On another Bitcoin portal where I am, there was a very interesting issue. I want to sell (for example) diamonds for a billion dollars and how can I protect myself against an attack 51% (I know that it is almost unrealistic, but a billion dollars “on the table” is a treat to make preparations).
The basic idea is that someone makes a transaction, e.g. waits for 1 day (so that as many confirmations as possible) and then the transaction takes place. But we have to waste this one day waiting.
I came up with such an idea (what do you think). The buyer opens the Lightning channel for a billion dollars to you. (We assume that there are no bugs in the implementation), he does it some time earlier, e.g. a week earlier.
When a transaction takes place, we immediately give a bag of diamonds and get a transaction in Lightning. We close the channel (if we want to) and return home.
It seems to me that a 51% attack is impossible at this stage. You should reverse transactions to the time when the Bitcoins were in your account before the channel was opened. It could be several hundred or ~thousand blocks.
If a person wants to prevent a channel from being closed, you have the latest transaction history so you can publish it each time.
The only option is to shut down the network, which is impossible.
What do you think about it?