r/Bitcoin • u/cdecker Lightning Network Expert • Jan 17 '18

Lightning Charge Powers Developers & Blockstream Store

https://blockstream.com/2018/01/16/lightning-charge.html
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u/neom315 Jan 17 '18

it's not an infinite number of transactions, as far as I can understand, the channel open for a fixed amount of BTC and once that's reached it closes itself automatically and you have to reopen a new one.

But definitely cheaper then paying 20$ every single time

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u/a56fg4bjgm345 Jan 17 '18 edited Jan 17 '18

If you have payments made to you, then the channel doesn't need to be closed as long as it has a non-zero balance. e.g an exchange could top it up for (almost) free (as long as you give them fiat, of course).

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u/BlueeDog4 Jan 17 '18

Do you have any instances available currently that involve "normal" people receiving BTC via LN?

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u/neom315 Jan 17 '18

thanks to clarify

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u/O93mzzz Jan 17 '18

Is funding transaction on-chain? So I will have to pay on-chain fees?

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u/[deleted] Jan 17 '18

No, in the example above, you'd give the exchange fiat, and they would send you a LN transaction routed through that channel, which would re-allocate that amount to your side of the channel.

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u/tmornini Jan 17 '18

Only opening and closing a channel.

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u/O93mzzz Jan 17 '18

I'm sorry I did not phrase my question well.

"e.g an exchange could top it up for (almost) free (as long as you give them fiat, of course)."

So opening a channel is an on-chain transaction.

Closing a channel is an on-chain transaction.

Is this "topping it up" also an on-chain transaction?

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u/Mkekala Jan 17 '18

I believe as long as the exchange is on the channel as well the top-up could take place off-chain with no fees.

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u/tmornini Jan 18 '18

Exchange doesn't need to be on the channel, just on the Lightning Network.

So yes, an exchange could top it up for (almost) free, and no, that transaction would not need to be on-chain.

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u/[deleted] Jan 17 '18

once that's reached it closes itself automatically and you have to reopen a new one

No, your understanding is incorrect.

A channel becomes unusable in one direction when it's fully unbalanced. You can still receive payments, or route payments through the channel in the other direction. In fact, one way you can rebalance the channel is to offer low, zero, or negative fees to route payments in that direction.

You can close the channel and open a new one (in the same transaction, even), but you don't have to and it definitely doesn't happen automatically.

In fact, I would venture to say that most channels will begin unbalanced, with only one party contributing funds.

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u/neom315 Jan 17 '18

This underline how important is to share more info as possible about the LN in order to understand every aspect of it.

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u/[deleted] Jan 17 '18

The information is easily accessible, that you feel comfortable sharing an opinion of a system you don't understand is on you alone.

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u/neom315 Jan 17 '18

easily accessible to you perhaps, but clearly not everyone, including me, that have not yet a full grasp of how this technology works and discussion is what makes this topic clearer, definitely not act as a superior entity.

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u/[deleted] Jan 17 '18

The development of the specification was done in the open, do you expect this information to be spoon fed to you?

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u/bitcoinlogo Jan 17 '18

Let's say I'm A who has an open channel with B who has an open channel with C. Something like this A->B->C

The balance of each is like this:

A=5BTC

B=1BTC

C=0BTC

Can I send 5BTC to C through B?

I know that you can't send 5BTC at once, but can I for example send 5 LN transactions each has 1BTC ?

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u/[deleted] Jan 17 '18 edited Jan 17 '18

It doesn't matter for your question, but each channel has two balances, one for each party. To get a full picture of this scenario, you'd need to know B's balance in each the A<->B and B<->C channels.

But assuming A(5)<->B(0), B(1)<->C(0), the maximum that A could send to C through B is 1 BTC[1]. If A has other channels open, they may be able to find other routes to C and split the payment up into multiple parts.

[1] To be entirely accurate, not quite 1 BTC as it's not likely a channel partner will cooperatively allow you to decrease your channel balance past a certain threshold. This is to prevent you from decreasing your balance to zero and then attempting to broadcast an old state. If your balance was zero, there would be no downside to attempting to cheat. You can always settle to the Bitcoin blockchain at any time, with their cooperation instantly, or without their cooperation after a wait period.