Re: [Taler] Suitability for recurring payments / subscriptions

[Jeff Burdges]

On Tue, 2017-09-05 at 12:49 +0200, David Seaward wrote:
> From what I have read so far, Taler would not be a suitable mechanism
> for recurring payments (e.g. a monthly subscription or donation). Have
> I missed something? If not, is this use-case something that is on the
> roadmap?

Recurring payments would require client side automation, maybe
integrated with the Taler wallet, but not necessarily.  In other words,
the user's Taler wallet would make a normal payment each month, probably
after first informing the user. 

If another third-party extension manages repeating payments, then the
wallet's API for making payments becomes a threat.

There is a crypto question though :  Should payments for different
months be unlinkable?  Assuming yes, how do you tell the wallet what to
buy?  Any generic product URL works for donations, but if you want an
account to receive credit then you must figure out how that account
evolves over time.  Anonymous identity service like UnlimitID address
this by making the accounts unlinkable across epochs, but that's quite a
big can of worms.  

If the wallet itself manages repeating payments, then some anonymous
identity services would require special support.  I suppose Taler tokens
can mediate authorization themselves or act as an anonymous tokens in
several ways, which simplifies some issues.

You can ask if the wallet should be able to make a payment without
visiting the merchant's website too, but that souds needlessly complex
if you might want unlinkability.

Jeff

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