From ZmnSCPxj at protonmail.com Thu Feb 14 04:07:53 2019 From: ZmnSCPxj at protonmail.com (ZmnSCPxj) Date: Thu, 14 Feb 2019 04:07:53 +0000 Subject: [Lightning-dev] Proof-of-payments In-Reply-To: References: Message-ID: Good morning Joao, C-lightning already does this. If it is given an invoice for a payment hash it already knows, it silently succeeds and returns the preimage without sending out any money. This should extend to any wallets built on top of C-lightning. I am uncertain what the other implementations do. Regards, ZmnSCPxj Sent with ProtonMail Secure Email. ??????? Original Message ??????? On Wednesday, February 13, 2019 7:53 PM, Joao Joyce wrote: > Hi, > > Recently I've asked about the possibility of user identification across multiple payments?which now I get that it is a bad idea. > > In that previous exchange?ZmnSCPxj suggested that for purposes of proving payments (for instance for a user to redownload an already bought document) the service could just ask for the preimage of an invoice that was already paid. > > I was wondering if there's interest in standardising a way for payment invoices to contain information to signal wallets that they can skip the payment process if they are able to provide the service with a preimage for a previous payment for that particular item. > > Use cases could extend beyond simple download of an item. For instance paying for 30 days of a service and every time you want to access that service you just scan the LN invoice. > > I'm aware that intermediate nodes know about this preimage but I'd rather not focus on that for now. > > Thank you, > Jo?o Joyce