Good morning! Excellent point. I would like to add that on a UX perspective, I would be a lot more worried about having a well connected node with well funded/balanced channels.
You can always refuse to pay a lesser invoice but having to wait for a new channel might be a deal breaker. Deducting routing fees is also important in my view. Felix On Tue, Jan 15, 2019 at 7:14 AM ZmnSCPxj <zmnsc...@protonmail.com> wrote: > Good morning Francis and list, > > Not directly related to the original question, but I would like to bring > up the issue of routing fees in such custodial cases. > > In your original post: > > > But for LN payouts (e.g. withdrawal from an exchange or a poker site), > the Sender is the services provider, and it is the Sender who will be > creating (most likely programatically) the terms of the payment. > > The issue is: when paying the user-provided invoice, does the Sender in > this case deduct also the routing fee from the user account or not? > > One possible attack on a custodial service is: > > 1. Acquire 1.0BTC in the custodial service (purchase by fiat, or simple > send via Lightning, etc.). > 2. Create 100,000,000 invoices of 1 satoshi each on a node the attacker > controls. > 3. Have the custodial service pay to the invoices. > > Paying 1-satoshi invoices will tend to lead to fees approximately equal, > or even greater to, the invoice amount. > > This is of course trivially fixable by imposing either a withdrawal limit > (number of invoices that can be paid in a day) or a minimum withdrawal > amount. > There is some degradation of service, but reasonable defaults (100 > withdrawal invoices per day) could still be useful for typical usage. > > Alternately, the custodial service may deduct the routing fees from the > account of the user. > However, this latter solution is also undesirable in general, as routes > (and thus fees) are controlled and selected by the sender, and in this case > the user is the receiver, not the sender. > > The custodial service can very easily lie about routing fees; even if the > user demands a report of the route, nodes along the route are allowed to > change their routing fees at any time, thus the route information is > potentially stale as soon as it is finalized and reported. > The custodial service might secretly control particular nodes on the > network and bias the routefinding algorithm towards those nodes even if > those nodes charge high fees. > > Overall, however, such issues are minimal. > Custodial services cannot be trusted to hold substantial money safely for > long anyway, so any UX problems with them are largely immaterial. > > Regards, > ZmnSCPxj >
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