While the bitcoin robothenryleak moving through the Bitcoin economy is increasing and thus the potential value of such an attack is increasing, the price bitcoin robothenryleak Bitcoins goes up with it, rendering the attack more expensive. Such a person or group could pick any chain they wanted and work exclusively on extending that chain. Now bitcoin robothenryleak if one person or coordinated group controlled more than half the hashing power in the world. Miners solve a computation challenge finding a particular hash to produce new blocks. Please see the Ripple Developer Center for up-to-date documentation and other resources.
When bitcoin robothenryleak block is produced, the chain with that block is longer than the chain without that block, so that block chain becomes the one bitcoin robothenryleak go by since it's the longest one. This prevents an ancient chain from being resurrected. Bitcoin uses a simple rule to determine which chain to go by -- the longest one.