No, the much more secure while at the same time liberty-preserving way to do this are heavily sandboxed secure enclaves with attestation, or even better standalone tamper-proof devices capable of attestation.
Like the ones practically every bank customer already has in their wallet, and for which most phones have a built-in reader these days... The only thing missing is a secure input and output channel, like a small built-in display and a button or biometric input.
In any case, I somewhat empathize with banks in that they want to ensure that my transaction confirmation device is not compromised, but getting to dictate what software does and doesn't run on my own hardware outside of maybe a narrow sandbox needed to do that is a no-go.
That is one of the reasons the crypto market is behaving like some radical innovation instead of just a group of bozos speedrunning financial history. For the first time since the invention of capital we have an asset class where it doesn't take the cooperation of a group of armed thugs to guarantee the integrity of the system.
Merkle trees can prevent tampering after the fact, yes.
But if you include collusion, there's no way for the blockchain itself to know who is colluding and where they are so.
Smart contracts may be vulnerable or malicious.
Wallets can be emptied.
Centralized exchanges and similar entities still exist.
Policing systems are still needed, because as long as there is something of value and there is still "evil" in the world, someone will try to steal it or damage it.
It's not money-preserving though. You need an extra device, and an extra phone number. The separate phone number is another privacy-preserving feature though.
A cheap Android phone is pretty much the opposite of a Yubikey, in terms of trusted computing base and attack surface.
My favorite, basic example is this: I'd like to create my own basic widget showing me my account balance on my phone's home screen. Doesn't have to be real-time, but accurate to +/- few minutes to what the bank app would say when I opened it. It has to be completely non-interactive - no me clicking to confirm, no reauthorizing every query or every couple hours. Just a simple piece of text, showing one number.
As far as I know it, there's no way of making it happen without breaking sandboxing or otherwise hacking the app and/or API endpoints in a way that's likely to break, and likely to get you in trouble with the bank.
It should not be that way. This is a basic piece of information I'm entitled to - one that I can get, but the banks decided I need to do it interactively, which severely limits the utility.
This is my litmus test. Until that can be done easily, I see the other side (banks, in cooperation with platform vendors) overreaching and controlling more than they should.
The point of the exercise isn't to just see the number occasionally; I can (begrudgingly) do that from the app. The difference here is that having the number means I can use it downstream. Instead of a widget on the phone screen, I could have it shown on a LED panel in my home office or kitchen[0], or Home Assistant dashboard. Or I could have a cron job automatically feeding it to my budgeting spreadsheet every 6 hours. Or I could have an LLM[1] remind me I've spent too much this week, or automatically order a pizza on Saturday evening but only if I'm not below a certain threshold. Or...
Endless realistic, highly individual applications, of a single basic number. The whole point of general-purpose computing empowering individuals. If only I could get that single number out.
--
[0] - Why would I want that is besides the point.
[1] - E.g. via Home Assistant.
Sure, you should definitely be able to do what you want with your computer, but you're actually demanding more here (at least in the case of transaction initiation and confirmation): For others to also trust the outcome of whatever you did on your own computer.
Banks are often legally required to cover losses resulting from unauthorized account access, so I can somewhat understand them wanting to minimize the chance of that happening. Sandboxed trusted computing, when done well, can strike that compromise much better than annoying non-solutions like root detection heuristics or invasive full-system attestation.
> As far as I know it, there's no way of making it happen without breaking sandboxing or otherwise hacking the app and/or API endpoints in a way that's likely to break, and likely to get you in trouble with the bank.
Banks should probably be required to make such a read-only API available (and in the EU, they are, to some extent – unfortunately only to "trusted", i.e. regulated and registered, service providers, raising the old question of who determines who is and isn't trusted). This is a very different story from transaction initiation.
Unfortunately, there are also caveats here. It's getting more and more common for companies to require me to "connect my bank account", which often means nothing less than granting them full and persistent account view access.
I think having the API still outweighs the downsides of others also starting to make demands for that access, but it's a slippery slope. For example, Airbnb not too long ago wanted full access to all(!) my Chase accounts to "verify my credit card".
Thats what is being required. The problem is making sure the policy is enforced correctly includes local business logic and user experience components. The money transfer needs to come from an authenticated user providing consent, not from some software that happens to have managed to get installed on the phone with sufficient permissions to interface with the secure element or to have their version of a library loaded.
That means one needs to validate user-facing software, and not just the API to a black box. Thus one is requiring a chain of custody validation up to the boot loader.
