Clarification of lightning network example (putting funds into lightning)

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I'm checking How does the Lightning network work in simple terms? answer example:

1) Putting funds into Lightning We both send 0.5 BTC into a shared 2-of-2 multisig address. This requires a transaction on the Bitcoin blockchain. As a "balance sheet", we each create a 2-of-2 multisig transaction that pays out 0.5 BTC to you and 0.5 BTC to me. I sign one payout transaction and give it to you. If you want to put it in effect, you need only add your own signature and broadcast it to the Bitcoin network. Vice versa, you give me your copy of the payout transaction that you have signed and I have not yet. The "balance sheet" is a regular 2-of-2 multisig transaction in the Bitcoin network, it just isn't valid yet, because it doesn't have all signatures.

So in the first step you make a regular transaction from your address A to our common 2-2 address C, and I make a regular transaction from my address B to our common 2-2 address C?

I have one key of this 2-2 multisig address C and you have another?

Address C now has 1BTC.

Now from this address C I return 0.5 of its 1 BTC to your address A and sign with my key, and you return remaining 0.5 to my address B and sign with your key?

croraf

Posted 2017-11-15T14:31:07.777

Reputation: 1 112

Answers

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So in the first step you make a regular transaction from your address A to our common 2-2 address C, and I make a regular transaction from my address B to our common 2-2 address C?

Yes, although in the current lightning spec and implementation, only one party funds the channel. However it could certainly be both parties that fund it.

I have one key of this 2-2 multisig address C and you have another?

Yes.

Address C now has 1BTC.

Now from this address C I return 0.5 of its 1 BTC to your address A and sign with my key, and you return remaining 0.5 to my address B and sign with your key?

Two transactions are formed at this point:

  • one that you make and sign and send to me that gives 0.5 BTC to you and 0.5 BTC to me,

  • one that I make and sign and send to you that also gives 0.5 BTC to you and 0.5 BTC to me.

Andrew Chow

Posted 2017-11-15T14:31:07.777

Reputation: 40 910

Regarding third part. I know that both must sign to be valid. I'm interested if in the second step we use the address C (we put funds in step one) to return funds? – croraf – 2017-11-15T15:43:08.557

Yes, address C is the one that is spent from to return funds. – Andrew Chow – 2017-11-15T15:55:05.073

Also in the third part, the transaction I make from 2-2 address has two outputs (0.5 to me and 0.5 to you), or just one output that sends 0.5BTC to you? – croraf – 2017-11-15T16:01:54.273

1It is two outputs – Andrew Chow – 2017-11-15T16:34:11.223

And the transaction you make from 2-2 address has also two outputs 0.5 to me and 0.5 to you? Thus only one of these transactions can be fullfiled, as each spends entire funds from address C? – croraf – 2017-11-15T19:36:43.723

No. Address C has 1 BTC, and the transaction spends that 1 BTC and sends 0.5 to me and 0.5 to you. – Andrew Chow – 2017-11-15T20:02:06.020

https://chat.stackexchange.com/rooms/68778/room-for-croraf-and-andrew-chow – croraf – 2017-11-15T20:12:43.390

Asked: 2017-11-15T14:31:07.777

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Active: 2019-04-29T03:50:18.727