The meaning of word revocation means that I can somehow cancel the tx, however given the nature of blockchain transaction I struggle to understand how this is possible. Could someone please explain meaning of revocation in this context?
When a new commitment transaction is made, the old one should become invalid. However commitment transactions are not broadcast to the network, rather they are kept private and only broadcast when you want the channel to close. But because all commitment transactions are technically valid, we need some way to prevent people from broadcasting old commitments as they would effectively allow them to steal money. That's where the revocation key comes in.
and here achow describes bank2.0 chargeback scheme
imagine [a:10-b:10] where the channel counterparties each funding 10btc
they make their first commitment to agree on who shares what of the 20btc available in the multisig(channel)
in human language its like
tx 1
[input A:10
B:10
output A:10, spendable if tx2 not confirmed in 3days
B:10, spendable if tx2 not confirmed in 3days
]
now A wants to buy something from B for 10. so the new commitment is made.
tx 2 [a:0-b:20]
but each party has a sight variation A in human language its like
tx 2
[input A:10
B:10
output A:0, spendable if tx3 not confirmed in 3days
B:20, spendable if tx3 not confirmed in 3days
]
B in human language its like
tx 2
[input A:10
B:10
output A:0, spendable if tx3 not confirmed in 3days
B:20, spendable if tx3 not confirmed in 3days
]
-note: they both have variations(but not shown varient) because the 'spendable if' can have extra outputs if TX2A is transmitted or TX2B is transmitted but that would take longer to explain
this way it become self destructive for a counter party to send a previous TX
but imagine if B was to not to deliver the goods and refuses to make a 3rd tx to refund A his 10btc
A is then going to be forced to send out tx1 to HOPE to get his 10btc back, because tx2 wont give him his 10btc back.
A transmits tx1, HOPING B stays offline/doesnt notice for 3 days
B can then transmit his tx2 to overrule A's tx 1 and then B not only gets to keep the goods, but also gets 20btc by blackmailing A into forcibly making A transmit tx1 to then allow B to use his tx2 CSV exception
(i think achow hates it when i highlight the pitfalls but LN is not the utopia people promote.. there are pitfuls)
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