Mastering the Lightning Network book

[darkv0rt3x]

Well, with the help of someone, I was able to fix this shit and kinda move on. I even created a small PR in this book github repository.
Tomorrow I'll continue with this!

[darkv0rt3x]

Back to reading the book.

I have a question in Chapter 7, Section Constructing the Funding Transaction.

They show the image of the way a Funding Transaction is created (conceptually) with a 2-of-2 multisig address.
Then, below the image, they say:

Alice does not broadcast this transaction because doing so would put her 140,000 satoshi at risk.

Actually, 2 questions:
1 - If this is a 2-of-2 multisig address, how could Alice broadcast it on her own?
2 - Even if shw can do that, in what sense whould her funds be at risk?

[ABCbits]

--snip--

Actually, 2 questions:
1 - If this is a 2-of-2 multisig address, how could Alice broadcast it on her own?
2 - Even if shw can do that, in what sense whould her funds be at risk?

You can find answer to these question if you continue reading chapter 7. I skimmed it and it looks like section "Cheating with Old Commitment Transactions" and "Cheating and Penalty in Practice" answer your question in detail. But the short answer is,
1. Alice simply broadcast TX which represent current or older state of LN channel.
2. After bob detect cheating attempt (by broadcast TX which represent older state of LN channel), Bob could broadcast penalty transaction where Bob take all coin on LN channel.

[BlackHatCoiner]

1 - If this is a 2-of-2 multisig address, how could Alice broadcast it on her own?

I think what the author means in that part is that Alice should not broadcast the funding transaction before she constructs the refunding transaction. The reason is that Alice must be sure she will get her money back, even non-cooperatively if needed.

2 - Even if shw can do that, in what sense whould her funds be at risk?

If you send funds to a 2-of-2 multi-sig, wherein you only possess 1 private key, then you might be unable to spend if your partner simply disappears. You need him to sign the refunding transaction, and then you can send the money knowing that even if he does not respond, you can refund the channel.

[darkv0rt3x]

Actually, I didn't even thought thoroughly about the question I made.
In fact, and correct me if I'm wrong, if it happens that one of the peers broadcast a old commitement transaction into the blockchain, this transaction is already constructed and signed by both parties, right?
My question was non-sense because I was asking how could Alice broadcast (I was thinking about constructing it and signing it rather than just broadcasting it) the transaction thinking she would be using only her private key when, this transaction is already signed by both but not yet broadcast!