Der Aktuelle Kursverlauf

Ich hatte hier mal behauptet, LN könne zu fractional reserve banking führen. Dies wurd angezweifelt (ich solle mich erst mal schlau machen wie LN funktioniert).

Justus Ranvier hat ein plausibles Szenario beschrieben, wie es passieren könnte daß sich fractional banking einschleicht, ohne daß die user es merken. Ich quote nicht das ganze Ding um den Thread hier nicht so zuzuspammen, aber einen relevanten teil:

Quote from: https://bitco.in/forum/threads/gold-collapsing-bitcoin-up.16/page-487#post-17813

Life is pretty good for Bob as long as his usage of this channel (sending vs receiving) remains in balance +/- 1 btc. If at any point the channel fills up in a particular direction, the only way to keep sending or receiving (depending on the direction in which it filled up) is to open a new channel. This will cost 1 on-chain transaction fee.

This creates a terrible user experience for LN. Imagine being the support representative tasked with explaining to customers why they can't receive money from their grandchildren any more without paying a relatively-large fee because their channel is full. In fact, once a channel is full it become uneconomical to send any more transactions in that direction whose value is less than the cost of an on-chain transaction.

There is a solution for this - LN wallets just need the ability to add and remove new inputs to a refund transaction. So going back to the first example, as soon as Bob purchases his first bitcoin, his friend Alice immediately wants to send him another 2 btc. Since this is more than the available liquidity it's not possible to do this while adhering strictly to the micropayment channel protocol, but Coinbase has decided that they don't like dealing with awkward support calls so they've altered the protocol slightly for their customers.

Rather than opening a new channel, whenever somebody tries to send Bob bitcoins when his existing channel is full Coinbase selects an input from their own wallet and adds it to the refund transaction. Bob's wallet accepts this either because he's using a Coinbase-branded LN wallet rather than a generic one, or else because even the generic LN wallets have been convinced to add this capability.

There's nothing wrong with this necessarily, however since that new input isn't part of the Bob-Coinbase micropayment channel, Bob has no way to confirm the input has only been added to his refund transaction. Coinbase could have overcommitted that input to 10, 100, or 1000 other refund transactions - nobody knows until somebody decides to close a channel. As long as Coinbase is confindent that most of the channels won't attempt to close at the same time, they don't have to worry about it too much. Whenever the first channel which includes an overcommitted input closes, they just update the other channels with a new input.

Coinbase doesn't actually do this, of course. When they rolled out their "liquidity protection" feature they explicitly promised to never overcommit inputs, and since they are regulated, law-abiding businesses we just have to look at the track record of financial regulations and their outcomes to know we have nothing to worry about.

[...]

Bob could use his LN client for the rest of his life blissfully unaware that he doesn't actually own any bitcoins at all.

Dieses Szenario ist übrigens nur dann wahrscheinlich, wenn der Kostendruck (fees) on-chain hoch genug ist.

(Auslöser für den Post von Justus war sein interview auf "the daily decrypt" gepaart mit der Tatsache daß er dort in's schwimmen kam als Amanda ihn nach einem solchen Szenario fragte).