Re: [Taler] A hybrid approach to allow Taler payments at an EMV payment terminal

[Jaap-Henk Hoepman]

Hi Marc, all

See some comments inline below.

On 18/06/2024 07:54, Marc Stibane via Taler wrote:
> Hi guys,
> [...]
>
> No more. Apple introduced a protocol named “CardSession” that does this:
> https://developer.apple.com/documentation/corenfc/cardsession 
> <https://developer.apple.com/documentation/corenfc/cardsession>

Cool, didn't know this. Thanks for pointing this out.

> > > 1) What are the fees that the card industry would charge you to 
> > > create such one-time EMV payment tokens? One key argument for 
> > > merchants to adopt GNU Taler is that it is cheaper. If the fees 
> > > become higher instead, that could be an issue. Now, in good news, the 
> > > fees would only be higher for merchants that accept Taler via 
> > > 'legacy' mechanisms, so maybe that's OK. I'd still like to know how 
> > > insanely high the fees would be, and if it would be possible to pass 
> > > _all_ of them onto the merchant. Because a customer probably won't 
> > > put 10 EUR into their Taler wallet to then buy an EMV token for 6 EUR 
> > > to buy a coffee for 5 EUR with the merchant still paying 50 cents in 
> > > fees.  So I would really like to understand the economics of the 
> > > approach. Do you have numbers?
> > No, I don't have numbers, unfortunately.

P.S.: Regarding fees, there are already some services that offer virtual 
credit cards (https://www.cardrates.com/advice/virtual-credit-cards/) 
for online shopping. They are typically free for customers as they get a 
portion of the interchange fee paid by merchants. AN incentive for such 
a financial service provider to join a scheme like Taler + EMV is that a 
fraction of the payment card transactions (and thus the interchange 
fees) are diverted to them.

> > [...]
> > and the wallet can be programmed to enforce a maximum balance, to 
> > address AML concerns.
>
> Nope. Open source, anyone could remove the limit.

In general, yes. But if such a wallet enforced limit was deemed 
important for AML, some kind of software attestation could be 
implemented (on smartphone platforms that support it) to only accept 
'approved' wallets with untampered limits.


> The main problem with CardSession is that on iOS the “slot” for opening 
> the wallet with a double-click on the (hardware) sleep button (Apple 
> nowadays sometimes calls this "side button" but that’s ambiguous since 
> the louder / softer buttons are also on the (other) side of the iPhone) 
> can only be used by ONE app. Most, if not all iPhone users probably want 
> to continue to launch the Apple Wallet with this double-click, thus we 
> cannot use this. Our users would need to manually launch the Taler 
> Wallet app, which then could use CardSession for HCE.
>
> The DMA forces Apple to provide a “choice” dialog for this double-click, 
> where the user can choose which app will be launched, but this doesn’t 
> exist yet since there are no alternative wallets, yet - AFAIK. Maybe 
> later in autumn when iOS 18 ships...

Once that is the case, it would be a no-brainer to write a small wallet 
select app that is triggered by the 'side-button' that allows the user 
to select the specific wallet to open; or the taler wallet could offer 
the user to open another wallet at start-up.

> Marc

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