What happens if a part of the network is isolated and then rejoins?

[davidpbrown]

Bitcoin makes a lot of sense and I'm looking then to understand how Bitcoin works in extreme scenarios; to have confidence in it's ability to be robust, I think that's necessary.


If there was a real world disruption to the internet and two bitcoin networks were running in isolation; each with enough instances to confirm transactions, then is there a risk that two instances of the same wallet could be used either side of the border and a wallet could then double spend?

[lucif]

Yes it could spend of particular output in each network, if the PK owner has access to both segments in a time.

After rejoin network will decide which spend was the first on vote basis. It will rebuild chain also on vote basis (highest would be main). In a rebuilding process, orphaned chain transactions will be recompiled into new blocks of longest chain. Obviously, the longest chain earlier spends will have priority. Spends of same outputs of orphaned chain will stay unconfirmed.

[MysteryMiner]

It is possible. When networks are joined together, the longest chain wins and transactions in shorter chain are reverted to 0/unconfirmed and will never confirm. Until then double spend on each network side is possible.

But if even single node talks to both networks, the network split will not happen.

[davidpbrown]

hmm.. perhaps it's unlikely to ever be an issue that couldn't be written off but I wonder that people using only their private keys and not a node; so debit cards for example, could do this unwittingly and then the innocent vendor that's in the minor network, for no fault of their own, might lose transactions?

[DannyHamilton]

hmm.. perhaps it's unlikely to ever be an issue that couldn't be written off but I wonder that people using only their private keys and not a node; so debit cards for example, could do this unwittingly and then the innocent vendor that's in the minor network, for no fault of their own, might lose transactions?

Explain?

As long as the vendor was connected to the network, they would see the transaction.  How would a user using a private key keep the vendor's network isolated?

[davidpbrown]

Where a part of the network is isolated - unlikely perhaps, then a minor network physically local to the major network could see the same private key with neither customer or vendor being aware. Perhaps if the card held the balance, that would avoid innocent errors or missing communication.

I think perhaps I'm still to get my head around how a debit card could work. If you contact the same node, it'll obviously be aware of the previous transactions; if you use a private key to contact a node that hasn't caught the latest transactions, those transactions won't be taken into account?