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

[Marc Stibane]

Hello again,

On 2024-06-18, at 08:36:57, Jaap-Henk Hoepman via Taler <taler@gnu.org> wrote:
> 
> Hi Marc, all
> See some comments inline below.
> 
> On 18/06/2024 07:54, Marc Stibane via Taler wrote:
> 
>> 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.

After some back-and-forth, this works when the originating iPhone runs iOS 17.7 
or later, and the receiving iPhone runs iOS 17 or 18.
But it doesn’t work with receiving iPhones running iOS 16 or older, and it 
doesn’t work with receiving Android phones.
Apple already admitted a bug, but didn’t fix it yet. And it’s probably too late 
for iOS 18.3.


>>>> 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 (external) fees at all.


> 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.

We don’t need an intermediary service for NFC - it already works for iPhone to 
iPhone, and after Apple fixes their bug(s) it will also work from iPhone to 
Android.
Needless to say that Android to Android and Android to iPhone already works...


>> 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.

With iOS 18.2 Apple introduced Settings -> Apps -> Default Apps where you can 
manage which app to be used as default for AppStore, Email, Messaging, Calling, 
Call Filtering, Browser, Passwords, and “Contactless” for wallets.
If Taler Wallet were to use that slot, when you double-click the side button 
which launches the default contactless app (Taler Wallet) but want to pay with 
a card, we might be able to launch Apple Wallet - but we most certainly cannot 
launch e.g. a 3rd party banking app wallet (which the user might want to use 
for card payments instead of Apple Wallet).

But I really don’t want to use that slot - even though Apple named it 
“Contactless”, I consider it being used for card payments only. Since there are 
millions of payment terminals in the world, users wouldn’t want to utilize the 
slot for digital cash but keep it for card payments.

Digital cash must co-exist with card payments, like banknotes and coins 
co-exist with banking and credit cards in your leather wallet. But that’s no 
problem at all. Since we only need to activate NFC emulation when we show a QR 
code (to broadcast the same talerURI), we don’t need the “Contactless” launch 
slot - Taler Wallet already runs at this moment on the initiating phone.
And since we emulate an NFC TAG, the receiver doesn’t need to launch the Taler 
Wallet manually, but the background NFC reader will automatically read the 
emulated talerURI and offer to launch the Taler Wallet. This already works fine…

I asked Apple for another slot in the Default Apps for Taler, where the user 
can specify which app should automatically be launched whenever iOS reads an 
NFC TAG with a "taler://“ URL, or the user taps on such talerURI in the 
browser, a messenger, a mail program… without asking the user over and over and 
over again - but I guess this will not happen until we have some 10 millions of 
users.



Marc