We would know if someone has more than 50% hashpower
Myth.
An attacker with more than 50% hashpower could be mining his own chain and not announcing it to the network (from the last checkpoint in bitcoind). As his chain will be longer, when he announces it will immediately propagate and override the current chain.
Myth.
An attacker with more than 50% hashpower could be mining his own chain and not announcing it to the network (from the last checkpoint in bitcoind). As his chain will be longer, when he announces it will immediately propagate and override the current chain.
There are two approaches, too. The March 11th hard fork was essentially a friendly 51% attack. The "attack" (the switch from the longest chain to the other side of the fork) didn't occur until long after transactions had confirmed post-fork.
- http://www.bitcoinmoney.com/post/47048259653
Then there is the stealth attack where the miner with 51% has been mining and not releasing blocks as they are mined.
Double spending
- http://en.bitcoin.it/wiki/Double_spending
