Dear fellow Lightning Developers, I was recently on an event where the visitors have been gifted 10k sats on a custodial wallet. They could spend those sats via some web interface and an NFC card. During the event I was contacted by several plebs who were confused about one particular thing:
It was impossible for them to withdraw the full amount from the service. Pasting an invoice for 10k sats would not work as the custodial service required a fee budget of 1%. However if people submitted an invoice for 9900 sats the remaining 100 sats were usually not fully required for the fees. Thus the users may have had a leftover of for example 67 sats. Now the problem repeated on the residual amount. While some services seem to have a drain feature for such a situation I find this frustrating and was wondering if we could help directly on a protocol level. Here is my proposal for a simple solution to this specific problem: `option_recipient_pays_routing_fees` This would be a new flag in invoices signaling that the recipient is willing to pay for the routing fees by releasing the preimage even if the full amount has not been arrived in htlcs at the recipient. So the workflow would be the following: 1. Alice creates an invoice for 10k sats setting the `option_recipient_pays_routing_fees` flag in the invoice and passes it either to custodial user Bob or to her own custodial account. 2. The payer parses the invoice and searches for a payment path or payment flow to Alice. 3. Because `option_recipient_pays_routing_fee` is set, the onion is not constructed in a way that the final HTLC will be for the amount of 10k sats but rather in a way that the first htlc will be for 10k sats and the following HTLCs will be of decreasing value so that routing nodes are compensated properly. 4. When the HTLC(s) arrive at Alice she will release the preimage if and only if not too many sats (e.g. 1% of the amount) are missing. Of course it would be good if the 1% was not hard coded in the protocol / software but configurable by Alice at the time of invoice creation. I think the main issue with this proposal is that instead of confusing users who wish to drain an account we may now have to educate users about two different invoice types. On the other hand I think this can probably easily be achieved via the current wide spread user interfaces. Of course it may be nice to have folks from the Bitcoin Design community to join this specific part of the discussion. With kind regards Rene Pickhardt -- https://www.rene-pickhardt.de
_______________________________________________ Lightning-dev mailing list Lightning-dev@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/lightning-dev
