we, private individuals, may lose it.

http://boingboing.net/2012/08/23/civilwar.html

My own incomplete attempt at cataloging the issue:

https://github.com/pjc50/pjc50.github.io/blob/master/pentagr...

The types of actors looking to control the phone/computer, other than the legitimate owner/user: <pre> Phishers, fraudsters, harassers Governments, policemen, censors & spies The media industry The advertising and marketing industry Platform holder (controller of the company store monopoly) Manufacturer (may be the same as the platform holder or may be rivals) Network operators (telcos or cable companies) </pre>

Very interesting writeup, thanks!

Yep. I keep thinking back to the term "trusted computing".

It comes out of the military, and it is not about the soldier trusting the computer they are using. It is about the generals, politicians and spooks trusting it to not reveal how deep in the shit hole the war has gone if the soldier (or someone else) press the "wrong" button.

As far as I understand, you can use open-source code for the monitor mode and also for the secure world of the TrustZone, so you're not required to use non-free software.

The question is who "you" is here – if the program is being secured against the user, and you are the user, then you don't have freedom 1 of the free software definition: "the freedom to study how the program works, and change it so it does your computing as you wish".

To paraphrase agent Smith, what good is the source code if you're unable to run it?

Not if the code in the internal boot ROM uses TrustZone and enters non-secure mode before executing any external code, preventing any other code from using the secure mode. As the article says, that's what many ARM SoCs do, but not all of them, so being able to run your own secure-mode code is dependent upon the SoC allowing it.

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