4 ms·

Wait for the next block broadcasted and make sure it references the last block. If you need more assurance you can wait for more confirmations.

• quickthrower2 9y ago
  It could be a fork though? With normal Bitcoin an attempt to do this would be massacred by the collective hashing power. But if all you have is the satellite link and no internet, you can't get confirmation from other peers.
  • smokeyj 9y ago
    It could be a fork, but forks dont last past two or three blocks. Unless you're the target of a massive double spend its not a big threat. So simply waiting for more blocks is good enough.
    • nicpottier 9y ago
      Forks don't last more than few blocks because the miners won't get paid. But I think GP raises a fair point that if the idea here is that we are broadcasting the current chain to places that have no other connectivity, then you have to trust that broadcast. By definition you don't have access to other peers to check. So if you imagine blockstream as an attacker, they could broadcast their version of the chain which say doesn't include payments they made on the main chain so that they could "double spend" them in places that rely solely on the satellite for truth. Or am I missing something? --- edit: I guess there's no way for blockstream to create blocks at the appropriate difficulty level fast enough, so it would be pretty obvious if they were trying to create their own fork. So I guess this does work..
      • quickthrower2 9y ago
        Yes that's my point. It could make blockstream a juicy target for hacking or rouge employees. Edit: responding to your edit. Yes a good point!
  • kobeya 9y ago
    You need some sort of ultra low bandwidth bidirectional communication for your transactions. You can use that to sync headers only and check if the sat chain is the same as the most work chain you know about.