How ARM’s TrustZone aims to make smartphones more secure

This week, ARM announced that it is rolling out a joint venture with Gemalto and Giesecke & Devrient (G&D) dedicated to securing the software on connected devices. The new venture will focus on the development of a Trusted Execution Environment (TEE) based on the established ARM TrustZone security technology. caught up with Rob Brown, secure solutions segment marketing at ARM, to find out more about TrustZone.

What is TrustZone?

TrustZone is a feature of the processor architecture, and it allows us to “hardware-separate” a rich operating system, from a much smaller, tiny, secure operating system.

Simplistically, it’s like a 32-bit processor but a TrustZone processor would be like a 33-bit processor, where one extra bit tags the data that goes through the processor core, through the buses and address lines and the caches, with an extra bit that tags the data as “secure” or “normal”.

The underlying hardware enforces a strong separation of data that is tagged as secure from data that is not. What it means in that a rich operating systems that could have potentially been compromised cannot access data that is tagged as secure.

What are the use cases for the technology?

The principal use case is around user authentication, which is really one of the big challenges in enterprise security and payments. It’s about identifying that the right user is at the right device, and that’s a real challenge when it comes to things like usernames and passwords.

You want usernames and passwords to be easy to remember by the users and difficult to guess for anybody else. The problem is that we’re asked to pick usernames and passwords so often, and we always end up picking the same ones. With TrustZone, the user authentication problem is solved, because we can capture PINs securely into that tightly-constrained secure OS, encrypt them and process them out of view of a rich operating system.

In terms of transaction values, is there an upper limit to what the user can process?

That’s going to be down to the individual banks to make an assessment on how much risk they want to take with their contactless technologies. We could see that evolve at some point where it’s actually the user who is making the decision about how much they would want to go through on a non-user authenticated transaction. We can empower the user to set that transaction limit, because £15 to one person might be a lot of money and £15 to somebody else might not be a lot at all. So why have this arbitrary transaction limit when users can manage their own risk?

There’s an obvious analogy with how much cash you tend to carry in your wallet. As a student living in a rough area, I wouldn’t be comfortable carrying £100. But now I’m older and have moved to a nicer area, I’d be happier carrying higher sums of cash.

How does TrustZone compare with other user authentication technologies used today?

It provides strong authentication built in to the device, which is not commonly done today with any other strong-authentication technologies.

They’re all extra bits of hardware that you have to carry around; things you have to plug cards in to generate one-time passwords. We’re able to remove those devices and that inconvenience for consumers and build the security into a more usable device – your phone.

Does TrustZone pose a threat to NFC?

NFC is a radio interface standard and what it’s used for is physically connecting one device to another device, like tapping your phone against a PoS terminal to initiate a transaction. What TrustZone can do there is protect the NFC transaction where you’re asking for the user to enter a PIN. At the moment, we’ve got security measures that demand that you type your 16-digit numbers, your delivery address, your billing address, security number on the back of your card, username and password – all that hassle – it’s not so great on a touchscreen . It’s ok on device with a keyboard where you’ve got that high memory and you’re used to entering that data so often, but can we make the mobile user experience better? And the answer is yes, because we’re shopping online with a device that has got your credit card built in to it. You don’t need to go and get it out of your wallet anymore, it’s already built into your phone.

So it’s more of a replacement to PayPal?

You could see it that way – it’s not a replacement for NFC, because TrustZone does not give you a radio interface. You could in theory, connect TrustZone through the radio interface but that’s not what we’re looking to do. We are looking to augment the secure element with some additional security in the apps processor to help with things like user authentication and that applies for internet transactions and NFC transactions.

Who are you partnering with to roll out the technology?

There are big handset manufacturers that have already got very large market shares of the Android base, but I can’t talk about which handsets will be launching first with the technology – that’s down to the handset manufacturers to reveal, which I’m sure they will very soon.  The real innovative step here is getting that small secure OS that you can deploy services to in the field and for that we’re working with G&D and Gemalto – they’re famous for smart card technologies and being able to manage smart cards over the air.

And in terms of financial services partners?

Gemalto and G&D are the ones who have those relationships but we do have those discussions with the major financial institutions and card schemes that would ultimately use the technology.

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